Black Holes

[santa claus]

My TV randomly recorded an episode of Horizon for me so I thought why not, let's give it a go.

It was about black holes. Yes, yes I know...snigger .

But it was interesting. At least now I know what an "event horizon" is and a "singularity".

Black holes do a bit of a number on physics and mess with Einstein's theories. It's fascinating and disappointing in a way. Think of all that science...y'know, when man gets closer to the truth about all that weird, black, nothingness.

Anyone got any theories of their own on the subject?

[Saracen]

Theories? Hell, no. But I try to keep up, in laymans terms, with the implications.

Was this the dark matter/dark energy Horizon, that dealt with the implications for standard models of cosmology, and physics?

If not, keep an eye open for that one, too. And keep a bottle of headache tablets handy if you try to understand it all.

[santa claus]

Yep, it all went over my head but it also left some seriously clever people tongue-tied when they were asked to explain what a black hole was made of.

Then a bloke was doing some equations. It was like they'd stop using English. I am rubbish at maths.

It made me think about Fraz and the hadron collider too. I wonder how that's going?

[MerxFM]

I did a module on Gravity and still don't truly understand how these things work, they're a very strange but incredible phenomena. Space-time gets very weird once you cross the Event Horizon. Not only can you NOT escape, but say your ship crossed the Event Horizon and you put on your thrusters in an futile attempt to get out of the Black Hole, it'll actually drive you further in towards the singularity as space-time is bent in such a way that you can only travel inwards. This is regardless of whether you move back in the 'direction' you came from. Weird huh?

[shaithis]

The thing about BHs that baked my noddle, was that there is one at the very centre of every galaxy. Something that was only quite recently discovered.

The entire topic of BHs is fascinating.

[Rob_B]

I thought if you went into one you'd find yourself stuck in a bookshelf throwing dust about the place?

[Lanky123]

The thing about BHs that baked my noddle, was that there is one at the very centre of every galaxy. Something that was only quite recently discovered.

And already there are plans to directly observe the BH at the centre of our galaxy (Sagittarius A*). http://en.wikipedia.org/wiki/Event_Horizon_Telescope So many awesome telescopes coming online in the next decade, in this case requiring angular resolution of ~30 micro arcseconds or 1/120,000,000 of a degree.

[MerxFM]

Yep, it all went over my head but it also left some seriously clever people tongue-tied when they were asked to explain what a black hole was made of.

It's a very tough question. There's no straight answer, but one way I think about it is that they're made of matter condensed into the smallest possible volume and its 'presence' is in fact the space-time distortions due to it's monumental, almost-infinite, density.

The thing about BHs that baked my noddle, was that there is one at the very centre of every galaxy. Something that was only quite recently discovered.

The entire topic of BHs is fascinating.

They also play also quite a strong role in star formation in galaxies, as well as keeping a galaxy together. One of the biggest unanswered questions in astronomy is whether they're responsible for the quenching of star formation, as there's a period in a galaxy's life where the rate of star formation just declines suddenly, and no-one really knows why.

Science is awesome.

[TheAnimus]

Black holes do a bit of a number on physics and mess with Einstein's theories. It's fascinating and disappointing in a way. Think of all that science...y'know

In a past life I implemented mathematical models to better protect our investors from certain shifts in market movement, and pick up some arbitrage opportunities.

I used to have this quote on my desk

all models are wrong, but some are useful

This is the thing, it's always going to be wrong, the complexity of the underlying reality is more complex than the model, so it can't be a perfect fit. So let's not forget that Newtonian physics was perfect, except for when it wasn't. For hundreds of years people thought you didn't need anything more. In fact it's only when scaled, say down to the very small level that the models don't hold.

This shouldn't be thought of as a bad thing. If we're building a simple airplane, we don't need anything more than the Newtonian principles, my plane pushes down enough air, that it has an equal and opposing reaction making it climb or stay level. Sure there are many more complex issues, hell many a talented post grad has written their thesis on something as mundane as just the very wing tip (remember how airplanes wing tips have changed in the last 15 years, this is why!).

Think not of it ever as said, but there is still more learning, more wonders left. Imagine how sad it would be otherwise, think of poor Alexander and how he wept when he saw the extent of his empire.

[MerxFM]

So many awesome telescopes coming online in the next decade.

I wholeheartedly agree, it's going to be an exciting decade for Astronomy. The Large Synoptic Survey Telescope in 2019, Euclid and the Square Kilometre Array in 2020. The list goes on.

This is the thing, it's always going to be wrong, the complexity of the underlying reality is more complex than the model, so it can't be a perfect fit. So let's not forget that Newtonian physics was perfect, except for when it wasn't. For hundreds of years people thought you didn't need anything more. In fact it's only when scaled, say down to the very small level that the models don't hold.

Great quote by the way! Exactly, people thought Physics was over around the 1900's. Then Quantum Mechanics and Relativity came along and was like 'lol nope'. In reality we'll never truly understand everything, all models pretty much break down at some point. We can only continue to improve on what we have. But that's what drives us as scientists.

[Jonj1611]

Blackholes are incredibly difficult and complex to understand, the last one I encountered took everything I had, never to be seen again. It had a technical term at the time, ah yes, wife

[santa claus]

It's such a relief to have a discussion on something interesting. A nice break from politics and the sex lives of the rich and famous. It's also humbling; there's just so much we don't know. I wonder if our galaxy is destined to be sucked into its black hole and the material spat out somewhere else in an even bigger bang?

It's also quite nice that I can ask stupid questions and no-one can call me stupid because even currently known physics can't provide a real answer.

Didn't know about the telescopes. Exciting indeed!

ps sorry about the wife episode jonj1611. Many are the models that are perfect; except when they are not (apologies to animus for twisting his quote )

[Jonj1611]

And without further a do, and for those that like a bit of Science, hope Santa doesn't mind :-

[aidanjt]

Black holes do a bit of a number on physics and mess with Einstein's theories.

Only everything beyond the event horizon, because everything beyond the event horizon is unobservable, which makes validating predictions... non-trivial, shall we say?

Anyway, if you think that's interesting, wait until you find out about Quasars.

[aidanjt]

I wonder if our galaxy is destined to be sucked into its black hole

Our black hole is rather muted beyond the hot fertile garden of star creation around it, everything beyond the inner ring of stars and gas clouds tend to be in very stable flat plane orbits. The Andromeda galaxy, on the other hand, is going to cause an awful lot of chaos for us, the two supermassive black holes dancing around each other is going to result in a boatload of ejected star systems from both galaxies, and, whether our Solar system is ejected is hard to predict. But life on Earth will be gone before that point anyway. It's actually quite hard to fall into a supermassive black hole because of the gravitational acceleration means you're going very very fast by the time you get near the inner end of a galaxy, so unless your orbital velocity is brought down to virtually zero (which may happen when two galaxies merge), you can end up being ejected from the galaxy by its core's gravity. But you can get close enough into such a dense gaseous region that all life around such star systems are sterilised by radiation. Which isn't much better (or being abandoned by both galaxies for that matter!)

and the material spat out somewhere else in an even bigger bang?

Probably not, in all likelyhood the material will likely sit in the singularity as energy/mass/whatever you want to call a quantum goo of everything squished together into a singular point, until the black hole finishes decaying away well into the black hole era around the 10^40 to 10^100 years period (more massive black holes will take longer to evaporate).

[santa claus]

The Andromeda galaxy, on the other hand, is going to cause an awful lot of chaos for us

Oooh this is getting a little creepy. Since childhood I have had a recurring nightmare. I won't bore you with the details but watching the programme on black holes rekindled it and it sort of provoked me into starting this thread. Andromeda is also a recurrent aspect of the nightmare. I'm doomed. Gulp

ps tell me about Quasars (in simple English please).