Oct
27th
2017
Nightmare Night. Dark Matter Day · 8:54pm Oct 27th, 2017
Is anyone at Nightmare Nights Dallas? I will be joining Needling Haystacks MLP Physics panel at 4pm on Saturday 28 October (by Skype link - while I would love to take a trip to Texas, it’s not very practical right now). Come along to hear a group of physicists discuss, and possibly argue, about the sonic rainboom, multiple timelines, and how things like orbital mechanics and genetics might work in Equestria.
Back home, I will be part of a slightly more serious (or maybe not) panel in Oxford on Dark Matter Day, Tuesday 31 October. There are similar public science events happening around the world to celebrate the invisible side of the Universe, so check out what’s going on near you at: Dark Matter Day.
So, do you need some dark matter for display purposes? I've got a couple pounds of the stuff building up in the filters in the house, and don't really need it.
4709519
I feel you, man. About 70% of my house by mass consists of dark matter.
I finally found the numbers I needed, dividing by approx the speed of light, at the Earth orbit due to teh sun, theres about 2 million neutrinos per cubic metre. Given theyre supposed to oscilate between three widely differeing masses, Id say take the highest mass and divide by 3, multiply by 2 million, and if it exceeds 10 billion, then thats dark matter?
4709519
A display of genuine dark matter wouldn't really work, since you can't see it. Thanks for the offer, but I'll let you keep it for your own DMD party.
4709545
Neutrinos were once a dark matter candidate, but they've now been ruled out. They're just too light, and move too fast to shape galaxies.
4709588
But molecules move too fast to form any structures, but over large enough sampled volume, they become an atmosphere, with currents and eddies and mass densities.
4709632
Neutrinos don't clump on scales as small as galaxies, but we know from rotation curves that dark matter dominates the mass of galaxies, so we need a cold dark matter candidate to explain small scale structures like the Milky Way.
4709645
How much does the mass energy of the gravity field of a galaxy weigh, relative to the overall missing mass?
Assuming the mass energy of the gravitational field of the sun is approximately equal to the mass of the Earth I think it was?
4709588 ....so.... it's like politicians' ethics, right? It exists in theory and there have been several experiments that lean toward its reality, but nobody has an actual sample, and even if they did, you can't examine it.
Unfortunately, I cannot attend.
For a moment I was like 'Noooo, I missed meeting you because I didn't check Fimfic for like a week and a half' due to, well, back to back pony cons.
Then I read the blog and relaxed. Phew!