6 ms·

How does one "find" what's already been "found"? We already know where dark matter is just by observing changes in gravity, we just need to know what it is. Nei

by eksith 14y ago

How does one "find" what's already been "found"? We already know where dark matter is just by observing changes in gravity, we just need to know what it is. Neil DeGrasse Tyson explains this the best : http://www.youtube.com/watch?v=QSeXyDEWgyc http://www.youtube.com/watch?v=QSeXyDEWgyc The tl;dr of that article is basically that Dark Matter is theorised to be made of WIMPs (weakly interacting massive particles) which are matter that are their own anti-matter. Mind boggling concept since when ordinary matter meets anti-matter, it's an Angels and Demons style explosion. But these particles are their own "matter" and anti-matter in one, if that's what they really are. These WIMPs give rise to positrons, which are basically anti-electrons (anti-matter variant of electrons) and this is what these sensors are alleged to have detected. WIMPs are what they think create positrons and regular electrons. "The smoking gun signature is a rise and then a dramatic fall" in the number of positrons with respect to energy, because the positrons produced by dark matter annihilation would have a very specific energy, depending on the mass of the WIMPs making up dark matter... Until they actually publish that paper with conclusive evidence, this is still all speculation and ad revenue for space.com .

nagrom 14y ago
"when ordinary matter meets anti-matter, it's an Angels and Demons style explosion" Oh goodness me, no. They annihilate to create a lepton pair. There is no explosion, really. Subatomic physics is much more boring than popular science would have you believe! You must try quite hard to get an explosion - it isn't chemistry, where things explode simply because it's Wednesday. Particles that are their own antimatter are not all that exotic either. Z bosons, gluons and photons are all their own antiparticles too, and perhaps neutrinos. As I understand it (and I am a nuclear physicist, not an astrophysicist) there are few (no?) observed natural interactions known to produce high energy positrons (i.e. with energy >1 GeV). So, if you find one coming from space, it is an indicator that something unexplained has happened. Since we know where there must be clusters of dark matter and WIMPs are theorised to produce such positrons, dark matter decay is the leading candidate for an explanation for a high energy positron coming from such a direction. Or it could be aliens, of course.
- eksith 14y ago
  Ah! I fear Hollywood and TV has corrupted my understanding of Anti-matter. Thanks for clearing that up :) Aliens could be enticing us to seek new frontiers for scientific knowledge, but unless this comes to us in messages hidden in crop-circles or revealed through abductions, I'm not buying it!

by eksith 14y ago

nagrom 14y ago

"when ordinary matter meets anti-matter, it's an Angels and Demons style explosion" Oh goodness me, no. They annihilate to create a lepton pair. There is no explosion, really. Subatomic physics is much more boring than popular science would have you believe! You must try quite hard to get an explosion - it isn't chemistry, where things explode simply because it's Wednesday. Particles that are their own antimatter are not all that exotic either. Z bosons, gluons and photons are all their own antiparticles too, and perhaps neutrinos. As I understand it (and I am a nuclear physicist, not an astrophysicist) there are few (no?) observed natural interactions known to produce high energy positrons (i.e. with energy >1 GeV). So, if you find one coming from space, it is an indicator that something unexplained has happened. Since we know where there must be clusters of dark matter and WIMPs are theorised to produce such positrons, dark matter decay is the leading candidate for an explanation for a high energy positron coming from such a direction. Or it could be aliens, of course.

eksith 14y ago
Ah! I fear Hollywood and TV has corrupted my understanding of Anti-matter. Thanks for clearing that up :) Aliens could be enticing us to seek new frontiers for scientific knowledge, but unless this comes to us in messages hidden in crop-circles or revealed through abductions, I'm not buying it!