Siegel: “It is time to take seriously the idea that dark energy might simply be a property inherent to the very fabric of space. Until we learn how to calculate the zero-point energy of empty space itself, or gain some bizarre, surprising, and unanticipated evidence, this will remain one of the biggest existential questions in all the universe.” So this is existentialism for physicists, right? Even Sabine Hossenfelder sounds sort of existential on this one.
Siegel: In the near future, observatories like the ESA’s Euclid, the NSF’s Vera Rubin Observatory, and NASA’s Nancy Roman Observatory will improve that uncertainty so that if dark energy departs from a constant by as little as ~1-2%, we’ll be able to detect it. If it strengthens or weakens over time, or varies in different directions, it would be a revolutionary new indicator that dark energy is even more exotic than we currently think.
If the two competing ideas are “equally wild,” couldn’t they be equally wrong?
Paul Sutter: By allowing for multiple quantum fields to generate dark energy, it might be possible for string theory to still be relevant in our universe, as these models may not be stuck in the “swampland.”
Why can’t they find dark matter, despite much search? Sheldon: The old joke is that a man is looking under a lamppost one night. The policeman asks what he is doing. “Looking for my keys” he replies. “Did you lose them here?” “No, but the light is better over here.” (And the funding is better for some research than for others.)
Throw in a multiverse and pop science will believe. Hey. We can’t help that.
Rob Sheldon: My takeaway is that dark energy is “pathological science,” using the words of Irving Langmuir to describe N-rays or polywater. It is science at the edge of messy data, finding what one is looking for by using poor statistical methods. It is precisely what astronomers are trained NOT to do, and therefore this whole Nobel Prize thing is a corruption of what had been a relatively unstained field.
Hossenfelder: “So, what’s the scientist to do when they are faced with such a discrepancy between theory and observation? They look for new regularities in the observation and try to find a simple way to explain them.” Okay but the question of whether the terms “dark matter” and “dark energy” correspond to anything that actually exists could be a different one.
Sheldon, our physics color commentator, writes to say, “I’ve mentioned before that Subir Sarkar at Oxford has questioned the existence of “dark energy” and by implication, the award of the 2011 Nobel prize. Sabine Hossenfelder’s blog links to a 7 minute summary of the Nobel prize and Sarkar’s work: But even more compelling is her Read More…
At Inside Science: “While most scientists still seem to believe that dark energy remains on solid ground, no one yet has any firm idea what it actually is.” Maybe dark energy is cosmic consciousness? Don’t laugh before you read this: “Could information be—at long last—the missing dark matter?”
Researcher: “Our analysis is data-driven but supports the theoretical proposal due to Christos Tsagas (University of Thessaloniki) that acceleration may be inferred when we are not Copernican observers, as is usually assumed, but are embedded in a local bulk flow shared by nearby galaxies, as is, indeed, observed. This is unexpected in the standard cosmological model, and the reason for such a flow remains unexplained.
Ethan Siegel: Why does empty space have the properties that it does? Why is the zero-point energy of the fabric of the Universe a positive, non-zero value? And why does dark energy have the behavior we observe it to have, rather than any other?
Sabine Hossenfelder: Given how much brain-power physicists have spent on trying to figure out what dark matter and dark energy is, I think it would be a good idea to definitely settle the question whether it is anything at all. At the very least, I would sleep better.
Siegel: In order for inflation to end, that energy has to get converted into matter and radiation. The evidence strongly points to that happening some 13.8 billion years ago.
Rob Sheldon: This article illustrates the reason why the scientific method is going extinct, not just in Darwin’s circular logic, but also in physics and cosmology.