Is there dark matter at the center of the Milky Way which also decays?
phys.org
phys.org
Actually, this is the default situation in our field, and it's a good one. The only issue is that typically only the "hottest" stuff get popular exposure, which usually means the most blaring declarations of discovery, like the hundreds of fifth force articles we just got hit with.
(My one minor complaint is that the headline by itself is misleading. The question is whether there is dark matter at the center of the Milky Way which also decays, leading to the signals mentioned in the article.)
Yes, I am sure the mystery goo theories would get much more exposure. The pitfalls of pop-sci probably. I mean wich kid will get out of bed for a boring pulsar these days?
> "I was pretty excited, because I knew the implications were very big—it meant that the dark matter explanation was back on the table"
I don't understand this. Isn't this basically feeding? Doesn't this just say we know less than we thought? Were we in danger of knowing everything?
> Instead some mystery goo that hides from our sight?
Maybe. We assume "dark matter" has to exists because it interacts with/creates gravity. The only thing we know that can do so is matter.
However this besides detecting gravity interactions with normal matter, this dark matter cannot be seen, not in any wavelenghts, nor does it block any light or radiation from normal matter that's behind it.
It's not like it's just a bunch of normal matter that hides in a corner we cannot see by normal means.
This isn’t really accurate. Everything interacts via gravity, notably radiation and gravitational waves. (The latter hasn’t been directly experimentally tested AFAIK.)
A major reason to think of dark matter as matter is its equation of state, i.e. how it behaves when stretched or diluted. If you put 10g of light in one box (this is possible in principle — it’s a lot of light, and you need a box with impossibly shiny walls) and put 10g of cool gas in another, they gravitate identically. But, if you expand the boxes the same amount, the light gets diluted far more than the gas. That is, if you double the box’s volume by moving one of the walls, you still have about 10g of gas but much less than 10g of light. If you had a third box full of 10g of dark energy and you double the box’s volume, you end up with 20g of dark energy. Yes, this is really weird.
And I say negligible only because my understanding is that even vacuum has a tiny amount of energy in it due to Heisenberg's uncertainty principle, so a box twice as large would contain a tiny bit more energy even if it was equally empty in both cases.
What's the name of the phenomenon you describe? I'd like to learn more.
Now put some gas, light, or dark energy in the cylinder and then pull the piston out to its full extension. You've doubled the volume, but you're also done some work by pulling out the piston. If the cylinder is full of gas or light, the pressure is positive, so you did negative work (received energy) by pulling out the piston, and the energy in the cylinder decreases. For dark energy, the pressure is negative (crazy, I know), and you had to pull hard to extend the piston, so you put energy into the cylinder and, in fact, doubled the total energy in the cylinder.
[0] In general relativity, on large scales, conservation of energy is complicated.
[1] With a real bike pump or car engine, nothing fundamental changes if you have air outside the cylinder, but when you're talking about cosmology, you start considering that the whole universe is full of more or less the same stuff and it gets a bit more complicated. It all works out in the end, though.
One of the authors vas a coauthor of the 2015 paper that was now disproven about its “it can’t be dank matter” claim:
"My hope was that this would be just the first of many studies of the galactic center region using similar techniques. But by 2018, the main cross-checks of the method were still the ones we'd done in 2015, which made me pretty nervous that we might have missed something."
And the whole article about this new paper is informative.
More "debunking the debunking" studies like this are needed.
It seems there is a bias and "debunking with a weak method" is much more likely to be accepted than "proving with a moderate method". Ok, the null hypothesis might be more likely, but some methods are just inappropriate.
But the amount us tiny, current estimates of the dark matter density in the Milky Way result in roughly 700 grams of DM in the Earths volume
If so, (I'm no scientist at all), that sounds like a very powerful matter indeed :-)
So yeah, the effect is basically zero.
I've also seen an article not long ago showing 'visualizations' of dark matter around a spiral galaxy, and it was mostly in teardrop-shaped lobes above and below the galaxy's center and aligned on the axis, rather than distributed through the disk. I didn't think of it at the time but now that I do, it seems like that distribution also indicates that light from the stars is pushing the dark matter away.
If dark mater is a particle, it rarely interacts with anything, including itself; so, it cannot collapse. Most of the particles will be in a constant state of free fall throughout the galaxy. Only if the particle just happens to have a nearly matching velocity would it get trapped in a star or planet. Even then, it would still be wobbling around with nothing to touch.
Article about a Dark Matter research detector using Xenon, not the element itself.
Snark aside, what's really interesting is the way that different fields respond to it when the model errors are discovered. Physics and Chemistry seem to be fairly (or at least comparatively) professional and receptive when they find out about mistakes. But mention a model error or data mismatch to someone in Neuroscience or Climatology? You're suddenly an anti-science heretic and probably murder kittens for fun.