In gravitational field one could travel equal to or faster than the speed of light?

Question

if there was a very massive body that its gravitational field extended very far and its acceleration of freefall was much higher(the accelerationn of freefall is same no matter how massive the body is).if a mass fell in the g.field of this body so that it will tavel a very long dist. before impact so that it would be accelerated to the speed of light(the infinite mass characteristic and need for infinite energy would not have any affect as acceleration of freefall is independent of mass and no energy is being supplied for acceleration) BUT THIS ACCELERATION EQUAL TO OR GREATER THAN SPEED OF LIGHT IS TOTALLY FORBIDDEN BY RELATIVITY.explain this..

to answerer2,
as u said that mass would require infinite energy to b accelerated to c.this is true because mass would itself become infinite.but in g.field acceleration is constant and is not affected by infinite mass and so infinite energy is also not required.so without this infinite mass/energy restriction,the mass would accelerate to the speed of light.
hope u understand wat i mean..

Answer 1

Hi addy

There is an interesting physical situation close to what you describe.

The geometry of space-time around a non-spinning black hole is called the Schwarzschild geometry (after the guy who first described it). Suppose you and I start from an infinite distance away from a schwarzschild black hole. I wave goodbye and start falling towards the hole. As I fall towards the hole I fire a light pulse back at you every minute, and you measure my speed (from your reference frame). As I approach the horizon you notice two strange things:
i) the light pulses I'm firing back at you are getting redshifted
ii) the time between successive pulses is increasing - this is time dilation!

You also notice my speed increasing (relative to you) alarmingly. By the time I reach the event horizon, from your reference frame you measure my time to have dilated infinitely, and my speed relative to you to have reached c! But there's a problem: I'm still accelerating (I haven't reached the centre of the hole), so what's going on?

Let's see what's happening from my (falling) perspective. According to me, my time isn't dilated at all. At the point where I cross where you think the event horizon is, I measure my speed relative to the geometry to be close to but still less than c. If I could see the horizon it would look like it is still off ahead of me.

So here we have two different pictures. According to you, at infinity, I reach c at the event horizon and my time dilation goes infinite. In fact, from your perspective, inside the event horizon time and space have flipped and the direction from the horizon radially to the centre is a *time* direction. From my perspective I don't reach c on my trip to the centre at all and there is no direction flip. This is a lesson in the importance of reference frames in relativity, different observers don't agree on very much about space travel!

IN this case the resolution is that there is a coordinate dependent singularity in the schwrazschild geometry at the event horizon. This singularity is responsible for the time dilation going infinite and the speed going to c from the perspective of an observer at infinity. The singularity is removed by a coordinate change (as we saw above when we shifted into my freefalling reference frame). You can see the singularity when you wrtite out the schwarzschild metric - one of the coefficients has a term which ends up dividing by zero when you substitute the event horizon for the radial distance. Importantly, however, there is a composite physical interpretation here: if (as above) I fell into a black hole and you watched from infinity you'd *never* see me cross the horizon - I'd be frozen at the horizon until my image winked out due to redshift from your perspective. However from my perspective I'd cross the horizon, get spaghettified and hit the central singularity in a very short time.


Hope this helps!
The Chicken

Answer 2

Imagine the universe as a water balloon that can stretch and expand in all places. Light travels at the same speed no matter where you are in this water balloon. To keep this rule, imagine that the water balloon stretches so distances between points grow and shrink so that this rule is never violated. That is what our universe does.

However, your special case can never occur since ever a small amount of mass would require more energy potential than is available in the whole universe to be accelerated to the speed of light. Mass can never achieve the speed of light. Nothing with information can travel faster than light.

Answer 3

Have you ever the book by Roger Penrose, "The Road To Reality"?...If you haven't, I highly recommend it...and by the nature of your question (which is a fairly good one, by the way), you would honestly enjoy it and keep your mind very busy considering things you've probly never considered. A few other book titles are: "Teleportation" by David Darling; "A Different Universe" by Robert B. Laughlin; "A World Without Time" by Palle Yourgrau; "A Briefer History Of Time" by Stephen Hawking...all of these are exellent "reads".

Answer 4

You can't go faster than the speed of light. Anything else would mean going back in time.

Remember everything is Relative. So if you go as fast as the speed of light, you are actually "not moving" according to "your view". In fact, everything you do is normal, at a normal pace to you, everything else is not at the same rate as you. If you toss a ball, it is only moving as fast as "you" tossed, even though you are traveling at the speed of light. You'd think that the ball is moving at the speed of light PLUS the speed of the toss.

Answer 5

Black Hole,,,if the gravity is preventing light from escaping then it only makes since that, any thing drawn in would travel to the mass faster then the speed of light.

Answer 6

So, do Neutrinos have information? They travel at the speed of light and only interact rarely with any form of matter.

Answer 7

Stop eating twinkies, and hop the next intergalactic flight to Cygnus X-1. Your explaination will be forthcoming!

Answer 8

This acceleration is totally forbidden by relativity of yours

Answer 9

wouldn't such large body make the light move faster as well?