If a person left earth when they were 20 years old, how old whould they be if they travles 20 light years to a planet and 20 light years back to earth? How old would people have to be able to become?
2007-04-25 11:24:01 · 15 answers · asked by Eryn v 3 in Science & Mathematics ➔ Astronomy & Space
at 30 000 km/h or what ever speed a space shutle travles at.
2007-04-25 11:31:41 · update #1
It's got nothing to do with how far you travel. It's to do with how fast you go.
Lets say that you stayed on Earth and this other person went away for 40 years.
If they travelled at half the speed of light then they would only age by 34.6 years compared to the 40 years that you would age.
If they travelled at 3/4 of the speed of light then they'd age by 26.5 years and you by 40 years.
At 99% the speed of light they'd age by 5.6 years.
This is because as you approach the speed of light time itself begins to slow down bya factor γ given by:
γ = sqrt [ 1 - v^2 / c^2]
where v is the speed at which you travel relative to somebody else and c = speed of light.
You may want to look up 'the twin paradox'.
2007-04-25 11:34:52 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Light years are a measure of *distance*, not of time. (A light-year is the distance light will travel in a year, about 5,878,499,814,210 miles!).
So, in Earth terms, the question you ask is about the same as "If a person went on a 40-mile round trip, how old would they be when they got back?"
The correct answer to both questions depends on *how long it took to make the trips*. And that depends on how fast they were going. On the Earth trip, if they travelled at 40 miles per hour, they would be one hour older when they got back; at 20 miles per hour, they'd be two hours older.
In space, if they travelled at the speed of light, each light-year would take an Earth year to travel, so they'd be 40 years older. But if they travelled slower than light, it would take longer. You'd have to know how much slower before you could get the exact answer.
Hope this helps.
2007-04-25 11:34:07 · answer #2 · answered by Brian E 3 · 0⤊ 1⤋
The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide. But the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang. "All the distance covered by the light in the early universe gets increased by the expansion of the universe, "Think of it like compound interest." Need a visual? Imagine the universe just a million years after it was born. A batch of light travels for a year, covering one light-year. "At that time, the universe was about 1,000 times smaller than it is today, "Thus, that one light-year has now stretched to become 1,000 light-years." All the pieces add up to 78 billion-light-years. The light has not traveled that far, but "the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away,".That would be the radius of the universe, and twice that -- 156 billion light-years -- is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger.
2016-05-18 22:20:21 · answer #3 · answered by ? 3 · 0⤊ 0⤋
Depends on how fast you were going. Since, as of now, NOTHING can exceed the speed of light, it would have to take at least 40 years, but probably a lot more, considering our bodies can't take speeds anywhere near that high.
2007-04-25 11:29:28 · answer #4 · answered by Anonymous 3 · 0⤊ 0⤋
If they were able to travel at the speed of light exactly and not exceed it then they would take 20 years to get to the planet and 20 years to get back.
That would make them at least 65 years old when they got home because no one would travel 20 years and not stay for at least 5 years.
2007-04-25 11:35:29 · answer #5 · answered by Bryan H 3 · 0⤊ 2⤋
Time is only relevant on the planet earth. Because on every other planet times moves at different speeds.
2007-04-25 11:34:26 · answer #6 · answered by ? 2 · 0⤊ 1⤋
This depends on speed. The closer to the speed of light you get, the slower time seems to go for you.
2007-04-25 11:31:23 · answer #7 · answered by quantumclaustrophobe 7 · 0⤊ 0⤋
It depends on how fast they were travelling, both because that would determine how long it would take to travel the 20 light years and because it would determine how extreme the effects of time dilation would be.
2007-04-25 11:28:26 · answer #8 · answered by Amy F 5 · 2⤊ 1⤋
If you left today in the shuttle to go to this new planet at 20 years old and came back immediately when you got there, you would be (approximately) 1.6 million years old when you got back to Earth.
2007-04-25 11:28:35 · answer #9 · answered by Spilamilah 4 · 1⤊ 2⤋
They would be 60 yrs old. However, technically, there is no time in space. If you went to the moon, there would be no night and day, because the moon doesnt have day and nigh like earth. So really you would never even age at all.
2007-04-25 11:29:44 · answer #10 · answered by Anonymous · 0⤊ 2⤋