Time Travel & Gravitational Time Dilation Function

Invutil
Messages
24
Reaction score
0
If you square both sides of the gravitational time dilation function for non-rotating spherical bodies, do you not get a "time travel function" that allows you to travel back in time with a massive enough body like a black hole?
 
Physics news on Phys.org
Invutil said:
If you square both sides of the gravitational time dilation function for non-rotating spherical bodies, do you not get a "time travel function" that allows you to travel back in time with a massive enough body like a black hole?

I don't understand what you mean by a "time travel function", but there's nothing that happens in the neighborhood of a non-rotating spherical black hole that allows you to travel back in time.
 
I must be not understanding something then. If 0 < 2GM/rc2 < 1 or 0 < r0/r < 1, then time in the gravity well is less than time at an arbitrarily far distance from it. For 0<x<1, 0<sqrt(x)<1, when (1-2GM/rc2) < 1 or (1-r0/r) < 1. The greater the mass M, the smaller the distance from center r, the farther the observer is in the past (t0). Might the value inside the square root become negative even, if 2GM/rc2 > 1 or r0/r > 1, (at a black hole?) and go to a higher dimension? Does it make sense? Since it's inside a square root, might it become a complex number and still make sense that way? Then, maybe the effect can be repeated to return back to real numbers (going through another black hole, assuming that doesn't totally annihalate whatever is pulled in)? This seems really amazing to me.
 
Last edited:
Invutil said:
I must be not understanding something then. If 0 < 2GM/rc2 < 1 or 0 < r0/r < 1, then time in the gravity well is less than time at an arbitrarily far distance from it.

No. For this range of the radial coordinate, you are inside the black hole's horizon, and there are no static observers there--i.e., no observers that "hover" at a constant ##r## (doing this inside the horizon would require moving faster than light). So there's no way to make the comparison of "time" that you are trying to make here.

Invutil said:
The greater the mass M, the smaller the distance from center r, the farther the observer is in the past (t0).

t0 doesn't appear anywhere in what you said. What is t0?
 

Thread 'I don't see how a black hole's event horizon can be crossed'

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...
View full post »

Thread 'Synchronizing clocks in an inertial frame if light is anisotropic'

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...
View full post »

Thread 'Is the variation of the metric ##\delta g_{\mu\nu}## a tensor?'

From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...
View full post »

Similar threads

B What does symmetry of time dilation really mean?
Replies
16
Views
2K
I Kinetic vs Gravitational Time Dilation: Perceived Speed
Replies
5
Views
2K
I You can't actually enter a blackhole?
Replies
40
Views
3K
B Trying to understand what "time" is (layperson)
Replies
21
Views
2K
I Time dilatopause for black holes
Replies
36
Views
4K
I Time Dilation at Moving Black Hole Event Horizon
Replies
16
Views
4K
I Effects of time dilation for near-speed-of-light travel
2
Replies
65
Views
10K
I Non-Inertial Relativistic Dynamics
Replies
18
Views
1K
I What Experiments Demonstrate Time Dilation?
Replies
46
Views
4K
B Entering a black hole -- I know I must be wrong (Help me understand why)
Replies
29
Views
2K

Hot Threads

Recent Insights

Back
Top