Astronomers See Evidence of Something Unexpected in the Universe

nwr writes: That's what I am questioning.

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.

So what mechanisms are you pointing to that could create this wavelength independent redshift that appears to increase with distance from the Milky Way?

I am not pointing to mechanisms.

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

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

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

nwr finds the evidence for expansion to be inadequate, so I thought I would at least discuss why I think it is adequate to draw a scientific conclusion (i.e. a tentative conclusion).

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.

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

Yes, as far as I know.

But they seem not to conclusively demonstrate expansion.

If you take red-shifted light, and red-shift it even more, you get microwave radiation. So I don't see that as independent evidence.

nwr writes: But they seem not to conclusively demonstrate expansion.

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.

I don't need to play word games.

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

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

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

nwr writes: I don't need to play word games.

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

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

I have the same question as Modulous.

--Percy

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

We use "theory" too casually.

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.

What does "conclusively demonstrate" mean to you in science?

It would have been better if I had used "convincingly".

A theory should establish standards for research in the area.

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'.

nwr writes: What does "conclusively demonstrate" mean to you in science? It would have been better if I had used "convincingly".

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

It would have been better if I had used "convincingly"

Duplicate

Edited by NoNukes, : No reason given.