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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
Isn't cosmogony caught between the Scylla of creation out of nothing or the Charybdis of an infinite regress of initial conditions, and existence tout court, which would attract the question: why should
anything be?
Akhtar Said - Pakistan
I think the answer is yes! However, faced with this problem all we can do is continue to search for a reason for the the initial conditions for creation out of nothing (as you put it), or continue to work our way back along the 'infinite regress' of initial conditions.
Chris Lintott
I have just finished preparing a talk for my local astronomy society and was reading Bang! I was surprised at the figure on p31 which states that the (observable) Universe is 10^25m. I would like to get this right as the talk involves a journey from the Planck length to the size of the universe!
Is the observable universe not much larger than this? The light that reaches us has travelled for 13.7 billion years, but during this time, the Universe has been expanding, so the territory it has already covered represents a greater distance than its travel time would suggest.
The article: http://en.wikipedia.org/wiki/Size_of_the_universe
gives a figure of about 100 billion light years diameter. Which is roughly 10^27m.
NOTE: even if we use the 13.7 billion light years figure, I make the diameter roughly:
2.8x10^10 x 10^16 = 2.8 x 10^26
Many thanks for any clarification.
Steve Hill - Bath, UK
Oops. You are correct, and we are wrong. Sorry!
Chris Lintott
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