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originally posted by: blackcrowe
a reply to: ErosA433
I know my questions were poor.
Hopefully a couple of generations of detection doesn't sound too far away.
As for DM clumping. I understand from Prof Lisa Randall video's. It will be clumped as a disk at the centre of our own galaxy. For example. We can't see our own centre to observe it even if we had the instruments to observe it directly.
Will the JWST help in the search for clumped DM in the centres of galaxies? Where the angle is better. Or maybe by it's observation of the earliest stars/galaxies?
It looks like the 2020's are going to be possibly very exciting. By which time. I will hopefully be able to understand it more clearly.
Whichever way it goes. It looks like the answers might not be too long off.
At least you admit the problem, which is a good start, when you say things like 'most people who disagree with relativity are sort of nuts, but I'm one of the few who can be taken seriously'. Bernard Haisch had a worse problem, where he said he's the only person in his entire field of trying to extract energy from the vacuum who is not a nut, and even he is not sure his device would work but he thinks it has enough theoretical foundation to test it if someone will fund the testing. He's probably right that he's the only non-nut in his field, and while I can't prove his device won't work, I wouldn't fund it and I have reason to think it won't work based on what I've seen of the way nature operates.
originally posted by: delbertlarson
What hope does a serious alternative have? With so much noise, all signals will have a hard time not getting lost.
Predicting how nature works is a very risky game. This theory and others like it are long shots.
One does a lot of hard work knowing that most of these ideas probably won't end up being true about nature. That's what doing theoretical physics is like. There are a lot of wipeouts.
Thanks. That's interesting to know, but disappointing that the writer who recently published the article seems to have no clue it was solved like two years ago!
originally posted by: ErosA433
I remembered the above and said, hey do you remember that ANITA result, was it ever solved? And his answer was "Oh that thing? Yeah that keeps popping up in news outlets, but it was solved like... two years ago"
I asked "CCQE?"
The reply "Yep, pretty much."
So you understand it? I don't understand where the second photon is coming from and where he is getting the angle θ of the second photon, can you explain that? From p40:
originally posted by: xpoq47
Thanks, moebius. Great paper. His new model looks good, but if correct will probably take a long time to be accepted.
"The lack of metals tells us this gas is pristine," Fumagalli said. "It's quite exciting, because it's the first evidence that fully matches the composition of the primordial gas predicted by the Big Bang theory."
originally posted by: Arbitrageur
So you understand it? I don't understand where the second photon is coming from and where he is getting the angle θ of the second photon, can you explain that? From p40:
originally posted by: ErosA433
I remembered the above and said, hey do you remember that ANITA result, was it ever solved? And his answer was "Oh that thing? Yeah that keeps popping up in news outlets, but it was solved like... two years ago"
I asked "CCQE?"
"Each interaction of a photon with a second photon, incident at a relative angle θ on an electron, produces a red-
shift of the photon which is then emitted in the direction of the second photon."
So, just a random photon from anywhere, not the same source.
originally posted by: xpoq47
He just mentioned "background light intensity Ibkg emitted by all other galaxies," but he goes into greater detail in section 3.3 of a 2009 paper, if I'm reading it correctly:
But my point was maybe you should consider both metallicity and redshift when looking for an explanation of a broad canvas of observations. If you're trying to isolate just looking at redshift and ignoring metallicity, that's not the big picture.
About the metallicity, I haven't really looked for explanations more prosaic than the big bang. So I don't know, and I'm not prepared to call it swamp gas.
originally posted by: xpoq47
a reply to: Arbitrageur
I look at accelerating expansion of the universe and the big bang as extraordinary claims requiring rigorous investigation of alternative explanations for the data. There are issues with metallicity, as well, like stars containing nothing more massive than helium and dated (probably mistakenly) at more than 14.5 billion years, but there could be extenuating circumstances with those stars. But if another explanation for the redshift can be proved, basing those extraordinary claims solely on metallicity to me seems insufficient to hold up in court.
That wasn't always the case, so as our knowledge has advanced our models have become better and more self-consistent now that we no longer have big problems with stars older than the universe, though our models are probably still flawed in some ways yet to be determined; we are still learning.
There is a remarkable accordance (within their respective uncertainties) between the age of the Universe inferred from the CMB, the age of the chemical elements (Roederer et al. 2009), and the ages of the oldest stars. The difficulty of determining accurate abundances, especially [O/H], will continue to limit the accuracy of stellar age determinations for the foreseeable future, including the era when accurate distances out to a few kpc are obtained from Gaia (Perryman et al. 2001).
I wouldn't characterize gravity as a pushing force as "a tough nut to crack", I'd say it's the opposite of what we observe.
Also, gravity as a pushing force is a tough nut to crack, but if it is the case, then couldn't that explain expansion of our universe (if the fabric of space outside our universe is less dense) better than a big-bang scenario?
Say hello to 1998! That's what everybody expected to find before the 1998 observations of supernovae were analyzed. The accelerating expansion was a big surprise to everybody who expected gravity to be slowing the expansion to varying degrees just as you suggest. Some people say we don't know why it's accelerating but I think it's more accurate to say we don't have any good models to predict it, because most seem to think it's accelerating because the vacuum has a very very small but non-zero amount of energy per unit volume referred to as the "cosmological constant". Space is so big that when you add that all up it ends up being the biggest mass-energy component of our current mainstream model, called "dark energy".
And if there was a big bang, shouldn't gravity as a pulling force be slowing the expansion? Why is it accelerating?
No worries, I almost never use PMs anyway, except to reply to a few PMs that people have sent me first. One high school student PMed me his theory which he didn't want to post publicly for example and asked for my feedback, but other than cases like that I generally don't use them.
Their only action was to then disable my PM server, which I didn't request. It is still locked, even though it probably contains legit PMs that I never saw."