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View Full Version : Do the event horizon co-ordinates link frames of reference to the future?

WaxRubiks
2019-Mar-20, 01:22 PM
If we forget a black hole frame of reference and take it as read that there is a co-ordinate system for an event horizon where time dilation is infinite, if we link our frame of reference to it, would that link our present frame of reference to all future frames of reference for the future where that event horizon still exists?

WaxRubiks
2019-Mar-22, 06:33 AM
please say if I have asked a stupid question, or one that doesn't seem to make sense.

Shaula
2019-Mar-22, 07:17 AM
If we forget a black hole frame of reference and take it as read that there is a co-ordinate system for an event horizon where time dilation is infinite,
The Schwarzschild metric has this property.

if we link our frame of reference to it, would that link our present frame of reference to all future frames of reference for the future where that event horizon still exists?
This bit makes no sense to me. How would you 'link' an frame of reference?

WaxRubiks
2019-Mar-22, 07:28 AM
This bit makes no sense to me. How would you 'link' an frame of reference?

well that's not something I'm sure about.....say you have a planet revolving around a black holes....is it possible to link frames of reference between them?...are they connectible at all?

Shaula
2019-Mar-22, 08:18 AM
well that's not something I'm sure about.....say you have a planet revolving around a black holes....is it possible to link frames of reference between them?...are they connectible at all?
As I said, I don't understand what you mean by linking reference frames. A reference frame is just a description of local coordinates that can be freely transformed to work out what other observers would measure when you know what you would measure locally. If you cannot define what you mean by link then I don't know what you are asking.

Grey
2019-Mar-22, 01:56 PM
If by "link", you're imagining some bidirectional transfer of information or objects, then no. We can send information to the future easily enough (and using a black hole we could arrange for something to be sent arbitrarily far into the future while experiencing an arbitrarily short amount of proper time), but there's no way for information or objects to travel back to us from the future.

Strange
2019-Mar-23, 12:16 PM
well that's not something I'm sure about.....say you have a planet revolving around a black holes....is it possible to link frames of reference between them?...are they connectible at all?

I don't know what you mean by :link", either.

Do you mean do some sort of transformation of the coordinates from one reference frame to the other? (Like the Lorentz transform in SR)

If so then (I think) in the case of Schwarzschild coordinates, you cannot do that for the event horizon because it is a singularity. But if you use a different coordinate system (eg. Gullstrand-Painleve) then you can.

WaxRubiks
2019-Mar-23, 01:56 PM
Do you mean do some sort of transformation of the coordinates from one reference frame to the other? (Like the Lorentz transform in SR)

that sounds like what I was meaning.