Astronomers See Evidence of Something Unexpected in the Universe

First there was the static universe, then an expanding universe slowing due to gravity, then an accelerating expansion, and now possibly a time-variable accelerating expansion?There were two independent research efforts based on different principles that established the accelerating expansion. I'd like to see something similar for this time-variable finding.--Percy

That was a long time ago now, I don't recall the details, so I went to Wikipedia and it makes it seem like the two efforts used the same techniques. They both observed Type 1a supernova, but not in the same way. High-Z Supernova Search Team, Supernova Cosmology Project gives some details:

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The High-Z team observed a large area near the celestial equator so they could observe both hemispheres for follow-up details. They aimed for a limiting magnitude (the faintest magnitude visible from Earth) that is slightly fainter than the expected maximum brightness (Schmidt, Suntzeff, et al).

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The Supernova Cosmology Project Team calibrated the maximum magnitudes of supernovae to use as standard candles in their redshift measurements. They observed seemingly empty sky until they found a dozen or so supernovae. This method increases the chances of finding the supernovae before max magnitude, so they could easily measure the max (Perlmutter).

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Supernovae, an accelerating universe and the cosmological constant also characterizes some of the differences:

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Meanwhile, the Supernova Cosmology Project (SCP) continued to search for high redshift supernovae. By 1997, the SCP had a preliminary result (14). Based on seven supernovae discovered in 1994 and 1995, the Caln/Tololo low redshift sample, and a variant of the luminosity-light curve relation, they concluded that the evidence favored a high matter density universe, Ωm = 0.88 0.6. They argued that the supernova data at that point placed the strongest constraint on the possible value of the cosmological constant, with their best estimate being ΩΛ = 0.05.

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Another group, the High-Z Supernova Team (of which I am a member) introduced a number of new developments, including custom filters, which help minimize the effect of redshift on interpreting the observed fluxes, and ways to use observations in two colors to estimate the absorbing effects of interstellar dust on the supernova light by measuring the reddening it produces. The High-Z team found its first supernova, SN 1995K, in 1995 (15) and now has detected more than 70 events. Fig. ​Fig.22 illustrates some of the high redshift supernovae discovered by the High-Z Team that have been observed with the Hubble Space Telescope (HST). The supernovae are, in general, found and studied from ground-based observatories, but the HST provides much better separation of the supernova from the background galaxy, which leads to more precise measurements of the supernova’s light curve.

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This refresher doesn't really sound familiar. What I recall from when I read the Scientific American article from 20 years ago (they don't make the archives available for free and I'm a cheapskate) is how greatly the different techniques employed by the two teams increased our confidence in the results, and it described the key differences.
What I quoted above doesn't seem to do that. You can tell they took different approaches, but not what it was about those differences that contributed to the confidence in the results.--Percy

I don't recall this now, but I hope my focus was on the lack of anomalous evidence pointing in the direction of your doubts, which seem based more on the general kind of concerns that can be raised about any field of science, i.e., a) the limitations of human knowledge; and b) knowledge is revised over time as we learn more.--Percy

I think Nwr's objection is more epistemological. He might agree that on one level what you describe is objective while seeing that objectivity dissolve into mere human consensus and assumptions on deeper levels. The best example I can think of is that we still haven't defined mass in terms of fundamental constants - there's still a standard kilogram kept in a vault outside Paris.--Percy

I have to admit that I see the same similarity that Caffeine sees. What you said in Message 19 that seemed to me so similar was: Here's an example of the point Creation was making in Falsifying a young Universe. (re: Supernova 1987A). This is from Message 676: Creation's expression is more primitive and he uses different terminology, so summarizing, Creation believes we can only know the laws of nature for the local region, what he calls the "fishbowl" that he concedes extends only as far as our deepest space probes, the Voyagers. He even echoed your comment on the speed of light. This is from Message 703: To me he *does* seem to be saying the same thing as you.--Percy

But Creation wasn't just arguing that "scientific laws might be different elsewhere." He was arguing that they might be different and that we can't know what they are. This seems not just very similar but identical to your position that we can't know whether scientific laws are different in other parts of the cosmos.NoNukes makes the point that Creation was focused on time, but Creation wasn't capable of generalizing and made his points with examples. Time was his initial example, but he moved on to say we couldn't know relativity behaved the same in deep space as it does here (Message 682), and he said we couldn't know the speed of light out there is the same as here (Message 703). He used examples rather than generalizations, but he obviously believed we can't know whether scientific laws out there are the same as here.You and Creation also have the same issue of identifying a boundary between the "here" where we understand how scientific laws operate and the "out there" where we don't. Creation gave the "here" a name, the fishbowl, and he was willing to grant that it extended at least as far out as our deepest probes, the Voyagers. Wouldn't you have to concede the same thing, that since the Voyager probes are still operating that the boundary between the "here" and the "out there" must be at least that far away?While the terminology and descriptions differ, to me your and Creation's positions are one and the same. Were you and Creation to find yourselves in a discussion about this with the rest of us you would find yourselves arguing on the same side.--Percy

Pushing through the difficulties involved in communicating fine distinctions may be rewarding in a couple of ways. You may eventually find success, and it could lead to unexpected insights, either for you or others.--Percy

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?--PercyEdited by Percy, : Typo.

I would like to understand your meaning. What does "conclusively demonstrate" mean to you in science? I have the same question as Modulous.--Percy

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

That's fine. Begin any time. Someone recently said, "I don't need to play word games." They seem good words to live by.--Percy