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Horizon on black holes
It seems I’ve been doing the scientists an injustice. There was a Horizon programme on BBC2 and BBC HD on the 3 November 2009 about current research into black holes which was not only hugely exciting but was also pretty easy to follow, even with my very limited scientific undestanding! It was billed as being about a group looking at black holes for clues to what was going on before The Big Bang. I’ve got the HD version on the hard drive of our FreeSat+ box, and I’ll be watching it several times. Even the first watching (aided by the pause button) produced eight pages of probably illegible notes (more-or-less decrypted at the end of this section)!
I had fallen into the trap of taking literally statements that The Big Bang was not just the beginning of the Universe, but of space and time themselves. Make that our Universe, our space and our time! I feel better about my simplistic ideas above now.
There was a lot of stuff emanating from the theoretical physics fraternity, but what was really exciting was the information about the guys looking for empirical evidence to help prove - or disprove - what the theorists come up with.
I’d always assumed that the death of a star was a pretty slow process, probably taking thousands or even millions of years. Forget that. 215 million light-years away is (or was, 215 million years ago) a galaxy which our telescopes can only see as a single bright blob - millions of stars appearing to us as just one. Close to it was a very bright object which turned out to be a huge star going supernova (dying explosively). Over a relatively short timespan it was possible to see this star explode and then vanish - short enough for the whole process to have been stored in the archives of the Hubble Space Telescope: from star to supernova to...nothing. The conclusion? That the total absence of radiation where the star should be (or have been, 215 million years ago) must mean that it collapsed to form a black hole.
Much closer to home, it has been discovered that there is a huge black hole at the very centre of our own galaxy, The Milky Way - a hole far too heavy to have been produced by the collapse of a single star (a stellar black hole), called a supermassive black hole. One scientist has plotted the orbits of the 30 stars closest to this monster and has been able to calculate that the mass of the ’hole’ is of the order of four million times that of our sun. It is now believed that a black hole exists at the centre of every galaxy, and produces the gravity that holds all the components of the galaxy in orbit around it. Other galaxies are believed to have supermassive black holes at their centres which are several thousand times the mass of ours - so maybe 20 billion (20,000,000,000) times the mass of the sun!
From this, black holes are now no longer seen as dangerous things but are now believed to be crucial to the whole structure of the Universe.
Shep Doleman, an astronomer working at an observatory outside Boston in the USA is engaged on an amazing project. By using a supercomputer to integrate data from radio-telescopes all over the USA, he is creating a single ’virtual’ telescope equivalent to a real one with a dish as big as North America. There’s a way to go with this - he needs to link in far more telescopes - but he already has a rack of arrays of very large hard drives full of telescope data, and hopes with 10 years to produc a to photograph of the area around our ’local’ supermassive black hole with sufficient resolution to reveal the ’halo’ which General Relativity predicts to be visible around every black hole. This is caused by the black hole’s monstrous gravity focusing the radiation from bodies behind the hole - bending the rays as they pass to concentrate them. I think the halo corresponds to the black hole’s ’event horizon’ (Doleman describes it as ’the shadow of the event horizon’) - but that’s getting a bit abstruse for me. However, he believes that this project could achieve a huge step towards the Holy Grail of a ’unified theory of everything’. Sadly, Doleman’s work doesn’t seem to have hit the Web in any form useful to the layman yet. I’ll keep googling him, and meanwhile I’ve just discovered that googling ’"black hole" "centre of galaxy"’ produces thousands of hits, with the early high-relevance ones offering all sorts of goodies!
And that, it seems, is much-needed. Apparently General Relativity is brilliant at predicting the behaviour of large objects - planets, stars and galaxies - but no use at all for very small objects such as atoms and the neutrons and electrons of which they are composed. Quantum mechanics, on the other hand, is great at the little stuff but useless for the bigger items. And, unfortunately, there’s a huge gap between the two branches of theoretical physics. As one scientist said: ’They just don’t talk to each other.’
To make matters worse, at the centre of each supermassive black hole there is a ’singularity’ - a point at which a huge amount of mass is concentrated in a very tiny body, like a less massive version of what is believed to have existed just before The Big Bang. To understand these black hole singularities would take us a long way towards understanding The Singularity which was, if you like, the embryo of our Universe.
Apparently Einstein’s Relativity equations break down completely when trying to deal with phenomena like black holes, producing results that equal infinity, so it appears that Quantum Mechanics may be needed for this because, for all its collossal mass, a singularity is very small.
The gap between Quantum Mechanics and General Relativity could, it is thought, be bridged by a new science of Quantum Gravity. The three together would then be the basis of a ’unified theory of everything’. All these are theories, but experimental projects like Shep Doleman’s may provide the empirical evidence needed to verify the theories and weld the whole structure together. And his project is expected to yield serious data in around ten years.
So I may yet live long enough to see the Holy Grail found at last.
If you have found what I say on this page remotely interesting, you should watch this amazing programme. It’s available on BBC iPlayer at http://www.bbc.co.uk/programmes/b006mgxf (does anyone know how to save programmes from iPlayer?).
If you know more science than I do, you may wish to comment on what I have written here. If so, please click the Contact me button on the right. I’ll be happy to quote any comments here, unless you ask me not to...
My notes (as far as I can read them)
Apologies for errors. Sitting in an armshair with a shorthand-notebook when your handwriting has suffered from 16 years’ dependence on word-processing is no way to record ideas and thoughts - even with the benefit of the pause button! The items in single-quotes, however frivolous, are all from heavyweight physicists! This lot were some of the cheeriest scientists I’ve ever seen.
’Black holes could force us to abandon everything we thought we knew about the Universe.’
’The symbol of what it is we don’t understand about the Universe.’
Black hole only believed to be at the location because scientists had photos of v bright star, then supernova, then nothing at the same spot in the sky. 215m light-years away. Supernova as bright as a galaxy. Hubble archive - 2ys wait doe supernova to disspiate - then nothing.
Gravity holds the whole Universe & all its components together. Gravity is caused by bending of space & time (General Relativity).
General Relativity predicted black hole - distorting space + time to breaking point. 3D analogies to describe? All theory based on maths, not evidence. Maths problem at heart of General Relativity description of black hole breaks down whole theory. Einstein thought black holes couldn’t form so theory not a problem - ’proved’ it - he wanted to know black holes could never exist.
1970’s - x-rays showed probable black holes - x-rays produced by high temperature of matter falling into black holes.
Centre of our galaxy (Milky Way) a black hole? 30 star orbits used to calculate mass of object at centre - 4m x sun! Size of orbits says object so small it must be a black hole. Too big for one [collapsing] star’s collapse. ’Supermassive black hole’. All galactic bodies orbit this black hole. Other galaxies - black holes up to several thousand times heavier. All galaxies? 1 billion x sun! Mass of galaxy found to be roughly proportional to that of black hole - 1000x. Galaxy forms round black hole? Also millions of stellar black holes in each galaxy.
’A dominant force in the evolution of the Universe?’ So millions of examples of General Relativity breakdown.
Quantum mechanics needed to describe particle behaviour cos General Relativity doesn’t work. Singularity at heart of black hole needs Quantum Mechanics? But can’t describe gravity. Kept separate - exception where objects v. small - black holes!
Quantum Gravity theory falls apart because Quantum Mechanics and General Relativity incompatible - ’most embarrassing problem we have in physics’. Failure of Quantum Mechanics and General Relativity to understand black holes means they are only approximations to laws governing Universe.
’The equations no longer make any sense!’
’Physics is having a nervous breakdown.’
’Nature is smarter than we are.’
’There aren’t any questions much bigger than this!’
Understanding black holes could [answer?] the biggest question of all. Singularities at centre of black holes & Big Bang. Understand black holes - understand Big Bang. What was there before the Big Bang?
Evidence? Shep Doleman. Trying to photograph black hole! Milky Way centre. Supercomputer [?] from many radio telescopes & integrates in ’virtual dish’ size of N.America. Much higher resolution than ever before. ’Shadow of event horizen’ of Milky Way black hole - 10 yrs? Need to link more telescopes. Ring of deflected radiation from bodies behind black hole.
’Unified Theory of Everything.’
Personal site for Paul Marsden: frustrated writer; experimental cook and all-round foodie; amateur wine-importer; former copywriter and press-officer; former teacher, teacher-trainer, educational software developer and documenter; still a professional web-developer but mostly retired.
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