Freeman Dyson, who is a brilliant physicist and a contrarian, he had pointed out based on some research — he’s 90 years old, but he had done some research over the years — I was in a meeting in Singapore with him when he pointed out that we really don’t know if gravity is a quantum theory. Electromagnetism is a quantum theory because we know there are quanta of electromagnetism called photons. Right now they’re coming, shining in my face and they’re going into the camera that’s being used to record this and we can measure photons. There are quanta associated with all of the forces of nature. If gravity is a quantum theory, then there must be quanta that are exchanged, that convey the gravitational force; we call those gravitons. They’re the quantum version of gravitational waves, the same way photons are the quantum version of electromagnetic waves. But what Freeman pointed out is that there’s no terrestrial experiment that could ever measure a single graviton. He could show that in order to build an experiment that would do that, you’d have to make the experiment so massive that it would actually collapse to form a black hole before you could make the measurement. So he said there’s no way we’re ever going to measure gravitons; there’s no way that we’ll know whether gravity is a quantum theory.This is correct. The whole subject of quantum gravity should be considered part of theology or something else, because it is not science.
He notes that the BICEP2 tried (unsuccessfully) to find evidence of quantization of an inflaton field, a related issue.
Does physics need philosophy?Philosophers have rejected XX century science, and have become more anti-science than most creationists. So asking whether physics needs philosophers is like asking whether biology needs creationists or whether astronomy needs astrologers.
We all do philosophy and of course, scientists do philosophy. Philosophy is critical reasoning, logical reasoning, and analysis—so in that sense, of course physics needs philosophy. But does it need philosophers? That’s the question. And the answer is not so much anymore. I mean it did early on. The earlier physicists were philosophers. When the questions weren’t well defined, that’s when philosophy becomes critically important and so physics grew out of natural philosophy, but it’s grown out of it, and now there’s very little relationship between what physicists do and what even philosophers of science do. So of course physics needs philosophy; it just doesn’t need philosophers.
Krauss was burned by a philosopher of physics who wrote a NY Times book review trashing Krauss's title, and without addressing the content of the book. Yeah, the title was overstated, but the reviewer should have been able to get past the title.