It’s a big big universe. The diameter of the Earth is about eight thousand miles, so the circumference is about twenty five thousand miles. If you could walk twenty miles a day and didn’t have to worry about little things like rivers and mountains and oceans, it would take you one thousand two hundred and fifty days to walk twenty five thousand miles. That’s over three years. The Moon is about two hundred and fifty thousand miles away. If you could walk to the Moon, it…
I’ve mentioned LIGO a couple of times in passing. You know, LIGO, the Laser Interferometer Gravitational Wave Observatory. Rainer Weiss of MIT had a lot to do with the idea back in the 1960s, as did Kip Thorne of Caltech. Things got serious in 1980 when the US National Science Foundation funded prototypes at Caltech and MIT, and funded Weiss to lead a study into a full size interferometer. Construction eventually started in 1994 and was finished in 1997. Observations eventually started in 2002 and stopped…
When you read the Einstein digital papers, you understand how gravity works. Einstein said things like “the curvature of light rays occurs only in spaces where the speed of light is spatially variable”. Note that he never abandoned this, and he never said light curves because it follows the curvature of spacetime. Instead he said a gravitational field is a place where space is “neither homogeneous nor isotropic”, he referred to Huygen’s principle, and he talked about “the refraction of light rays by the gravitational field”. So did Newton, see…
I saw Luboš Motl’s blog post Most laymen completely misunderstand what a black hole is. When I read the title my irony meter skipped a beat, so I thought I’d take a closer look. Especially since he said this in his opening paragraph: One of those invalid memes that I want to discuss… is the idea that the point of the black hole is the singularity. That is what makes a black hole a black hole and that's also where the mysteries of black holes hide.…
I read Sabine Hossenfelder’s latest blog post yesterday. The title was A brief history of black holes. I left a couple of comments. One was a reply to Louis Marmet, and referred to Oppenheimer’s 1939 frozen star black hole. I said I think the black hole grows like a hailstone, from the inside out. The other was addressed to Hossenfelder, and referred to Einstein talking about the variable speed of light. I said that IMHO this had to mean Penrose/Hawking singularity theorems were wrong. I found…
Sorry I haven't posted much lately. I've been run off my feet with work. Like that woman at the end of Twelve Monkeys, I'm in insurance, and work is pressing. But anyhow, very briefly, I wanted to show you something I saw yesterday evening: L- shaped contrails. At least that's what they looked like: There appears to be two, one lower, one higher. Here's another picture I took a few seconds later: I was in Poole looking west, at circa 18:53 GMT. Interesting, that! NEXT
This is in response to a query from Jonas K. See my post you can lead a horse to water, and take a look at the comments. OK, I’ll start again from the beginning, Jonas, you're blue: Textbook optical clocks of the bouncing-photons-kind go slower when lower in a gravitational field, yes. So do Cesium-based atomic clocks, by exactly the same amount. Why is that? It’s because a Cesium-based atomic clock has an electromagnetic nature. Take a look at the NIST caesium fountain clock: Image courtesy…
If you’ve ever read James Clerk Maxwell’s 1865 paper A Dynamical Theory of the Electromagnetic Field, you might have noticed his Note on the Attraction of Gravitation. It’s at the end of part IV. Maxwell ends up saying energy is essentially positive, and that “the presence of dense bodies influences the medium so as to diminish this energy wherever there is a resultant attraction”. Then he said this: “As I am unable to understand in what way a medium can possess such properties, I cannot go…
Clunk. That’s the sound of my head hitting my desk. Because the $3m special breakthrough prize has just been awarded to the “discoverers” of supergravity. Yes folks, that’s one of those mathematical “discoveries”. It isn’t like discovering America or penicillin. It’s the sort of “discovery” that people peddle when they’re hyping a hypothesis for which there’s no evidence at all. The prize was awarded to Sergio Ferrara, Daniel Freedman, and Peter van Nieuwenhuizen for an “Influential Theory Combining Gravity with Particle Physics”. Only it isn’t influential…
I think it’s safe to say that there are some misconceptions in physics. The issue of course, is how many. That’s where I part company with your average physicist. He’ll tell you that whilst we don’t understand everything, we do understand some things, such as black holes. Only he doesn’t. Take a look at the Wikipedia black hole article. It says this: “a black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing - no particles or even electromagnetic radiation such as…