Time

From Slashdot.org:

Particle Physicists Confirm Arrow of Time Using B Meson Measurements108

Posted by Unknown Lameron Monday November 19, @06:50PM
from the one-way-trip dept.

ananyo writes with bad news for John Titor. From the article: "Four years after its closure, researchers working with data from the Stanford Linear Accelerator Center's particle physics experiment BaBar have used the data to make the first direct measurement confirming that time does not run the same forwards as backwards — at least for the B mesons that the experiment produced during its heyday. The application of quantum mechanics to fundamental particles rests on a symmetry known as CPT, for charge-parity-time, which states that fundamental processes remain unchanged when particles are replaced by their antimatter counterparts (C), left and right are reversed (P), and time runs in the reverse direction (T). Violations of C and P alone were first seen in radioactive decays in the 1950s, and BaBar was used to confirm violations of CP in B meson decays in 2001. To keep CPT intact, that implies that time reversal is also violated, but finding ways to compare processes running forward and backward in time has proven tricky. Theoretical physicists at the Universityof Valencia in Spain worked with researchers on BaBar to exploit the fact that the experiment had generated entangled quantum states of the meson Bzero and its antimatter counterpart Bzero-bar, which then evolved through several different decay chains. By comparing the rates of decay in chains in which one type of decay happened before another, with others in which the order was reversed, the researchers were able to compare processes that were effectively time reversed version of each other. They report in Physical Review Letters today that they see a violation of time reversal at an extremely high level of statistical significance."

Comments

[joared]

What are the practical applications of this finding, or is the primary significance in relation to other research?

[Ole Phat Stu]

Damn, that ruins my current blogpost ;-)

[Ole Phat Stu]

@Joared,
here is Sean Carroll's take :-
http://blogs.discovermagazine.com/cosmicvariance/2012/11/20/time-reversal-violation-is-not-the-arrow-of-time/

Stu

[Cop Car]

Joared--The core of the article that Stu so kindly steers you to is contained in the statement (from the article), "...the confusion between time reversal and the arrow of time often leads smart working physicists to think they have discovered something interesting about the arrow of time when really they’re addressing a completely different problem."

My answer to your question is that I doubt either of us will live long enough to care whether there is a practical application. I'll let the Sheldon Coopers wrestle with the issue. ; )

[Hattie]

Does this mean that time always runs forwards, as one would intuitively believe? Or is that just a dumb non-scientist interpretation?

[Cop Car]

Hattie--I'll give you my best answer to your first question and depend upon smarter physicists (Stu) to correct me: Time always runs forward.

Hopefully, to clarify, here is the first paragraph from the article by Michael Zeller, Department of Physics, Yale University, New Haven, CT 06520, USA Published November 19, 2012 | Physics 5, 129 (2012) | DOI: 10.1103/Physics.5.129 Viewpoint: Particle Decays Point to an Arrow of Time

"Time moves irrevocably in one direction. Things get old, decay, and fall apart, but they rarely ever reassemble and grow young. But at the particle level, time’s arrow is not so clearly defined. Most collisions and other particle interactions look the same whether run forwards or backwards. Physicists have, however, identified a few reactions that appear to change when time is reversed, but the reasoning has assumed certain relations between fundamental symmetries of particle physics. The BaBar collaboration has now observed time-reversal violation directly and unambiguously in decays of B mesons. The measured asymmetry, reported in Physical Review Letters [1], is statistically significant and consistent with indirect observations."

[Lauren]

I don't even understand the references I hear on 'Big Bang Theory' so all I understood here was that 'time moves in one direction and things get old, decay and fall apart'.
I can't begin to wrap my head around a method of reversing time! Love your blog though!

[Cop Car]

Lauren--Thanks for dropping by (from Ronni's?) and for the kind words. Unless you are employed or have a strong avocation in the science/technology/engineering/math arena, you may be excused for not understanding all of the references on TBBT. Even Hunky Husband (an engineer who, on occasion accompanies me to physics seminars) misses many of the references and allusions on the program. AND...who's to say that I catch them all?!