1. The Big Bang model is simply the idea that our universe expanded and cooled from a hot, dense, earlier state. We have overwhelming evidence that it is true.
2. The Big Bang event is not a point in space, but a moment in time: a singularity of infinite density and curvature. It is completely hypothetical, and probably not even strictly true. (It’s a classical prediction, ignoring quantum mechanics.)
3. People sometimes also use “the Big Bang” as shorthand for “the hot, dense state approximately 14 billion years ago.” I do that all the time. That’s fine, as long as it’s clear what you’re referring to.
4. The Big Bang might have been the beginning of the universe. Or it might not have been; there could have been space and time before the Big Bang. We don’t really know.Sean Carroll, “True Facts About Cosmology (or, Misconceptions Skewered)” at Preposterous Universe
From Rob Sheldon: Sean Carroll, an avowed atheist in the “scientism” camp of Bill Nye and Jerry Coyne, has made a list of apologia for the Big Bang (hereafter BB). You might wonder why there needs to be any apology at all if, as he himself says, “We have overwhelming evidence that it is true.”
One answer might be that BB is many things to many people. Only a single version has “overwhelming evidence,” so we need a clarifying definition. A better answer than he offers might be that BB enthusiasts have made a lot of specious claims that they attempt to attach to the BB’s sterling reputation. So we need to debarnacle the ship. But perhaps the best answer might be that critics have undermined a lot of the “overwhelming evidence” so that the very idea of a single valid theory is under attack.
For all these stated reasons, as well as the unstated atheist reasons, Sean mounts a siege wall around BB. Here’s my take on his claims.
1. Sean gives a minimalist definition of a BB model as “hot” and “dense”. Historically it had a few more attributes, but like the Monitor gunboat, Sean is trying to lower the size of the target.
2. Sean separates the timing from the model, and then claims the model is true but its timing is only hypothetical. That’s a bit like saying that BigFoot is real, but sightings of him are hypothetical. Now, we can see the rhetorical point of the minimalist definition–by never specifying what “hot/dense” means, he can accommodate alternative BB models that never had a singularity, and therefore have only a hypothetical “starting point.”
3. Sean acknowledges that sometimes “BB” is defined as this “hypothetical starting point” that probably doesn’t exist. (“BigFoot sightings” is just vulgar shorthand for “people’s confused impressions” not to be taken as evidence.)
4. Sean really believes that we can never know if the universe had a beginning. We must be a dedicated agnostic about the timing, but faithful believers about its effects.
(At this point, readers, please go back to Dr. Carroll’s blog to read the other 19, comments on which appear below:)
5. Even if we are agnostic about BB timing, Sean tells us, we must be orthodox Democriteans, “nothing comes from nothing”. No possible doubts about “ex nihilo”. No Augustine and certainly no Aquinas is permitted here.
6. What about that mathematical proof that agnosticism is impossible because “bouncing BB” will violate special relativity? Just close your eyes and remember, it is just math, not evidence of the real world like the “overwhelming evidence” of #1.
7. “Bubble universe” enthusiasts (yes, Sean’s talking to you, Lawrence Krauss) are cranks. (No argument from me.)
8. But, Sean avers, we shouldn’t dismiss BB as violating energy conservation, because gravity is negative energy that neatly balances the positive energy of matter. (But Sean, how would we know, since it isn’t derivable from any law of nature or math? Once again, Sean wants us just to believe, on the long shot that maybe the multiverse turns out to be right after all.)
9. Sean doesn’t believe in mass-energy conservation even if it is dogma in the BB. (So where does it go Sean, into the fifth dimension? It’s hard to know what Sean holds most dear–mathematical rigor or physical intuition. He seems to waffle at all the critical moments.)
10. Sean displays a bit of philosophy to show why cosmologists live on a higher-dimensional plane than the rest of us.
11. Sean is not agnostic about inflation, just a gambler hedging his bets. (If you actually looked at the way the theory has evolved, with one kludge added on top of another to create these tottering towers of speculation, it says a lot about your politics to admit being a bettor.)
12. Sean tries to solve the BB entropy problem the same way he solved the BB energy problem: First he says that it doesn’t exist and then he says that gravity solves it.
13. Sean treats dark matter the way he treats BigFoot–no sightings but it must exist. (Of all the reasons to infer dark matter, he picks the weakest, a model-dependent analysis of cosmic background radiation. I happen to think that the original galaxy rotation rates are the best data, but Sean is trying to avoid the politics of the MOND battle, so he went for the circular logic proof. Of course he would.)
14. This is the BigFoot argument once again. But someday we will have the technology to find him. (My patience isn’t lacking, Sean; it’s my pocketbook.)
15. More betting language on the existence of dark energy—but we knew already that Sean doesn’t believe in the conservation of mass-energy. (Sean believes only in the Democritean conservation of nothing.)
16. Not sure who this diatribe is directed against, Sean reminds us that energy and force have different units. (Can’t disagree with him there.)
17. More betting language on the theory of dark energy.
18. He admits he doesn’t have a theory of dark energy either.
19. But don’t dare compare dark energy to a disgraced 200-year old theory of aether!
So what has Sean’s apologia accomplished? Despite many contortions, he managed only two lines in the sand: The multiverse doesn’t exist and dark matter does. And I’m sure if we put a bit of pressure on him, we might get him to change his mind about multiverse and dark matter too.
It’s getting hard to find a principled atheist nowadays.
See also: Rob Sheldon on the physics wars: Stagnation or no?
Cosmologist Sean Carroll: A Multiverse Is “Beyond Falsifiability” – And That’s Okay With Him
Cosmologist Sean Carroll: Is anything constant? Rob Sheldon replies to Sean Carroll
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