what is a light year?

Question

if an alien waved at us from jupiter, would we see it in another thousand years?? OK yes I know there are no aliens on jupiter or there might be, but that's not the point. Because we are some light years away from different planets, would be able to see whatever happens on jupiter now, in another few thousand years?? because that's what my physics teacher has taught me yesterday...

I just don't understand what a light year is. yes it is the distance light travels at in one year but It just doesn't make sense.... ??

Answer 1

Earths distance from Jupiter varies depending on where each planet is in its orbit of the sun. At the farthest it is 576,682,810 miles from Earth, closest: 390,682,810 miles . Light travels at 186,282 miles per second. So the shortest amount of time it would take us to see an alien waving at us from Jupiter would be between 25 and 52 minutes depending on where there are. I dont know what your physics teacher was thinking.

Answer 2

We are NOT light Years away from planets in this solar system.



A Light Year is the Distance Light will travel in ONE YEAR.



Light takes 8 Minutes 19 Seconds to get from the Sun to the Earth and About 7 Hours to get to Pluto.



1 light year = 5.87849981 × 10^12 miles (5.8 Times 10 to the 12 power) or just move the point 12 places to the right....

Answer 3

A light year is a measure of distance, or the distance a particle of light will travel through a pure vacuum in one Earth year.



This distance is approximately 5.8785 x 1012 [5.87 trillion] miles, or 9.4605 x 1012 [9.46 trillion] kilometers.



In a vacuum, light travels at more than 186,000 miles every second so in a minute it will travel 60 times this amount (as there are 60 seconds in a minute). In 1 hour (60 mins) it will travel 60 times this amount. In 1 day (24 hrs) it will travel 24 times this amount. In 1 year (365 days) it will travel 365 times this amount. This amount is equivalent to almost six million, million miles.



The nearest star (Proxima Centauri) is 4 1/4 light years away or approx. 25 million, million miles. The galaxy is 100,000 light years across The known universe is over 13 billion light years across. If a star is 10,000 light years away, we are seeing it today as it was 10,000 years ago - as the light that started out then is only just reaching us now. Similarly, if there were aliens looking at us through a powerful telescope on a planet 4 light years away, then they would just today be seeing what happened here 4 years ago.



The measurement of a light year is useful in finding distances to very distant objects, and as we're assuming that there is a pure vacuum between here and there, we can then determine how long ago, in Earth years, that light originated from its source. It is entirely possible that some of the stars we see from Earth are simply no longer there!

Answer 4

A light year is a unit of distance. It's the distance light travels in a year or 9460730472580800 meters. So, now what's easier a light year or an huge number of meters (nearly 10 trillion)?



If your alien waved from Jupiter, it would take from 35-52 minutes to see it.

Answer 5

We use it as a measurement as nothing can travel faster, and the universe is so damn big it wouldn't make sense to try and measure distances in miles etc. as the number would be too big to be meaningful. It takes about 8 minutes for light to reach us from the sun, Jupiter is about 5 times further so say about 40 minutes.



So you are way out with 1000 LY away and maybe misunderstood your physics teacher. The nearest star to our solar system is 4 light years, to give you an idea.

Answer 6

If someone like SassyBabe shows that they have little knowledge of space or distances, why do you all start providing huge decimal numbers and powers of numbers.



Try writing for your audience. I would bet she has no idea what 10^12 is.



SassyBabe, a light year is about 6 trillion miles or 10 trillion kilometres.



The planets are "only" hundreds of millions to a few thousand million miles. So, distances using speed of light in our planetary system come out as light-minutes (Mars at its nearest) to light-hours for Neptune and Pluto.



In contrast, the nearest star is just over 4 light-YEARS, the farthest individual stars we can see with our eyes are a couple thousand light-years.



The farthest stars in our galaxy (Milky Way) are about 100,000 light years on the other side of the galaxy.



Other galaxies range from millions to billions of light years away.



So, you see, the planets are almost on our doorstep. Even so, our fastest probes take months to many years to reach them.



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Just one more. The moon is about 1.5 light-SECONDS.



That means if you could shine a bright light at the moon, bright enough to reflect off it and back to Earth, you would see the light about 3 seconds after you turned it on.

Answer 7

a light year is the distance light travels in a year (in a vacuum): about

9.5 × 10^12 km.

Jupiter is only about 30 light minutes away.

in fact, no planet in our solar system is so far as a light year.

the nearest star (other than the Sun) is Proxima Centauri, about 4.2 light years away.

Answer 8

A light year is a unit of length, just as is an inch, a mile or a meter. But it is a very large unit. It is the distance that light would travel in one year.



► When you see something, the light from that object travels from it to your eyes. It takes a certain amount of time to make the trip.

~ If the object is in your back yard then light would make the trip in far less than a second; so short a period of time that you may consider it instantaneous.

~ Jupiter is so far away that it takes light about 45 minutes to travel all the way to Earth and reach your eyes. As you look at Jupiter in the night sky, you would see what it looked like 45 minutes ago when the light first left it.

~ If you are looking at a galaxy that is 1000 light years away (with a telescope) then the light from that galaxy would have been traveling to Earth for 1000 years to reach your eyes. You would see that galaxy as it was when the light left there 1000 years ago.

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Light travels at exactly 299,792,458 meters per second (about 186,282.397 miles per second), so:

1 light year equals about 9,460,730,472,600 kilometers.

1 light year equals about 5,878,625,373,200 miles.

(The speed of light is exact but an Earth year varies.)

~ The International Committee for Weights and Measures has set the "official" SI (International System of Units) length for the light year to exactly 9,460,730,472,580.8 kilometers.



For comparison:

~ Earth is 0.000015812 light years from the sun.

~ One of the fastest objects people have ever sent into space, the Voyager I space probe, is presently leaving the solar system at 17.1 kilometers per second. At that speed it would take 17,532 years to travel one light year of distance.

~ The closest star to our sun is Proxima Centauri at 4.2 light years away.

~ Our galaxy, the Milky Way, is around 100,000 light years in diameter.

(As Jupiter and Earth move in their orbits, they are sometimes closer and sometimes farther apart. At their closest, light takes 36 minutes to make the trip; at their farthest, a little over 52 minutes.)

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How can the speed of light be measured exactly?

In 1983, the meter was redefined in the International System of Units as the distance traveled by light in 1⁄299,792,458 of a second. As a result, the numerical value of the speed of light in meters per second is now fixed exactly by the definition of the meter.

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Answer 9

the speed of light is faster than anything no 1 has ever known sey it take you 1 year to travel from earth to mars when you reach millions of years denmark the fastest way to put it light years 1 light year is 9.999.999 millions of years in 1 if you could see at the speed of light that mean everything goes on now get it that's the best I could do

Answer 10

A light year is the distance that light travels in one year's worth of time.

Answer 11

1 light year = 9460528400000 Kilometers

Answer 12

A lIght year is how many years it takes for light to reach us.

Answer 13

one light year is 100 years and there r no aliens duh