E46Fanatics - View Single Post - The Official Science Thread
View Single Post
Old 11-20-2012, 01:59 PM   #1514
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 871
My Ride: '01 TiAg M3 Vert
Originally Posted by cowmoo32 View Post
Maybe Mash can come in and simplify things, but if I'm reading this correctly I think they've experimentally proven that time does have a direction
I'll write up something about the actual experiment when I get a chance (maybe later tonight). I just read the first few paragraphs before they explained exactly what they did. I'll try and explain that one a little better than the article.

In particle physics, there are 3 symmetries, Charge (c), Parity (p), and Time (t). In a reaction in particle physics, if you take one of these symmetries and make it opposite, the reaction still works. That is, if you take charge for example, if you change all of the charges of the particles in the reaction (make + to - and - to +), the reaction still works. If you run the clock backwards (time), it still works. If you change +x to -x, +y to -y, and +z to -z (parity), it still works.

However, when I say the reaction still works, I mean that it usually still works. In some cases, the symmetry is violated and it doesn't work exactly the same way. They realized this when they were checking the parity symmetry. Some decays work differently if you look at different spins of the particles. However, they realized that if you change the charge AND parity (called cp), it turns out the be the same.

Well, not exactly still. In some cases, even cp can be violated, so that if you change the charge and the parity, it still will work differently. BUT, if you change charge, parity, and time (cpt), then it will ALWAYS be the same, and the cpt symmetry is not violated. Now, when they say that cp is violated, it is equivalent to saying that the t symmetry (time) is violated. Up until now, even though the cp and the t symmetry violations are equivalent, they could only check the cp symmetry. It looks like now they've been able to directly probe the t symmetry.

Editted for some accuracy.

Last edited by my ass; Yesterday at 11:15 PM.

Last edited by mash20; 11-20-2012 at 02:03 PM.
mash20 is offline   Reply With Quote