Recent content by Physics Detective

No. Like predators like meat. Fresh. Still warm if possible. Or better still, still alive. This is a very good reason for not using death ray disintegrator weapons as per Mars Attacks! That's if your aliens are the bad guys of course. Apologies if I missed something on that.

I've seen what appeared to be satellites making abrupt right-angle turns. On one particular occasion there were two of them, one tracking slowly North to South, the other tracking slowly South to North, both on the same line, both at about the same apparent speed as a satellite. This was above...

@SleipnirTheHorse : how about because they like meat.

I think you can be sure of the distinction between genuinely possible things, and speculative things for which we have no evidence whatsoever. General relativity is one of the best-tested theories we've got. See The Confrontation between General Relativity and Experiment by Clifford M Will...

We will have to agree to differ on that.

How about a gamma railgun?

Make it a "gamma gun". A gun which emulates a gamma ray burst, and is powered by the 100% conversion of matter into energy. The amount of matter converted to propel each bullet would be tiny. The bullets would be small too, but very fast. Let's a say a bullet has a kinetic energy of 1000 Joules...

Is a table levitating possible, even at a minuscule probability? No. Some of the examples above are associated with genuine probability. Like tossing a coin. It's possible to get two heads in a row. It's also possible to get ten heads in a row, but the probability is reduced. The OP also refers...

OK noted.

All points noted Mitchell. Yes I guess it would be a major thread derail. Apologies, I will leave it there.

You will be aware of Newton's infinite universe. It's mentioned here and here. Gravity should have caused all the stars to "fall down in the middle" and there "compose one great spherical mass". However if the universe was infinite, each and every star would be pulled on all sides by other...

Ouch. That paper is above my pay grade, Mitchell. I'm an amateur, an IT guy who's read a lot of old papers, not a mathematical physicist. But something jumped out at me straight away. It's to do with the distinction between Euclidean space and Lorentzian spacetime. See this in the abstract: "a...

I remember when people used to say "the universe was once the size of a grapefruit". Then after the WMAP results in 2006 I think, this morphed into "the observable universe was once the size of a grapefruit". Then some other people started saying the universe must be infinite because it's flat...

Tim: at 38 pages, this is a big paper. Apologies, I've only looked at the abstract and the discussion, with my historian hat on. It would take me a week to plod through the whole thing. I dislike the reference to "the energy of the coherent gravitational field of the universe". I say that...