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Dramatic Difference In Matter Vs. Antimatter
jma34 writes "The Stanford Linear Accelerator Center (SLAC) recently put up a press release announcing a 13% asymmetry between the interactions of matter and anti-matter. In most interactions matter and antimatter are mostly interchangeable, however our universe is matter dominated. This research helps to answer the question of where did all the antimatter go. PRL article here."
Gas-cloud mapping shows that the universe isn't that well segregated, and if it isn't perfectly segregated, hydrogen-antihydrogen annhilation produces a distinctive signature.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
photons are their own antiparticles in the standard model.
Because once the antiphotons hit our eyes we'd all annihilate
No such thing. Or, at least, the photon is its own anti-particle, as far as I can find. I am not a particle physicist, nor do I play one on TV, but my limited understanding is that matter is a type of "frozen" energy with certain charge and spin, and anti-matter is the same phenomenon but with opposite charge and spin.
Photons are just energy, with no properties you can put backwards as in anti-matter. I did find a number of pages out there that talk about anti-photons as somehow photons moving backwards in time, but I can't quite wrap my mind around that one.
Anti-matter would "look" the same as matter from a distance, I think. The glow of an anti-matter star would be pretty and warm, until you got close enough for the anti-matter solar wind to start annihilating you.
- Peter
INsigNIFICANT
Huh? SLAC's whole purpose in life is to fire electrons and positrons at each other. The resulting collisions create the deacys they study. Why would this make "the area around the Sand Hill Road exit on I-280 in Menlo Park" no longer exist?
If all of the energy of one positron and one electron were released in a collsion in the SLAC, something like 3 billionths of a Joule. Well, there could be a lot of particles... Hrm... digging around http://www.slac.stanford.edu/ and crunching their numbers... I get a total output on the order of 3000 kJ/s if all of their particles collide with each other. Gasoline has a heat of combustion of about 43MJ/kg, so that is the same amount as burning 7 thousandths of a kilo of gas per second.
I think Menlo Park and the surrounding are are quite safe.
You do realise that they are not claiming 1606 decays is 98% of 200 million pairs, but rather that they expected to see X events and they saw ~98% of what they expected.
The events they want to observe ar so rare that there is less than 2000 of then in >200 million particle interactions.
I'm no astrophysicist, but yeah, it would be "loud enough" for us to see. It has an extremely sharp and "hot" energy signature. Quite distinctive. Even a low level would blaze above the cosmic background if you look at the specific frequency.
About the only way we could miss it would be if we we so "deep inside a matter boundry" that in every direction the boundary was outside the limit of the visible universe, some 15 billion or so light-year radius.
Assuming adjacent galaxies could be opposite doesn't really work. Not only is there is far too much contact through intergalactic gas, but galaxies collide with each other almost routinely. It is believed that essentialy all elliptical galaxies (about 10% of all galaxies) are the result of roughly equal mass galaxies colliding, and that many "normal" galaxies have collided-with/gobbled-up smaller galaxies and restabilized.
Here is a Hubble photo of actual colliding galaxies, and here is a really neat 7.3 meg MPG of a galaxy collision simulation.
Needless to say, it would be kinda hard to miss the fireworks from a matter-antimatter galaxy collision. It would likely be visible in broad daylight.
Even aside from the radiation signature, large scale regioning doesn't work either. If it were within the range of current galaxy mapping (some 7 billion light-years or so) we would see the exact opposie of what we do actually observe. Matter-antimatter anihilations would carry the mass-energy away from the border zones. The lower gravity in the buffer regions would produce "walls" of low-density vacuum surrounding blobs of gravitating mass. Instead the large-scall mapping projects show "walls" of mass surrounding bubble-voids.
To explain that better, the large-scale structure has been compared to a foam. The bubbles in the foam are voids in space in the foam-film is made up of galaxies. And like the soap film, the galaxies are essentially all linked together in sheets and walls rather than being surrounded by anihilation bubbles.
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>When did author lists get so long?
The author lists got so long when the experiments became too expensive and complicated for any one group to run by themselves. Because so many different groups contribute in many different ways (through construction, testing, writing specialized software, or analyzing results) they all have to be acknowledged.
I'm author #104 of #113 on a different paper (I went to a university very near the end of the alphabet), and it doesn't bother me at all that I have realtively few publications or that I'm one among so many authors. In this field, people realize the extreme difficulty of writing experimental papers in small groups. The only particle physics papers you will see these days with only a few authors are theoretical, and not experimental.