Black Holes, Gravitational Waves & Gravitons Explained

In summary: Also, the ergosphere is not a region where matter can "quickly dip" and "transfer energy outside". It is a region where the frame dragging effect is strong enough to make it impossible for objects to remain stationary. This has nothing to do with the emission of gravitational waves. In summary, gravitational waves do not escape from the interior of a black hole and can only be observed outside the event horizon. They are not compression waves and are generated by stress-energy distributions with a changing quadropole moment. On the other hand, electromagnetic waves can escape from outside the event horizon and are generated by accelerating charges. The innermost stable orbit is outside the event horizon, but material inside will continually spiral inward until it reaches the event horizon.
  • #1
Raffaele
6
0
I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do.
What is the difference between the two kind of waves?
And between gravitons and photons?

thank you for your attention
 
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  • #2
Raffaele said:
I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do.
Gravitational waves do not escape from the interior of a black hole. They emerge from the region of space-time outside the event horizon(s).
 
  • #3
Gravity waves are a warpage of spacetime behaving similar to a compression wave, caused by the relative motion of two masses and propagating at lightspeed. Gravity begins at the surface of the BH event horizon, the motion of the horizon sends a wave of warped spacetime beginning at that point. Electromagnetic waves come from moving charges, and those generated outside the ergosphere of the event horizon can escape, just like gravity waves, but any electromagnetic waves beginning inside the event horizon cannot be detected, nor can any gravity waves caused by the singularity itself.
An observable 'naked singularity' has been theorized for the early pre-bang universe but nothing conclusive has come of it.
 
  • #4
Torbert said:
Gravity waves are a warpage of spacetime behaving similar to a compression wave, caused by the relative motion of two masses and propagating at lightspeed.
Nitpick: gravity waves are a kind of surface wave on water. You are talking about gravitational waves.

Gravitational waves are not compression waves, which are longitudinal mechanical waves, but are transverse tensor waves which change the notion of distance in two direction perpendicular to their direction of travel. And they are generated by stress-energy distributions with a changing quadropole moment, not just "two masses in relative motion".
Torbert said:
Gravity begins at the surface of the BH event horizon, the motion of the horizon sends a wave of warped spacetime beginning at that point.
Gravitational waves can never be traced back to events inside a black hole, true, but this does not mean that "gravity begins at the event horizon". We are able to describe the interior of black holes using general relativity - our current best theory of gravity. And "motion of the horizon" is a rather difficult thing to adequately describe since the horizon in this case is a null surface in a non-stationary spacetime. That's why "changing quadropole moment" is used as the source, not relative motion.
Torbert said:
Electromagnetic waves come from moving charges
Accelerating charges, in fact.
Torbert said:
those generated outside the ergosphere of the event horizon can escape,
The ergosphere and the event horizon are two different things. Electromagnetic waves generated outside the event horizon can escape.
 
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  • #5
Ouch, simplifying and not looking up the facts does not go far here. Compression waves would require aether, I actually know that but didn't go far in making it obvious.
The innermost stable orbit is outside the event horizon but material inside will relentlessly spiral inward until the event horizon is reached.
I thought this was the same as the ergo sphere where a quick dip with an unstable orbit would transfer energy outside. But if energy could be collected then the in fall is not inevitable.
I will do better reviewing before posting in the future.
 
  • #6
Torbert said:
Gravity begins at the surface of the BH event horizon

This is wrong. A correct statement would be that gravitational waves observable far away are emitted from outside the horizon. But "gravity" is not limited to regions from which gravitational waves are emitted that are observable far away.

Torbert said:
An observable 'naked singularity' has been theorized for the early pre-bang universe

What are you talking about here? Can you give a reference?

Torbert said:
The innermost stable orbit is outside the event horizon but material inside will relentlessly spiral inward until the event horizon is reached.
I thought this was the same as the ergo sphere where a quick dip with an unstable orbit would transfer energy outside. But if energy could be collected then the in fall is not inevitable.

None of this has anything to do with emission of gravitational waves.
 

FAQ: Black Holes, Gravitational Waves & Gravitons Explained

What is a black hole?

A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. It is formed when a massive star dies and its core collapses under its own gravity.

How are black holes detected?

Black holes cannot be directly observed, but their presence can be inferred through their effects on surrounding matter and light. Scientists use various methods such as observing the movement of stars and gas around a suspected black hole or detecting the gravitational waves emitted when two black holes merge.

What are gravitational waves?

Gravitational waves are ripples in the fabric of space-time that are produced when massive objects, such as black holes or neutron stars, accelerate. These waves were predicted by Einstein's theory of general relativity and were first detected in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO).

What is the role of gravitons in black holes and gravitational waves?

Gravitons are hypothetical particles that are thought to be the carriers of the force of gravity. They play a crucial role in the theory of quantum gravity, which aims to reconcile the theories of general relativity and quantum mechanics. Gravitons are believed to be involved in the interactions between black holes and the production of gravitational waves.

Can black holes and gravitational waves be used for space travel?

At the moment, black holes and gravitational waves are not practical for space travel. The intense gravitational pull of black holes would tear apart any known material, and the strength of gravitational waves is too weak to be harnessed for propulsion. However, studying these phenomena can provide valuable insights into the nature of space and time, which may lead to advancements in space travel technology in the future.

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