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Particle Physicists Confirm Arrow of Time Using B Meson Measurements
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."
Arrow of Time confirmed... Wheel of Time fans disappointed.
Well, reading the article backwards still results in WTF?
They would be more specific about the arrow of time. I get that they have confirmed it and all, but which direction is it pointing?
Time flies like an arrow. Fruit flies like a banana.
That's all I've got to contribute. Carry on.
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
Time does not run the same way backward as it does forward. It, like, runs forward and does not run backward.
After reading the whole thing, I still don't understand a thing it said. Maybe I'm illiterate.
I'm totally lost. So they tracked the decay of particle in the past by having them entangled with with particles from the future? Sorry, my feeble little brain has obviously reached its limit.
Bet you wish you had unicode now, eh?
I wouldn't really describe this as confirming the arrow of time.
The really powerful arrow of time is the thermodynamic one. The second law of thermodynamics says that entropy always increases. This thermodynamic arrow is essentially the same arrow as the psychological one, which allows us to remember the past but not the future, and all the other ones we see in nature, such as the laws of black hole thermodynamics, which say that the area of a black hole's event horizon always grows with time. This group of time-arrows, which are all essentially the same time-arrow, appear to occur because the big bang was fine-tuned to be extremely low in entropy, with its gravitational-wave degrees of freedom inactive. Nobody knows why we had a low-entropy big bang, when a random choice of initial conditions would be overwhelmingly more likely to produce a maximum-entropy one. (In particular, inflation doesn't explain it. Also, statistical mechanics doesn't explain it, because to produce the second law from statistical mechanics, you need to assume a low-entropy initial state.)
This paper is about an arrow of time that is obscure and completely unrelated to the others. It has to do with the weak nuclear force. Unlike the others, it has essentially no effect on the world we see around us.
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Well that took enough time, didn't it.
DaveyJJ
) time travel. (Please ignore everything between the parenthesis, thank you)
Come on people, how hard is it to include the arXiv link? Just google the title, it's usually the first hit.
http://arxiv.org/abs/1207.5832
The summary is a bit confusing if you don't know what it's talking about. The title is even worse, since it implies the exact opposite of what it actually means. Let me try to explain it.
First: physicists believe that the "arrow of time" isn't a fundamental property of the laws of nature. There's no fundamental difference between "forward in time" and "backward in time". The laws of physics operate identically in both directions. So why do those directions seem so different? Why do objects fall down but not up? Why can you make an egg into an omelet, but not an omelet back into an egg? Why can you remember the past, but not the future? This turns out to be a property of our local region of spacetime. More precisely, we live very close (a mere 13.5 billion years or so) away from a point of incredibly low entropy (known as "the big bang"), and that creates an entropy gradient throughout our region of spacetime. What we call "forward in time" simply means "the direction of increasing entropy", or more simply, "away from the big bang".
A good analogy (not involving a car - sorry!) is the direction "down". It seems obvious to you that one particular direction in space is fundamentally different from all other directions. Objects fall down. They don't fall in any other direction. Yet to person on the other side of the earth, the direction they call "down" is completely different from the direction you call "down". That's because the "arrow of gravity" is not a fundamental property of the laws of nature, just a property of our local region of space. "Down" means "toward the center of the earth." In the same way, "forward in time" means "away from the big bang".
Second: what I just said swept a few details under the rug. You see, the true symmetry is not time reversal (which would imply that simply reversing the direction of time would leave all laws of physics unchanged), but a slightly more complicated symmetry called CPT invariance. That stands for Charge, Parity, and Time. It says that if you multiply the charge of every particle by -1 (so positive charges become negative and negative become positive), flip space as if in a mirror so that your left and right sides are reversed (a "parity inversion"), and reverse the direction of time, then all the laws of physics are left unchanged.
Scientists had previously observed a violation of CP. That is, swapping only charge and parity is not an exact symmetry of the universe. If CPT is an exact symmetry (which scientists generally believe), that implies that T is not - changing only the direction of time without also swapping charge and parity should change the laws of physics. But testing that experimentally turned out to be very hard to do. Well, they've finally done it. And the results are exactly what people expected: it appears that CPT really is an exact symmetry of the universe.
"I'm too busy to research this and form an educated opinion, but I do have time to tell everyone my uninformed opinion."
IANAP, but here is my understanding of the experiment. They knew that two different decay chains occur from some positron/electron collisions. If time is symmetric, there should be equal numbers of both chains. By making the beam energies different between the positron and electron (e-e+) beams, they were able to differentiate the decay order. If time symmetric decay occurred then there would be one spacial pattern in the results, and if time was asymmetric there would be another. The results conclusively show that for this subatomic event time runs in the direction we know as "forward". This is a big deal for subatomic physics.
Why is Snark Required?
"(Please ignore everything between the parenthesis, thank you)"
Um
In a Newtonian universe, light will follow the same path backwards if it's direction is reversed (bounced perfectly normal to a mirror). My question is "does this hold under relativity?". I thought the answer was yes, but IANAPhysicist so don't know if that's the accepted answer. If it does hold then there are some very interesting consequences that are never talked about.
The arrow of time is the reason why random bits of shrapnel and chemicals don't fly together and "un-detonate" to become hand grenades.
No, that is entropy. The reason that balls fall off tables and rarely bounce onto them (when provided with enough heat energy) is because there are many, many more states where the balls atoms vibrate incoherently and only one state (or a tiny handful) where the vibrations are organized enough to cause it to bounce back onto the table.
With mesons you can study a particle oscillating between two states. What you find is that the P(A -> B) is not equal to the P(B -> A) where B is the anti-particle state of A and there is no entropy involved. It's all to do with something called CPT symmetry which is a result of relativity and, since CP together are violated (anti-matter is not exactly the same as matter) we expect that T (time reversal symmetry) is also violated so this is an expected result.
Arrow of Time confirmed... Wheel of Time fans disappointed.
Physicists on the CPLEAR experiment will be disappointed as well - they actually discovered this effect (called T-violation) back in the 1990's before Babar was running by looking at kaon oscillations produced in low energy proton/antiproton collisions [Phys. Lett. B 444 43 (1998)]. So Babar was certainly not the first experiment to see the "arrow of time" although it is the first to do so using B mesons.
No. You know why? Cuz time don't go back.
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
It's very hard to write something inside of a parenthesis. The plural of 'parenthesis' is 'parentheses'.
emit fo worra diputS
Recycle PCs and build a wireless community network www.hillsborough.org.nz
Well, except for being necessary for CP violation, which in turn is the only way we have of explaining why there isn't much antimatter around.
No, CP violation doesn't explain baryon asymmetry. CP violation is part of the standard model. Baryon asymmetry isn't explained by the standard model.
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...but then I took an arrow of time in the knee.
time runs in the reverse direction (T)
oh he's making it up as he goes along!
Q: Why did the cat slide off the roof?
A: It didn't have enough Mu.
bahahahahahahahahahahaha!!!!!!! i found that on some random physics jokes website and its the funniest joke i think i've ever heard... sad huh
?yaw thgir eht si, yaw hciW
...elephant.
It's trunk is already hanging out.
"Time flies like an arrow. Fruit flies like a banana." Is it still a banana going backwards or do fruit flies now like an ananab? Also, can anyone explain what this paper means in English for an average moron like me?
Funny - I read the article backward and I got that Paul is dead.
What does it say forward? Is it "Monsieur, monsieur, monsieur, how 'bout another one" like the end of "I'm So Tired", or "Cranberry sauce" like the end of "Strawberry Fields Forever"?
According to physicist Sean Carroll, who specializes in this sort of thing. I figured people might enjoy reading this, in case it hasn't been posted.
Whenever I read stuff like this I think there are a bunch of physicists snicking and laughing in front of a screen watching Slashdot and saying "Oh my spaghetti monster I can't believe they are buying into this bullshit. We can say anything we want and they'll believe us. Quick, post an article about time unicorns and looms that predict the future. he he he".
I haven't thought of anything clever to put here, but then again most of you haven't either.
noob
I couldn't quite tell from reading ...
Hm...
http://mr.crossref.org/iPage/?doi=10.1070%2FPU1991v034n05ABEH002497
For the subscription impaired, the summary from Wikipedia:
Oh, and just to address the rest of your statement:
http://en.wikipedia.org/wiki/Baryogenesis#Baryogenesis_within_the_Standard_Model
you've never seen my code so you're getting pretty desperate, but at least you're calling them error "handlers" now rather than noobish "traps"
only a noob like you would feel a need to wrap an exception handler around a print statement... maybe you should have put an exception handler around your exception handler, just in case you fucked that up too
rhetorical question: which is more bug prone, and which one actually has a bug?
...and the funniest part is that he either can't even see it, or can but doesn't want to acknowledge it and instead wants to keep posting his incompetent garbage all over slashdot
s = "123"
s = s[::-1]
print s
or...
code here: http://slashdot.org/comments.pl?sid=3258205&cid=42015649
answer: APK's bullshit code has a Python indentation bug on the fifth line!
you might have a couple of exception handlers APK, but the code in the linked post won't even interpret let alone handle any errors!
noobs may not use exception handlers, but noobs also use exception handlers incorrectly, which you have. exception handlers are good for handling specific exceptions (user input particularly).
wrapping swathes of code in exception handlers stinks of noob.
i already debugged it. not hard to debug 3 lines of code. it doesn't need exception handlers.
...and at least i actually debug my code; you still can't acknowledge the bug in yours - example here http://developers.slashdot.org/comments.pl?sid=3258205&cid=42014957
another rhetorical question: how does adding error handlers make code easier to debug?
exception handlers are very useful for any kind of input or api calls etc
i wouldn't just wrap all my code in an exception handler though. i would wrap certain calls in handlers to handle specific and expected exceptions
exception handlers have absolutely nothing to do with code debugging
wrapping code in exception handlers won't get rid of bugs (surely that's obvious to you)
so where's the printer driver code in your buggy function douchebag?
i didn't see any code running... for all i know you could have manually typed the supposed output
there is a bug in your posted code though. if you can't see it, then you're an incompetent noob (especially since i've spelled it out to you on a few occasions)
yep... the bug is in at least two of those posts (i didn't bother clicking on the rest but i'm sure they are the same)
if you are using a script, it isn't the same as the one you post, because your posted code has an indentation bug and won't interpret (and no amount of error handling will change that lol)
leave the bug in there... at least i'll be able to continue to highlight it to the rest of the slashdot readership and they can decide how much of a noob you are for themselves
what if an alien spaceship tried to infect your rediculous Python code with some alien virus? you would be totally fucked without exception handlers i'm sure :)
exception handlers aren't for debugging... fool... they are for.... (drum roll)... handling exceptions!!!! hahahaha!!! (and if you are wrapping code in handlers for unknown exceptions you're doing it for the wrong reason... exception handlers are for handling expected exceptions - popping up a message that says something like "oh oh something fucked up and the programmer has no idea what" isn't very reassuring for the user).
maybe you need a bit more practice debugging to understand how it differs (try debugging your stupid function first)
google also no doubt has some handy tips
You said to use error handlers for input from users ONLY?
bullshit moron... learn to read... what i said (quoted from my message) was "exception handlers are very useful for any kind of input or api calls etc".
did you see the "etc" on the end there?
Ever heard of using keypress events in entry fields and validating entry there instead
i use onchange events etc for validation, but in those events, i usually wrap my single line of code for converting from string to integer (or whatever the case) with an exception handler, and the handler code changes the color of the label or something like that.
when you dump structured error handlers you get what is wrong a good 95% of the time and it's correct and saves you time debugging
no you don't and no it doesn't... maybe you should look up the definition of "debugging"
anyway, i've had enough educating you. if you want more advice you're going to have to start paying by the hour... and i double the rate for idiots like you
my story is straight... you're confused because you think debugging has something to do with error handling... you poor ignorant moron
you CAN'T EVEN PROGRAM IN C
just because i don't doesn't mean i can't
and i get paid for programming php/html/js/css/sql, so why would i give a shit about c?
Oh, so NOW 'CruTcHy' (lol) "flips the script" changing what he said, lol, "adding on to it"
i quoted from the original message dipshit. i didn't add anything.
getting pretty desperate aren't you?
On user inputs, you USE KEYPRESS EVENTS in entry fields to trap bad data users may input.
that's one way, but not necessarily the best because you may be trying to validate incomplete user input, so if a user startes by entering a minus symbol with the intention of entering a negative number, how can you validate that on keypress? the next key may be a number, which would make it valid, or they may move on leaving just an invalid minus symbol. using a keypress event handler is similar to a change event handler in that you can do something non-intrusive (like change the color of the text box label to red) as the user types until a valid input is achieved, but you shouldn't show any kind of intrusive error message until the user has actually finished entering their input (with an lostfocus or similar event).
anyway, i know you won't even read this let alone understand it.
you're also starting to get boring APK, so unless you can step up the intelligence of your conversation i'm probably going to move on
Easy - ALLOW for it during your checks in your filtering tests!
you're right that it is easy to filter inputs, but not on keypress. you will need another event to handle that. that's why i mentioned events such as lostfocus, but there are of course others (keypress is definitely one event that can be used for partial input validation, but not on its own).
if you have your so called "filter tests" (noobish terminology much) only in a keypress event, you will either allow invalid input (such as a lone "-" symbol) or you will prevent entering of valid inputs (such as "-5.4" for example).
you are about as noob as they come APK, but you are definitely the most arrogant self-rightious noob I have ever come across, which makes you look even more stupid on this very public and open forum.
btw, have you found that bug yet?
you appear to have difficulty comprehending basic english... maybe you should actually look up "don't" and "can't" in the dictionary
as i said before (not that i expect it to sink in any more than the last time i said it) but just because i don't program c doesn't mean i can't... i can program c if i need to. i just don't need to
you're an idiot. nothing more
last time i checked delphi wasn't primarily for web programming, but i guess you're a noob when it comes to delphi as well so what more can i expect from such a noob as yourself