If someone is traveling the speed of light to our closest star how long would it take?
Would the time it took them on the space ship be different from the time back here in earth? Why is that?
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answers:
Athena say: About four years earth time.
Shorter on the ship though due to time compression.
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roberto say: 4,2 years
alpha mominlawry,she rents property there
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nineteenthly say: Four and a bit years. Yes it would be, although travelling at the speed of light is impossible. Because the speed of light is the same for all observers, time travels more slowly the faster you go because you're starting to catch up with the speed of light.
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Jeffrey K say: You can't go at the speed of light. If you were going very close to the speed of light, people on earth would say it took you 4.3 years to get to Alpha Centori. But only a few day or hours would pass for you. The closer to light speed, the less time that passes for you.
Special relativity shows that time passes slower for moving objects. It gives a precise mathematical formula for this time dilation.
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Ronald 7 say: 8 Minutes to the Sun, but why ?
Nobody is quite sure
Up to Light Speed there is some time dilation
But we have yet to get there
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Clive say: 8 minutes. If you meant the nearest star other than the Sun, 4.2 years. That's assuming they're going at the speed of light already and don't slow down at all before getting there.
If they were actually travelling at the speed of light, time for them would stop and it would appear to take no time at all. However, at the speed of light, the mass of the spaceship would be infinite, so this is impossible as there is no way there could be enough fuel in the entire universe to get it going that fast. (Light can only go at the speed of light because it has no mass.) Maybe it could have enough fuel to go at a good fraction of the speed of light, and then it would appear on the spaceship to take less time than it looks to us left behind. The amount time slows down is given by the Lorentz transformations - look these up in a textbook on special relativity.
It's just how the mathematics works out if you really look at it properly, as Einstein did, and published in 1905 in a scientific paper called "On the Electrodynamics of Moving Bodies". The title is probably enough to cure you of any desire to read the thing, but he did work all this out - that you can't just keep adding speed without it doing something to mass and time, and the speed of light really is the cosmic speed limit. You won't notice anything happening unless you go at a significant fraction of the speed of light, which is probably why nobody noticed or thought about it before. But all actual observations since, where this should make a difference, have proved that Einstein got it right.
The universe just IS this way. If light has a definite speed, everything else follows from that.
To go any further, I have to say this is university-level stuff. I did it in the first year and we had a whole lecture course on special relativity to fully explore the maths and such things as inertial and relative frames of reference. (With lectures that usually started something like "Kirk and Spock are travelling towards each other at a relativistic velocity..."! I can safely say that the lecturer knew his audience.)
Just for more Star Trek-related fun, our high-speed astronaut would also need time to accelerate to the speed of light (ignoring the fact that he or she couldn't because of the increase in mass). That would take years and that's going to affect how long it takes. If he or she accelerated to light speed all at once, they'd be instantly mashed to a pulp against the back of the cabin. Maybe they'd never get to light-speed at all unless the trip is to a much further star. That's why I said at the start "assuming they're at the speed of light already".
It's bad enough as it is for astronauts going to and from the ISS, which is why they have to train in centrifuges to learn to cope with the effects of high acceleration and deceleration, like learning how to breathe when it feels like an elephant is sitting on your chest. Star Trek deals with this by saying that starships have inertial dampers that prevent this, and the only answer Gene Roddenberry ever gave to "how do inertial dampers work?" was "very well, thank you!"
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tham153 say: speed of light to the closest star is 8 minutes 19 seconds on average, the closest star being the sun
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John P say: A little over 4 years, unless you count the Sun as the "nearest star" - which indeed is correct - and in that case 8.3 minutes if travelling in a direct line.
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billrussell42 say: travel at the speed of light is impossible.
closest star is about 4 LY away, guessing that you exclude our sun, which is actually the closest star.
If it were 99% of the speed of light: at that speed, the dilation factor is 7, and an outside observer would see 4 years. Someone in the spaceship would see 4/7 of a year
If it were 99.9% of the speed of light: at that speed, the dilation factor is 22, and an outside observer would see 4 years. Someone in the spaceship would see 4/22 of a year, 2 months
If it were 99.99% of the speed of light: at that speed, the dilation factor is 70, and an outside observer would see 4 years. Someone in the spaceship would see 4/70 of a year, 21 days
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Eddie say: 8 minutes from the observer's point of view to the nearest star.
Pretty much instantaneous from the view of the passenger due to time dilation.
Update: It is also important to note that scientists have slowed the speed of light down to 38mph. This was with lasers and extremely cold sodium atoms. Therefore, another answer would be 3,873,333 days or 10,611 years to reach the sun at 38mph.
But, that's just a bit of fun, and doesnt take into effect gravity etc.
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Bill say: If you want to do the math, the formula is: Distance = Speed x Time.
Since the distance is fixed, as in the 4.3 light years referenced, you'd have speed and time to work with. As the speed increased time has to decrease. Note that in the calculation that the speed cannot ever reach the speed of light as then time would be zero, and anything multiplied by zero equals zero.
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drake say: About 4.3 years to us here on earth. Instantly to the observer at the speed of light. As things approach light speed, the passage of time slows down or time dilates. At the speed of light, things can reach any other distance instantly. Nothing can go the speed of light, (including light), because there is no such thing as truly empty space. Light collides with other things, slowing it down, and refracting it.
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poldi2 say: It would take 4.22 years, since the closest star is 4.22 light years away.
That is the time it would take measured from Earth, but time on the ship would be much shorter due to time dilation effects.
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say: darpa has perfected the warp engine .
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Zardoz say: 500 seconds in our time. Instantly in their time.
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Dixon say: You can not understand time and space dilation by just getting the answers. It doesn't follow your intuitive understanding of how they operate at normal speeds. If you really want to get some degree of understanding rather than just be quote stuff, you have to put in the time and learn it. The mathematics can be reduced to pretty much Pythagoras theorem if you look for material aimed at the general public and which explains the theory, rather than an overview.
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