Is the inflationary universe a scientific theory? (backreaction.blogspot.com)

49 points by mpweiher 128 days ago

17 comments

neom 128 days ago

This is generally a really good interview with Penrose - Additionally, there are a few spots scattered through it where he specifically talks about why he has come around to Inflation as a reasonable theory.

Sir Roger Penrose: What We All Need to Know About Physics https://www.youtube.com/watch?v=QNqnbELDO5A

badosu 128 days ago

I really cringed at the title and explanation on the subsequent article, even though it presents good information.

Rigorously speaking a theory is a body of established scientific knowledge, in which case is classically defined to be a set of propositions that describe phenomena and has proved to be the case for some measure of accuracy via experimentation.

So the theory of inflation was never a theory in this sense, just an hypothesis that seems to hold some water, more akin to a conjecture. 'Theory' in this case, and in most of human interaction, being used for practical purposes to signal that we're talking about something scientists take seriously and waste time upon.

That's not a problem for me, just an annoyance when people use the term in a more serious and controversial manner without understanding this distinction.

    mannykannot 128 days ago

    The inflation hypothesis is too important an issue for cosmology to be dismissed as an issue of the usage of terms defined in a single paragraph. No great harm comes from calling it a theory, and nothing of importance is settled by instead calling it a hypothesis or conjecture.

    Nevertheless, the article was prompted by a spat between scientists over just that issue. What this article does, however, is to lift the curtain and give us a look at what the real issues are: it is a debate about whether inflation is failing in its bid to become established science, and whether it is time to give up on it, or at least look more earnestly for and at alternatives.

    For someone who is not a scientist, but who is familiar with the history of science and the works of Popper and Kuhn, it might seem that the distinctions between conjecture, hypothesis and theory are both clear-cut and important, but the fact is that when science is done (as opposed to being written about afterwards), there is a good deal of uncertainty, and sometimes confusion, with many false starts, dead-ends and half-understood truths.

      badosu 128 days ago

      > No great harm comes from calling it a theory, and nothing of importance is settled by instead calling it a hypothesis or conjecture.

      It's fine to believe in this, however one must wonder why it is that an individual may hold String Theory to the same standard as General Relativity or Evolution, and when finally it is observed that String Theory is not the case (or some other Theory gets trendy) this individual loses credibility on Science as a whole. - Just the other day you scientists had a theory that the universe was expanding!! How can I believe in your other theories?

      It should not be required to the casual curious reader to understand this distinction. A notable scientist on the other hand, specially one that has visibility, carries some responsability when (s)he writes about such matters.

        mannykannot 128 days ago

        You have a point, though in English, we already have that problem with the difference between 'theory' in general usage, and in science.

    Retric 128 days ago

    Astronomers conduct experiments. They make predictions then design a device that collects brand new photons in some way. Those photons may or may not agree with the initial prediction.

    The critical part of experiments is predictions then new data such that the possibility of falsification exists.

    philipov 128 days ago

    The salient quality of a theory, or a scientific hypothesis if you prefer, is that it can be tested, at least in principle. I am not a physicist, but it seems like, at least in principle, there's a way to falsify the inflation hypothesis, even though we might not be able to practically carry it out.

    Personally, I'm a fan of Penrose's idea that what appears as inflation is instead the infinite limit of a previous universe, and that there's no big bang at all: just an endless stream of infinitely expanding universes.

    > "The group’s fight against inflation isn’t news."

    Oh! What an unfortunate turn of phrase for someone to use to describe their topic. If even the reporter doesn't think this is newsworthy, why are they writing about it?

      growt 128 days ago

      >> "The group’s fight against inflation isn’t news."

      > Oh! What an unfortunate turn of phrase for someone to use to describe their topic. If even the reporter doesn't think this is newsworthy, why are they writing about it?

      I think the author of the article is german (I'm german too) and this sentence is maybe a "false friend". What she most likely meant is that the groups goals are already well known.

      badosu 128 days ago

      > The salient quality of a theory, or a scientific hypothesis if you prefer, is that it can be tested, at least in principle. I am not a physicist, but it seems like, at least in principle, there's a way to falsify the inflation hypothesis, even though we might not be able to practically carry it out.

      The existence or not of a way to falsify a proposition does not qualify it as a knowledge, if it matches the criteria for scientific truth than it is knowledge and may be part of a larger set of propositions that encompass a theory.

        philipov 128 days ago

        Agreed, it is only enough to qualify it as a scientific hypothesis. The article, and the critics, are right to point out that it too early to give it the status of scientific truth.

        I think that it is overly polemical to say that inflation is not a scientific theory because the technical definition of a theory is hazy for most people, but calling something unscientific is crystal clear, and this is misleading.

          badosu 128 days ago

          I fully agree with you, if news written like this influences lay people, they'll hold theories like General Relativity, Quantum Field Theory or even Evolution to the same standards as the next trendy, and almost impossible to falsify, subject of study...

      mpweiher 128 days ago

      > If even the reporter doesn't think this is newsworthy

      The "reporter" is a working physicist, not a "reporter"

      http://backreaction.blogspot.ie/p/about.html

        badosu 128 days ago

        My rant's motivation is the usual lack of consideration for philosophy by qualified scientists, which is not bad per se, just when they create a title that reads:

        > Is the inflationary universe a scientific theory? Not anymore.

        Which is not wrong, just requires making sense to be wrong.

    lr4444lr 128 days ago

    The average person might know scientific discoveries and principles, but few understand what the human enterprise of science entails - hypothesis, theory, law, reproducibility, statistical significance, falsifiability, etc. I've found trying to explain these things causes discomfort, distrust, and creates more problems than it solves. Most people seem to prefer to associate science with precision, correctness, and infallibility.

Chiba-City 128 days ago

The ease of repeating a calculation against a data set or recording such a dataset from instrument readings is not exactly the same repetition of a lab or factory recipe outcome. Science concerns data collected and copied yesterday. Tekne concerns repeatable outcomes reproduced tomorrow. Distinctions between the endless feast of science and endless labors of tekne are pretty clear.