Dark Matter Found? $2 Billion Orbital Experiment Detects Hints

astroengine writes "A $2 billion particle detector attached to the International Space Station has detected the potential signature of dark matter annihilation in the Cosmos, scientists have announced today. The Alpha Magnetic Spectrometer (AMS) was attached to the space station in May 2011 by space shuttle Endeavour — the second-to last shuttle mission to the orbital outpost. Since then, the AMS has been detecting electrons and positrons (the electron's anti-particle) originating from deep space and assessing their energies. By doing a tally of electrons and positrons, physicists hope the AMS will help to answer one of the most enduring mysteries in science: Does dark matter exist? And today, it looks like the answer is a cautious, yet exciting, affirmative."

Dark matter

[Intrepid imaginaut]

So if I have this right and someone please correct me if I don't, dark matter is transparent, we can see right through it, it's intangible and doesn't appear to interact with normal matter except through gravitational effects. Could such a thing be used to make some sort of dark matter highway to provide a gravity well between stars for ships to travel down without expending much energy?

interesting first results...we'll see

[ganv]

That is a very interesting result. Their first measurements of the positron energy spectrum are consistent with super-symmetry ideas about dark matter collisions creating positron-electron pairs. If it turns out to be right, it will be the first non-gravitational detection of dark matter. But there is not much experimental support for the super-symmetry ideas being used to connect dark matter with positrons, and there are other possible sources of the positron spectrum at the current accuracy. So we'll see. It is great to see they have some results...this experiment has taken a long time and a lot of money. But when you introduce a much more precise way to measure, it usually turns out to be worth the cost and effort in the end.

Re:interesting first results...we'll see

[TheRealMindChild]

The Large Hadron Collider has more or less proved that Supersymmetry doesn't exist

Re:interesting first results...we'll see

[DMUTPeregrine]

Not even close to true. The LHC has shown that certain variants of supersymmetry can't exist, and shown nothing at all about other variants. Just because I didn't find my keys on my desk doesn't mean they haven't fallen between the couch cushions.

Excellent Question!

[Roger W Moore]

Why would Dark Matter be more diffuse? If it only interacts via gravity, shouldn't it be more compact than ordinary matter

That's a very intelligent question! That's exactly what you might expect but you need to go a little deeper. Think about a planet forming from a cloud of dust and rocks. Once a clump of a few rocks has formed it starts to pull in more dust and rocks from the surrounding cloud and a planet starts to form because rocks in the cloud are pulled in my the gravitational field of the clump until they smash into it and stop. This increases the mass of the clump so it pulls in more rocks and grows.

The critical part is that the only reason that the rocks stop when they hit the clump of material is because of the electromagnetic repulsion between the atoms in the rock and the atoms in the clump. This is the same reason that you do not fall to the centre of the Earth - the atoms on the soles of your feet are repelled by the atoms of whatever you are standing on.

Now lets think about Dark Matter. It has no electrical charge and so feels no electromagnetic force. So when a Dark Matter particle is attracted towards a clump of other Dark Matter particles it simply passes right through them without any interaction! It then starts to slow down under their gravitational field until it, eventually, turns around and flies back through the centre. Effectively all a "clump" of Dark Matter is is a group of particles oscillating back and forth in their shared gravitational well. This is why Dark Matter is so diffuse - it can form structures but only on a very large scale.

This is not quite the entire picture - there may be a very small chance of an interaction when Dark Matter particles pass by each other. This will help the particles to clump more but it will be a very, very slow process - and this is only the case if Dark Matter feels the weak force which is not certain. These interactions might also involve two Dark Matter particles annihilating which, if true, may give the positron signal which AMS sees. However to confirm this they need to look at a sightly higher energy which they claim they already have the data for.