can we travel 100 light years

What is a light-year?

Light-years make measuring astronomical distances much more manageable.

How far is a light-year?

Why use light-years, alternatives to light-years.

A light-year is a measurement of distance and not time (as the name might imply). A light-year is the distance a beam of light travels in a single Earth year, which equates to approximately 6 trillion miles (9.7 trillion kilometers). 

On the scale of the universe , measuring distances in miles or kilometers is cumbersome given the exceedingly large numbers being discussed. It is much simpler for astronomers to measure the distances of stars from us in the time it takes for light to travel that expanse. For example, the nearest star to our sun , Proxima Centauri , is 4.2 light-years away, meaning the light we see from the star takes a little over four years to reach us. 

The speed of light is constant throughout the universe and is known to high precision. In a vacuum, light travels at 670,616,629 mph (1,079,252,849 km/h). To find the distance of a light-year, you multiply this speed by the number of hours in a year (8,766). The result: One light-year equals 5,878,625,370,000 miles (9.5 trillion km). At first glance, this may seem like an extreme distance, but the enormous scale of the universe dwarfs this length. One estimate puts the diameter of the known universe at 28 billion light-years in diameter .

Measuring in miles or kilometers at an astronomical scale is impractical given the scale of figures being used. Starting in our cosmic neighborhood, the closest star-forming region to us, the Orion Nebula , is a short 7,861,000,000,000,000 miles away, or expressed in light-years, 1,300 light-years away. The center of our galaxy is about 27,000 light-years away. The nearest spiral galaxy to ours, the Andromeda galaxy , is 2.5 million light-years away. Some of the most distant galaxies we can see are billions of light-years from us. The galaxy GN-z11 is thought to be the farthest detectable galaxy from Earth at 13.4 billion light-years away.

Like degrees, the light-year can also be broken down into smaller units of light-hours, light-minutes or light-seconds. For instance, the sun is more than 8 light-minutes from Earth, while the moon is just over a light-second away. Scientists use these terms when talking about communications with deep-space satellites or rovers. Because of the finite speed of light, it can take more than 20 minutes to send a signal to the Curiosity rover on Mars .

Measuring in light-years also allows astronomers to determine how far back in time they are viewing. Because light takes time to travel to our eyes, everything we view in the night sky has already happened. In other words, when you observe something 1 light-year away, you see it as it appeared exactly one year ago. We see the Andromeda galaxy as it appeared 2.5 million years ago. The most distant object we can see, the cosmic microwave background , is also our oldest view of the universe, occurring just after the Big Bang some 13.8 billion years ago.

Astronomers also use parsecs as an alternative to the light-year. Short for parallax-second, a parsec comes from the use of triangulation to determine the distance of stars. To be more specific, it is the distance to a star whose apparent position shifts by 1 arcsecond (1/3,600 of a degree) in the sky after Earth orbits halfway around the sun. One arcsecond is equal to 3.26 light-years.

Whether it's light-years or parsecs, astronomers will continue to use both to measure distances in our expansive and grand universe. 

Additional resources: 

• Watch astronomer Paul Sutter's " We Don't Planet" Episode 9: The Cosmic Distance Ladder . 
• Learn more about how astronomers measure the universe , from the International Astronomical Union.
• Watch " Powers of Ten" (1977) , which gives perspective on the size of the universe.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

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Jonathan is the Editor of All About History magazine. He has a degree in History from the University of Leeds. He has previously worked as editor of video game magazines games™ and X-ONE and tech magazines iCreate and Apps. He is currently based in Bournemouth, UK.

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Cosmic Distances

The space beyond Earth is so incredibly vast that units of measure which are convenient for us in our everyday lives can become GIGANTIC. Distances between the planets, and especially between the stars, can become so big when expressed in miles and kilometers that they're unwieldy. So for cosmic distances, we switch to whole other types of units: astronomical units, light years and parsecs.

Astronomical units, abbreviated AU, are a useful unit of measure within our solar system. One AU is the distance from the Sun to Earth's orbit, which is about 93 million miles (150 million kilometers). When measured in astronomical units, the 886,000,000-mile (1,400,000,000-kilometer) distance from the Sun to Saturn's orbit, is a much more manageable 9.5 AU. So astronomical units are a great way to compress truly astronomical numbers to a more manageable size.

Astronomical units also make it easy to think about distances between solar system objects. They make it easy to see that Jupiter orbits five times farther from the Sun than Earth, and that Saturn is twice as far from the Sun as Jupiter. (This is because, technically, you're expressing every distance as a ratio of the distance from Earth to the Sun. Convenient!)

For much greater distances — interstellar distances — astronomers use light years. A light year is the distance a photon of light travels in one year, which is about 6 trillion miles (9 trillion kilometers, or 63,000 AU). Put another way, a light year is how far you'd travel in a year if you could travel at the speed of light, which is 186,000 miles (300,000 kilometers) per second. (By the way, you can't travel at the speed of light, as far as we know, but that's a whole other story...) Like AU, light years make astronomical distances more manageable. For example, the nearest star system to ours is the triple star system of Alpha Centauri , at about 4.3 light years away. That's a more manageable number than 25 trillion miles, 40 trillion kilometers or 272,000 AU.

Light years also provide some helpful perspective on solar system distances: the Sun is about 8 light minutes from Earth. (And yes, there are also light seconds !) And because light from objects travels at light speed , when you see the Sun, or Jupiter or a distant star, you're seeing it as it was when the light left it, be that 8 minutes, tens of minutes or 4.3 years ago. And this is fundamental to the idea that when we're looking farther out into space, we're seeing farther back in time. (Think about it: you're seeing all the stars in the sky at different times in history — some a few years ago, others hundreds of years ago — all at the same time!)

Finally, parsecs. This is the unit used when the number of light years between objects climbs into the high thousands or millions. One parsec is 3.26 light years. The origin of this unit of measure is a little more complicated, but it's related to how astronomers measure widths in the sky. Astronomers use "megaparsecs" — a megaparsec is 1 million parsecs — for intergalactic distances, or the scale of distances between the galaxies.

And at the point when distances between galaxies become so epic that even megaparsecs get unwieldy, astronomers talk about distances in terms of how much a galaxy's light has been shifted toward longer, redder wavelengths by the expansion of the universe — a measure known as "redshift." Now that's astronomical.

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1.5: Consequences of Light Travel Time

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There is another reason the speed of light is such a natural unit of distance for astronomers. Information about the universe comes to us almost exclusively through various forms of light, and all such light travels at the speed of light—that is, 1 light-year every year. This sets a limit on how quickly we can learn about events in the universe. If a star is 100 light-years away, the light we see from it tonight left that star 100 years ago and is just now arriving in our neighborhood. The soonest we can learn about any changes in that star is 100 years after the fact. For a star 500 light-years away, the light we detect tonight left 500 years ago and is carrying 500-year-old news.

Because many of us are accustomed to instant news from the Internet, some might find this frustrating.

“You mean, when I see that star up there,” you ask, “I won’t know what’s actually happening there for another 500 years?”

But this isn’t the most helpful way to think about the situation. For astronomers, now is when the light reaches us here on Earth. There is no way for us to know anything about that star (or other object) until its light reaches us. But what at first may seem a great frustration is actually a tremendous benefit in disguise. If astronomers really want to piece together what has happened in the universe since its beginning, they must find evidence about each epoch (or period of time) of the past. Where can we find evidence today about cosmic events that occurred billions of years ago?

The delay in the arrival of light provides an answer to this question. The farther out in space we look, the longer the light has taken to get here, and the longer ago it left its place of origin. By looking billions of light-years out into space, astronomers are actually seeing billions of years into the past. In this way, we can reconstruct the history of the cosmos and get a sense of how it has evolved over time.

This is one reason why astronomers strive to build telescopes that can collect more and more of the faint light in the universe. The more light we collect, the fainter the objects we can observe. On average, fainter objects are farther away and can, therefore, tell us about periods of time even deeper in the past. Instruments such as the Hubble Space Telescope (Figure \(\PageIndex{1}\)) and the Very Large Telescope in Chile (which you will learn about in the chapter on Astronomical Instruments), are giving astronomers views of deep space and deep time better than any we have had before.

How Far is a Light Year?

How far is a light-year ? It might seem like a weird question because isn’t a ‘year’ a unit of time, and ‘far’ a unit of distance? While that is correct, a ‘light-year’ is actually a measure of distance. A light-year is the distance light can travel in one year.

Light is the fastest thing in our Universe traveling through interstellar space at 186,000 miles/second (300,000 km/sec). In one year, light can travel 5.88 trillion miles (9.46 trillion km).

A light year is a basic unit astronomers use to measure the vast distances in space.

To give you a great example of how far a light year actually is, it will take Voyager 1 (NASA’s longest-lived spacecraft) over 17,000 years to reach 1 light year in distance traveling at a speed of 61,000 kph.

Related Post: 13 Amazing Facts About Space

Why Do We Use Light-Years?

Because space is so vast, the measurements we use here on Earth are not very helpful and would result in enormous numbers.

When talking about locations in our own galaxy we would have numbers with over 18 zeros. Instead, astronomers use light-time measurements to measure vast distances in space. A light-time measurement is how far light can travel in a given increment of time.

• Light-minute: 11,160,000 miles
• Light-hour: 671 million miles
• Light-year: 5.88 trillion miles

Understanding Light-Years

To help wrap our heads around how to use light-years, let’s look at how far things are away from the Earth starting with our closest neighbor, the Moon.

The Moon is 1.3 light-seconds from the Earth.

Earth is about 8 light-minutes (~92 million miles) away from the Sun. This means light from the Sun takes 8 minutes to reach us.

Jupiter is approximately 35 light minutes from the Earth. This means if you shone a light from Earth it would take about a half hour for it to hit Jupiter.

Pluto is not the edge of our solar system, in fact, past Pluto, there is the Kieper Belt , and past this is the Oort Cloud . The Oort cloud is a spherical layer of icy objects surrounding our entire solar system.

If you could travel at the speed of light, it would take you 1.87 years to reach the edge of the Oort cloud. This means that our solar system is about 4 light-years across from edge to edge of the Oort Cloud.

The distance between the Sun and Interstellar Space. NASA/JPL-Caltech .

The nearest known exoplanet orbits the star Proxima Centauri , which is four light years away (~24 trillion miles). If a modern-day jet were to fly to this exoplanet it would not arrive for 5 million years.

One of the most distant exoplanets is 3,000 light-years (17.6 quadrillion miles) away from us in the Milky Way. If you were to travel at 60 miles an hour, you would not reach this exoplanet for 28 billion years.

Our Milky Way galaxy is approximately 100,000 light-years across (~588 quadrillion miles). Moving further into our Universe, our nearest neighbor, the Andromeda galaxy is 2.537 million light-years (14.7 quintillion miles) away from us.

The Andromeda Galaxy is 2.537 million light-years away from us.

Light, a Window into the Past

While we cannot actually travel through time, we can see into the past. How? We see objects because they either emit light or light has bounced off their surface and is traveling back to us.

Even though light is the fastest thing in our Universe, it takes time to reach us. This means that for any object we are seeing it how it was in the past. How far in the past? However long it took the light to reach us.

For day-to-day objects like a book or your dog, it takes a mere fraction of a fraction of a second for the light bouncing off the object to reach your eye. The further away an object is, the further into its past you are looking.

For instance, light from the Sun takes about 8 minutes to reach Earth, this means we are always seeing the Sun how it looked 8 minutes ago if you were on its surface.

The differences between Lunar Distance, an Astronomical Unit, and a Light Year. Illustration by Star Walk .

Traveling back through our solar system, Jupiter is approximately 30 light-minutes from Earth, so we see Jupiter how it looked 30 minutes ago if you were on its surface. Extending out into the Universe to our neighbor the Andromeda galaxy, we see it how it was 2.537 million years ago.

If there is another civilization out in the Universe watching Earth, they would not see us here today, they would see Earth in the past. A civilization that lives 65 million light-years away would see dinosaurs roaming the Earth.

Helpful Resources:

• How big is the Solar System? (Universe Today)
• What is an Astronomical Unit? (EarthSky)
• How close is Proxima Centauri? (NASA Imagine The Universe)

How Long Would It Take To Travel A Light Year

Using the fastest man-made vehicle, NASA’s Juno spacecraft, which travels at 165,000 mph (365,000 kmph), it would take 2,958 years to travel a light year. A light year is equivalent to about 5.88 trillion miles (9.46 trillion kilometers).

Traveling at the speed of light would be the fastest way to cover vast distances in space, but current technology makes it impossible for humans or even our most advanced spacecraft to reach this speed.

Can people match the speed of a light year?

According to Einstein, it is impossible to match the speed of light. It is because light is the fastest thing in the universe, traveling at 186,000 miles per second (300,000 kilometers per second). There is not one thing that we could invent that could even match a fraction of how fast light travels.

Some scientists have theorized that a new type of engine, called a warp drive , could potentially allow humans to reach the speed of travel required to match the speed of light. However, even if future spacecrafts were able to achieve this level of propulsion, it would still take thousands of years to travel from one star system to another.

Despite the challenges, scientists continue to study space travel at faster-than-light speeds, as they are optimistic that one day we will be able to explore the vast reaches of our universe and even discover life on other planets.

For now, it would take many thousands of years to travel a light year using current technology. However, scientists remain hopeful that one day we will be able to explore the far reaches of space and perhaps even discover other life forms in distant star systems. Until then, we can continue marveling at the

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Space Travel Calculator

Table of contents

Ever since the dawn of civilization, the idea of space travel has fascinated humans! Haven't we all looked up into the night sky and dreamed about space?

With the successful return of the first all-civilian crew of SpaceX's Inspiration4 mission after orbiting the Earth for three days, the dream of space travel looks more and more realistic now.

While traveling deep into space is still something out of science fiction movies like Star Trek and Star Wars, the tremendous progress made by private space companies so far seems very promising. Someday, space travel (or even interstellar travel) might be accessible to everyone!

It's never too early to start planning for a trip of a lifetime (or several lifetimes). You can also plan your own space trip and celebrate World Space Week in your own special way!

This space travel calculator is a comprehensive tool that allows you to estimate many essential parameters in theoretical interstellar space travel . Have you ever wondered how fast we can travel in space, how much time it will take to get to the nearest star or galaxy, or how much fuel it requires? In the following article, using a relativistic rocket equation, we'll try to answer questions like "Is interstellar travel possible?" , and "Can humans travel at the speed of light?"

Explore the world of light-speed travel of (hopefully) future spaceships with our relativistic space travel calculator!

If you're interested in astrophysics, check out our other calculators. Find out the speed required to leave the surface of any planet with the escape velocity calculator or estimate the parameters of the orbital motion of planets using the orbital velocity calculator .

One small step for man, one giant leap for humanity

Although human beings have been dreaming about space travel forever, the first landmark in the history of space travel is Russia's launch of Sputnik 2 into space in November 1957. The spacecraft carried the first earthling, the Russian dog Laika , into space.

Four years later, on 12 April 1961, Soviet cosmonaut Yuri A. Gagarin became the first human in space when his spacecraft, the Vostok 1, completed one orbit of Earth.

The first American astronaut to enter space was Alan Shepard (May 1961). During the Apollo 11 mission in July 1969, Neil Armstrong and Buzz Aldrin became the first men to land on the moon. Between 1969 and 1972, a total of 12 astronauts walked the moon, marking one of the most outstanding achievements for NASA.

In recent decades, space travel technology has seen some incredible advancements. Especially with the advent of private space companies like SpaceX, Virgin Galactic, and Blue Origin, the dream of space tourism is looking more and more realistic for everyone!

However, when it comes to including women, we are yet to make great strides. So far, 566 people have traveled to space. Only 65 of them were women .

Although the first woman in space, a Soviet astronaut Valentina Tereshkova , who orbited Earth 48 times, went into orbit in June 1963. It was only in October 2019 that the first all-female spacewalk was completed by NASA astronauts Jessica Meir and Christina Koch.

Women's access to space is still far from equal, but there are signs of progress, like NASA planning to land the first woman and first person of color on the moon by 2024 with its Artemis missions. World Space Week is also celebrating the achievements and contributions of women in space this year!

In the following sections, we will explore the feasibility of space travel and its associated challenges.

How fast can we travel in space? Is interstellar travel possible?

Interstellar space is a rather empty place. Its temperature is not much more than the coldest possible temperature, i.e., an absolute zero. It equals about 3 kelvins – minus 270 °C or minus 455 °F. You can't find air there, and therefore there is no drag or friction. On the one hand, humans can't survive in such a hostile place without expensive equipment like a spacesuit or a spaceship, but on the other hand, we can make use of space conditions and its emptiness.

The main advantage of future spaceships is that, since they are moving through a vacuum, they can theoretically accelerate to infinite speeds! However, this is only possible in the classical world of relatively low speeds, where Newtonian physics can be applied. Even if it's true, let's imagine, just for a moment, that we live in a world where any speed is allowed. How long will it take to visit the Andromeda Galaxy, the nearest galaxy to the Milky Way?

We will begin our intergalactic travel with a constant acceleration of 1 g (9.81 m/s² or 32.17 ft/s²) because it ensures that the crew experiences the same comfortable gravitational field as the one on Earth. By using this space travel calculator in Newton's universe mode, you can find out that you need about 2200 years to arrive at the nearest galaxy! And, if you want to stop there, you need an additional 1000 years . Nobody lives for 3000 years! Is intergalactic travel impossible for us, then? Luckily, we have good news. We live in a world of relativistic effects, where unusual phenomena readily occur.

Can humans travel at the speed of light? – relativistic space travel

In the previous example, where we traveled to Andromeda Galaxy, the maximum velocity was almost 3000 times greater than the speed of light c = 299,792,458 m/s , or about c = 3 × 10 8 m/s using scientific notation.

However, as velocity increases, relativistic effects start to play an essential role. According to special relativity proposed by Albert Einstein, nothing can exceed the speed of light. How can it help us with interstellar space travel? Doesn't it mean we will travel at a much lower speed? Yes, it does, but there are also a few new relativistic phenomena, including time dilation and length contraction, to name a few. The former is crucial in relativistic space travel.

Time dilation is a difference of time measured by two observers, one being in motion and the second at rest (relative to each other). It is something we are not used to on Earth. Clocks in a moving spaceship tick slower than the same clocks on Earth ! Time passing in a moving spaceship T T T and equivalent time observed on Earth t t t are related by the following formula:

where γ \gamma γ is the Lorentz factor that comprises the speed of the spaceship v v v and the speed of light c c c :

where β = v / c \beta = v/c β = v / c .

For example, if γ = 10 \gamma = 10 γ = 10 ( v = 0.995 c v = 0.995c v = 0.995 c ), then every second passing on Earth corresponds to ten seconds passing in the spaceship. Inside the spacecraft, events take place 90 percent slower; the difference can be even greater for higher velocities. Note that both observers can be in motion, too. In that case, to calculate the relative relativistic velocity, you can use our velocity addition calculator .

Let's go back to our example again, but this time we're in Einstein's universe of relativistic effects trying to reach Andromeda. The time needed to get there, measured by the crew of the spaceship, equals only 15 years ! Well, this is still a long time, but it is more achievable in a practical sense. If you would like to stop at the destination, you should start decelerating halfway through. In this situation, the time passed in the spaceship will be extended by about 13 additional years .

Unfortunately, this is only a one-way journey. You can, of course, go back to Earth, but nothing will be the same. During your interstellar space travel to the Andromeda Galaxy, about 2,500,000 years have passed on Earth. It would be a completely different planet, and nobody could foresee the fate of our civilization.

A similar problem was considered in the first Planet of the Apes movie, where astronauts crash-landed back on Earth. While these astronauts had only aged by 18 months, 2000 years had passed on Earth (sorry for the spoilers, but the film is over 50 years old at this point, you should have seen it by now). How about you? Would you be able to leave everything you know and love about our galaxy forever and begin a life of space exploration?

Space travel calculator – relativistic rocket equation

Now that you know whether interstellar travel is possible and how fast we can travel in space, it's time for some formulas. In this section, you can find the "classical" and relativistic rocket equations that are included in the relativistic space travel calculator.

There could be four combinations since we want to estimate how long it takes to arrive at the destination point at full speed as well as arrive at the destination point and stop. Every set contains distance, time passing on Earth and in the spaceship (only relativity approach), expected maximum velocity and corresponding kinetic energy (on the additional parameters section), and the required fuel mass (see Intergalactic travel — fuel problem section for more information). The notation is:

• a a a — Spaceship acceleration (by default 1   g 1\rm\, g 1 g ). We assume it is positive a > 0 a > 0 a > 0 (at least until halfway) and constant.
• m m m — Spaceship mass. It is required to calculate kinetic energy (and fuel).
• d d d — Distance to the destination. Note that you can select it from the list or type in any other distance to the desired object.
• T T T — Time that passed in a spaceship, or, in other words, how much the crew has aged.
• t t t — Time that passed in a resting frame of reference, e.g., on Earth.
• v v v — Maximum velocity reached by the spaceship.
• K E \rm KE KE — Maximum kinetic energy reached by the spaceship.

The relativistic space travel calculator is dedicated to very long journeys, interstellar or even intergalactic, in which we can neglect the influence of the gravitational field, e.g., from Earth. We didn't include our closest celestial bodies, like the Moon or Mars, in the destination list because it would be pointless. For them, we need different equations that also take into consideration gravitational force.

Newton's universe — arrive at the destination at full speed

It's the simplest case because here, T T T equals t t t for any speed. To calculate the distance covered at constant acceleration during a certain time, you can use the following classical formula:

Since acceleration is constant, and we assume that the initial velocity equals zero, you can estimate the maximum velocity using this equation:

and the corresponding kinetic energy:

Newton's universe — arrive at the destination and stop

In this situation, we accelerate to the halfway point, reach maximum velocity, and then decelerate to stop at the destination point. Distance covered during the same time is, as you may expect, smaller than before:

Acceleration remains positive until we're halfway there (then it is negative – deceleration), so the maximum velocity is:

and the kinetic energy equation is the same as the previous one.

Einstein's universe — arrive at the destination at full speed

The relativistic rocket equation has to consider the effects of light-speed travel. These are not only speed limitations and time dilation but also how every length becomes shorter for a moving observer, which is a phenomenon of special relativity called length contraction. If l l l is the proper length observed in the rest frame and L L L is the length observed by a crew in a spaceship, then:

What does it mean? If a spaceship moves with the velocity of v = 0.995 c v = 0.995c v = 0.995 c , then γ = 10 \gamma = 10 γ = 10 , and the length observed by a moving object is ten times smaller than the real length. For example, the distance to the Andromeda Galaxy equals about 2,520,000 light years with Earth as the frame of reference. For a spaceship moving with v = 0.995 c v = 0.995c v = 0.995 c , it will be "only" 252,200 light years away. That's a 90 percent decrease or a 164 percent difference!

Now you probably understand why special relativity allows us to intergalactic travel. Below you can find the relativistic rocket equation for the case in which you want to arrive at the destination point at full speed (without stopping). You can find its derivation in the book by Messrs Misner, Thorne ( Co-Winner of the 2017 Nobel Prize in Physics ) and Wheller titled Gravitation , section §6.2. Hyperbolic motion. More accessible formulas are in the mathematical physicist John Baez's article The Relativistic Rocket :

• Time passed on Earth:
• Time passed in the spaceship:
• Maximum velocity:
• Relativistic kinetic energy remains the same:

The symbols sh ⁡ \sh sh , ch ⁡ \ch ch , and th ⁡ \th th are, respectively, sine, cosine, and tangent hyperbolic functions, which are analogs of the ordinary trigonometric functions. In turn, sh ⁡ − 1 \sh^{-1} sh − 1 and ch ⁡ − 1 \ch^{-1} ch − 1 are the inverse hyperbolic functions that can be expressed with natural logarithms and square roots, according to the article Inverse hyperbolic functions on Wikipedia.

Einstein's universe – arrive at destination point and stop

Most websites with relativistic rocket equations consider only arriving at the desired place at full speed. If you want to stop there, you should start decelerating at the halfway point. Below, you can find a set of equations estimating interstellar space travel parameters in the situation when you want to stop at the destination point :

Intergalactic travel – fuel problem

So, after all of these considerations, can humans travel at the speed of light, or at least at a speed close to it? Jet-rocket engines need a lot of fuel per unit of weight of the rocket. You can use our rocket equation calculator to see how much fuel you need to obtain a certain velocity (e.g., with an effective exhaust velocity of 4500 m/s).

Hopefully, future spaceships will be able to produce energy from matter-antimatter annihilation. This process releases energy from two particles that have mass (e.g., electron and positron) into photons. These photons may then be shot out at the back of the spaceship and accelerate the spaceship due to the conservation of momentum. If you want to know how much energy is contained in matter, check out our E = mc² calculator , which is about the famous Albert Einstein equation.

Now that you know the maximum amount of energy you can acquire from matter, it's time to estimate how much of it you need for intergalactic travel. Appropriate formulas are derived from the conservation of momentum and energy principles. For the relativistic case:

where e x e^x e x is an exponential function, and for classical case:

Remember that it assumes 100% efficiency! One of the promising future spaceships' power sources is the fusion of hydrogen into helium, which provides energy of 0.008 mc² . As you can see, in this reaction, efficiency equals only 0.8%.

Let's check whether the fuel mass amount is reasonable for sending a mass of 1 kg to the nearest galaxy. With a space travel calculator, you can find out that, even with 100% efficiency, you would need 5,200 tons of fuel to send only 1 kilogram of your spaceship . That's a lot!

So can humans travel at the speed of light? Right now, it seems impossible, but technology is still developing. For example, a photonic laser thruster is a good candidate since it doesn't require any matter to work, only photons. Infinity and beyond is actually within our reach!

How do I calculate the travel time to other planets?

To calculate the time it takes to travel to a specific star or galaxy using the space travel calculator, follow these steps:

• Choose the acceleration : the default mode is 1 g (gravitational field similar to Earth's).
• Enter the spaceship mass , excluding fuel.
• Select the destination : pick the star, planet, or galaxy you want to travel to from the dropdown menu.
• The distance between the Earth and your chosen stars will automatically appear. You can also input the distance in light-years directly if you select the Custom distance option in the previous dropdown.
• Define the aim : select whether you aim to " Arrive at destination and stop " or “ Arrive at destination at full speed ”.
• Pick the calculation mode : opt for either " Einstein's universe " mode for relativistic effects or " Newton's universe " for simpler calculations.
• Time passed in spaceship : estimated time experienced by the crew during the journey. (" Einstein's universe " mode)
• Time passed on Earth : estimated time elapsed on Earth during the trip. (" Einstein's universe " mode)
• Time passed : depends on the frame of reference, e.g., on Earth. (" Newton's universe " mode)
• Required fuel mass : estimated fuel quantity needed for the journey.
• Maximum velocity : maximum speed achieved by the spaceship.

How long does it take to get to space?

It takes about 8.5 minutes for a space shuttle or spacecraft to reach Earth's orbit, i.e., the limit of space where the Earth's atmosphere ends. This dividing line between the Earth's atmosphere and space is called the Kármán line . It happens so quickly because the shuttle goes from zero to around 17,500 miles per hour in those 8.5 minutes .

How fast does the space station travel?

The International Space Station travels at an average speed of 28,000 km/h or 17,500 mph . In a single day, the ISS can make several complete revolutions as it circumnavigates the globe in just 90 minutes . Placed in orbit at an altitude of 350 km , the station is visible to the naked eye, looking like a dot crossing the sky due to its very bright solar panels.

How do I reach the speed of light?

To reach the speed of light, you would have to overcome several obstacles, including:

Mass limit : traveling at the speed of light would mean traveling at 299,792,458 meters per second. But, thanks to Einstein's theory of relativity, we know that an object with non-zero mass cannot reach this speed.

Energy : accelerating to the speed of light would require infinite energy.

Effects of relativity : from the outside, time would slow down, and you would shrink.

Why can't sound travel in space?

Sound can’t travel in space because it is a mechanical wave that requires a medium to propagate — this medium can be solid, liquid, or gas. In space, there is no matter, or at least not enough for sound to propagate. The density of matter in space is of the order 1 particle per cubic centimeter . While on Earth , it's much denser at around 10 20 particles per cubic centimeter .

Dreaming of traveling into space? 🌌 Plan your interstellar travel (even to a Star Trek destination) using this calculator 👨‍🚀! Estimate how fast you can reach your destination and how much fuel you would need 🚀

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ol{padding-top:0px;}.css-4okk7a ul:not(:first-child),.css-4okk7a ol:not(:first-child){padding-top:4px;} Spaceship and destination 👩‍🚀👨‍🚀

Spaceship acceleration

Spaceship mass

Mass of spaceship excluding fuel.

Destination

Select a destination from the list or type in distance by hand.

Which star/galaxy?

If you want to input your own distance, select the 'Custom destination' option in the 'Which star/galaxy?' field.

Calculation options

Do you want to stop at destination point? If yes, the spaceship will start decelerating once it reaches the halfway point.

Calculations mode

You can compare Einstein's special relativity with non-relativistic Newton's physics. Remember that at near-light speeds only the former is correct!

Travel details 🚀

Time passed in spaceship

Time passed on Earth

Time passed in the resting frame of reference. It could be an observer on Earth.

Required fuel mass

Assuming 100% efficiency.

Maximum velocity

Note that our calculator may round velocity to the speed of light if it is really close to it.

Additional parameters

Fuel energy equivalent

Required fuel mass multiplied by c².

Maximum kinetic energy

Beta parameter for the maximum velocity.

γ [1/√(1 - β²)]

Lorentz factor for the maximum velocity.

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Light Year Calculator

Master the cosmos: light year calculations simplified by newtum.

Embark on an interstellar journey with Newtum's Light Year Calculator. Unlock the secrets of the cosmos and measure astronomical distances in light years with a click. Let curiosity lead you into the depths of space.

Understanding the Astronomical Distance Measurement Tool

The Light Year Calculator is a sophisticated tool designed to convert vast cosmic distances into light years. It seamlessly translates the astronomical units, parsecs, and kilometers into a standard light year measurement, facilitating easier comprehension of space's enormity.

Decoding the Light Year Calculation Formula

Grasp the essence of converting cosmic distances using our Light Year Calculator. This formula is crucial for astronomers and space enthusiasts to understand the scale of the universe.

• Define the input units (kilometers, astronomical units, parsecs).
• Use the constant speed of light in a vacuum: approximately 299,792 kilometers per second.
• Calculate the time it takes for light to travel the input distance in a year.
• Translate the time into light years as the output.

Step-by-Step Guide: Utilizing the Light Year Calculator

Our Light Year Calculator is user-friendly and straightforward. Follow the simple instructions below, and you'll be able to calculate astronomical distances in light years effortlessly.

• Enter the distance you want to convert into the calculator.
• Select the unit of measurement for your input.
• Click 'Calculate' to see the distance in light years.
• Use the results for your astronomical research or curiosity.

Why Choose Newtum's Light Year Calculator? A Feature Showcase

• User-Friendly Interface: Easy navigation and operation.
• Instant Results: Immediate conversion into light years.
• Data Security: All calculations are performed on your device, ensuring privacy.
• Accessibility Across Devices: Use the tool on any device with a web browser.
• No Installation Needed: Access directly online without downloading.
• Examples for Clarity: Understand the concept with practical examples.
• Transparent Process: Clear and open calculation method.
• Educational Resource: A learning aid for students and educators.
• Responsive Customer Support: Ready to assist with any queries.
• Regular Updates: The tool stays current with the latest web standards.
• Privacy Assurance: Your data never leaves your computer.
• Efficient Distance Retrieval: Quick calculations for any distance.
• Language Accessibility: Available in multiple languages.
• Engaging and Informative Content: Makes learning about space fun.
• Fun and Interactive Learning: Engage with the tool interactively.
• Shareable Results: Easily share your findings with others.
• Responsive Design: Adapts to any screen size for optimal viewing.
• Educational Platform Integration: Can be incorporated into learning systems.
• Comprehensive Documentation: Detailed guidance on using the tool.

Exploring the Applications and Uses of the Light Year Calculator

• Calculate distances between stars and planets.
• Assist in astronomical research and education.
• Convert astronomical units and parsecs for space-related projects.
• Enhance understanding of the universe's scale.
• Aid in planning space missions and satellite launches.

Practical Examples: Understanding the Light Year Calculator Formula

For example, if an astronomical object is 93 million miles away (the approximate distance from the Earth to the Sun), the Light Year Calculator can determine how many light years that distance represents. Similarly, if another object is 2.5 million light years away (the distance to the Andromeda Galaxy), the Calculator helps visualize this immense distance in terms that are easier to understand.

Ensuring Data Security with Our Light Year Calculator

In conclusion, the Light Year Calculator stands as a testament to the power of modern technology fused with the user's need for security. All calculations are performed locally on your device, ensuring that your data remains with you. This tool is not just a simple calculator; it's a gateway to understanding the vastness of space while maintaining the utmost privacy. No data is sent to servers, which guarantees that your curiosity about the cosmos doesn't compromise your data security. Explore the universe with peace of mind, knowing that your interstellar inquiries are safe and sound.

Frequently Asked Questions: Light Year Calculator Insights

• What is a light year and how is it calculated?
• Can I convert distances from kilometers to light years?
• Is the Light Year Calculator accurate for calculating distances to faraway galaxies?
• How does the Calculator maintain my data's privacy?
• Can I use the Light Year Calculator for educational purposes?

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What Is a Light-Year?

An image of distant galaxies captured by the NASA/ESA Hubble Space Telescope. Credit: ESA/Hubble & NASA, RELICS; Acknowledgment: D. Coe et al.

For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!

Looking Back in Time

When we use powerful telescopes to look at distant objects in space, we are actually looking back in time. How can this be?

Light travels at a speed of 186,000 miles (or 300,000 km) per second. This seems really fast, but objects in space are so far away that it takes a lot of time for their light to reach us. The farther an object is, the farther in the past we see it.

Our Sun is the closest star to us. It is about 93 million miles away. So, the Sun's light takes about 8.3 minutes to reach us. This means that we always see the Sun as it was about 8.3 minutes ago.

The next closest star to us is about 4.3 light-years away. So, when we see this star today, we’re actually seeing it as it was 4.3 years ago. All of the other stars we can see with our eyes are farther, some even thousands of light-years away.

Stars are found in large groups called galaxies . A galaxy can have millions or billions of stars. The nearest large galaxy to us, Andromeda, is 2.5 million light-years away. So, we see Andromeda as it was 2.5 million years in the past. The universe is filled with billions of galaxies, all farther away than this. Some of these galaxies are much farther away.

An image of the Andromeda galaxy, as seen by NASA's GALEX observatory. Credit: NASA/JPL-Caltech

In 2016, NASA's Hubble Space Telescope looked at the farthest galaxy ever seen, called GN-z11. It is 13.4 billion light-years away, so today we can see it as it was 13.4 billion years ago. That is only 400 million years after the big bang . It is one of the first galaxies ever formed in the universe.

Learning about the very first galaxies that formed after the big bang, like this one, helps us understand what the early universe was like.

This picture shows hundreds of very old and distant galaxies. The oldest one found so far in GN-z11 (shown in the close up image). The image is a bit blurry because this galaxy is so far away. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

More to explore

What Is a Galaxy?

How Far Away Is the Moon?

What Is a Nebula?

If you liked this, you may like:

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• NGC 1097 (Spitzer)
• Helix (Spitzer)
• Flame Nebula (WISE)
• Galactic Center (2MASS)
• Cool Andromeda (Herschel)

Space Terms

• What is a satellite?
• What is an Astronomical Unit?
• What is gravity?
• What does escape velocity mean?
• What is absolute zero?

What is a light-year?

The fastest thing that we know of is light which travels at a speed of 186,000 miles or 300,000 kilometers per second in empty space. To get an idea of how fast this is, light can travel about seven times around Earth in one second! Astronomers use the speed of light to measure how far away things are in space. A light-year (ly) is the distance that light can travel in one year. In one year, light travels about 5,880,000,000,000 miles or 9,460,000,000,000 kilometers. So, this distance is 1 light-year. For example, the nearest star to us is about 4.3 light-years away. Our galaxy, the Milky Way, is about 150,000 light-years across, and the nearest large galaxy, Andromeda, is 2.3 million light-years away.

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A guide to lightyears, the unit used by astronomers to measure vast distances in the cosmos

Using lightyears to measure distance in the Universe and how long it would take to travel one lightyear by foot, car, plane and rocket.

Jenny Winder

The numbers we use in astronomy are, literally, astronomical. It can be hard to get your head around so many zeros.

If we were to use kilometres and miles it would be like measuring your commute in millimetres.

To try to simplify things, when we discuss objects within our Solar System, we use the Astronomical Unit (AU) to measure distance.

One AU is the average distance between the Earth and the Sun or 150 million kilometres (93 million miles). Our Solar System has a diameter of just 1,921 AUs. So far so good.

To measure vast distances across space , scientists use the Parsec , the distance 1AU subtends an angle of 1 arc-second (1/3600 of a degree) which is 206,265 AUs, or 30.9 trillion km (19.2 trillion miles) and difficult for most of us to comprehend.

So the lightyear is the standard measure of distance for anything outside the Solar System.

A simple definition of lightyear

Put simply, a lightyear is the distance light travels in space in a year, 9.46 trillion km (5.88 trillion miles) or 63,241 AU, 0.30 parsecs.

Nothing travels faster than light. It travels nearly one million times faster than sound. A lightsecond equals 300,000 km (186,000 miles).

A lightminute is about 18 million km ( 11 million miles) and a lighthour is 1.1 billion km.

One AU equals 8.3 light minutes and a Parsec equals 3.26 lightyears.

Lightyears and looking back in time

The further we look into space, the farther back in time we see.

Proxima Centauri , the nearest star is 4.25 lightyears away, so the light we see from it today, started its journey four years and three months ago.

If Proxima Centauri exploded today it would take 4 years and 3 months before we saw it happen.

The radius of the observable Universe and so the farthest we can see into space is 46.6 billion lightyears.

Travelling a lightyear

Our crewed spaceships, like Apollo, reach speeds of around 39,400 km/h (24,500 mph). It would still take around 27 thousand years to travel one lightyear.

A plane travelling at 965 km/h (600 mp/h) would take 1 million years to travel one lightyear.

A car with an average speed of 90 km/h (56 mph) would take 12 million years, and if you fancied a walk, at 5 km/h (3 mph) it would take you a whopping 216 million years to travel one lightyear, with no comfort breaks!

Earth orbits the Sun at 107 thousand km/h or 67 thousand mph, so it would take 10 thousand years for Earth travel one lightyear.

But our Solar system is also travelling through the Galaxy at 720 thousand km/h (448 thousand mph) which takes just 1,500 years to travel one lightyear.

Travelling at the speed of light

Currently, faster-than-light travel seems an unreachable goal, despite movies showing us using wormholes , warp drives and spore drives in the future.

The closest proposition is to use the energy and momentum of light itself to propel a spacecraft.

A city-sized arrangement of synchronised lasers, firing photons to push a small hand-sized spacecraft to 25 per cent the speed of light.

That would get us 4.25 light years to Proxima Centauri in under 20 years.

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By Darin Anthony - Last Updated: April 17, 2024

How Many Years in a Light Year? Time vs. Distance

Article Contents

Understanding the scale of empty space in the universe requires grappling with vast distances far beyond anything we humans experience.

To simplify a huge number that could quickly fill the width of a page, astronomers adopted the light-year (LY) as a unit of measurement for distance that would make the vast expanse of the universe more manageable. But how many years in a light year?

The answer will depend on the moving object’s rate of speed. If the object is traveling at the  speed of light,  then the time it will take to cover the distance of a light year is one Earth year. If traveling at half the speed of light, it would take twice as long, two Earth years, and so forth.

Let’s go over what a light-year represents to get a better understanding of the concept.

Key Takeaways

• A light year is a measure of distance equivalent to how far light travels in one single Earth year.
• It’s a fundamental unit for expressing astronomical distances, crucial for space exploration and understanding the scale of the universe.
• Light years are used to calculate the total distance between space objects, not as a measurement of time in the cosmos.

The Concept of a Light-Year

The speed of light , the fastest thing currently known in the universe, travels through the vacuum of space at approximately 186,000 miles (299,792 km) per second . That means the distance a beam of light travels during one year here on Earth is about 5.87 trillion miles (9.46 trillion km) . 

The name can be confusing, but it’s essential to understand that a light-year is a unit of distance, not a unit of time . It does not measure a span of years but how far a light photon travels in the span of one year on Earth .  

It’s a unit of measurement to help everyone better comprehend the huge distances between stars, galaxies, and other celestial objects in space. Let’s look at a couple of examples. 

The nearest star to our Sun, Proxima Centauri , is about 4.24 light years away from Earth. That means the light from Proxima Centauri takes over four years to reach us! When we look at that star, we’re actually seeing it as it was over four years ago.

But how long would it take you to travel light-years to Proxima Centauri in a spaceship moving at 100 mph (160.9 km)? It would take you a “never-gonna-get-there” 6.7 million Earth years just to make it, roughly a quarter of the journey, one light-year .

Our Milky Way galaxy spans 100,000 light-years. It takes light one hundred thousand Earth years to travel from one edge of the Milky Way to the other side.

So if one-light year is 5.87 trillion miles (9.46 trillion km) you can understand why expressing distance as 100,000 (ly) is much easier than multiplying 5.87 trillion (9.46 trillion km) by 100,000.

The Andromeda Galaxy, the nearest spiral galaxy to us, is approximately 2.5 million light years away. The light we see from Andromeda has taken two million and five hundred thousand years to reach our eyes. If we had the capability to send a probe traveling at light speed toward Andromeda, it would take 2.5 million years to arrive.

Distances in space are so immense that customary units like miles or kilometers don’t work very well. That’s why astronomers rely on light-years and other special units of distance, like astronomical units and parsecs . 

Measuring Cosmic Distances

Astronomers have several units of measurements they will use depending on how great of a distance needs to be noted.

Astronomical Units (AU)

An astronomical unit (AU) refers to the Earth-Sun distance. One (AU) equals the distance from the Earth to the Sun – about 93 million miles (150 million km) .

It is considered for the notation of smaller units of distance. One light year is roughly 63,241 times greater than an (AU).

A  parsec  equals 3.26 light years, around 19 trillion miles (31 trillion kilometers).

This term originated from the method of parallax, where one parsec is the distance at which an astronomical object would appear to shift by one arcsecond against the backdrop of more distant stars in the Earth’s six-month orbital traverse.

The concept of parsecs is essential for communicating astronomical distances beyond our solar system and throughout the galaxy, providing a standardized measurement for interstellar space.

Light Years & Light Minutes

As we discussed earlier, a light-year represents the distance of 5.87 trillion miles (9.46 trillion km). But there are times when describing shorter distances, it is easier to express a distance in light minutes.

It’s the distance light travels during minutes here on Earth. An example is 186,000/miles per second multiplied by the number of seconds in a minute (60 seconds) = 11,160,000 mi.

The average distance to Mars from Earth is 139,808,475 miles . It could also be expressed as 12.5 light minutes .

How to Calculate the Distance of One Light Year

The formula to calculate the distance of 1 light-year is:

(d) Distance = (r) Rate x (t) Time

Our variables are:

Speed of light = (r) Distance of Light = (d) Time = (t)

This equation would look like:

Speed of light x 1 Earth Year = Distance of a light year

Since we know the speed of light, let’s calculate how many seconds in a year:

60 seconds x 60 minutes = 3600/secs in 1 hour 3600 seconds x 24 hours = 86,400 secs in 1 day 86,400 seconds x 365 days = 31,536,000 seconds 1 year.

Now we have our time variable:

Rate x Time = Distance 186,000/mps x 31,536,000/spy = 5.87 Trillion Miles

Here is a light-year calculator .

To understand how many years in a light year first remember a light-year is always a measurement of distance and not time . Astronomers will use light-years, light-minutes, parsecs, and astronomical units to express these unimaginable distances in our beautiful, mysterious universe.

So, the answer to how many years in a light year will always depend on how fast the object is moving. How many years to travel 20 light-years? At the speed of light 20 Earth years. At the speed of Voyager 1 (37,132/mph), 18,065 years . So its all relative to speed.

Anything less than the speed of light will take many, many years to make the incredibly long distant journey of a light-year.

Astronomy has peaked my curiosity and imagination from an early age. I am always thrilled to read about the latest galactic discovery or planning my next celestial observation. More about me [..]

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Lightyears 101: Are We Watching the Stars In Real Time?

One lightyear can take you 6 trillion miles away in space..

Rupendra Brahambhatt

Yuri_B/Pixabay

In our solar system, Saturn is the farthest planet from Earth that can be seen with the naked eye. And if it is destroyed by an asteroid while you are watching it (with or without a telescope), the ringed planet would still be visible to you for around 80 minutes, on average, even after it’s in bits and pieces. This happens because the average distance between Saturn and Earth is 0.00015 light-years, which means that the light from Saturn takes approximately 80 minutes to reach your eyes at Earth. 

So if any star that you are observing from Earth is 100 light-years away then what you are watching from your telescope is not its current status but what the star was 100 years ago. This is also why sometimes telescope is called an astronomical time machine . Measuring astronomical distances in miles or kilometers is impractical because of the huge distances and the scale of figures being used. Measuring in light years also allows astronomers to look back in time. Because light takes a standard amount of time to travel to our eyes, everything we can view in space has already happened. So, when you observe something exactly two lightyears away, you see it as it appeared exactly two years ago. 

What is a lightyear?

The speed of light is a constant. In a vacuum, light also travels at speed of 670,616,629 mph (1,079,252,849 km/h). In one Earth year of 364.25 days (8,766 hours), light travels a distance of 5,878,625,370,000 miles (9.5 trillion km). This distance is referred to as one light year.

Since the distance between cosmic bodies mostly came out in the form of millions and billions of kilometers, a more convenient measuring unit was required to easily express such large distances and this led to the lightyear being used as a unit for measuring astronomical distances.

As the value suggests, light year (or lightyear/ly) is a unit of distance. One common misconception about lightyear is that it is a unit of time, which is wrong. Lightyear is generally used to express the distance between Earth and celestial bodies outside our solar system. 

Speed of light and the discovery of lightyear

For scientists to correctly figure out light year, it was important that they have the value of the speed of light. The ancient Greek philosophers disagreed onthe nature of light speed. The philosopher  Empedocles thought that light traveled and so must have a rate of travel. Aristotle, in contrast, argued that light was instantaneous.

In the mid-1600s, Galileo Galilei conducted experiments on the speed of light using people placed on hills around a mile apart, holding lanterns.  But the distance wasn’t far enough to record the speed of light, only to conclude that light traveled faster than sound.

In 1676, Danish astronomer Ole Rømer , accidentally came up with a new estimate for the speed of light, while trying to create a reliable astronomical clock for sailors at sea. He used observations of the eclipses of Jupiter’s moon, Io, to estimate the speed of light at about 124,000 miles per second (200,000 km/s).

However, this is different from the speed of light that we know today (299,792 km/s), but this anomaly was not because Rømer’s method was flawed, but due to the fact that at that time the actual diameter of Earth (12,742 km) was not known. Later, Dutch mathematician Christiaan Huygens calculated the speed of light as 220 thousand miles per second (much closer to the actual) by applying the true value of Earth’s diameter in Rømer’s calculations. 

In 1729, English astronomer James Bradley put forward his theory concerning aberration of light (apparent motion of stars relative to their velocity) before the Royal Society. In his study, he estimated the speed of light at 185,000 miles per second (301,000 km/s) , which is within about 1% of the value that we know today. 

Two separate attempts in the mid-1800s, by French physicists Hippolyte Fizeau and Leon Foucault, each came within about 1,000 miles per second (1,609 km/s) of the speed of light.

In 1879, physicist Albert A. Michelson used mirrors and lenses to measure the speed of light at 186,355 miles per second (299,910 km/s). Forty years later, he used a mile-long depressurized tube of corrugated steel pipe to simulate a near-vacuum and give a better measurement, which was only slightly lower than the accepted value of the speed of light today.  

In 1838, German physicist Friedrich Wilhelm Bessel used the value of the speed of light to measure the distance between Earth and binary star system 61 Cygni. Though he didn’t explicitly mention the word ‘light year’, he explained that light would take 10.3 years to reach from 61 Cygni to Earth. This was the first time, a physicist used light year as the measure of distance, and therefore, Bessel is also credited as the person who discovered lightyear. 

The term ‘lightyear’ was mentioned for the first time in a Germany-based publication called Lichtjare in the year 1851. By the time Einstein came up with his theory of Special Relativity (E=mc 2 ) positing that light always travels with a finite speed, lightyear had already become a popular unit for measuring astronomical distances among scientists.

Light year vs astronomical unit vs lunar distance vs parsec

Apart from lightyear, there are other units as well such as astronomical unit (AU), lunar distance (LD), and parsec (pc) which are used to measure the distance between different objects in space. In astronomy, lunar distance,  or Earth-moon characteristic distance, is the semi-major axis of the geocentric lunar orbit. It is approximately 400,000  km , which is a quarter of a million miles, or 1.28 light seconds. Lunar distance is commonly used to express the distance to near-Earth object encounters. 

An astronomical unit (AU) is equal to the mean distance from the center of the Earth to the center of the sun.

Both lunar distance and astronomical units are used to express the distance between objects within our solar system whereas, lightyear and parsec are employed to measure the distances outside our solar system (such as the distance between galaxies).

A Parsec is the distance at which the radius of  Earth ’s  orbit  subtends an angle of one second of arc (an angle is subtended by an arc when its two rays pass through the endpoints of that arc). Thus, a  star  at a distance of one parsec would have a  parallax  (the angular difference in direction of a celestial body as measured from two points on the Earth’s orbit) of one second.  One lightyear is equal to 63,241 AU but one parsec is equal to 3.26 ly or 206,265 AU.  

Some interesting facts about light years

A lightyear can be further divided into light hours, light minutes, light seconds, and even light nanoseconds, for example, light from the Sun takes eight minutes to reach Earth, which also means that Sun is eight light minutes away from Earth. Here are some interesting facts related to lightyears:

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• Voyager 1, a space probe launched by NASA in 1977 transmitted a signal in November 2021 from a distance of 21.31 light hours (14.45 billion miles). This is the farthest distance any artificial object has traveled in space.
• The nearestknown galaxy to the Milky Way (our galaxy) is the Canis Major Dwarf Galaxy, which is 25,000 light years from the Sun. The Sagittarius Dwarf Elliptical Galaxy is the next closest  at 70,000 light years from the Sun.  The most distantly located known-galaxy from Earth is called GN-z11, it was detected by the Hubble telescope in 2016 and at that time it was believed to be 13.4 billion light years away from Earth, or 134 nonillion kilometers (that’s 134 followed by 30 zeros). 
• A radar system that uses radio waves to detect a flying aircraft measures time in nanoseconds to figure out how far a target is because radio waves travel at the speed of light. A nanosecond is equal to one billionth part of a second. L ight travels at 1 foot (30cm) per nanosecond.  
• NASA recently claimed that its Parker Solar probe has “touched the Sun”. It is also believed to be the fastest human-made object in space and is expected to reach speeds of 430,000 mph (690,000 kph) . That’s fast enough to get from Philadelphia to Washington, D.C., in under a second. 

Great American astronomer Edwin Hubble once said, “The search will continue, the urge is older than history, it is not satisfied and will not be suppressed”. Space exploration can also be considered a search for what lies beyond Earth and stars. As a unit of distance, the lightyear is also a reminder to us of just how vast the universe is, and how much humanity and science still have to learn.

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Rupendra Brahambhatt Rupendra Brahambhatt is an experienced writer, researcher, journalist, and filmmaker. With a B.Sc (Hons.) in Science and PGJMC in Mass Communications, he has been actively working with some of the most innovative brands, news agencies, digital magazines, documentary filmmakers, and nonprofits from different parts of the globe. As an author, he works with a vision to bring forward the right information and encourage a constructive mindset among the masses.

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The huge solar storm is keeping power grid and satellite operators on edge

Geoff Brumfiel

Willem Marx

NASA's Solar Dynamics Observatory captured this image of solar flares early Saturday afternoon. The National Oceanic and Atmospheric Administration says there have been measurable effects and impacts from the geomagnetic storm. Solar Dynamics Observatory hide caption

NASA's Solar Dynamics Observatory captured this image of solar flares early Saturday afternoon. The National Oceanic and Atmospheric Administration says there have been measurable effects and impacts from the geomagnetic storm.

Planet Earth is getting rocked by the biggest solar storm in decades – and the potential effects have those people in charge of power grids, communications systems and satellites on edge.

The National Oceanic and Atmospheric Administration says there have been measurable effects and impacts from the geomagnetic storm that has been visible as aurora across vast swathes of the Northern Hemisphere. So far though, NOAA has seen no reports of major damage.

The Picture Show

Photos: see the northern lights from rare, solar storm.

There has been some degradation and loss to communication systems that rely on high-frequency radio waves, NOAA told NPR, as well as some preliminary indications of irregularities in power systems.

"Simply put, the power grid operators have been busy since yesterday working to keep proper, regulated current flowing without disruption," said Shawn Dahl, service coordinator for the Boulder, Co.-based Space Weather Prediction Center at NOAA.

NOAA Issues First Severe Geomagnetic Storm Watch Since 2005

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"Satellite operators are also busy monitoring spacecraft health due to the S1-S2 storm taking place along with the severe-extreme geomagnetic storm that continues even now," Dahl added, saying some GPS systems have struggled to lock locations and offered incorrect positions.

NOAA's GOES-16 satellite captured a flare erupting occurred around 2 p.m. EDT on May 9, 2024.

As NOAA had warned late Friday, the Earth has been experiencing a G5, or "Extreme," geomagnetic storm . It's the first G5 storm to hit the planet since 2003, when a similar event temporarily knocked out power in part of Sweden and damaged electrical transformers in South Africa.

The NOAA center predicted that this current storm could induce auroras visible as far south as Northern California and Alabama.

Extreme (G5) geomagnetic conditions have been observed! pic.twitter.com/qLsC8GbWus — NOAA Space Weather Prediction Center (@NWSSWPC) May 10, 2024

Around the world on social media, posters put up photos of bright auroras visible in Russia , Scandinavia , the United Kingdom and continental Europe . Some reported seeing the aurora as far south as Mallorca, Spain .

The source of the solar storm is a cluster of sunspots on the sun's surface that is 17 times the diameter of the Earth. The spots are filled with tangled magnetic fields that can act as slingshots, throwing huge quantities of charged particles towards our planet. These events, known as coronal mass ejections, become more common during the peak of the Sun's 11-year solar cycle.

A powerful solar storm is bringing northern lights to unusual places

Usually, they miss the Earth, but this time, NOAA says several have headed directly toward our planet, and the agency predicted that several waves of flares will continue to slam into the Earth over the next few days.

While the storm has proven to be large, predicting the effects from such incidents can be difficult, Dahl said.

Shocking problems

The most disruptive solar storm ever recorded came in 1859. Known as the "Carrington Event," it generated shimmering auroras that were visible as far south as Mexico and Hawaii. It also fried telegraph systems throughout Europe and North America.

Stronger activity on the sun could bring more displays of the northern lights in 2024

While this geomagnetic storm will not be as strong, the world has grown more reliant on electronics and electrical systems. Depending on the orientation of the storm's magnetic field, it could induce unexpected electrical currents in long-distance power lines — those currents could cause safety systems to flip, triggering temporary power outages in some areas.

my cat just experienced the aurora borealis, one of the world's most radiant natural phenomena... and she doesn't care pic.twitter.com/Ee74FpWHFm — PJ (@kickthepj) May 10, 2024

The storm is also likely to disrupt the ionosphere, a section of Earth's atmosphere filled with charged particles. Some long-distance radio transmissions use the ionosphere to "bounce" signals around the globe, and those signals will likely be disrupted. The particles may also refract and otherwise scramble signals from the global positioning system, according to Rob Steenburgh, a space scientist with NOAA. Those effects can linger for a few days after the storm.

Like Dahl, Steenburgh said it's unclear just how bad the disruptions will be. While we are more dependent than ever on GPS, there are also more satellites in orbit. Moreover, the anomalies from the storm are constantly shifting through the ionosphere like ripples in a pool. "Outages, with any luck, should not be prolonged," Steenburgh said.

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The radiation from the storm could have other undesirable effects. At high altitudes, it could damage satellites, while at low altitudes, it's likely to increase atmospheric drag, causing some satellites to sink toward the Earth.

The changes to orbits wreak havoc, warns Tuija Pulkkinen, chair of the department of climate and space sciences at the University of Michigan. Since the last solar maximum, companies such as SpaceX have launched thousands of satellites into low Earth orbit. Those satellites will now see their orbits unexpectedly changed.

"There's a lot of companies that haven't seen these kind of space weather effects before," she says.

The International Space Station lies within Earth's magnetosphere, so its astronauts should be mostly protected, Steenburgh says.

In a statement, NASA said that astronauts would not take additional measures to protect themselves. "NASA completed a thorough analysis of recent space weather activity and determined it posed no risk to the crew aboard the International Space Station and no additional precautionary measures are needed," the agency said late Friday.

People visit St Mary's lighthouse in Whitley Bay to see the aurora borealis on Friday in Whitley Bay, England. Ian Forsyth/Getty Images hide caption

People visit St Mary's lighthouse in Whitley Bay to see the aurora borealis on Friday in Whitley Bay, England.

While this storm will undoubtedly keep satellite operators and utilities busy over the next few days, individuals don't really need to do much to get ready.

"As far as what the general public should be doing, hopefully they're not having to do anything," Dahl said. "Weather permitting, they may be visible again tonight." He advised that the largest problem could be a brief blackout, so keeping some flashlights and a radio handy might prove helpful.

I took these photos near Ranfurly in Central Otago, New Zealand. Anyone can use them please spread far and wide. :-) https://t.co/NUWpLiqY2S — Dr Andrew Dickson reform/ACC (@AndrewDickson13) May 10, 2024

And don't forget to go outside and look up, adds Steenburgh. This event's aurora is visible much further south than usual.

A faint aurora can be detected by a modern cell phone camera, he adds, so even if you can't see it with your eyes, try taking a photo of the sky.

The aurora "is really the gift from space weather," he says.

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When could you see the northern lights? Aurora forecast for over a dozen states this weekend

Read the latest on the northern lights this weekend: Saturday's forecast says parts of U.S. could see auroras .

A series of strong solar flares that the sun has been emitting since Wednesday morning could cause the northern lights to become visible this weekend to a wide swath of the United States.

The coronal mass ejections (CMEs) hurtling toward Earth prompted the National Oceanic and Atmospheric Administration to issue a rare  Severe (G4) Geomagnetic Storm Watch on Thursday for the first time in 19 years. The geomagnetic storms that the CMEs would produce pose a limited threat to our communications, but they can also trigger the aurora borealis, better known as the northern lights.

And because the sun is at the height of its 11-year-cycle, the auroras have a very good chance of being seen by more Americans than usual .

Here's what to know about the northern lights, and when and where you may catch a glimpse of them this weekend.

Good news on northern lights: Experts predict years of awesome aurora viewing

What are the northern lights?

The auroras are a natural light display in Earth's sky that are famously best seen in high-latitude regions.

The northern lights materialize when energized particles from the sun reach Earth's upper atmosphere at speeds of up to 45 million mph, according to Space.com . Earth's magnetic field redirects the particles toward the poles through a process that produces a stunning display of rays, spirals and flickers that has fascinated humans for millennia.

Geomagnetic storm: Solar storm is powerful enough to disrupt communications: Why NOAA says not to worry

When might the northern lights be most visible?

This week's solar activity brings with it the increased possibility of seeing the aurora across the U.S.

Though the timing is uncertain and the northern lights can be a particularly fickle forecast , officials at NOAA said the coronal mass ejections could reach Earth as early as Friday evening into Saturday, Shawn Dahl, a space weather forecaster at SWPC, told reporters Friday morning during a news briefing.

Experts from NOAA said auroras could be visible into Sunday.

The best aurora is usually within an hour or two of midnight (between 10:00 p.m. and 2:00 a.m. local time). These hours expand towards evening and morning as the level of geomagnetic activity increases, according to NOAA.

Where might the northern lights be best seen in the US?

The northern half of the U.S. is forecasted to be in the view path where the auroras may be most visible.

The best chances appear to be in northern Montana, Minnesota, Wisconsin and the majority of North Dakota, according to SWPC's  experimental Aurora viewline . The visibility for viewing will also depend on local weather conditions and city lights.

Experts at NOAA said the northern lights may even be visible as far south as Alabama and Northern California. If all else fails, experts even recommend taking a photo of the night sky with your cell phone – you never known what you may capture.

"Things that the human eye can't see, your phone can, so it'll be interesting to see just how far south we're getting aurora images this time," said Brent Gordon, Chief of Space Weather Services Branch for SWPC, on the Friday call with reporters.

The National Weather Service on Friday shared an aurora forecast for Friday night and early Saturday morning, showing more than a dozen states with at least a chance to see the lights.

How does the solar maximum influence the northern lights?

Explosive bursts of radiation known as solar flares and coronal mass ejections (eruptions of solar material) drive the geometric storms, releasing solar particles and electromagnetic radiation toward our planet.

As the frequency of coronal mass ejections increases at the height of its 11-year cycle,  which NASA said is expected to be in 2025 , electromagnetic activity on the sun peaks. What that so-called "solar maximum" means for us is that the risk increases for disruption to satellite signals, radio communications, internet and electrical power grids.

'God's Hand' revealed in cosmos: Telescope images reveal 'cloudy, ominous structure' known as 'God's Hand' in Milky Way

Last December , a powerful burst of energy created the largest solar flare that NASA had detected since 2017.

The last G4 level solar storm hit Earth in March , one of only three storms of that severity observed since 2019, according to NOAA's Space Weather Prediction Center .

Just like in March, the upcoming solar storm will have particles flowing from the sun that get caught up in Earth's magnetic field, causing colorful auroras to form as they interact with molecules of atmospheric gases. The resulting glowing green and reddish colors of the aurora may be quite a sight to see.

Contributing: Doyle Rice, USA TODAY

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]

A mysterious object has been spotted that's 10 million times as bright as the sun. Scientists can't work out why it hasn't exploded.

• Ultraluminous X-ray sources are objects that shine 10 million times as bright as the sun. 
• Scientists have said they are too bright to exist, as they break the Eddington limit.
• A new study confirmed the brightness of a ULX — leaving the mystery of how it exists unsolved. 

Scientists have been left baffled by a mysterious celestial object so bright that physics dictates it should have exploded. 

NASA has been tracking so-called ultraluminous X-ray sources , objects that can be 10 million times as bright as the sun, to understand how they work. 

These objects are impossible in theory because they break the Eddington limit, a rule of astrophysics that dictates an object can be only so bright before it breaks apart. 

A new study categorically confirms that M82 X-2, a ULX 12 million light-years away, is as bright as previous observation suggested.

But the question remains: How can it exist? 

Objects that luminous should push matter away

The principle behind Arthur Eddington's rule is simple. Brightness on this scale comes only from material — like stardust of remnants of disintegrating planets — that falls inward toward a massive object , such as a black hole or a dead star. 

As it's pulled by the object's intense gravity, the material heats up and radiates light. The more matter that falls toward the object, the brighter it is. But there's a catch.

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At a certain point, so much matter is being pulled in that the radiation it's emitting should be able to overwhelm the power of the gravity from the massive object. That means at some point, the radiation from the matter should push it away, and it should stop falling in.

But if it's not falling in, the matter shouldn't be radiating, which means the object shouldn't be that bright. Hence the Eddington limit.

M82 X-2 is achieving the impossible

Because of the Eddington limit, scientists have questioned whether the ULX's brightness was indeed caused by enormous amounts of material falling into it.

One theory, for instance, is that strong cosmic winds concentrated all the material into a cone. In this theory, the cone would be pointed toward Earth, which would create a beam of light that would look much brighter to us than if the material was scattered evenly around the ULX. 

But a new study looking at M82 X-2, a ULX caused by a pulsating neutron star in the Messier 82 galaxy, put the cone theory to rest. 

(A neutron star is a superdense object left behind when a star has run out of energy and dies.)

The analysis, published in The Astrophysical Journal in April, found that M82 X-2 pulled in about 9 billion trillion tons of material per year from a neighboring star, or about 1.5 times the mass of Earth, a NASA statement said. 

That means the brightness of this ULX is caused by limit-breaking amounts of material.

Superstrong magnetic fields may squish atoms into submission

Given this information, another explanation has become the leading theory to explain ULXs. And it's even more bizarre.

In this theory, superstrong magnetic fields shoot out of the neutron star. These would be so strong that they would squish the atoms of the matter falling into the star, turning the shape of these atoms from a sphere into an elongated string, NASA's statement said.

In this case, the radiation coming from these squished atoms would have a harder time pushing the matter away, explaining why so much matter could fall into the star without breaking apart. 

The problem is that we'll never be able to test this theory on Earth. These theoretical magnetic fields would have to be so strong that no magnet on Earth could reproduce them.

"This is the beauty of astronomy. Observing the sky, we expand our ability to investigate how the universe works. On the other hand, we cannot really set up experiments to get quick answers," Matteo Bachetti, an author on the study and astrophysicist with Italy's National Institute for Astrophysics' Cagliari Observatory, said in NASA's statement.

"We have to wait for the universe to show us its secrets," he said. 

Watch: Why the sun has two giant holes, and what that means for Earth

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Can MLB save the starting pitcher? The search for solutions to baseball’s ‘existential crisis’

Who’s pitching tonight?

For 100 years, that wasn’t just a casual question. It was the question that defined baseball.

The answer always had a chance to give you goosebumps. Maybe it was Tom Seaver versus Steve Carlton. Maybe it was Sandy Koufax versus Bob Gibson. Maybe it was Pedro Martinez versus Randy Johnson.

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They weren’t just a reason to watch. They were the reason to watch. They threw the first pitch of the game. They often stuck around to throw the last pitch of the game. When the stars hold the ball in their hands 100 times a game, from the first minute of a game to the last, that’s where so much of the magic comes from. But now, those nights of pitchers’ duel magic are slipping away.

Ten active major-league starting pitchers have won a Cy Young Award — and nine of them have spent time on the injured list in 2024. The only exception: Baltimore’s Corbin Burnes. But no need to remind you of all the aces who aren’t healthy enough to ace. There are larger forces at work here that are just as big a concern for the people who chart the future of this sport.

The issue is not only the health of the modern starting pitcher , but the role those starters play in the sport these days. Those two things are also connected. Here’s only one recent example:

May 6, Wrigley Field. San Diego Padres versus Chicago Cubs . Theoretically, this was one of those pitching matchups to savor: Yu Darvish , onetime Cubs ace, starting for the Padres versus Justin Steele , a 2023 All-Star and the Cubs’ 2024 Opening Day starter. But was it the stuff of goosebumps? No. The score at the end of five innings was 0-0. Both starting pitchers had allowed only three hits apiece … and, naturally, neither of them was still in the game. Seven relievers ate up the last 25 outs. Just another slice of baseball life in 2024.

True, both starters had spent time on the injured list this season, so they were being handled carefully. But those injuries — and how teams respond to them — are part of a crisis that seems to loom larger over baseball every year.

Should Major League Baseball sit back and let starting pitchers practically disappear? Should it let them recede in prominence, giving  away the essential entertainment value they’ve provided for the last century? Or should it act? Should the league step in to halt this trend the way it stepped in only one year ago, when it introduced a pitch clock before the sport arrived at a place where every game dragged toward a midnight finish?

“I think everybody agrees,” says Texas Rangers ace Max Scherzer , a three-time Cy Young winner currently working his way back from (what else?) another injury. “You’ve got to get the starting pitcher back. From an entertainment standpoint, people watch the matchups. That’s a big part of baseball. If you don’t have that matchup, every day is the same.”

Once every day becomes the same, is that when your sport is officially in trouble? Maybe that feels like a question for another day, another season. Except that in reporting this story, The Athletic talked with three longtime baseball executives who used the term “existential crisis” to describe the state of starting pitching.

When one of those executives was asked, as a follow-up question, if he honestly believed that term reflected the depth of this problem, he replied, pointedly: “I do. I think the game is totally broken from that standpoint.”

What could baseball do?

Let’s draw a football analogy. Suppose the analytics gurus in the NFL suddenly decided the best way to win a game was Quarterback by Committee … so every team rolled out four quarterbacks and Patrick Mahomes might never throw a pass in the fourth quarter of any game. How fast do you think that league would change its rules?

“It would outlaw that in about six minutes,” said one of the baseball executives interviewed for this story. All of them were granted anonymity so they could speak candidly about an issue viewed as especially sensitive in their sport.

But in baseball, the league has largely stayed out of the way as teams’ analytics departments took the sport down a similar road: Overload the roster with eight relief pitchers who can throw a baseball 98 miles per hour. Then stop waiting around for the starting pitcher to get tired. Get him out of the game and cue the parade of fireballers out of the bullpen.

The data may show that approach is the most efficient way to get outs. But the best baseball strategy isn’t always the best entertainment strategy. Inside most front offices, that’s not a major concern. But in reporting this story, The Athletic did find a few executives willing to ask why more of their front-office peers weren’t more worried about this trend.

“For the industry, it doesn’t have to be that way,” said one of them. “Can we take a step back and look at our sport from 20,000 feet?”

The league proved, with its rule changes a year ago, that it can act when it sees a crisis approaching. But has the starting pitcher crisis risen to that level? MLB officials declined to comment for this story. However, industry sources tell The Athletic that while the league views  this issue as a priority, it is still gathering information, via an extensive study of pitching injuries . So it is likely years away from taking action. And even then, some of those changes would need to be phased in over several years, because the repercussions would trickle down all the way to youth baseball, where the health of young arms is also a growing concern.

In the meantime, however, the brainstorming has already  begun. What rule changes could the league consider to help keep pitchers healthier and restore the prominence of the starter? The Athletic has spent the past few months collecting ideas proposed by executives, players and coaching staffs.

They all would address this issue. But they also were all met by so much fierce debate that it illustrated the challenge the league would face to get everyone on board with any of them.

“I think that’s why it’s hard,” said one American League exec. “There are no easy answers. If it were just one thing that we could easily turn a dial … there wouldn’t be a lot of really smart people at the club and league level trying to work on this. But it’s very complicated.”

Here are four potential rule changes you could see someday.

New rule idea: Every starter has to go six innings

Last year, the length of the average major-league start plunged to an all-time low: 15 outs (or five innings) per start. Not even starting pitchers themselves think that’s anything to brag about. So here’s a goal some in the sport would love to shoot for:

How about the starter goes six (or more) in almost every game — barring extenuating circumstances? Is that doable? Why not? That used to happen, you know, and not 100 years ago.

Even 10 years ago, as you can see in the graph above, the percentage of starters who made it through six innings wasn’t that dramatically different from what we saw  in the 1970s, a pitching era so golden that it produced 10 Hall of Fame starting pitchers. It’s only in the last five or six seasons that it began to change so significantly. So would it be outrageous to require that every starter get back to that six-inning standard — barring injuries, 10-run blowups, inflated pitch counts or other exceptions that could be negotiated later?

Why “require” it? Ultimately, the league might not push in this direction. But here’s why it might: The best rule changes are the simplest. So instead of a more subtle rule that the league might hope would lead to longer starts, it would take its best, simplest shot and just say: This is now the rule.

What would the penalty be? What would happen if a manager hooked their starter before six — and that starter didn’t meet any of those extenuating  circumstances? Good question. The league could say that pitcher had to be placed on the injured list. It could also impose discipline, via fines or suspensions.

Or what about a case like that Yu Darvish-Justin Steele game, in which both starters were being handled more cautiously as they built back from a previous injury? Sorry. The league probably would say that pitcher should still be on the IL working his way back on a minor-league rehab option.

Who would complain? Relief pitchers, obviously, would grumble about almost all of these ideas because this would dramatically change their job description — even if that’s the whole point. But almost every analytically inclined front office would complain just as loudly.

Why, they’d ask, should their teams be forced to push their fifth starter through the sixth inning when they have five unhittable relievers who could rescue him? And how can anyone be sure, they’d wonder, that even those fifth starters would be on board with this?

“It’s really hard to force pitchers to start and go (six innings),” said one exec, “because in my opinion, you’re going to get into all sorts of situations where you ask: Is someone faking an injury? How do they feel? Even if they’re not hurt, they might think: ‘They forced me to stay out there when I wasn’t effective and then I got hurt.’”

So it’s possible, even likely, that a rule requiring six-inning starts would be so harsh, it would gain very little support. If that’s the case, the league could pivot to rules that simply incentivize teams to push their starters deeper into a game. There are several options. Here’s one we’ve written about before.

New rule idea: The “Double Hook”

Unlike most of these ideas, the Double Hook already exists. The independent Atlantic League, a longtime testing ground for MLB rule changes, first experimented with this rule in 2018. Back then, here’s how it worked: When your starting pitcher leaves the game, your designated hitter also has to leave the game (or, at least, go play a position).

But after teams complained, the Atlantic League began tinkering. So by 2023, it used this version: If your starting pitcher leaves the game before the end of the fifth inning , only then does your DH have to leave with him.

What was wrong with the original rule? Would any team really prefer a rule that would keep its best hitter from ever coming to the plate late in a game? Think about all those dramatic walk-off October home runs David Ortiz once hit as the Red Sox DH. It will answer that question.

Why might the Double Hook actually work? You would be surprised by how many people in baseball like this rule. If the idea is to incentivize (but not require) keeping a starting pitcher in the game, what works better than this? Leave your pitcher out there or bench one of your most dangerous hitters? The concept is brilliantly simple.

Who likes it? Some of the most prominent starting pitchers in baseball — Scherzer, Justin Verlander and Adam Wainwright, among others — have been the Double Hook’ s biggest public fans . But more front-office minds also seem open to this concept than many others they’ve heard.

“I have been in favor of the Double Hook for a while,” a National League executive said. “I think it would be interesting to have. It adds an extra element of strategy into the game for managers to think about, gives them another decision they have to make in-game, which I don’t think is a bad thing in general.”

Who hates it? The Designated Hitters of North America aren’t sold, for one thing. And one AL executive spoke for his fellow front-office critics when he called it “one of the worst ideas I’ve ever heard.”

“We want close games, right?” that exec said. “We don’t want blowouts. And if you’ve got the Double Hook, you’re going to have a boatload of blowouts. (If you lose your DH) you’re playing a man short, basically, like a soccer team with a player on a red card. Or you attempt to not play a man short, and the game gets out of hand because you’re trying to leave the starter in there for that extra hitter. Then that turns into three or four or five runs, and now you’re done.”

So is there an alternative to the alternative? At this point, everything is on the table. Scherzer, for one, sees no limit to possible incentives you could dangle to keep starters in the game.

“You could sit there and say: You get a free substitution,” Scherzer said. “You could pinch run for a catcher. You could make an instantaneous defensive replacement for an inning, you know what I mean? Keep upping the ante, if the starter goes out and does his job, how much extra stuff would you get as a benefit? So the idea would be if you pull your starter, you’re going to lose a ball game because you pulled your starter early.”

New rule idea: No more than 11 pitchers on the roster

Roster limits are another idea that has been tossed out there publicly, even by commissioner Rob Manfred . Two decades ago, teams got along fine with five- or six-man bullpens. So if those in-game rule changes don’t catch on, roster limits might move to the front of MLB’s line.

How would roster limits help starters? With eight relievers hanging out in your bullpen, what would stop a team from using four, five or even six a night? But if the league gradually drops the maximum number of relievers to seven, then six, then possibly even five, the value of a six-inning start — or longer — would skyrocket.

Why do front offices hate this? Many front offices think forcing fewer pitchers to bear the burden of so many innings is a recipe for even more injuries. And this furious debate sums up why there is so much disagreement over how to address this entire pitching crisis.

“There are people on one side of this,” one skeptical executive said, “who want to have less pitchers, make them pitch more … and I just don’t understand how that’s going to work. To me, rested pitchers are probably healthier pitchers. So our positions are totally misaligned with each other. And I’m not sure how to resolve this because we’re not seeing eye to eye at all.”

So why might it still make sense? The small group on the other side sees this so differently. Too many teams, one of those executives said, are ignoring the ripple effects of regularly pulling starters for a fresh reliever at the first opportunity, then mixing and matching relievers every time the data says so.

“You’re not just playing one game,” that exec said. “And you’re not just playing one inning. There are consequences. And the consequences are that you’re going to fry your bullpen by mid-summer, let alone September and October.”

New rule idea: Outlaw the sweeper 

Why are so many aces getting hurt? It’s a complicated problem, but let’s think it through.

If you’re a dominating starting pitcher in this era, it probably means you throw harder than the average pitcher. You create more spin and movement than the average pitcher. And you probably have some dominant pitch — or more than one — that most other pitchers can’t throw, or you just added one.

Now draw up the factors most injury experts point to as most likely to cause catastrophic arm injuries: Velocity … check. Spin … check. Throwing pitches that cause the most stress on the human arm … check.

So would MLB be out of line to make it illegal to throw one of those pitches it viewed as hazardous to pitchers’ health? Could it possibly act to ban a pitch like the sweeper, which has been identified as a source of undue stress on the elbow? That may sound radical, but what if MLB’s study of pitcher health recommends the league wipe out dangerous pitches the way it banned home-plate collisions a few years back?

Why a sweeper ban isn’t as extreme as it sounds: One executive said he wouldn’t be shocked if the league actually did ban a pitch or two someday.

“What if they came to the conclusion, empirically, that the sweeper is a dangerous pitch, and it’s leading to a lot of pitching injuries?” he mused. “To me, it’s not crazy that (MLB) would consider outlawing it, because there’s lots of dangerous behavior that is not allowed on the field because it leads to injuries.”

Could the league even target high velocity? If the league is so concerned with pitches it views as dangerous, could it even look to tone down velocity itself? If it can’t agree on other changes that would force pitchers to take their foot off the gas in order to go deeper into games, one idea that has made the rounds is this shocker: Make it illegal to throw any pitch over 94 mph.

Don’t bet on that one happening. But a subtle element of many of these ideas is to motivate pitchers to pitch at less than max velocity. And that’s a volatile topic unto itself.

We mentioned to one pitcher we spoke with that rule changes are being discussed that would incentivize, or even require, pitchers not to throw every pitch at max velocity. He was borderline livid at that whole idea.

“That would be like telling an NFL running back not to run as fast as he can on every run,” he said. “That’s ignoring the competitive side of it.”

He’ll be heartened to know that many baseball executives agree.

“I don’t know what incentive structure we can create,” said one of those execs, “that’s going to actually convince athletes to not try and throw as hard as they can. Because they know with certainty that they will be better pitchers, even for a short amount of time, if they do throw hard.”

He’s not wrong. But is it time for MLB to step in anyway? Is it time for Manfred to tell all those pitchers: We feel your pain — literally. But we can’t let you do it that way anymore because this injury rate is just not sustainable ?

In a sport that has always been slow to change, it’s easy to find people who would tell the commissioner: Please stay out of this. But remember that term, “existential crisis”? One executive who used those words says it’s time to heed them. This latest rash of pitching injuries represents more than just bad luck, he said.  It’s a warning siren begging everyone to act.

“What if it gets worse?” that exec wondered. “It’s easy to say everything’s fine, and it’s all fun and games, until you look up and the product is truly horrible because no one has enough pitching. So it’s going to take someone to say, ‘All right, listen, guys. We can keep lying to ourselves, but this sport is broken. And we have to change it.'”

Additional reading

• People in the industry came up with solutions for baseball’s starting pitching “existential crisis.” Some of them are extreme.
• Justin Verlander and Max Scherzer, two of the sport’s most prominent pitchers, weigh in on the crisis.

 (Top image: Eamonn Dalton / The Athletic ; Photos: J. Conrad Williams, Jr./Newsday RM via Getty Images; Matthew Grimes Jr. / Atlanta Braves via Getty Images)

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