Comments on: Questions Show – Running Out of Gravitons and Hitting the Brakes at Light Speed http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/ Take a weekly facts-based journey through the cosmos with Astronomy Cast. Thu, 11 Mar 2010 05:19:48 +0000 http://wordpress.org/?v=2.9.1 hourly 1 By: themondo http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/comment-page-1/#comment-1114 themondo Thu, 16 Oct 2008 04:23:23 +0000 http://www.astronomycast.com/?p=386#comment-1114 I have a question for all of you smarts out there. Does a black hole represent all 4 fundamental forces of nature, in the universe, unified into one 'super unified' force because of it's density and its capability of stopping light. This capability must be faster than the speed of light, however small. So does this not say that faster than light speed is capable, only if a black hole can cause it? What say you all? I have a question for all of you smarts out there. Does a black hole represent all 4 fundamental forces of nature, in the universe, unified into one 'super unified' force because of it's density and its capability of stopping light. This capability must be faster than the speed of light, however small. So does this not say that faster than light speed is capable, only if a black hole can cause it? What say you all?

]]> By: Mike Corfield http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/comment-page-1/#comment-1105 Mike Corfield Tue, 14 Oct 2008 13:18:03 +0000 http://www.astronomycast.com/?p=386#comment-1105 Andrew, light booms exist - it is called Cerenkov radiation caused by particles travelling faster than the local speed of light (Nb light slows down when it travels through a medium). it is often seen in cooling ponds around nuclear reactors and is also produced by cosmic rays Mike Andrew, light booms exist – it is called Cerenkov radiation caused by particles travelling faster than the local speed of light (Nb light slows down when it travels through a medium). it is often seen in cooling ponds around nuclear reactors and is also produced by cosmic rays

Mike

]]> By: Jasper http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/comment-page-1/#comment-1087 Jasper Thu, 09 Oct 2008 12:48:35 +0000 http://www.astronomycast.com/?p=386#comment-1087 Andrew, the flaw in your reasoning is that you simply add velocities as if you were in a moving car on Earth. Since you are so close to the speed of light you have to take the relativistic effects into consideration. Remember that as you speed up - time slows down. This is where you and a stationary observer are different. Imagine your spaceship being capable of traveling at 99% of the speed of light and that you are on your way from Earth to Alpha Centauri, 4.36 lightyears away. Now, for someone on Earth, it would seem like your travel time takes slightly longer than 4.36 years, but for you it would only take a few minutes! So now you are on your way to Alpha Centauri, but you still have to entertain yourself for several minutes until you arrive, so you decide to have some fun with the ball you brought. You get your ball and you throw it to the front of the space ship (incredibly fast) at 6 million metres per second. (2% the speed of light). (You're throwing it so unrealisticly fast because you are trying to exceed the speed of light.) At the same time an astronomer on Earth, with an incredible telescope, that can see your every move, is looking at you. As you throw the ball you see it moving away from you at 6 million metres per second - really fast, but no where near the speed of light. It doesn't disappear or create a singularity. You are disappointed. The astronomer on Earth sees you throwing a ball too, but he sees you in slow motion. In the time it takes you to pick up and throw your ball the astronomer has lived a whole year. For him, the ball doesn't break the speed of light either. Though the cumulative speed of the ball and the space ship is very high, it is still below the speed of light. You can calculate the speed of the ball like this: w = u + v / ( 1 + uv / c² ) Where w is the speed of the ball as seen by the astronomer on Earth, u the speed of the space ship, v the speed of the ball as seen by you *on* the space ship and c the speed of light. Notice that for whatever speeds u and v (provided they are below the speed of light, as they should be, because at or above the speed of light is not possible) the cumulative speed as seen by a stationary observer is always less than the speed of light. Just remember - special relativity says nothing can go faster than the speed of light, ever. If you think something can go faster than the speed of light, time will be distorted to make it impossible. Andrew, the flaw in your reasoning is that you simply add velocities as if you were in a moving car on Earth. Since you are so close to the speed of light you have to take the relativistic effects into consideration.

Remember that as you speed up – time slows down. This is where you and a stationary observer are different. Imagine your spaceship being capable of traveling at 99% of the speed of light and that you are on your way from Earth to Alpha Centauri, 4.36 lightyears away. Now, for someone on Earth, it would seem like your travel time takes slightly longer than 4.36 years, but for you it would only take a few minutes!

So now you are on your way to Alpha Centauri, but you still have to entertain yourself for several minutes until you arrive, so you decide to have some fun with the ball you brought. You get your ball and you throw it to the front of the space ship (incredibly fast) at 6 million metres per second. (2% the speed of light). (You're throwing it so unrealisticly fast because you are trying to exceed the speed of light.) At the same time an astronomer on Earth, with an incredible telescope, that can see your every move, is looking at you. As you throw the ball you see it moving away from you at 6 million metres per second – really fast, but no where near the speed of light. It doesn't disappear or create a singularity. You are disappointed. The astronomer on Earth sees you throwing a ball too, but he sees you in slow motion. In the time it takes you to pick up and throw your ball the astronomer has lived a whole year. For him, the ball doesn't break the speed of light either. Though the cumulative speed of the ball and the space ship is very high, it is still below the speed of light.

You can calculate the speed of the ball like this:

w = u + v / ( 1 + uv / c² )
Where w is the speed of the ball as seen by the astronomer on Earth, u the speed of the space ship, v the speed of the ball as seen by you *on* the space ship and c the speed of light.

Notice that for whatever speeds u and v (provided they are below the speed of light, as they should be, because at or above the speed of light is not possible) the cumulative speed as seen by a stationary observer is always less than the speed of light.

Just remember – special relativity says nothing can go faster than the speed of light, ever. If you think something can go faster than the speed of light, time will be distorted to make it impossible.

]]> By: Andrew http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/comment-page-1/#comment-1061 Andrew Tue, 07 Oct 2008 16:02:53 +0000 http://www.astronomycast.com/?p=386#comment-1061 One nagging little question that i keep on thinking of is.... you cannot go faster than the speed of light, ok... so if you are in a spaceship, going close to the speed of light, and you throw a ball toward the front of the ship. The ball would be travelling at current speed + thrown speed. What if the ball exceeded the speed of light?! Would it blink out of existance?! Or would your arm blink out of existance since your arm had to exceed the speed of light to throw the ball!? I keep thinking of the old thought that the speed of sound was the limit, then we broke that.... will we some day find out that there is such a thing as a light boom? like a sonic boom but with light? One nagging little question that i keep on thinking of is…. you cannot go faster than the speed of light, ok… so if you are in a spaceship, going close to the speed of light, and you throw a ball toward the front of the ship. The ball would be travelling at current speed + thrown speed. What if the ball exceeded the speed of light?! Would it blink out of existance?! Or would your arm blink out of existance since your arm had to exceed the speed of light to throw the ball!? I keep thinking of the old thought that the speed of sound was the limit, then we broke that…. will we some day find out that there is such a thing as a light boom? like a sonic boom but with light?

]]> By: Anders http://www.astronomycast.com/listeners/questions-shows/questions-show-running-out-of-gravitons-and-hitting-the-brakes-at-light-speed/comment-page-1/#comment-1004 Anders Sun, 05 Oct 2008 07:20:15 +0000 http://www.astronomycast.com/?p=386#comment-1004 David, two things: a) Einstein could be wrong. His General Theory of Relativity could be one way to look at it, but not necessarily the correct way. It has happened before. b) IIUC, these are not real particles but virtual particles, which allows for all kinds of weird stuff, including breaking the conservation of energy over short periods of times. Interesting question about iron and magnetism. Would this mean that a long steel wire would experience magnetic tidal forces? David, two things:

a) Einstein could be wrong. His General Theory of Relativity could be one way to look at it, but not necessarily the correct way. It has happened before.

b) IIUC, these are not real particles but virtual particles, which allows for all kinds of weird stuff, including breaking the conservation of energy over short periods of times.

Interesting question about iron and magnetism. Would this mean that a long steel wire would experience magnetic tidal forces?

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