Anti-Gravity

One of our favorite science blogs (to pick on) has taken on an interesting question. From Ask Ethan: If The Universe Ends In A Big Crunch, Will All Of Space Recollapse?

When you describe the Big Crunch, you talk about a race between gravity and the expansion of space. It’s not clear to me that if gravity wins that race, whether space stops expanding, or simply that the matter in space stops expanding. I’d love to hear your explanation of this.

It's an interesting question because it's obviously absurd, yet follows logically from the standard model of astrophysics. Ethan tends not to shy away from these questions, but his normal routine is to ramble through the standard dogma, assert all kinds of theoretical constructs as absolute fact, and then fail to answer the initial question.

This is a complex question, but the physics we know today allows us to rise to the challenge and give a definitive answer.

It's not really that complex. If the "fabric of spacetime" is expanding because of dark energy, then will it still be expanding even if the gravitational attraction of the material contents of the universe overcomes the expansion, and it all crunches back? The answer should be yes, because the expansion is driven by a hypothetical force that is independent of the matter that the spacetime contains. It must be independent, because otherwise it would just have to be called anti-gravity. Scientists would have to explain how matter is attracted to other matter by gravity, but also repelled by anti-gravity. Universal expansion was concocted specifically to make that contradiction goes away. Since he is the expert, I'm sure Ethan will address all this in his "definitive answer."

He goes on to explain redshift theory, which should be familiar to regular readers here who slog through the science posts. It should also be familiar to the readers of his own astrophysics blog, but that is another matter. After padding out a half dozen or so paragraphs under the assumption that his readers are unfamiliar with one of the most famous conclusions of the field, he turns more directly to the question at hand.

Galaxies do move relative to one another, as the gravitational forces from the matter in the Universe push and pull everything around. But the fabric of spacetime itself cannot remain constant, either.

It's sloppy language to state that gravitational forces "push and pull" everything around. Gravity is only supposed to pull! But, in all reality, scientists have indirectly invented anti-gravity that pushes, so his verbal error is inadvertently apt. He then asserts that the fabric of spacetime cannot remain constant. Why not? He explains.

In General Relativity, spacetime is a dynamic entity. When you have a Universe like ours — where matter and energy are relatively evenly distributed on the largest scales — any relativistic solution that results in a static Universe is fundamentally unstable. The Universe must be expanding or contracting, as it cannot remain in an unchanging state. We cannot necessarily know which one it’s doing from first principles alone; we require measurements to teach us what’s going on.

Spacetime is not a dynamic entity under general relativity. In fact, Einstein later regretted that he had not thought of dynamic spacetime himself. This author doesn't know what he's talking about even in his own area of specialty. He then tells us that a "universe like ours" - implying that a universe is just some common, mundane thing - is inherently unstable, and doomed to either a Big Crunch caused by contraction, or a slow heat death caused by infinite expansion. It's the kind of worldview that really appeals to materialistic hedonists who follow I F*cking Love Science on Facebook. [It especially draws liberal losers, who love the notion that the universe is arbitrary and doomed, that there will be no judgement, that nothing matters because winners and losers alike are all doomed to the same pitiful demise.]

He goes on to say that we need measurements to determine which of the two tragic fates awaits us, because it can't be determined from "first principles alone." As if any of this is first principles! The expanding universe itself is merely a hypothesis to explain the redshifts, which weren't predicted by any theory. The observation itself is suspect, as it relies on the assumption that Type 1-A supernovas are standard candles, to which there is some contradictory evidence. The theory that they are standard candles comes from the assumption they are caused by the accretion of fissionable material from a binary companion star. There is no corroborating evidence for this theory. In fact, there is only the contradictory evidence of supernova recurring at the same star. And yet, Sherlock's Theory holds. They can imagine no other explanation that conforms to their beliefs, thus they proclaim the shaky theory to be a scientific fact, and then proceed to construct yet more theories upon it.

He then reviews the possible scenarios for galactic doomsday and concludes that the Big Crunch seems unlikely, with one caveat.

Unless, of course, dark energy is dynamical, and capable of changing over time.

This is very reminiscent of what the geneticists do. Genomic sequencing was supposed to validate the conclusions made by biologists and paleontologists regarding species hierarchies and timelines, but has caused more conflicts that it has solved. Explanations normally propose variations in the genetic random mutation rate. Here, we have Ethan suggesting that the cosmological constant is not constant after all. In modern science, the theories truly are axiomatic. They'll even downgrade a universal constant to a volatile variable before they'll question the stacks of assumptions on which their theories rest.

In the final paragraph, Ethan gives an answer to the original question.

But the link between all the matter and energy in the Universe, on one hand, and the expansion of the fabric of space itself, on the other, cannot be denied. We live in a Universe that, on the largest scales, is isotropic, homogeneous, and governed by General Relativity. In a very general sense, that means there’s a connection between how the Universe expands and what’s present within it.

If all the matter in the Universe stops expanding away, reverses itself, and begins to recollapse towards us, then that necessitates that the fabric of space is going to recollapse, too. There truly is a cosmic race occurring: between the expansion of the Universe and the force of gravity. Right now, it looks like the expansion’s going to win, but if dark energy is dynamical, that throws the outcome into doubt.

He concludes that the contraction of matter means the contraction of the fabric, in opposition to my assumption. (I don't actually believe in spacetime "fabric"... just running with their logic.) He says there's a connection between matter and spacetime fabric that "cannot be denied." Well, duh. The whole point of expanding spacetime was to explain the apparent motion of the matter. But that connection goes only one way. The expansion was made intrinsic to spacetime and immune to the effects of matter for a reason. Otherwise, it would just be an effect of the matter itself. In other words, anti-gravity. This buffoon has just stumbled into the explanation that the theory is constructed to avoid in the first place! But the alternative would be to say that spacetime will continue to expand indefinitely, while matter collapses to a singular point. You can appreciate the dilemma, at least.

Not only is his grasp of his own field comically lacking, so is his writing.

If gravity does wind up winning, and the Big Crunch is our ultimate fate, someone, a long time from now, might live to see the entire shebang recollapse into a singular state.

No, no one is going to survive a big crunch nor see a singular state. It makes no sense whatsoever. I'm as cynical about science and science writers as anyone out there, but I'm truly baffled by how awful this is.