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A pair of researchers from the University of Nevada, Reno, in an attempt to detect and better define dark matter, have pulled off a pretty amazing science experiment. The team used 16 years worth of GPS data to turn the whole planet into a massive detector that might detect clumps of dark matter that could extend beyond the solar system.
Dark matter makes up roughly 85% of all matter in the universe, which is a real bummer for us humans — as we simply have no idea what it is, what it looks like, nothing. Astrophysics has provided multiple evidence that it actually exists, but so far, it’s always been beyond our grasp. As generally tends to happen when faced with great unknowns, we do however have quite a lot of hypotheses pertaining to its nature.
"So, the two gathered data from the 32 satellites that make up the 31,000-mile-wide GPS constellation and ground-based GPS stations, retrieving figures recorded every 30 seconds for the last 16 years. Data was retrieved from sources around the world, and in particular from NASA’s Jet Propulsion Laboratory. They then used a model to sift through this data, looking for irregularities in atomic clock signals.
[...] Aaaaaaand they didn’t find anything. It’s a bit disappointing, sure, but it’s not really surprising given how elusive dark matter has proven itself to be up to now. It has to be said, however, that while the team didn’t find any definitive proof to support their theory, it could be that the effect is simply more subtle than anything we can pick up, or that the Earth crosses lumps of dark matter very rarely."
https://www.zmescience.com/science/earth-dark-matter-sensor-gps/
(Score: 2) by FatPhil on Sunday November 05 2017, @10:55AM (7 children)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Informative) by maxwell demon on Sunday November 05 2017, @01:21PM (6 children)
Wikipedia disagrees. [wikipedia.org] Emphasis by me:
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by HiThere on Sunday November 05 2017, @05:36PM (3 children)
Wikipedia is a lousy source for this kind of argument. Pick an astronomy site.
That said, I believe that a galactic halo is a thick, roughly spherical shell. Not a sphere, the inside has been generally eaten away by a black hole. OTOH, I don't have a link for this, and maybe the central black hole is normally counted as a part of the halo, but I wouldn't take Wikipedia's word that this was true. Also, it's not really spherical, even as a shell, because it's rotating (to varying degrees) which squashes it into an approximate ellipsoid of rotation. (Even that isn't quite right, but in the first place it's not a simple solid with a name, and in the second place when you start getting detailed, different galaxies are different, sometimes considerably.)
However, as an argument about dark matter, I have no opinion. I find I really dislike the theory, but it is the only one I know of that fits most of the evidence without LOTS of custom adjustment. Come up with something better. (MOND doesn't appear to be that "something better" as it is reported to need lots of custom adjustment.)
This is sort of why I don't like string theory. It can predict nearly anything when you tune all the adjustable factors that can't be determined from theory. If string theory is correct, then I have to side with either the parallel or sequential multiverse (i.e., either every choice that can be made is made at the same time, or the universe oscillates through cycles of expansion and compression, with lots of arbitrary "constants" give random values with each big bang.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Interesting) by Gaaark on Sunday November 05 2017, @06:02PM (2 children)
An interesting read here:
http://physicsfromtheedge.blogspot.ca/ [blogspot.ca]
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by HiThere on Sunday November 05 2017, @07:33PM (1 child)
I am very tempted by the arguments presented, particularly since I don't believe in continuity, though I tend to think the scale on which the universe should be discontinuous should be around 10^-33cm. I have trouble, however, with distances seeming to be independent of orientation.
OTOH, I don't feel myself competent to really accept or deny any cosmological argument. I know there's lots of evidence I don't know. What I feel competent to do is *try* to understand what is generally agreed. I don't always agree with it, but I acknowledge that my disagreeing isn't a valid sign that it isn't correct.
So while I'm tempted by the arguments, it seems the scale at which is being proposed for discontinuity isn't what I expect, and in any case I don't feel qualified to judge. Also I didn't see any peer reviewed papers on Renzo's rule. If I had I couldn't have evaluated them, but their absence is, in and of itself, a point against it (to someone who can't independently evaluate it against the evidence).
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Interesting) by Gaaark on Sunday November 05 2017, @08:10PM
I'm kinda the same: I'm willing to look at alternatives.
I believe there has to be something wrong with his theories where time travel is possible; the whole travel back in time and kill your grandfather so you could never be born so you could never go back in time and kill your grandfather, so you WERE born so you COULD go back in time so....
You read about physicists saying "something" would stop you from killing him: the gun would magically jam, or the knife would magically 'jam': shite like that.
I'd rather believe Einstein, or an interpretation, is wrong in some way. That is why I like the people looking at alternatives, the likes such as Julian Barbour:
https://en.m.wikipedia.org/wiki/Julian_Barbour [wikipedia.org]
He is working from a Machian point of view where time and space are separate (which is what Einstein originally believed, but found the math would be an agonizing beyotch and went with time and space being inseparable instead).
Time travel goes away when you separate time and space (or, like Mr. Barbour, believe time exists only as a product of movement in space (the sun moves, creating the illusion of time, etc etc).
I don't like kludges, and to me, dark matter is a kludge to make General Relativity work. I'd rather say "something is not right with GR: let's find out what is wrong.
Analogy: your car is leaking oil.
Dark matter theory: it's leaking oil because magic.
Better theory: something is wrong....hmmm...oh! Your plug is loose! Let's tighten it!
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by cubancigar11 on Sunday November 05 2017, @05:37PM
Maxwell solving difficult physics problems, even as a demon! Thank the lord for rejecting his application to heaven.
(Score: 2) by FatPhil on Monday November 06 2017, @10:49AM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves