If it's been 13-14 billion years since the Big Bang, and the known Universe has a radius of 46.6 billion light years, and since c is the "speed limit", there seems a discrepancy that apparently is explained ...by the link below...something enormously powerful is pushing the expansion of the Universe. (At light speed I would think the radius would be no more than 13-14 billion light years.)
http://www.nytimes.com/2011/01/16/opinion/16greene.html
Wally
Quadrillian
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Your estimation assumes that the universe is expanding as a whole and the outer boundary simply moves outwards at the expansion rate. In fact every unit of space is suject to expansion, so overall the expansion of the universe is cumulative.
Think of a flat page. If the page expands at one inch per minute, then after ten minutes it will be ten inches bigger. However if the page is expanding at one inch per minute per square inch then after ten minutes the page will be far larger (I'll leave you to work it out) as the expansion is cumulative.
Like the sheet in the latter example, the universe is expanding all over, not just at the outer reaches, so after 13.7 billion years it can indeed be 45 or so billion light years across.
Cheers!.
Raymond
You are mixing units.
The radius of the known universe is not known and it could be infinite.
The radius of the Visible Universe in look-back units is 13.7 billion light-years.
The radius of the whole universe is at least three times that of the visible universe. AT LEAST three times does not mean that it is that. It could be much bigger. For all we know, it could be infinite.
The radius of the visible universe in co-moving units is around 47 billion light-years.
If the universe is infinite, then its radius is infinite.
Using the look-back units, the Visible Universe cannot appear larger than the age of the universe multiplied by light speed. But that does not prevent the whole universe from being much bigger.
The problem is not that expansion can have a rate greater than the speed of light. After all, if the universe is infinite, then the maximum rate of expansion is also infinite.
The problem is that the rate of expansion is NOT slowing down as it should (the gravity of the universe should be sufficient to slow down expansion). Since it is not slowing down, then we conclude that there must be some kind of force that keeps it going too fast.
Roughly ten years ago, this force was called Dark Energy (where the word "dark" means unknown).
John S
Actually space can expand faster than the speed of light. That is what inflation is all about.