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Origin of Cosmic Rays Revealed
neutron_p writes "An international team of astronomers has produced the first ever image of an astronomical object using high energy gamma rays, helping to solve a 100 year old mystery - an origin of cosmic rays. The astronomers studied the remnant of a supernova that exploded some 1,000 years ago, leaving behind an expanding shell of debris which, seen from the Earth, is twice the diameter of the Moon. Cosmic rays are extremely energetic particles that continually bombard the Earth, thousands of them passing through our bodies every day."
These things are very powerful. The Russians have been conducting experiments on the sea floor for years and lots of them are energetic enough to go through. It's been assumed for a while that supernovas are the source of cosmic rays but it has been hard to pinpoint their origin, since cosmic rays can be deflected by magnetic fields.
It's almost as if time was slowed down for these high-velocity particles... and indeed this is the case. It's a classic demonstration of relativity in action.
Real Daleks don't climb stairs - they level the building.
What's the highest frequency EM raidation that can be detected/measured with the technology we have today?
Could there be massive amounts of EM radiation flying around the universe that is simple undetectable? Could this not be the "missing mass" that is conjectured in discusions of universal inflation and what not?
Anyone know?
Now that we've veered off onto neutrinos, let me point out how unbelievably cool neutrino detectors are. Start your journey via Google Images.
Here's what I do: Bitty Browser & Andromeda
This has, along with semi-conductor material and process defects etc., led to the whole field of Error Correcting Codes in computers - where such kind of errors can be prevented by things such as parity bits and what not. This works on the presumption that the probability of such bitswaps occurring on two bits is very small compared to just 1 bit. So, high-reliability computing servers etc. always tend to use memories with good ECC.
I have heard anecdotal evidence that IBM did some thourough testing of how such a behavior of bit-flipping due to cosmic rays changes at different elevation. When the elevation was high (7000 feet or so) - it occurred far more often then at the sea level. They did such tests below the surface of the earth and as they went deeper into the earth - such cosmic rays bit-flipping effect decreased but still remained. Only, after they went something like 40 feet or so below the surface of the earth - such behavior completley went away.
So, next time you wonder why you are paying more for ECC-RAM - think of cosmic rays (and material defect and what not ...)
Osho
Went looking around for more information, and came up with this:
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http://www.pparc.ac.uk/frontiers/archive/update.a
It includes a picture of the telescope array as well as a small image of the gamma ray map.
liqbase
Much like your own DNA.
We all think that mutations happen daily, but that is far from the case. In fact genetic mutation is very rare because we have error correcting enzymes which travel back and forth on DNA strands correcting them as they change. Typically the DNA "code" is changed as subatomic particles rip through your body, just as you've explained with RAM.
Yes, our DNA mutates. It doesn't stay that way however. Statistically there are more errors in a 300 page book then in a mile long DNA sequence. Actually there are about 0 errors in DNA because of this self-correcting mechanism.
* Source: Shadows of Forgotten Ancestors by Ann Druyan and Carl Sagan.
Get your Unix fortune now!
A long time ago (early 80s) I worked in a lab that used scintillation counters to measure biological activity (Background: you'd put a radioactively labelled (eg with tritium or C14)reagent in with the other cocktail for a test you're conducting in a little test tube. After say 5 mins you'd stop the reaction (say with perchloric acid), syphon off the top layer and put it into scintillation liquid (not sure what it was, but largely based on toluene) and put the vials into the scintillation counter which would have hundreds of little tubes in a conveyor belt and one by one drop the tubes deep inside the lead shielding to measure flashes of light as the isotopes decayed, hence telling you v accurately how much of the original substance under test had bound to the labelled reagent).
Anyway, every few days the counter would go completely stupid, and every few weeks copletely bananas (a technical term). It turned out the major machine crashes coincided with all scintillation counters in the building going crazy at the same time. We had over a dozen of these machines (all different brands) and they had about 6inches of lead around the detectors, so that was quite some energetic particles we were getting. The all the manufacturers' reps said there was little we could do to fix this, unless we wanted to be underground.
Talking to a friend at the local uni cosmic ray observatory (500+ scintillation counters spread over about a square kilometer), he said the more energetic showers were smaller in radius as the particles have less time to spread out from the initiating collision of a cosmic particle with the upper atmosphere. Usually they spread out to 50 to a few hundred metres across, with a massive cascade of all sorts of particle by the time it reaches ground level.
Interestingly, the initial byproducts of cosmic ray collisions have a v short life which means they should decay before reaching sea level. However as they travel close to the speed of light the depth of the atmosphere is foreshortened (Lorenzian contraction) to only a few hundred metres deep - a simple proof of relativity in action (or likewise, time is going slower for the cosmic particles).
It has been said that cosmic rays are the largest contributor to genetic mutations, beyond background radiation levels due to radioactive isotopes occuring naturally in the ground. Similarly, work place studies show airline hostesses/stewards have the far largest dosage of radiation of any occupation as they spend so much time above the bulk of the atmosphere. (Pilots spend less time in the air due to safety/fatigue regulations).
I also recall reading that it's extremely difficult to work out where cosmic rays originate as they are usually charged particles that follow curved paths through space due to the small but significant magnetic fields of stars and the galaxy itself. Due to timing of shows hitting detectors we can easily measure the angle a particle was going when it hit the atmosphere, but the particle took a very convoluted path prior to that, so finding a close source (100ly) is significant.
pithy comment
The cosmic rays that the article discusses are not muons, they are most often protons. The muons are what we encounter on Earth. The proton (also called the primary cosmic ray) comes in, hits our atmosphere, and a shower of subatomic particles is produced. The muon is the most powerful of these subatomic particles that is commonly produced. The fact that muons have a short half-life, and yet they can still reach us, has been cited as proof of relativity, and the idea that when you travel close to the speed of light (which these things do), time will slow down.
This is NOT the first gamma-ray image. I work on Glast which is the second generation of gammay observation satelites. EGRET was the most recent satelite to provide gamma-ray skymaps. Googled
BUT, it's not that simple. Redshift is really due to an integral of pointwise expansion wherever the photon happens to be. Since space is not expanding at a constant rate, we need to know how fast it is expanding at each point in space and time that the photon travels through. That can lead to some very strange results. If space is not expanding for most of the photon's journey, and then suddenly space right in front of the detector expands like crazy, you'll get a huge redshift, and infer that the object is MUCH farther than it really is. Or, if the object suddenly accelerates after it emits the photon, you'll think it's CLOSER than it really is!
The point is, "x lightyears away" doesn't mean much. It doesn't mean the object was x lightyears away when it exploded, it doesn't mean it exploded x years ago and it doesn't mean it is x lightyears away now. You can get pretty close to any of these values by taking redshift and pluging it into some very complicated formulae, but of course, for 1,000 lightyears, this doesn't even apply... anyway, back to work.
Quid festinatio swallonis est aetherfuga inonusti?
Africus aut Europaeus?
Hate to be picky, but muons are actually considered pretty long lived. They have a half life of over 2 microseconds. That sounds short, but it's a lot longer than a free neutron (for example), and it means they're really useful for probing materials.
-"It seems like you're trying to exploit a security hole. Would you like help?"
Cosmic Radiation makes up about 8% of the 360 mREM annual average background dose someone in the US receives. See the National Council on Radiation Protection and Measurements NCRP 93, 1988, for more information. Murray's "Nuclear Energy" has a pie chart of all sources and might be in your local library. This looks good too.
If you have a Sodium Iodine detector set and a scope, you can see it. Most common energies seen are around 20 MeV. They are big pulses next to the puny normal ones but you will detect one every twenty seconds or so.
You are correct, however, to note that most of these particles are blocked by the atmosphere and that you do get dosed at higher elevations. A person at 80,000 ft. according to the lesson plan cited above, gets about 10 R/hr. Each hour that's five hundred times the dose you get per year on the surface, ouch. By comparison, plants have a cow if you get more than a few unplanned mR.
Friends don't help friends install M$ junk.
The article doesn't state how distant that supernova is/was, only that it happened 1,000 years ago. Does that mean the supernova explosion was observable from Earth 1,000 years ago (saying nothing about its distance), or that the explosion actually happened 1,000 years ago (putting it at a distance of 1,000 lightyears)?
In either case, if the shell of debris has now travelled half a degree of angular separation from the original point of explosion (uniformly in all directions), I suppose that debris will eventually reach Earth when the shell has achieved an angular diameter of 180 degrees (if it has been expanding for 1,000 years, it would arrive here some 113,592 years from now). Hopefully the debris will then be diluted enough not to hit any sensitive parts of our solar system... Will that debris still be emitting gamma rays?
A few comments on your points aXis: 1) This is dependent on your geomagnetic position on Earth. The high energy cosmics go through it anyway and we are shielded from them by the atmosphere more than the weak magnetic field. 2)There's no neutrons in the primary cosmic rays since they decay AND neutrons *do* interact with matter a *lot*. The neutrons come from the interactions of charged particles with the atmosphere. They are the second highest dose inducer after muons at sea level, and the primary at an altitude of ~4km. You must be confusing them with neutrinos.http://www.triumf.ca/safety/rpt/rpt_4/no de3.html
3)There's not that many gamma-rays in the radiation that hits us on earth and they are mainly muons - which are charged particles and actually do some harm to us but not as much as the average amount of X-rays we get per year.
So the way I would put it is that we are transparent to the highest fluxes of particles (neutrinos) and that the radiation that reaches us from interactions of cosmic rays in the atmosphere induce lower doses than other ambient radioactivity sources..