Sheldon: “… dark matter and dark energy (aka Λ) have become science fantasy with no shortage of storytellers. It’s time to tell everybody the party’s over.”
Hossenfelder: “… the evidence is mounting that the cosmological principle is a bad assumption to develop a model for the entire universe and it probably has to go. It increasingly looks like we live in a region in the universe that happens to have a significantly lower density than the average in the visible universe.”
These specialty controversies are an interesting backdrop to the current war on math. Sabine Hossenfelder and Rob Sheldon would likely agree that 2 + 2 = 4. But survey the vast degreed hordes for whom such a statement is an instance of white supremacy and colonialism and we will see the real problem facing our civilization: Far too many people have degrees (and grievances!) but no insight into what knowledge is.
Part of a physics seminar series called “Golden Webinars.”
It’s not just theists who have problems with the multiverse. Sabine Hossenfelder explains her reservations.
Hossenfelder: The physicists who believe in this argue that unobservable universes are real because they are in their math. But just because you have math for something doesn’t mean it’s real. You can just assume it’s real, but this is unnecessary to describe what we observe and therefore unscientific.
This is the kind of thing she said: What about Avi Loeb’s claim that the interstellar object `Oumuamua was alien technology? Loeb has justified his speculation by pointing towards scientists who ponder multiverses and extra dimensions. He seems to think his argument is similar. But Loeb’s argument isn’t degenerative science. It’s just bad science. He jumped to conclusions from incomplete data.
Hossenfelder: If you are standing still and then begin to walk, that does not only change your position in space, it also changes which direction you are going in space-time. You are now moving into a direction that is a combination of both time and space.
At least some media types noticed that such a claim is pretty far out. Maybe they don’t “Trust the Science” like they should?
Exotic particles that don’t survive a news cycle. She shows how they’re artifacts of the fact that very large numbers often show what appear to be patterns but are just noise.
She thinks the solution now is to combine dark matter with modified gravity. Now that will be a challenge. We kind of wish she would go back to denying free will and fine-tuning of the universe.
Hossenfelder: If one adds 7 dimensions of space to our normal three dimensions, then one can describe all of the fundamental forces of nature geometrically. And that sounds like a really promising idea for a unified theory of physics. Indeed, in the early 1980s, the string theorist Edward Witten thought it was intriguing that seven additional dimensions of space is also the maximum for supergravity. However, that numerical coincidence turned out to not lead anywhere. This geometric construction of fundamental forces which is called Kaluza-Klein theory, suffers from several problems that no one has managed to solved.
Rob Sheldon: Hawking did not get the Nobel, however, because he hung his hopes on the radiation emitted by BH–the so-called “Hawking radiation”. And it was never observed. Sabine tries to explain why. But one argument that Sabine doesn’t make, is that Hawking radiation may never have been observed because BH are themselves never observed.
Hossenfelder ends by reminding us, re phosphine on Venus, that “ absence of evidence is not evidence of absence.” True, but that’s just a corollary of the fact that one can’t prove a negative. No, we can’t but that doesn’t prevent us from drawing reasonable conclusions. The proverb has been used to cover far too many situations where a more realistic conclusion would be “There is no particular reason to believe this.”
Hossenfelder: It’s no secret that I myself am signed up to superdeterminism, which means that the measurement outcome is partly determined by the measurement settings. In this case, the cat may start out in a superposition, but by the time you measure it, it has reached the state which you actually observe. So, there is no sudden collapse in superdeterminism, it’s a smooth, deterministic, and local process.