traveling at the speed of light

[tolbiny]

i doubt i need a disclaimer for my lack of background in physics, as my question will soon expose that.

According to relativity the closer to the speed of light that you travel, the slower time goes- Does time not move at the speed of light?
If so, if we were able to travel at the speed of light couldn't we travel anywhere in the universe instantaneously (from our perspective?)

[benkahuna]

Time doesn't have a speed. It's another aspect of existence. Speed is a change in distance divided by time. And the speed of light is a constant, ~186,000 miles per second.
Speed defines a rate of change of position. You need time for a change in position to occur (otherwise you violate the physical principle of locality--an object may only be in one place at a single instance of time). Time's just a weirdo doing it's own thing, marching on.

You can entangle the concepts of time and speed if you want, but if you do, you're just making stuff up.

[AleoMagus]

[ QUOTE ]
If so, if we were able to travel at the speed of light couldn't we travel anywhere in the universe instantaneously (from our perspective?)

[/ QUOTE ]

This is correct. Of course, we cannot travel at the speed of light but I suppose we could get really close, and in terms of practicality still travel anywhere we wanted in a pretty short time.

Understand the implications of this though. When you get there, the time it took to get there will still have passed.

For example, I could get in a spaceship to go to Alpha Centauri (which is a little over 4 light years from us), fly at very near the speed of light, and it would only seem like a few second trip. I could then fly home again and in total, it might seem like a day or so of exploring. Except for the fact that everyone else will have aged almost 9 years.

Regards
Brad S

[Piz0wn0reD!!!!!!]

[ QUOTE ]


For example, I could get in a spaceship to go to Alpha Centauri (which is a little over 4 light years from us), fly at very near the speed of light, and it would only seem like a few second trip.

[/ QUOTE ]

it would take you 4 years to get there.

IIRC to reach the speed of light, your mass must become infinite. That is just impossible to comprehend.

to the OP, you should read Mr tompkins (sp?) in wonderland. It describes time, speed and relativity in a childrens book style. Its quite good for non-scientists like us.

You ignored the words in the quote you were replying to?!

It would seem to the traveller as a short period of time, but to his original reference point it woul dbe 4 years.

Am I right in thinking this is actually observable with atomic clocks travellinglong distances in planes and landing slightly slower than there stationary counterpart, or have I just made that up?

[benkahuna]

I think you're making it up. I was taught that until you get very close to lightspeed (say .9c), classical mechanics applies and things don't get weird.

From here (http://www.neh.gov/news/humanities/2005-03/elasticity.html)

"In 1971, a team of scientists who were experts in the use of atomic clocks set out to detect and measure time dilation and other relativistic effects. The research team was able to devise a cheap and effective plan, which received some support from the Office of Naval Research. We are told that the researchers purchased three around-the-world tickets on regularly scheduled commercial airliners-two tickets for the accompanying scientists and one for an array of four atomic clocks. The clock array had its own seat; it sat, belted in for safety, between its two caretakers. Before leaving on the trip, the clocks were synchronized with a master clock at the U.S. Naval Observatory. The four clocks then went around the world, following which they were compared again with their counterpart, which had stayed behind at the Naval Observatory. After correcting for the rotation of the earth and the variation of the force of gravity with altitude, it was found that the clocks that had been in motion in their journey around the earth had in fact slowed as compared with the clock at the Naval Observatory, and by exactly the amount predicted by the theory of relativity. The result was further confirmed in a second around-the-world flight in the opposite direction. "

just the first one i found on google

[benkahuna]

I stand (sit) corrected (maybe). I was told by a relative that the faster you go the slower time goes. I also remember taking physics and being told that this idea is not exactly true. Could the change in gravity (and the resulting curvature of space-time) be the main issue here? If you're in a plane, you're further from the center of the earth so the gravitational force you experience is lessened. I looked. Answer: No. Less gravity actually makes for slower time.

Ok, found a formula:

t = t0 / sqrt(1-(v^2/c^2))

t0 = normal time
sqrt = square root
v = speed
c = speed of light (3*10^8 m/s)
t = the "new" time

So if you move at... let's say 0.6 times the speed of light for 1 minute

t=60/sqrt(1-0.6^2) = 75

I'm still quite unsatisfied. At .6c, time dilation is pretty dramatic as you're only experiencing 80 percent of the time that an outside observer is.

I suspected that it was just a low (negatively) slope curve until you get really close to the speed of light, and then the slope begins to change in absolute value dramatically.

I think it might have been redshift/blueshift that started to occur at .9c but not at lower velocities, but I know it was something! Oh well.

[BluffTHIS!]

The Fabric of the Cosmos by Brian Greene is also a good book and explains why star trek won't work regarding so called faster than light warp travel or the use of worm holes.

[Piz0wn0reD!!!!!!]

[ QUOTE ]
You ignored the words in the quote you were replying to?!

It would seem to the traveller as a short period of time, but to his original reference point it woul dbe 4 years.

Am I right in thinking this is actually observable with atomic clocks travellinglong distances in planes and landing slightly slower than there stationary counterpart, or have I just made that up?

[/ QUOTE ]

this has actaully been tested. The clocks were very slightly off.

[ChromePony]

[ QUOTE ]
I stand (sit) corrected (maybe). I was told by a relative that the faster you go the slower time goes.

[/ QUOTE ]

One way to think of it is that time and space (are related (hence the term space-time), and the more quickly you pass through one, the slower you pass through the other. To me saying that time slows down is confusing, I think its easier to think of time as a constant entity that is just there, and we are the ones passing through it at different rates...but I guess it essentially amounts to the same thing.

[baggins]

[ QUOTE ]
I was told by a relative that the faster you go the slower time goes.

[/ QUOTE ]

i hope that pun wasn't intended.

[KeysrSoze]

[ QUOTE ]
Answer: No. Less gravity actually makes for slower time.


[/ QUOTE ]

I'm not sure you're right depending on how you meant that statement. Actually an observer inside a gravity well will observe that time is apparently moving faster in a frame of reference farther out of the gravity well, and from outside looking in, time would appear to be moving slower deeper in the well. For instance, if two spaceships come across a blackhole, and one goes into orbit very close to its event horizon and then returns (assuming it wasnt crushed in the process, had the tremendous energy required to reach escape velocity, nit nit etc.), millions of years may seem to have passed on the outside while they were in, while for an observer on the second ship looking in, time would appear to have almost stopped on the first ship.

[benkahuna]

Yeah, you're right. I either said it wrong or read it wrong. Either way, what I posted was wrong. More gravity, relative shortening of time by objects in the gravity well relative to objects outside the well.

We talked about the spaceship example in the Astro course that I took. It would take immense energy, but it looks like only best way to time travel that we know of right now. You of course would only be able to go into the future and you would age some on the way there.