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Physicists observationally confirm Hawking’s black hole theorem for first time

news.mit.edu

11–20 of 73 posts

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#11
post #9
post #4

Earlier quoted context omitted.

They're not reconciled, it's just garbage reporting. The 'area theorem' they are referring to was by Bekenstein and others, not Hawking. It's basically the equivalent of the second law of thermodynamics for black holes (dA/dt>=0 instead of dS/dt>=0). Hawking's insight was that this formula was wrong and the area could decrease due to radiation.

It is a pity about the reporting. But it is a fascinating area of research. I never expected that we could measure gravitational waves in our life time.

I'm amazed - to the point of skepticism - that with such minute forces they can extrapolate so much information and prove theories.

I mean I'm no astrophysicist, I like the "pop sci" bits, but when I look closer I'm seeing a lot of small numbers and statistics that imply something - e.g. exoplanets based on minute wobbles and brightness variations, water on said exoplanets based on spectrography. It's theories based on tiny but statistically significant data.

The pop sci then comes in and makes statements like "second Earth found!11", which is like, whoa hold on, when you look closer all they found is a wobble or dimness variation that kind of implies there might be a planet at a certain distance from its host star.

Anyway I don't dispute the findings or that there are exoplanets or whatever, I'm just impressed that they are able to make confident claims on what little information we can receive from here.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#12
post #8

so they're 95% sure.. how do they even come up with a figure like that? they didn't bother saying. might be equivalent to 'give or take a few trillion tonnes'

https://www.zmescience.com/science/what-5-sigma-means-042342...; 95% means 2-sigma, when it comes things like the Higgs boson, they announced the results with 5-sigma certainty, which is a very good indication of statistical significance and confidence.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#13
post #9

Earlier quoted context omitted.

It is a pity about the reporting. But it is a fascinating area of research. I never expected that we could measure gravitational waves in our life time.

I'm amazed - to the point of skepticism - that with such minute forces they can extrapolate so much information and prove theories. I mean I'm no astrophysicist, I like the "pop sci" bits, but when I look closer I'm seeing a lot of small numbers and statistics that imply something - e.g. exoplanets based on minute wobbles and brightness variations, water on said exoplanets based on spectrography. It's theories based…

It's fascinating what's possible.

For example, we know more about the chemical composition of other galaxies than we know about the centre of the earth. Just because we can infer so much from their light spectrum.

(For empirical information about the centre of the earth, we are basically limited to seismic data and perhaps the magnetic field and bumps in gravity?)

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#14
post #3

Alright, I'm confused. How does this square with Hawking radiation? How can a black hole shrink without shrinking? The article mentions both in the context that they are reconciled but not how they are reconciled.

Yes, black holes shrink because of Hawking radiation, but in reality this doesn't really happen because black holes are much colder than their surrounding space. Actually they are the coldest objects in nature. Stellar black holes have a temperature of a few Nanokelvins and the average temperature of space is 2.7 K so there's a net gain of energy/mass from absorbed photons from CMB radiation vs emitted photons via Ha…

> In order to have a higher temperature than the CMB a black hole would have to be really small with a mass about half of that of the moon.

Either that, or you just wait a couple eternities for the CMB to cool down enough.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#15
post #9

Earlier quoted context omitted.

It is a pity about the reporting. But it is a fascinating area of research. I never expected that we could measure gravitational waves in our life time.

I'm amazed - to the point of skepticism - that with such minute forces they can extrapolate so much information and prove theories. I mean I'm no astrophysicist, I like the "pop sci" bits, but when I look closer I'm seeing a lot of small numbers and statistics that imply something - e.g. exoplanets based on minute wobbles and brightness variations, water on said exoplanets based on spectrography. It's theories based…

It is not just gravitational waves, they look at light, with telescopes (visible, infra and ultra), spectrographs, interferometers, radio signals, gamma rays...

Then they combine all that info to come up with cohesive theories. LIGO just by itself would be almost useless.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#16

Anyone can think of any practical effect this might have or is this something that at the moment seems to have only scientific relevance.

Well, if the result had turned out the other way, we might have seen some practical effects, because it would overturn some well-established theories that we also use for predicting more practical things.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#17
post #9

Earlier quoted context omitted.

It is a pity about the reporting. But it is a fascinating area of research. I never expected that we could measure gravitational waves in our life time.

I'm amazed - to the point of skepticism - that with such minute forces they can extrapolate so much information and prove theories. I mean I'm no astrophysicist, I like the "pop sci" bits, but when I look closer I'm seeing a lot of small numbers and statistics that imply something - e.g. exoplanets based on minute wobbles and brightness variations, water on said exoplanets based on spectrography. It's theories based…

Sometimes I think the claims are overstating things, but since nobody can use the claim to actually do anything it gets a pass.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#18
post #3

Alright, I'm confused. How does this square with Hawking radiation? How can a black hole shrink without shrinking? The article mentions both in the context that they are reconciled but not how they are reconciled.

Yes, black holes shrink because of Hawking radiation, but in reality this doesn't really happen because black holes are much colder than their surrounding space. Actually they are the coldest objects in nature. Stellar black holes have a temperature of a few Nanokelvins and the average temperature of space is 2.7 K so there's a net gain of energy/mass from absorbed photons from CMB radiation vs emitted photons via Ha…

From the outside they must look cold since they can't radiate heat any more than light. That doesnt imply anything about the inside.

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#19
post #14

Earlier quoted context omitted.

Yes, black holes shrink because of Hawking radiation, but in reality this doesn't really happen because black holes are much colder than their surrounding space. Actually they are the coldest objects in nature. Stellar black holes have a temperature of a few Nanokelvins and the average temperature of space is 2.7 K so there's a net gain of energy/mass from absorbed photons from CMB radiation vs emitted photons via Ha…

> In order to have a higher temperature than the CMB a black hole would have to be really small with a mass about half of that of the moon. Either that, or you just wait a couple eternities for the CMB to cool down enough.

Or primordial black holes with such a small mass actually do exist, who knows...

Re: Physicists observationally confirm Hawking’s black hole theorem for first time

#20
post #3

Alright, I'm confused. How does this square with Hawking radiation? How can a black hole shrink without shrinking? The article mentions both in the context that they are reconciled but not how they are reconciled.

This might help https://physics.stackexchange.com/questions/169886/black-hol...

A black hole merger of this size is unlikely to have any significant quantum aspect

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