Large Hadron Collider (LHC) News

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Re: Large Hadron Collider (LHC) News

#421  Postby Pulsar » May 01, 2012 4:08 pm

twistor59 wrote:For his Conformal Cyclic Cosmology model, Roger Penrose wanted to get rid of all the matter if you wait long enough - he saw electrons as a significant stumbling block because they wouldn't go away no matter how long you waited.

That's right. Not that I understand Penrose's idea, though.
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Re: Large Hadron Collider (LHC) News

#422  Postby lpetrich » May 02, 2012 2:12 am

Dudely wrote:The experimental lower bound for the electron's mean lifetime is 4.6×10^26 years, at a 90% confidence level.

Are you sure that you are not confusing electron decay and proton decay?

I ask that because I've seen numbers like that for proton decay.
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Re: Large Hadron Collider (LHC) News

#423  Postby THWOTH » May 02, 2012 5:51 am

Pulsar wrote:...Not that I understand Penrose's idea, though.

Give it 20 minutes and and then try again dear.


:whistle:
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Re: Large Hadron Collider (LHC) News

#424  Postby JoeB » May 02, 2012 7:56 am

Dudely wrote:For this reason no particle can exist in the same spot in time and space because that would represent the same 'ripple' in the field. This is why supernovae happen; gravity crushes the particles so close together they start to try to inhabit the same space. . . and, well, you know what happens next.

Are you sure about this? It's the first time I've heard that as an explanation for supernovae (rather than a star's surface bouncing off its solid metallic core during its final collapse), is it string theory? How do black holes fit into this?
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Re: Large Hadron Collider (LHC) News

#425  Postby klazmon » May 02, 2012 8:50 am

lpetrich wrote:
Dudely wrote:The experimental lower bound for the electron's mean lifetime is 4.6×10^26 years, at a 90% confidence level.

Are you sure that you are not confusing electron decay and proton decay?

I ask that because I've seen numbers like that for proton decay.


From wiki for protons:

Wiki wrote:To date, all attempts to observe these events have failed. Recent experiments at the Super-Kamiokande water Cherenkov radiation detector in Japan gave lower limits for proton half-life, at 90% confidence level, of 6.6×1033 years via antimuon decay and 8.2×1033 years via positron decay. Newer, preliminary results estimate a half-life of no less than 1.01×1034 years via positron decay.

Electron decay is a bit problematic. Is there any charge carrier of lower mass than an electron? Otherwise such decay would violate the conservation of charge.
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Re: Large Hadron Collider (LHC) News

#426  Postby klazmon » May 02, 2012 8:57 am

JoeB wrote:
Dudely wrote:For this reason no particle can exist in the same spot in time and space because that would represent the same 'ripple' in the field. This is why supernovae happen; gravity crushes the particles so close together they start to try to inhabit the same space. . . and, well, you know what happens next.

Are you sure about this? It's the first time I've heard that as an explanation for supernovae (rather than a star's surface bouncing off its solid metallic core during its final collapse), is it string theory? How do black holes fit into this?


Sounds like a confused description of a type II supernova
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Re: Large Hadron Collider (LHC) News

#427  Postby Dudely » May 02, 2012 1:01 pm

klazmon wrote:
JoeB wrote:
Dudely wrote:For this reason no particle can exist in the same spot in time and space because that would represent the same 'ripple' in the field. This is why supernovae happen; gravity crushes the particles so close together they start to try to inhabit the same space. . . and, well, you know what happens next.

Are you sure about this? It's the first time I've heard that as an explanation for supernovae (rather than a star's surface bouncing off its solid metallic core during its final collapse), is it string theory? How do black holes fit into this?


Sounds like a confused description of a type II supernova


Haha, yes, you've got it. I didn't want to go into the details of it since the only relevant fact is that once fusion runs out the star can no longer increase its temperature to support it against collapse; it is supported only by the degeneracy pressure of electrons. Matter in the core is so dense that further compaction would require electrons to occupy the same energy states. As I mentioned before this is forbidden for identical particles such as the electron—a phenomenon called the Pauli exclusion principle. This doesn't cause the collapse, but it is a critical piece in understanding why it happens.

EDIT: Since it was asked, I will explain it a bit more.
[Reveal] Spoiler:
Stars which have a core over the "Chandrasekhar limit" of about 1.4 solar masses, will find that once fusion completely runs out "degeneracy pressure" (a fancy word for the pressure electrons have against being compacted any further due to the Pauli exclusion principle) can no longer support all the layers of the star (the core is now solid iron and the rest are layers of other elements like silicon, oxygen, hydrogen, etc.), and so a catastrophic collapse begins!

At this point gravity has won. As the outer core rushes towards the center of the star it reaches speeds of up to 70,000 km/s (23% of the speed of light!). Because heat is just a description of the relative movement of atoms this causes the core to heat up like a motherfucker. The heat is so intense that it spontaneously produces high-energy gamma rays that decompose iron nuclei into helium nuclei and free neutrons by way of "photodisintegration" (which, by the way, is totally badass). As the core's density increases it becomes energetically favorable for electrons and protons to merge into neutrons, which also produces another elementary particle called a neutrino. Because neutrinos are totally messed up as far as particles go they rarely interact with normal matter- they can escape from the core, carrying away energy and making the collapse go even faster (the whole thing takes less than a second depending on what you consider the beginning). Because the closer layers fall towards the core faster this briefly creates a gap between the core and the other layers of the star. Some of the neutrinos are absorbed by the star's outer layers (the outer layer has a lot more mass spread over a far greater area, so it absorbs a lot more than the core), which begins the Type II supernova explosion.

The result is that the outer layers are blown away and the core remains as a neutron star. If this core is above the Tolman-Oppenheimer-Volkoff limit of (roughly) 3 solar masses the repulsive effect a neutron has against another neutron is overcome and it converts itself into a quark star. If the core is above even the limit of a quark star a black hole is formed.

So it is the fact that electrons cannot get any closer together- combined with the fact that fusion has ceased- that triggers the collapse. In this way the Pauli exclusion principle defines exactly if and when a star will collapse because if there was no degeneracy pressure every star would explode.
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Re: Large Hadron Collider (LHC) News

#428  Postby JoeB » May 03, 2012 8:06 am

Great (and very funny) explanation, thanks Dudely! I thought the outward pressure was mainly from photons, and that once fusions stopped no more photons would be emitted, thus triggering the collapse by gravity. (holy crap 23% lightspeed!).
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Re: Large Hadron Collider (LHC) News

#429  Postby Dudely » May 07, 2012 12:52 pm

JoeB wrote:Great (and very funny) explanation, thanks Dudely! I thought the outward pressure was mainly from photons, and that once fusions stopped no more photons would be emitted, thus triggering the collapse by gravity. (holy crap 23% lightspeed!).


Exactly. Once you run out of fusion gravitational collapse occurs. However, stars below the 1.4 limit mentioned above will remain as a stable white dwarf due to the fact that gravity in these stars is not strong enough to overcome that good ol' degeneracy pressure electrons have against being pushed closer together.

Thing of it like two magnets with their like poles facing each other. When you try to push them together you encounter resistance, but this doesn't mean you can't just keep pushing until the magnets touch (this is sort of a bad example because it confuses electromagnetism with quantum mechanics, but hey, it works, so shoot me :P) For 97% of stars (including our sun) gravity will not be strong enough to "make the magnets touch" so to speak.
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Re: Large Hadron Collider (LHC) News

#430  Postby twistor59 » May 07, 2012 1:01 pm

Talking of the LHC, if you want a taste of what it's like to work on the cutting edge of human endeavour, read this:

http://ompp.wordpress.com/2012/05/05/the-live-blog-everyones-been-waiting-for/
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Re: Large Hadron Collider (LHC) News

#431  Postby hackenslash » May 07, 2012 1:05 pm

:rofl:

Brilliant.
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Re: Large Hadron Collider (LHC) News

#432  Postby newolder » May 08, 2012 3:07 pm

Computing in Hungary: http://press.web.cern.ch/press/PressRel ... 2.12E.html
that's many cores. :phew:
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Re: Large Hadron Collider (LHC) News

#433  Postby THWOTH » May 08, 2012 4:34 pm

twistor59 wrote:Talking of the LHC, if you want a taste of what it's like to work on the cutting edge of human endeavour, read this:

http://ompp.wordpress.com/2012/05/05/the-live-blog-everyones-been-waiting-for/

Nice. :thumbup:
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Re: Large Hadron Collider (LHC) News

#434  Postby newolder » May 14, 2012 3:46 pm

dansin 2 teh muzik ov tyme... http://press.web.cern.ch/press/PressRel ... 4.12E.html

like stranGE clowds? :ask:
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Re: Large Hadron Collider (LHC) News

#435  Postby THWOTH » May 14, 2012 4:52 pm

CERN PR wrote:“It will be fascinating to see how Gilles Jobin explores particle physics through dance and movement following creative dialogues with CERN scientists and science,” said CERN Director General Rolf Heuer.


Hmm. Something like this perhaps..?

[youtube]http://www.youtube.com/watch?v=-6gUfpSzQYE[/youtube]

:dance:
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Re: Large Hadron Collider (LHC) News

#436  Postby newolder » May 16, 2012 12:46 pm

xpektid and observed beauty @ teh faktree: https://cdsweb.cern.ch/journal/CERNBull ... es/1449100
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Re: Large Hadron Collider (LHC) News

#437  Postby akigr8 » May 18, 2012 6:50 pm

Image
I once applied for a job as a mustard cutter.

But unfortunately I wasn’t quite good enough.
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Re: Large Hadron Collider (LHC) News

#438  Postby THWOTH » May 19, 2012 11:09 am

newolder wrote:xpektid and observed beauty @[color=#CC0000][b] teh[/b][/color] faktree: https://cdsweb.cern.ch/journal/CERNBull ... es/1449100

So how does one say Λb then? Can ya tell ya mama her name?
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Re: Large Hadron Collider (LHC) News

#439  Postby newolder » May 19, 2012 1:59 pm

^ teh simbles/script as shown (sed as lambda sub b) describes a beautiful hard1 (in a dizleksik sens). :lol:
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Re: Large Hadron Collider (LHC) News

#440  Postby THWOTH » May 19, 2012 2:38 pm

Lamba Sub B eh? Sounds like an urban classic. :cheers: I've been trying to process the 'beautiful' bit. I can understand 'up' and 'down' in terms of vectors or orientations, but beautiful...

[youtube]http://www.youtube.com/watch?v=7iiB9yECBok[/youtube]

:ask:
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