Recent content by RogerWaters

Thanks for clearing this up. I’m reading ‘heart of darkness’ by Ostriker and Mitton which is in between popular science and actual physics, but closer to popular science - it is a fantastic historical account of the development of LCDM model of cosmology, but the chapter on dark energy is a bit...

Right, I read this frequently and understand the intuition as far as resulting in flatness but not mass-energy density being at the critical value. I appreciate now that these are one and the same thing, as opposed to critical mass-energy density being a side effect. However, exponential...

Nope not at all.

I'm sure it just comes out of the math that way, but are there any analogies or thought experiments that might help one understand why inflation does this? I am supposing the critical density for flatness to be a mass-energy (or stress-energy) density of the universe (or inflaton field) which...

I've been reading this over a few times. How did inflation change the critical density, such that it become equal to the mass-density of the universe (which was then the stress-energy density of the inflaton field)? As a side note, you say (and I have commonly read) that the stress-energy...

Was this the BOOMERanG experiment?

Thanks - that's very helpful. These are no doubt obtuse questions I'm asking, but I hope questions coming from non-physicists are not deemed too excruciating on these boards.

This? I'm not sure what you are suggesting I take from it by just saying 'read it carefully'. Ibix related the causal sequence in a way which made sense to me, so if what he said is correct then it's all good. I'm still interested, though, in how cosmic inflation was such a robust process for...

For sure, I just found the NASA page to be a nice inventory of a bunch of different hypotheses I've been reading about in books but which were overlapping in my head.

Thanks Ibix (andPeroK). So inflation causes critical density, which in turn causes flatness. How does inflation produce the right density of matter and energy so robustly? Is it possibly to relay the idea here in vague terms?

Now I’m really confused. I thought you originally said that it’s not dark energy (by extension, density, dark energy making up the critical density) that causes flatness but cosmic inflation. Now I interpret you to be saying that mass/energy density causes flatness, in line with the second...

Thanks for clearing that up guys. The mass/energy density of the universe needs to be a certain number because we know the universe is flat. Without dark energy that density was measured to only around 30 percent of the needed value. Dark energy was then discovered and, remarkably, made up the...

Thanks Peter, In that case, before the discovery of accelerating expansion, why is the 70 percent mass-energy contributed by this dark energy described as 'missing': missing in relation to the universe being flat? If cosmic inflation happened, wouldn't it have pushed any initially-curved amount...

When it comes to explaining some phenomena, I think in terms of mechanisms whereas physics explains through mathematics. With this in mind, I'm trying to compare and contrast the differences between the candidate explanations for dark energy, as nicely summarised on the NASA website...

As I understand, the main theoretical virtue of Guth's inflation hypothesis is that it explains a bunch of otherwise hard-to-account-for phenomena under the standard big bang model without inflation: the Horizon Problem, the Flatness problem, the Monopole problem, and also the problem of how...