Falling Object at c: Relativistic Position Expression for the Attracted Object

AI Thread Summary
The discussion centers on the relativistic position expression for a falling object in a gravitational field, particularly as it approaches the speed of light. Participants agree that while mass cannot reach the speed of light, they explore the equations governing the acceleration and position of an object influenced by a massive body. They emphasize the need for relativistic equations when speeds become significant, referencing resources for further understanding. The conversation highlights the complexities of gravitational effects on motion in a relativistic context. Overall, the thread provides insights into the theoretical implications of falling objects near massive gravitational sources.
Imagine
Gedenke experiment: Falling object upto c?

Bonjour,

I would like to know the relativistic position expression for a falling object that could reach the speed of light.

Thanks.

P.S.: Suppose the only things, that exist in the universe, are a BIG attractive mass and the attracted "object".
 
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Nothing with mass could be accelerated to c.

Even if it were to go into a black hole, starting an infinite distance away, once it crosses the event horizon, it is in a different spacetime.
 
Gedenke experiment: Falling object upto c?

Bonjour Brad,

I shall agree with your mass issue.

Suppose, isolated in the universe , a small energetic object, with zero initial relative speed, somewhere far-far-far away from a non-negligeable gravitationnally attractive accumulation of energy (both with mass equivalence (m & M) for gravitational purpose ).

"m" shall be accelerated by "M", following gravitational effect, right?

While m's speed is within non-relativistic speed, I got no problem to express acceleration, speed and position equations.

What would be these equations when relativistic speed's effect is non-negligeable? (Should I ask this in Theoretical forum?)

P.S.: ............
 
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For relativistic versions of those, some tinkering with the equations here: http://www.wikipedia.org/wiki/Relativistic_equation

might help you to get them.

Also, http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

note that it has the equations you are looking for.
 
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Welcome to Physics Forum, Imagine! :smile:
 
Originally posted by Brad_Ad23
For relativistic versions of those, some tinkering with the equations here: http://www.wikipedia.org/wiki/Relativistic_equation

might help you to get them.

Also, http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

note that it has the equations you are looking for.

Phobos, merci pour votre mot de bienvenue.

Brad, I red the rocket page. I also understand the origin of the following restriction: "The acceleration of the rocket must be measured at any given instant in a non-accelerating frame of reference traveling at the same instantaneous speed as the rocket".

Thanks, that was exactly what I searched.
 
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