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Physicist Rob Sheldon on a cosmologist’s recent claim that there were two Big Bangs

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First, the claim, from Ethan Siegel:

When cosmologists?—that’s the sub-field of astrophysics dealing with the origin and evolution of the Universe?—speak about the Big Bang, they mean one of two things:

– The hot, dense, expanding state that our observable Universe emerged from, that expanded, slowed, cooled, and gave rise to elements, atoms, stars, molecules, planets, and eventually us.

– The initial singularity that represents the birth of space and time.

The only problem is, while these two explanations were interchangeable back in say, the 1960s, they no longer are.

The first explanation?—“the hot, dense, expanding state—still makes sense as “the Big Bang,” but the second one no longer does. In fact, as far as the question of where space and time come from goes, there is still plenty of debate on all sides, and this recent paper that came out is simply another drop in the ocean of that debate: nothing more.

The biggest thing you should learn from all this? That “the Big Bang” represents where everything we see in the Universe comes from, but it is not the very beginning of the Universe anymore. We can go back before this explanation is any good, to an inflationary Universe, and we have good reasons to argue over and debate the finer points of what, exactly, that means for the ultimate origin of everything we know.

Also: From Synopsis:

It’s making headlines everywhere we go: the recent paper stating that quantum equations prove that there is no Big Bang.

He means this story presumably: The latest no-Big Bang theory relies on a quantum fluid of hypothetical massless particles  Siegel elaborates:

Honestly, it depends on which definition of the Big Bang you’re using. As it turns out, there are two of them, and there’s a good (historical) reason for that. But in the context of what we know today, one of them isn’t a good definition anymore, and hasn’t been for decades.

Funny, because the Planck data simply haven’t provided much support for these no-Bang, two-Bang, everywhere-a-bang bang universes. See Mathematician: Planck data disappoints multiverse claims.

Hey, awesome graphics, though. But wait a minute …

Dr Sheldon
Rob Sheldon

We asked Rob Sheldon Rob Sheldon to comment:

There are many “slight-of-hand” ambiguities in both words and figures of this post.

Post-modernism doesn’t just destroy language, it destroys graphs and pictures too. There was a great chapter in C. S. Lewis’ That Hideous Strength on the destruction of Art in the “re-education room.” If he were to write that story today, Mark would be surrounded by Hubble Space Telescope pictures all modified by graphic artists from NASA.

Let’s begin with the standard model. The idea is that if we look with the Hubble Space telescope up, down, left or right, we see the Cosmic Microwave Background Radiation of the Big Bang red-shifted “behind” all these distant galaxies and even more distant quasars. This CMBR glow was emitted at very high temperature, so the argument goes, everything between us and the “wall” of radiation at the edge of the universe, is the entire mass of the “observable” universe, and was once compressed down to the size of a pea or less to heat produce the CMBR wall.

This of course, really bothered the Epicurean Materialists, such as Fred Hoyle, who wanted an eternal universe. Various “fixes” were proposed: steady state creation of matter, “near-miss Big Bangs”, bouncing compression/expansion, etc. None of them worked.

Then along came the idea of inflation. If we assume that the universe can expand faster than the speed of light (in “starts with a bang” he calls this inflation due to the dark energy. If you are smelling metaphysics, you are right) then time doesn’t go linearly back to a beginning. Instead, and I’m just trying to find a useful metaphor, time is created along with space. You get as much space-time as you want, since there are no longer any speed limits. Space can be infinite, and time infinite, and we are just seeing a little local patch of it. CMBR is no longer the “shell of the cosmic egg” but the permeating remnant of an inflationary explosion that occurred infinitely everywhere.

So what does that graph of time and space mean? Absolutely nothing. We’ve done away with linear time, so you can draw any curve you want for an inflationary universe. It’s sort of like multiverses, but with time instead of space.

Yet here is how Ethan Siegel describes this monstrous theory, this hideous metaphysics:

“In particular, we’ve learned that in addition to matter and radiation, the Universe also contain an amount of energy inherent to space itself, or dark energy, or cosmological constant, or vacuum energy (all synonyms).

It contains a relatively small amount of this now, but it contained a fantastically large amount of this energy early on.

Never mind that he is conflating Einstein’s volume-dependent cosmological constant, with Alan Guth’s “inflationary potential”, which have totally different vacuum properties. Because you would have no idea reading this that we have learned no such thing, but have hypothesized this unobservable quantity, which has been disproven 3 times (most recently by Planck data), and no one knows how to revive the theory a fourth time, yet the data cannot dissuade Ethan from what he’s “learned”.

Nothing of the sort, what he’s learned is how to write winning proposals.

Yes, for sure, in an age when narrative and spin trump facts and evidence, great graphics stand in for a rigorous argument.

And most of the reasons these people hate the Big Bang theory have little to do with physics.

See also: Universe “roughly tuned” for computing? Instead of fine-tuned for life? (Actually, it really doesn’t matter what the argument is, or whether or not it makes sense, as long as it is against fine-tuning for life. Opposite arguments can get along fine with each other, as long as they oppose that.)

and Big Bang exterminator wanted, will train

also:

But who needs reality-based thinking anyway? Not the new cosmologists

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Ethan Siegel:

5 Replies to “Physicist Rob Sheldon on a cosmologist’s recent claim that there were two Big Bangs

  1. 1
    skram says:

    The title of the OP is wrong. Segel does not say that there were two Big Bangs. He says that there are two definitions of the Big Bang. And that the two definitions are not equivalent.

    And on that score, he is entirely right.

  2. 2
    skram says:

    The first definition—the hot, dense state of an expanding Universe—is not in dispute. The second—that there was an initial singularity—is.

    The positing of the initial singularity assumes that we can extrapolate the laws of classical theory of gravity (general relativity) all the way back to the point (in spacetime) where the Universe had zero size. We know that this extrapolation becomes invalid when the size of the Universe is comparable to Planck’s length scale. Here quantum mechanics must be taken into account. Exactly how we don’t know as there is no theory of quantum gravity.

    This point is entirely correct: the claim of the initial singularity is based on an unwarranted extrapolation back in time. We don’t know well how the quantum evolution of the Universe proceeded. But quantum mechanics certainly smoothed the singularity. That isn’t controversial.

  3. 3
    News says:

    Skram at 1: It’s not entirely clear what he is saying, but to the extent that he thinks that there was a period before the Big Bang that featured an inflationary universe, he either means that there were two Big Bangs or he is arguing for an eternal universe.

    Or he is great with graphics. The News desk is going with option 3.

  4. 4
    skram says:

    News, can you offer a quote from the article that says “there were two Big Bangs” or something to that effect? I don’t think you can do that.

  5. 5
    skram says:

    Instead we find this:

    When cosmologists—that’s the sub-field of astrophysics dealing with the origin and evolution of the Universe—speak about the Big Bang, they mean one of two things:

    1. The hot, dense, expanding state that our observable Universe emerged from, that expanded, slowed, cooled, and gave rise to elements, atoms, stars, molecules, planets, and eventually us.

    2. The initial singularity that represents the birth of space and time.

    The only problem is, while these two explanations were interchangeable back in say, the 1960s, they no longer are.

    So, Siegel is talking about two definitions of the Big Bang and that they are not equivalent.

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