Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: rvt on 07/10/2014 20:33:11

Title: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: rvt on 07/10/2014 20:33:11
let's say you drop over the event horizon of a black hole. You cannot communicate back anymore using 'conventional' techniques because space is traveling faster then the speed of light (as how I currently understand the event horizon).

Now, let's say you bring some sort of device, perhaps be a gravitational wave generator that allows you to 'push/pull' on space-time, so you bring out your good old morse code book and operate the device based on morse code.. pull pull pull push push push pull pull pull.

Would you then be able to communicate through the event horizon of a black hole if on the other site somebody sit's with a detector that can detect disturbances in space/time and decode your morse code message?

Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: jeffreyH on 07/10/2014 21:04:16
No
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: Bill S on 07/10/2014 21:32:05
Quote
Would you then be able to communicate through the event horizon of a black hole if on the other site somebody sit's with a detector that can detect disturbances in space/time and decode your morse code message?

Hi rvt, are you talking about communicating from outside in, inside out or in both directions?
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: JohnDuffield on 08/10/2014 12:35:59
let's say you drop over the event horizon of a black hole. You cannot communicate back anymore using 'conventional' techniques because space is traveling faster then the speed of light (as how I currently understand the event horizon)...
It isn't travelling faster than light. A gravitational field alters the motion of light and matter through space, it doesn't suck space in. Unfortunately there are some cosmologists who talk about the black hole "waterfall analogy". I'm afraid it's totally wrong and it's badly misleading.
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: rvt on 08/10/2014 15:25:33
Bill,

inside out. But I guess that would be the same as outside in...

John,
thank's for that information, I need to update my understanding :)
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: PmbPhy on 08/10/2014 16:42:17
No.

re - "because space is traveling faster then the speed of light (as how I currently understand the event horizon).
"

Is wrong. You can't speak of space as moving. That's what relativity is all about.
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: evan_au on 12/10/2014 03:47:43
Quote from: rvt
communication... inside -> out.
Gravitational waves only travel at the speed of light. But the escape velocity of a black hole exceeds the speed of light, so gravitational waves can't escape either.

Quote from: rvt
But I guess that would be the same as outside -> in
Information & matter can easily travel from outside the event horizon to inside the event horizon (it's unknown how garbled they would be after they cross the event horizon).
Neither matter or information can go from the inside of the black hole to the outside (as far as we know), so it is quite asymmetric.
Title: Re: Communicate through the event horizon of a black hole by push/pulling on space time?
Post by: jeffreyH on 12/10/2014 11:43:41
Quote from: rvt
communication... inside -> out.
Gravitational waves only travel at the speed of light. But the escape velocity of a black hole exceeds the speed of light, so gravitational waves can't escape either.

Quote from: rvt
But I guess that would be the same as outside -> in
Information & matter can easily travel from outside the event horizon to inside the event horizon (it's unknown how garbled they would be after they cross the event horizon).
Neither matter or information can go from the inside of the black hole to the outside (as far as we know), so it is quite asymmetric.

It has not been established how fast gravitational waves travel.