Q & A

CME & Comets Tail Query --- I bought BANG and I watch The Sky at Night and even though I do not understand what is going on out there the subject fascinates me, I think it should be simple but it isn't and where my amateurishness shows through is on my initial thoughts on looking at the image. i.e. If light has no mass what was it that bent and tore off the tail.?

I know I am going to feel silly for asking this but if you don't ask you will never truly learn.

Al the best to you

Gordon Jennings

Gordon Jennings, UK

A very sensible question, actually, Gordon. Yes, you're completely right about light having no mass. Strangely enough, though, it seems that light can still get deflected by gravity, or perhaps 'appear to be deflected' might be a more appropriate description - since according to Einstein, in his brilliant General Relativity theory, it is SPACE that is distorted by gravity, and light is still taking the shortest path.

HOWEVER !!! This has nothing at all to do with the tail of this unfortunate comet ! The tail is made of gas and dust, which simply reflects light, the same as any other object ... it's a bit like a cloud of smoke on earth, for instance. So when the high-speed material material ejected from the Sun hits it, the tail matter gets swept away, just as our cloud of smoke would ... even more so, since there is no air around it to slow it down out there in space. It's pretty spectacular, isn't it ?! I love these things which turn up and have not been predicted. Once we have seen this, it's easy to come up with reasons why it happens ... but until this series of pictures was taken, to the best of my knowledge, nobody had ever predicted this phenomenon.

I love Astrophysics !!!

Cheers !

Brian May

First of all, congratulations for the thesis and I wish you all the best for August 23rd! And of course, thank you for the beautiful music. I was discussing these topics some days ago, with a friend. What do you think about them?

1. If the second law of thermodynamics establishes that Entropy (measure of disorder) always increases… why, from the chaotic state of post-Big Bang, this universe --more complex and organized-- was built?

2. And, If the universe was created as a result of the Big Bang, why all the galaxies don’t move away from a single common point (where the explosion occurred), but they get farther away from each other as if the space between them grew?

Mariana de Giuli - Buenos Aires, Argentina.

1. Well, the entropy of that (theoretical) tiny embyo universe was actually very low. You see, entropy, or order, is partly defined by how confined (or defined) in space everything is. It's like if you swept up all the dust in your room and confined it to a small dustpan. You would have decreased the entropy of the dust. But the second law of Thermodynamics would still apply, because you would have dissipated so much energy (in heat and noise, etc) in doing the job.

As the Universe expands, the matter in it becomes more and more spread out, so, overall, its entropy is increasing. Stephen Hawking has discussed the consequences of the possibility of us being in a collapsing universe. In this situation, entropy ought to decrease with time. But since we seem to measure the direction of the arrow of time by Entropy anyway, presumably time would be running backwards, and so we would not know !!! Intriguing ideas.

2. The second part of your question is a little harder to visualise. I recommend our BANG! book for a full explanation. But the analogy of ink spots on an expanding balloon has often been used to give an idea of what is going on. On the two-dimensional surface of the balloon (analogous to the 3-dimensional universe we live in), as we blow up the balloon, the spots move away from each other. But there is no 'centre' to their motion ... an ant could walk all around that balloon surface, measuring the rate at which the spots were moving apart. He would never come to a boundary, and he would never find a centre. But all the spots would be moving apart at the same rate.

The reason there is no 'special' place or centre, is because ALL points in our universe AND ALL THE SPACE THEY EXIST IN were in that tiny embryonic speck. Space did not exist outside the primeval 'atom'. So it is not a question of stuff expanding into an already existing space. Like the surface of our balloon, it pretty much did not exist before the expansion. I hope this helps !!!

cheers

Brian May

First of all, a big thankyou to the three authors involved. By far the best Xmas present my mother has bought me in my 44 years on this Planet. (I cant speak for any other Mothers I might have had on other Planets, if I have. So, apologies to them, just in case.) It seems that we are only able to view the universe back to about 13 Billion years, as stated in your book. And our observations all seem to indicate that the Universe is expanding at an ever greater rate. Does this mean that we cannot work out in which direction from whence we came, and in which direction we are going relative to the Galaxies around us?

Could it be that the Big Bang is an on-going process and we
just cannot see back far enough to observe this. If this was the case and the Universe was like a Bell that had been rung, could it be that the expansion is caused by space trying to flatten itself out (back to its normal state of stable nothingness) and Gravity is in fact a consequence of this. So the force of empty space and normality is greater. In other words. The greater the space between regions of mass, the greater the force of expansion. I was thinking about the mystery of Dark Energy and maybe there is no such thing. It is just the need for normality reacting to an abberation, a fault in the lining, so to speak. Please excuse my lack of understanding. I regularly hurt my head with this stuff and love doing it.

Richard Upson - Malvern, Worcs, England

I'm not sure you'll like the answer, but there is no direction from which we came! As space itself is expanding ALL the galaxies (apart from the very local ones) are moving away from us, and from each other. Thus the Universe is expanding, but it's not as though we started in one place.

Chris Lintott

I seem to be stuck on p36, the cosmic conspiracy. I have tried searching the web for more info but it just comes up with UFO stories. Can you point me to an explanation for dummies. Many thanks
for a great book. PS My daughter of 3 months loves the cover.

John O'Brien - Birmingham

An excellent, more detailed explanation of the issues involved in inflation is 'The elegant Universe' by Alan Guth. If you don't have time for that, you might have more luck googling the 'horizon problem', the conspiracy's other name. The really short version is that astronomers are uncomfortable with the idea that two parts of the Universe far enough apart so that light can never have travelled from one ot the other, nevertheless will look broadly similar.

Chris Lintott

Am i right in thinking the general consensus nowadays is that nearly every galaxy contains a super massive blackhole? And if so is there any conjecture that these blackholes may have originated from the super massive first generation stars you mention in your book? Or is simply not enough know yet? I'd appreciate any thoughts on this and thanks very much for a great book!

Jamie Farr - London

As you say, nearly every large galaxy (small things like the Magellenic clouds don't count) seems to contain a black hole at its centre. The evidence is best for the Milky Way, but we see their traces in other galaxies too. How they got there is an open question; it seems that there hasn't been enough time in the Universe to build up such massive black holes if you start with a star-sized one. They may have formed directly from collapsing gas during the early stages of star formation, or perhas
something more complicated (merging black holes, perhaps?) is happening. We simply don't have enough data to decide.

Link : Milky Way black hole

Chris Lintott

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I seem to be stuck on p36, the cosmic conspiracy. I have tried searching the web for more info but it just comes up with UFO stories. Can you point me to an explanation for dummies. Many thanks for a great book. PS My daughter of 3 months loves the cover.

I seem to be stuck on p36, the cosmic conspiracy. I have tried searching the web for more info but it just comes up with UFO stories. Can you point me to an explanation for dummies. Many thanks
for a great book. PS My daughter of 3 months loves the cover.