Message 61 of 86 (829859) 03-15-2018 2:57 PM

Reply to: Message 60 by nwr 03-15-2018 11:32 AM

So what mechanisms are you pointing to that could create this wavelength independent redshift that appears to increase with distance from the Milky Way? Why do you see expansion as a questionable conclusion?

A second check on the conclusion of space expansion is the CMB. If you run the expansion backwards you would predict that all matter would have been crammed into a very small space, and would have been really, really hot. Initially, this matter would be a plasma and would be opaque to EM radiation. Some time later, as the matter expanded and cooled, would you get atomic hydrogen which does allow EM radiation to move freely in the universe. That prediction was confirmed in the form of the CMB which is EM radiation that is coming from everywhere in the universe.

Message 62 of 86 (829863) 03-15-2018 4:09 PM

Reply to: Message 61 by Taq 03-15-2018 2:57 PM

I am suggesting that conclusions about expansion are premature. We do not know nearly enough to jump to such conclusions.

Message 63 of 86 (829864) 03-15-2018 4:14 PM

Reply to: Message 62 by nwr 03-15-2018 4:09 PM

Would you agree that all of the observations we have thus far are consistent with expansion?

Message 64 of 86 (829891) 03-16-2018 11:00 AM

One of the hallmarks of a well supported theory in science is the consilience of multiple lines of evidence. It is always a bad idea in science to draw strong conclusions from a single experiment, or even a single type of experiment. Most recently, the Higgs boson was discovered at CERN, and this discovery was made by two separate and isolated labs using two different instruments. The fact that their conclusions agreed with one another only further strengthened their conclusions.

So what are the independent lines of evidence for the Big Bang and the continued expansion of space? There are at least 3:

1. The correlation between redshift and distance.

2. The cosmic microwave background.

3. The ratio of light elements.

The third piece of evidence has to do with the expected ratios of hydrogen, helium, and lithium in the universe. If the universe started out as a really hot and dense ball of matter and energy then we would expect to see about a 3 to 1 ratio of hydrogen to helium with all other elements making up about 2% of the total which is exactly what we see, as discussed here.

So we have three completely independent lines of evidence, all of which match the predictions made by the Big Bang theory which includes continued expansion of the universe. This is why I agree that the Big Bang model deserves to be accepted as tentatively true. I think it has passed the tests needed to gain consensus within astrophysics.

I would be interested in hearing why people think that these independent lines of evidence are inadequate.

Edited by Taq, : No reason given.

Message 65 of 86 (829917) 03-17-2018 4:00 PM

Reply to: Message 63 by Taq 03-15-2018 4:14 PM

But they seem not to conclusively demonstrate expansion.

Message 67 of 86 (829921) 03-17-2018 4:35 PM

Reply to: Message 65 by nwr 03-17-2018 4:00 PM

Do you mean "conclusively" as the opposite of "tentatively"? If so then I think everyone would agree merely on the principle that science demonstrates nothing conclusively, only tentatively.

But if by "conclusively" you do not mean the opposite of "tentatively" then what would be an example of something science has "conclusively" demonstrated?

--Percy

Edited by Percy, : Typo.

Message 68 of 86 (829922) 03-17-2018 4:56 PM

Reply to: Message 67 by Percy 03-17-2018 4:35 PM

I don't see that big bang theory does anything for us. So better to call it an hypothesis, rather than a theory.

Message 69 of 86 (829923) 03-17-2018 6:04 PM

Reply to: Message 68 by nwr 03-17-2018 4:56 PM

You think utility determines whether something is a theory or a hypothesis?

Message 70 of 86 (829927) 03-17-2018 6:17 PM

Reply to: Message 68 by nwr 03-17-2018 4:56 PM

I would like to understand your meaning. What does "conclusively demonstrate" mean to you in science?

I have the same question as Modulous.

--Percy

Message 71 of 86 (829934) 03-18-2018 12:20 AM

Reply to: Message 69 by Modulous 03-17-2018 6:04 PM

A theory should establish standards for research in the area. The Hubble red shift did that, by providing a new standard for measuring distance to remote galaxies. I'm not seeing anything comparable with BB.

Message 73 of 86 (829952) 03-18-2018 3:12 PM

Reply to: Message 71 by nwr 03-18-2018 12:20 AM

Could you explain what you mean? I mean I think the classic "a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment." is fine, and not at all 'casual'.

Message 74 of 86 (829957) 03-18-2018 4:13 PM

Reply to: Message 72 by nwr 03-18-2018 12:23 AM

Okay, so using the base word "convince"...

If one considers the *convincing* evidence that Taq enumerated in Message 64:

1. The correlation between redshift and distance.
   
2. The cosmic microwave background.
   
3. The ratio of light elements.

And if one considers that the response in Message 66 was wholly *unconvincing* in terms of rebuttal or any indication the evidence described was understood.

And if one considers that this information has *convinced* a consensus of scientists within the relevant scientific community about what this information means as theory.

And if one considers the details of how a theoretical consensus is built as Modulous describes in Message 73, "a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment."

And if one considers that the explanation, the theory, has made successful predictions.

Mustn't one concede that expansion has been *convincingly* demonstrated to science, though of course still tentative and open to change?

It is understood that some might demur from the consensus, but to this point no *convincing* arguments have been advanced against it. Wikipedia has a section on alternatives: Redshift periodicity and intrinsic redshifts. Halton Arp receives a good deal of mention.

--Percy

Message 75 of 86 (829960) 03-18-2018 4:28 PM

Reply to: Message 72 by nwr 03-18-2018 12:23 AM

Duplicate

Edited by NoNukes, : No reason given.