On Wednesday, January 22, 2020 at 10:41:31 PM UTC-7, Brent wrote: > > > > On 1/22/2020 8:18 PM, Alan Grayson wrote: > > > > 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 know what "bias" would mean in that context. They don't say it is > flat. They hypothesize, consider, contemplate,...they say, "If is flat, > maybe it is because..." > > *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 * > > > Their claim is they have new data that favors positive curvature over zero > or negative curvature to a significant degree (in the statistical sense of > significance). >
What's your opinion of the claim? Is it plausible? AG > > Brent > > > 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] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/86894144-8602-47ff-8d8b-30ce4a58dd6c%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/86894144-8602-47ff-8d8b-30ce4a58dd6c%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- 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/23fc2890-3eaa-40b6-901c-3df516ea7b4f%40googlegroups.com.
