## travel at Light speed

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yorkieron

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Message 434371 - Posted: 11 Oct 2006, 1:27:23 UTC

I am not a scientist but i like to ask questions
if we could travel at light speed how long would it take a manned flight to reach it taking into account mans limited resistance to g force
ID: 434371 ·
Solomon

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Message 434396 - Posted: 11 Oct 2006, 3:14:18 UTC - in response to Message 434371.

I am not a scientist but i like to ask questions
if we could travel at light speed how long would it take a manned flight to reach it taking into account mans limited resistance to g force

Even if we accelerated for an infinite length of time, we would never reach the speed of light.
ID: 434396 ·
Andy Lee Robinson

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Message 434464 - Posted: 11 Oct 2006, 7:58:21 UTC - in response to Message 434396.

I am not a scientist but i like to ask questions
if we could travel at light speed how long would it take a manned flight to reach it taking into account mans limited resistance to g force

Even if we accelerated for an infinite length of time, we would never reach the speed of light.

You know that non-scientists don't like these kind of answers!

Observed from the spaceship, accelerating at 1g would reach 0.77c after 1 year.
Observed from Earth, it would take 1.19 years, and would have travelled 0.56 light years.

After two years on the ship at 1g, you would reach 0.97c, however 3.75 years would have elapsed on Earth and you would have covered 2.90 light years. Viewed from the Earth, your mass would have increased 4x, and you would be a quarter of your size!

After five years on the ship, you would reach 0.99993c. 83.7 years would have elapsed on Earth, and you would have covered 82.7 lightyears. You would stand about an inch high, and have a mass of about 6 tons as seen from Earth, though you would not notice any difference.

After 8 years, you would reach 0.9999998c. 1,840 years would have elapsed on Earth. Great, you are far from what was your home. 400 US presidents came and went. What is more, you are now 1mm high and have a mass of 140 tons.

Nothing to lose now, lets go on, still at 1g...

After 12 years, you would be travelling 0.99999999996 c. By now you would have crossed the galaxy and be 113,000 light years from home. Time is now running 117,000 times more slowly for you than on Earth. You stand 15 microns tall, and your mass is about 9000 tons.

So, in fact you have travelled "faster than light" by covering 113,000 light years in 12 of your years, but well and truly burnt your bridges in doing so.
You have also become a very significant problem for any destination, and would require 12 years too to slow down at 1g, assuming you have survived the deadly blueshifted light and cosmic radiation.

I don't think we'll get the hang of FTL travel for a while yet - bicycles are much cleaner and healthier.

```   T          t         d          v                gamma
1 year    1.19 yrs  0.56 lyrs  0.77c              1.58
2         3.75      2.90       0.97               3.99
5        83.7      82.7        0.99993            86.2
8     1,840     1,840          0.9999998         1,890
12   113,000   113,000          0.99999999996   117,000
```

http://www2.corepower.com:8080/~relfaq/rocket.html
ID: 434464 ·
Diego -=Mav3rik=-

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Message 435002 - Posted: 12 Oct 2006, 6:20:48 UTC - in response to Message 434371.

I am not a scientist but i like to ask questions
if we could travel at light speed how long would it take a manned flight to reach it taking into account mans limited resistance to g force

It would take 353,7 days of constant 1G (9,81 m/s^2) acceleration to reach the speed of light. In that time you would travel 4,58 billion Km.

But the human body can take more than 1G, not sure what's the limit, and for how long.
---------------------

Note: That's 353,7 years from wherever you want to observe it. LoL.
/Mav

We have lingered long enough on the shores of the cosmic ocean.
We are ready at last to set sail for the stars.

(Carl Sagan)
ID: 435002 ·
Mattias Johnsson

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Message 435030 - Posted: 12 Oct 2006, 8:57:15 UTC - in response to Message 435002.

It would take 353,7 days of constant 1G (9,81 m/s^2) acceleration to reach the speed of light. In that time you would travel 4,58 billion Km.

You can't reach the speed of light. Andy has the right numbers above; effectively the closer you get to lightspeed the less effective your "push" actually is in accelerating you. Your calculation just assumes Newtonian rules and doesn't take relativity into account.

But the human body can take more than 1G, not sure what's the limit, and for how long.
---------------------

Note: That's 353,7 years from wherever you want to observe it. LoL.

I assume you mean days, but where you observe it does make a difference. The clock of a person moving at high speed runs slow from the point of view of someone standing still. So less time always seems to pass on the spaceship that's accelerating compared to someone back on earth.
ID: 435030 ·
Diego -=Mav3rik=-

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Message 435195 - Posted: 12 Oct 2006, 17:54:47 UTC - in response to Message 435030.

It would take 353,7 days of constant 1G (9,81 m/s^2) acceleration to reach the speed of light. In that time you would travel 4,58 billion Km.

You can't reach the speed of light. Andy has the right numbers above; effectively the closer you get to lightspeed the less effective your "push" actually is in accelerating you. Your calculation just assumes Newtonian rules and doesn't take relativity into account.

I know about those theories, but yorkieron started his question with "if we could travel at light speed" so regardless of relativity, I was trying to answer his question.

where you observe it does make a difference. The clock of a person moving at high speed runs slow from the point of view of someone standing still. So less time always seems to pass on the spaceship that's accelerating compared to someone back on earth.

You said it yourself, "the clock"... "seems"... ;)
/Regards
/Mav

We have lingered long enough on the shores of the cosmic ocean.
We are ready at last to set sail for the stars.

(Carl Sagan)
ID: 435195 ·
yorkieron

Joined: 30 Jun 00
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Message 435368 - Posted: 12 Oct 2006, 23:59:53 UTC - in response to Message 435195.

It would take 353,7 days of constant 1G (9,81 m/s^2) acceleration to reach the speed of light. In that time you would travel 4,58 billion Km.

You can't reach the speed of light. Andy has the right numbers above; effectively the closer you get to lightspeed the less effective your "push" actually is in accelerating you. Your calculation just assumes Newtonian rules and doesn't take relativity into account.

I know about those theories, but yorkieron started his question with "if we could travel at light speed" so regardless of relativity, I was trying to answer his question.

where you observe it does make a difference. The clock of a person moving at high speed runs slow from the point of view of someone standing still. So less time always seems to pass on the spaceship that's accelerating compared to someone back on earth.

Forget it I don't think I have enough time left

You said it yourself, "the clock"... "seems"... ;)
/Regards

ID: 435368 ·

Message boards : SETI@home Science : travel at Light speed