"Observation" of Black Hole Merger

In summary: Premise 1 is not false - the black hole will eventually evaporate. However, the merger process will take an infinite amount of time, so it is impossible to observe the actual merger.
  • #1
ObjectivelyRational
150
9
Premise 1: From the frame of reference of the earth, observing a thing falling into a black hole (crossing the Schwarzschild radius) is impossible -> the thing is observed falling toward but never reaching the radius, i.e. the process takes an infinite amount of time.

Premise 2: Observation includes any manner of measurement and/or signal detection etc.

Premise 3: Another black hole qualifies as "a thing" which can fall toward the black hole

Conclusion: Actual black hole merger can never be observed, only a process leading toward it but taking an infinite amount of time.

Question1: If the conclusion is correct, observation of black hole merger is impossible, then WHAT was observed by LIGO, and why is not still occurring (granted the signals may be weakening... but I assume that in our frame of reference the black holes are still merging.. and will continue to do so "forever") i.e. Did LIGO detect an actual merger or only an approach towards merger?

Question 2: If the conclusion is incorrect which of the premises is false or how do the set of premises not logically necessitate the Conclusion?
 
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  • #2
Premise 1 is based on a static space-time with the "thing" not really perturbing the static Schwarzschild solution. This is definitely not the case for a black hole merger. The merger is very very far from being a static solution.

Apart from that, the signal is generated in the inspiral phase and then settles down as the black holes merge into a single rotating black hole.
 
  • #3
Thank you!
 
  • #4
@Orodruin, I have a question. My belief is that Premise 1 is false and I'd like to know why you seem to think that's not the case. My argument is that assuming Hawking Radiation is real then in the far far future the black hole will evaporate down to nothing. As it finishes evaporating, the view seen by the observer (clearly not on Earth since that will have long vanished) will change and the photons showing the in-falling object actually falling in will be released.

Thanks
 

1. What is a black hole merger?

A black hole merger is a phenomenon in which two black holes come together and combine into a single, larger black hole. This process is also known as a binary black hole merger.

2. How are black hole mergers observed?

Black hole mergers are typically observed through the detection of gravitational waves, which are ripples in space-time caused by the massive objects moving and colliding with each other.

3. What is the significance of observing black hole mergers?

Observing black hole mergers can provide valuable insights into the nature of gravity and the behavior of black holes. It can also help us better understand the evolution and formation of galaxies.

4. How do scientists identify a black hole merger from other gravitational wave signals?

Scientists use sophisticated algorithms and computer simulations to analyze the data from gravitational wave detectors and identify the unique signature of a black hole merger.

5. Can black hole mergers be observed with traditional telescopes?

No, black hole mergers cannot be observed with traditional telescopes as black holes do not emit any light. They can only be detected through their gravitational effects on surrounding matter and the emission of gravitational waves.

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