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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?
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?
Richard Upson - Malvern, Worcs, EnglandI'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
John O'Brien - Birmingham |
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