Tinlad wrote:I realise this is probably not a great explanation. I'll try and do better if you want! Because I love this shit.
Au contraire mon ami - you explain it extremely well.
I may be a bit thick (shut up!

) but I find I need to "feel" something in my bones before I can understand it.
I've read one book on relativity 7 times in an effort to comprehend on a human level what "spacetime" actually means in reality.
I'm getting there, I rekcon 40 or so more times will be the charm.

Anyway, could it be that spacetime
appears flat because the actual universe (as opposed to the observable universe) is of such an enormous size?
I mean the way say Britain for example
appears flat on the surface of the earth when you're walking around on it because the earth is so big,
but the same landmass stretched over the moon would be more obviously curved.
I've read that conservative estimates for the rate of expansion of the universe during the first fractions of a second of the rapid phase of expansion after the big bang would mean that what the observable universe is to the actual universe would be like what a grain of sand is to the observable universe.
My maths is truly terrible but the conservative figure I remember seeing was something like a factor of whatever the number was to a power of 10 - but the expansion rate could have been as much as to a power of 90.

So could the universe just be
so big that spacetime
appears flat to us?