# speed of light

crazyfox
Science 03 Apr '08 22:09
1. 03 Apr '08 22:09
I read where if one was to travel close to the speed of light you would age slower then on earth. For example: you got on a spaceship and went at 90% the speed pf light for about 5 years and then come back to earth. You been gone for about 10 years but on earth you been gone for about (just say about) 1000 years. If this make sense.
What ya’ll thoughts on this?
2. 04 Apr '08 01:21
Einstein's theory of relativity proves a lot of the time slows. I'm not an expert, but the faster
a thing moves, the slower the time passes around it. Perhaps light is walking the line between the 4th and 5th dimension?
3. 04 Apr '08 11:04
Originally posted by Petman3000
Einstein's theory of relativity proves a lot of the time slows. I'm not an expert, but the faster
a thing moves, the slower the time passes around it. Perhaps light is walking the line between the 4th and 5th dimension?
You mean the time dimension and another time dimension?
Do you think there are two time dimensions, one on each side of the light speed?
4. shavixmir
Guppy poo
04 Apr '08 12:23
Originally posted by crazyfox
I read where if one was to travel close to the speed of light you would age slower then on earth. For example: you got on a spaceship and went at 90% the speed pf light for about 5 years and then come back to earth. You been gone for about 10 years but on earth you been gone for about (just say about) 1000 years. If this make sense.
What ya’ll thoughts on this?
No.

Say the distance from point A to point B is a light year.
If you travel from point A to point B in 2 seconds and then take 2 seconds coming back, you will have been gone 4 seconds.

However, since you traveled a light year going and a light year coming back, Point A will be two years, minus 4 seconds further on.
5. sonhouse
Fast and Curious
04 Apr '08 15:571 edit
Originally posted by crazyfox
I read where if one was to travel close to the speed of light you would age slower then on earth. For example: you got on a spaceship and went at 90% the speed pf light for about 5 years and then come back to earth. You been gone for about 10 years but on earth you been gone for about (just say about) 1000 years. If this make sense.
What ya’ll thoughts on this?
Well at 0.9C, the time dilation ratio is about 2.2 to one. In other words, you on the spacecraft THINK you are going 2.2 times the speed of light, and in fact you age 1 year in your craft for every 2.2 going by on earth. So you go out 22 LY, say, and for you the trip takes about 10 years. you spend a year on your newly discovered earthlike planet, come back home, and on Earth, 45 years have passed, the one year you spent on the planet was at about the same velocity as on Earth so that year for you and earth is the same. So you take 10 years getting there, 10 years getting back and one year there. So you are 21 years older when you get back to earth but 45 years have actually gone by for everyone on Earth. The formula is pretty easy:

T1=Spaceship time, T=Earth time, V=spaceship velocity, C=Speed of light. So: T1=T/Sqrt (1-(V^2/C^2))

0.9C is 186,282 MPS *0.9=167,653.8 MPS squared/186,282 MPS Squared, about 2.811E10/3.47E10
or 0.81.
1 minus 0.81= 0.19
Sqrt of 0.19 is 0.435 and change, inverted is about 2.3 which is the grand answer for the time dilation going at 0.9C.
6. sonhouse
Fast and Curious
04 Apr '08 18:13
When you look at #'s close to C, for this exercise we will call C
186,282 MPS. This business of getting close to C to go interstellar is not what it's cracked up to be. Using that figure for C, and we are in a spaceship going 1 MPS less than C, or 186,281 MPS, you are effectively going only 305 times C. So if you go 152.5 LY away, it takes 6 months according to clocks on the spaceship, and you spend say, 10 years at your nice new planet, go back at that speed again, you have been gone 11 years according to your calander, shipboard time. But when you get back, say you left in the year 2050, then you get back in the year 2365. You might think, wow, look at my bank account now, but after 315 years, your COUNTRY might not even exist, to say nothing of your children, grandchildren, great-great-great-great-great-great grandchildren, all dead, at least with our lifespans. Maybe in 300 years humans live to be 1000. Wouldn't THAT be a trip.
Come home, find your wife not only still alive, but looking younger than when you left, say you were both 50, she gets a youth treatment, ends up internally as a 20 year old, while you come back and you are now 61. Bummer!
7. O Artem O
ParTizan
13 Apr '08 14:18
well this dosen't have to do with time but if you are traveling in a space ship close to the speed of light your space ship and every thing in it get smaller. if you are traveling a couple of miles below the speed of light you will almost be flat!!! there is also a formula for this if your interested
8. sonhouse
Fast and Curious
13 Apr '08 15:08
Originally posted by O Artem O
well this dosen't have to do with time but if you are traveling in a space ship close to the speed of light your space ship and every thing in it get smaller. if you are traveling a couple of miles below the speed of light you will almost be flat!!! there is also a formula for this if your interested
We discussed this in Puzzles and Posers. In my above posts I said the guy would THINK he is going faster than C but my buddies said I was wrong, the distance to the star would be shorter too so if you measure you velocity, it will always be less than C. You should be able to see you are personally going faster than C, Vs the rest distance, but you are really just taking a one way trip into the future faster than you would at slower velocities. It is an easy formula, like I said, going at 0.9C allows you to get to a star about twice as fast as it should if GR were not true. You age less so if you go to Alpha Centauri at 0.9C, it takes about 2 of your years to get there but 4 years have still gone by on earth and Alpha Centauri. Your ship is squashed in half lenghtwise and the distance to Alpha Centauri, you think is now only about 2 light years because of the distance foreshortening so you are not going faster than light but your time/distance relation changes. I like to think of it as squashing the plank constant as you get closer to C, kind of like traveling through a universe of rubber bands, as you go faster, you force more rubber bands together, that being space and time.
9. KellyJay
13 Apr '08 15:37
Originally posted by shavixmir
No.

Say the distance from point A to point B is a light year.
If you travel from point A to point B in 2 seconds and then take 2 seconds coming back, you will have been gone 4 seconds.

However, since you traveled a light year going and a light year coming back, Point A will be two years, minus 4 seconds further on.
In theory.
Kelly
10. Nemesio
Ursulakantor
14 Apr '08 03:09
Originally posted by KellyJay
In theory.
Kelly
What reason do you have to doubt this, KellyJay? This 'in theory' business of yours is pretty
tiresome. Since we can prove the formula up until the speeds we can achieve, and since the
formula regarding the 'loss of time' is dead accurate up until that point -- that is the practice
follows the theory -- what on earth would lead you to suspect that somehow for some unexplained
reason that it would not be accurate in fact?

Nemesio
11. sonhouse
Fast and Curious
14 Apr '08 03:17
Originally posted by Nemesio
What reason do you have to doubt this, KellyJay? This 'in theory' business of yours is pretty
tiresome. Since we can prove the formula up until the speeds we can achieve, and since the
formula regarding the 'loss of time' is dead accurate up until that point -- that is the practice
follows the theory -- what on earth would lead you to suspect that somehow for some unexplained
reason that it would not be accurate in fact?

Nemesio
For him, it's true only if god says so, and of course we all know who we are talking about there.....
12. 14 Apr '08 10:14
Originally posted by crazyfox
I read where if one was to travel close to the speed of light you would age slower then on earth. For example: you got on a spaceship and went at 90% the speed pf light for about 5 years and then come back to earth. You been gone for about 10 years but on earth you been gone for about (just say about) 1000 years. If this make sense.
What ya’ll thoughts on this?
Are you asking whether or not time dilation actually occurs? If so the answer is yes it does and it has been tested by various means including putting highly accurate clocks on satellites and measuring the effect directly.
13. 14 Apr '08 10:15
Originally posted by KellyJay
In theory.
Kelly
And in practice so far - unless you know of an exception?
14. sonhouse
Fast and Curious
14 Apr '08 10:20