Gravitational Lensing

[Мастер]

I've been trying to work out to what extent (if any) dark matter is something qualitatively different than invisible elves.

Is it?

[Lance]

Honestly, I don't think so.

But, can you prove invisible elves don't exist?

[Arneb]

I've been trying to work out to what extent (if any) dark matter is something qualitatively different than invisible elves.

Is it?

I think so. If the choice is between "invent more matter thn we can currently detect" and "overthrow a deep theory of gravity that has been confirmed countless times", positing more matter isn't unreasonable - and there is nothing in particle physics that presents high hurdles against the existence of a particle or particles that happen not to couple strongly to what we see as "normal matter". You could have said essentially the same about the neutron and the the neutrino (or, for that matter, Neptune), before they were confirmed to exist. So IF Dark Matter is an invisible elf, invisible elves have a clear streak of success in physics.

If you were following this discussion on CQ only (but surely, you aren't. Are you?), you could get the impression that anyone even entertaining the idea that a set of laws without Dark Matter is even conceivable is, ipso facto, a crackpot. But that is of course not the case. I discovered a wonderful blog by an extermely sharp physicist, Sabine Hossenfelder: Backreaction. She knows a hell of a lot about the foundations of physics, and she gave a three post rundown of the current state of the discussion about a month ago. It makes for splendid reading, I highly recommend it.

[Enzo]

I still think dark matter is just regular matter dimensionally removed. One brane over, so to speak.

[Мастер]

You could have said essentially the same about the neutron and the the neutrino (or, for that matter, Neptune), before they were confirmed to exist.

All excellent points!

If you were following this discussion on CQ only (but surely, you aren't. Are you?), you could get the impression that anyone even entertaining the idea that a set of laws without Dark Matter is even conceivable is, ipso facto, a crackpot.

I have not followed this discussion, but I have come across some with that tone. This is the sort of thing to which I was reacting. The whole thing seems a bit - well, tentative to me.

But that is of course not the case. I discovered a wonderful blog by an extermely sharp physicist, Sabine Hossenfelder: Backreaction. She knows a hell of a lot about the foundations of physics, and she gave a three post rundown of the current state of the discussion about a month ago. It makes for splendid reading, I highly recommend it.

Will have a look. Maybe after dinner, when I'm back on the island