On 1/22/2020 6:26 PM, Alan Grayson wrote:
On Wednesday, January 22, 2020 at 6:29:32 PM UTC-7, Brent wrote: On 1/22/2020 5:08 PM, Alan Grayson wrote:When you measure something and it is so close to zero as to be indistinguishable from zero, then taking it to be zero is not an assumption.*Why don't you compare the measured value with the curvature of a sphere 1 LY in diameter, or !0^6 LY in diameter? Do you really think the curvature would be significantly different from the measured value of the universe? I doubt it. So, taking it to be zero, is just what you prefer, nothing more. CMIIAW, AG*No, because zero is a physically interesting value. There maybe some unrecognized symmetry principle that makes it zero. It's unlikely that there's some symmetry principle that makes it 1e-6. That's why physicist look at the data as evidence for zero. Of course they may be wrong. But it's not because they are just pulling assumptions out of thin air. Brent*Why assume there's some symmetry principle to drive the curvature to zero? *
You keep using the word "assume" which means to "take as given to be true". Scientists hypothesize, they only "assume" for purposes of testing the consequences.
*It could be just because the universe is huge. *
Or it could be because some principle makes it zero. The latter would be a more interesting discovery, so that's why cosmologists consider it.
*I don't think the cases are distinguishable by measurements. OTOH, the article points to some measurements of the CMBR that imply a spherical universe. Are they in any way persuasive? AG *
Nobody gets persuaded by one observation that contradicts the prior observations. What if they had happened in reverse time order...you'd be asking if the evidence for flatness is persuasive.
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