Cosmic Horizons

Proton: a life story  by Geraint F. Lewis 10 35 years: I’ve lived a long and eventful life, but I know that death is almost upon me. Around me, my kind are slowly melting into the darkness that is now the universe, and my time will eventually come. I’ve lived a long and eventful life… 10 -43 seconds: A time of unbelievable light, unbelievable heat! I don’t remember the time before I was born, but I was there, disembodied, ethereal, part of the swirling, roaring fires of the universe coming in to being. But the universe cooled. From the featureless inferno, its character crystalized into a seething sea of particles and forces. Electrons and quarks tore about, smashing and crashing into photons and neutrinos. The universe continued to cool. 1 second: The intensity of the heat steadily died away, and I was born. In truth, there was no precise moment of my birth, but as the universe cooled my innards, free quarks, bound together, and I was suddenly there!...

I've written an article 'On the Relativity of Redshifts: Does Space Really "Expand"?' which has appeared in Australian Physics (2016, 53(3), 95-100). For some reason, the arXiv has put the article on hold, so you can download it here . I like it :)

Obligatory "sorry it's been a long time since I posted" comment. Life, grants, student, etc All of the usual excuses! But I plan (i.e. hope) to do more writing here in the future. But what's the reason for today's post? Namely this video posted on your tube. The conclusion is that humans are destined to explore the Local Group of galaxies, and that is it. And this video has received a bit of circulation on the inter-webs, promoted by a few sciency people. The problem, however, is that it is wrong. The basic idea is that accelerating expansion due to the presence of  dark energy  means that the separation of objects will get faster and fast, and so it will be a little like chasing after a bus; the distance between the two of you will continue to get bigger and bigger. This part is correct, and in the very distant universe, there will be extremely isolated bunches of galaxies whose own gravitational pull overcomes the cosmic expansion. But the rest, just ho...

Things are crazily busy, with me finishing teaching this week. Some of you may know, that I am writing a book, which is progressing, but more slowly than I hoped. Up to just over 60,000 words, with a goal of about 80 to 90 thousand, so more than half way through. I know that I have to catch up with papers, and I have another article in  The Conversation  brewing, but I thought I would write about something interesting. The problem is that my limited brain has been occupied by so many other things that my clear thinking time has been reduced to snippets here and there. But one thing that has been on my mind is tests of cosmology. Nothing I post here will be new, but you might not know about it. But here goes. So,  the universe is expanding.  But how do we know? I've written a little about this previously, but we know that almost 100 years ago,  Edwin Hubble  discovered his " law ", that galaxies are moving away from us, and the further away they are, ...