On Wednesday, January 22, 2020 at 8:51:50 PM UTC-7, Brent wrote: > > > > 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. >
*OK, then let's say when the measured value is close to zero, which can't distinguish flat from spherical, cosmologists have a bias toward saying it is flat. I don't mean they assume they're claiming "flat" is the Gospel. AG * > *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. > *They should consider everything of course -- I have no problem with that -- but spherical implies finite, which you have to admit is pretty amazing! AG * > > *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. > *OK, then taking all the points the authors raise, what probability would you give that it's curved, not flat? I just want your sense of the paper's main claim, or suggestion. AG * Brent > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/86894144-8602-47ff-8d8b-30ce4a58dd6c%40googlegroups.com.
