Are you sure you want to accept 's answer? will be rewarded with the bounty, the zomb will be closed, and all other participants will be notified.
Are you sure you want to mark answer from as spam? This choice cannot be undone!
Sorry, you have not enough credits to pay results fee.
Are you sure you want to withdraw your application?
What is dark matter?
I'm hoping a physicists who is involved in this area can succinctly explain why:
- We believe dark matter exists
- What it's made from
- Why we didn't think it existed until fairly recently?
On a side not, are there many other cases where we "know" that something exists but can't prove it at this time? For instance, I believe that when the periodic table was first created several spots were reserved for elements that were not yet discovered.
Jul 20, 2011
We have two major observational sources we base our knowledge of dark matter on. First, we realized that galaxies didn't rotate the way we'd expect if stars and gas and dust were the only matter within them. http://en.wikipedia.org/wiki/Galactic_rotation_curve Second, we can use the fact that mass causes light to bend to measure the amount of mass in a region. The most important observation here is the bullet cluster http://en.wikipedia.org/wiki/Bullet_cluster . Taken together, we realized that there had to be more mass out there in galaxies that doesn't reflect or emit light. (Since our earlier measurements were based on light measurements) Well that's okay, we know of particles that don't interact with light, they're neutrinos. But neutrinos are too lightly massed. They flit about the universe at very nearly the speed of light, so they aren't "cold" enough to settle around galaxies like we observe this missing mass to do. So we're looking for "cold dark matter."
Right now, the leading candidate is a new family of particles that we may observe at the LHC in a few years. The idea is that all of our regular fundamental particles have supersymmetric "partners" that are really massive. The supersymmetric partners to the bosons (photons, W, Z bosons, gluons) have a particle called the neutralino. We expect that the neutralino will be the lowest mass supersymmetric partner particle we can find. And if we find it, we think that it may be the particle giving us cold dark matter. http://en.wikipedia.org/wiki/Neutralino
Why didn't we know about it? Well it took the advent of modern astronomy. Great telescopes on earth and space to make really accurate measurements. We're building more telescopes and some earth-based experiments to try and suss out the details even more.
No comments yet.
Keep your profile up to date. The launcher will look at your qualifications, experience and feedback.
Read the zomb description carefully. Ensure you answer any queries about your skills or experience
Take a look at what other members are bidding. If you're going to place a bid amount that's higher than other members, ensure you are the best candidate!