Gravitational acceleration VS the speed of light

Accuser
Messages
3
Reaction score
0
Three preconceptions for our thought experiment:

1. Gravity's effects propagate at a rate faster than the speed of light. This is demonstrated by the fact that the Earth is not thrown out into space due to the constantly shifting position of the Sun and an 8.3 min delay of "gravity waves" pulling us toward the Sun's previous position.

2. Gravity increases proportionately to an object's mass.

3. There is no functional limit to the distance over which gravity may have an effect (the effect decreasing by the square of the distance, of course).

Imagine a Universe with physical laws identical to our own. Imagine it with no matter, anti-matter, energy, etc (excepting what I'll colloquially call "quantum turbulence"). Now imagine 2 very massive bodies which are stationary and extremely far from each other.

With only 2 bodies in this Universe, each would eventually experience the other's gravitational effects and begin to accelerate toward the other body. Assume the distance between them is sufficient that there is enough time in their transit to accelerate to near light speed. Relativity states that no body can achieve the speed of light due to the increase of mass and the slowing of local time with increased speed. However, wouldn't increased gravity exactly compensate for the increased mass of acceleration? Is there a reason that these two bodies would not achieve at least gravitational speed, given their initial position was far enough apart?

My apologies if this has been answered before, but I can't seem to find it elsewhere. Also, if you can provide an answer, I would deeply appreciate the use of layman's vocabulary ^_^
 
Last edited by a moderator:
Physics news on Phys.org
I have removed the the URL, which violates Physics Forums rules, to which everyone agrees when they register.

One of the main goals of PF is to help students learn the current status of physics as practiced by the scientific community; accordingly, Physicsforums.com strives to maintain high standards of academic integrity. There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion. Personal theories/Independent Research may be submitted to our Independent Research Forum, provided they meet our Independent Research Guidelines; Personal theories posted elsewhere will be deleted. Poorly formulated personal theories, unfounded challenges of mainstream science, and overt crackpottery will not be tolerated anywhere on the site. Linking to obviously "crank" or "crackpot" sites is prohibited.

Accuser said:
Three preconceptions for our thought experiment:

1. Gravity's effects propagate at a rate faster than the speed of light. This is demonstrated by the fact that the Earth is not thrown out into space due to the constantly shifting position of the Sun and an 8.3 min delay of "gravity waves" pulling us toward the Sun's previous position.

The effects of gravity do not propagate faster than the speed of light. See

https://www.physicsforums.com/showthread.php?p=2818297#post2818297.
 
My apologies on the worthless link then. It wasn't "obviously 'crank' or 'crackpot' as I read it, but I'll chalk that up to a lack of thorough understanding of the topic.

But to get on to the question, what is it that would limit the speed of the objects?

EDIT:
To be more precise, why would they not reach the same speed as the effect of gravity?
 
Last edited:
To be more precise, why would they not reach the same speed as the effect of gravity?
They would. That speed is the speed of light.
 
Ich said:
They would. That speed is the speed of light.

Fair enough, thanks for the fast and informative responses!
 
OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
In this video I can see a person walking around lines of curvature on a sphere with an arrow strapped to his waist. His task is to keep the arrow pointed in the same direction How does he do this ? Does he use a reference point like the stars? (that only move very slowly) If that is how he keeps the arrow pointing in the same direction, is that equivalent to saying that he orients the arrow wrt the 3d space that the sphere is embedded in? So ,although one refers to intrinsic curvature...
ASSUMPTIONS 1. Two identical clocks A and B in the same inertial frame are stationary relative to each other a fixed distance L apart. Time passes at the same rate for both. 2. Both clocks are able to send/receive light signals and to write/read the send/receive times into signals. 3. The speed of light is anisotropic. METHOD 1. At time t[A1] and time t[B1], clock A sends a light signal to clock B. The clock B time is unknown to A. 2. Clock B receives the signal from A at time t[B2] and...

Similar threads

Back
Top