Hello everybody
I've been asking my question at Dr. David P. Stern autor of the website:
Educational Web Sites on Astronomy, Physics, Spaceflight and the Earth's Magnetism (
http://www.phy6.org/), and he has given me a lot of answers, perhaps some of you might be interested. Here's a report of the emails I've send and got back. My questions are in white his replies in yellow.
-------------
Question 1:
I've been trying to catch up on cosmic-rays and such, after all the fuzz about the recent startup of the lhc particle accelerator here in Europe. And I have some questions, … perhaps you might solve the mysteries:
In the experiment particles are speed up to high speeds and collide, smashing protons into "jets". I asked some people if these jets could also smash up surrounding protons and I always get the answer no because jets have far less energy. But they can never tell the energy difference, so the question that I have is how much energy do these jets actually have compared to the accelerated protons, in the sense of striking force. And what is actually the minimum striking force needed to make a single proton disperse?
--
The particles generated by jets CAN create secondary jets, and these can generate more and more jets, as long as enough energy is available.
In the 1930s Pierre Auger in France found that if one spread an array of Geiger counters (http://www.phy6.org/Education/wgeiger.html) across a field and timed their discharges, often several would fire simultaneously--more if they were placed near each other, fewer as the distances increased. He deduced that an "air shower" was created by cosmic ray collisions high up, which produced gamma rays (from the decay of neutral pions), which by pair production produced pairs of electrons and positrons, which created more gamma rays by bremsstrahlung and annihilation… producing a simultaneous shower of thousand or millions of electrons, positrons and gamma rays on the ground. From that he deduced the existence of a few very high-energy cosmic ray primaries. The "Hess Observatory" (http://www.phy6.org/Education/wcosray.html) detects such showers.
But the shower also contained particles which could penetrate a thick lead shield, or be observed deep underground. They were mostly identified as muons. The idea is that when a primary cosmic ray charged particle hits an atmospheric nucleus, it also creates charged pions and all sorts of heavier particles . Charged pions decay to muons, some of whom are detectable underground, but others, with enough energy (which by special relativity extends their lifetime in the frame of the atmosphere), create further nuclear collisions and jets, and so on, yielding a "nucleonic shower". Those particles are fewer that the electrons (and absent in showers initiated by gamma rays, as seen by the "Hess Observatory) and form a more compact shower, but they do exist, and suggest cosmic ray primaries with energies up to 10^20 electron volt (though they are rare, months apart).
See also under "Pierre Auger Observatory."
-------------
Question 2:
The particles generated by jets CAN create secondary jets, and these can generate more and more jets, as long as enough energy is available.
If they can keep on generating jets, isn't than the thing done at the lhc, a bit of a risky business? Because primary-cosmic-ray collisions happen far away at 20 km above the ground, on the top of our atmosphere, where the air is very thin and it softly borders space, so shock-wave energy from the "bang" can be lost into open space. This in contrast to ground-level experiments, where there is a lot more atmospheric pressure, the density of matter is far higher, and it is much warmer here, so a lot more energetic matter existing down here than Up there. Also in nature the showers can run for miles and miles, while the air gets gradually thicker, and they start off from only one particle bumping into a stationary atom, in contrast to the head-on collisions of accelerated particles. People say that if it was dangerous, the moon would have been done already some seriously harm, but it actually is a to dust reduced place, that smells like gunpowder, with no atmospheric pressure and it's icy cold, I don't think that it is a good reference of an unharmed place?
--
The LHC and other high-energy accelerators indeed produce high energy showers, which is one reason why they are constructed in tunnels underground. The people working with such devices are well aware of radiation (I would not be surprised is they wore film badges, developed periodically to assess the total irradiation dose).
Among the biggest an most costly attachments to such accelerator are observing arrays. If you look at a picture of a high energy jet on film (like the one on my web page), all you see is straight lines: once a charged particle approaches the velocity of light, the track it leaves on he film gives no clue to its energy (except that it exceeds some minimum). The arrays have many detectors of various kinds, also plates in which secondary showers are produced (and maybe magnets to separate positive from negative--not sure). The tracks are recorded and analyzed by a computer, a difficult business.
The radiation hazard of natural cosmic rays is small. They pack about as much energy as starlight. The "shock waves" produced are actually light waves, which is what the HESS array observes.
-------------
Question 3:
During the millions of collisions at the new particle accelerator, there is talk that there are going to be temperatures reached far higher than in the sun, and this at a very tiny spot, while jets will be bursting in all directions.
Isn't it possible that it might trigger a sub-atomic-chain-reaction where a bunch of surrounding nuclei could be smashed and start to jet and jam? Generating shockwaves that release light, but also heat and radiation, like the ignition of a nuclear bomb causes atoms to split. But these bombs are made out of very rare atoms that are specially enriched and they need to be tampered.
In contrast to such a sophisticated bomb, you can simply start a forest-fire by lighting a match when the woods are dry. I once read that the rocks who build up our planet, are actually a crystalized concrete made of condensed gas, so one could say that these rocks are dried up material, and with enough heat they could start to combust in an autocatalytic way.
I know this sounds like a Superman type of scenario, and I have let my imagination run wild. So to keep myself in check, I find it interesting to know, what the actual energy difference would be between the accelerated protons that crush each other, and the jets that they produce, and if them jets would be at some point, powerful enough to be within the range of having nuclei-smashing-abilities. Isn't it for such an off the wall type of concept important to know what the produced energy levels of jets are?
--
One thing seems to hold (so far!) for all processes in the universe--the conservation of energy. Atoms can be smashed or transformed, but the total energy stays the same. Yes, we can release energy by nuclear fission, by taking advantage of unstable heavy nuclei (see http://www.phy6.org/stargaze/SnucEnerA-0.htm and pages linked from there), and energy can be released to more familiar forms by nuclear fusion and gravitational collapse, but these are not relevant here.
What I want to stress is that when a very fast cosmic ray proton smashes into an atmospheric proton (say) and produces a jet, its energy is shared by the fragments, and further collisions only further subdivide the energy. No new energy is added, no sub-atomic chain reaction.
On the atomic scale, that energy can seem enormous, but on the scale of objects you and I can see (sticks and stones, and grains of sand) it is usually negligible. The "shock wave" is a very brief flash of light ("cherenkov radiation") caused when a particle moves through air faster than light (faster than light IN AIR, but not faster than light in a vacuum, the top speed of anything). As explained in the section on HESS in "cosmic rays" (http://www.phy6.org/Education/wcosray.html), it may take sensitive light detectors and large mirrors to detect such flashes.
The dust on the moon probably comes from meteorite impacts, most of them early in the history of the solar system. And no, rocks won't burn: even on if placed on the Sun, they may evaporate in the heat, but won't release energy, just absorb it.
-------------
Question 4:
What I want to stress is that when a very fast cosmic ray proton smashes into an atmospheric proton (say) and produces a jet, its energy is shared by the fragments, and further collisions only further subdivide the energy. No new energy is added, no sub-atomic chain reaction.
I think the above quote is where I am/was looking for "the energy" that might sustain an chain-reaction, like the heat of a candle keeps it burning, but I guess I have misunderstood how nuclei work.
I thought that a certain amount of energy during the collision, disrupted the binding interaction within the proton and that it was mainly this energy that was released. Like some sort of spring-mechanism that makes the quarks and the gluons in the proton going, and gives the solidity to the proton, a bit like a spinning top has a lot of energy, while it actually stands still. And once the mechanism would be broken, the different parts of the protons could shoot into different directions, and jet.
I guess I have a lot of catching up to do …
--
Yes you have a lot of catching up to do, but you are on the right track. Forces that hold matter together are mostly attractive--gravity, nuclear forces, even electric forces between negative electrons and positive nuclei, they hold particles together, though they and nuclear forces really operate by quantum laws (and certainly quark forces, which hold nuclear particles together--won't discuss those).
Thus to smash a nucleus apart, you must usually INVEST energy to overcome nuclear attraction-- you cannot extract any. That's why creating high-energy jets puts in energy and does not add to it--just distributes it among more and more particles. When protons combine to helium in the core of the Sun, they release nuclear energy--as gamma rays and fast particles, which keeps the Sun hot and puffed up.
There exists one exception. Because of the nuclear weak force, nuclei contain about equal numbers of positive protons and neutral neutrons, and these protons repel each other electrically. Furthermore, the electric force has a longer range than the nuclear force: the nuclear attraction is mainly to neighboring protons and neutrons, but the repulsion affects the entire nucleus.
Suppose we build up a nucleus by adding protons and neutrons one by one. Because of the nuclear attraction, energy is released--e.g. when creating helium, which is what heats the Sun. But after a while, adding a proton does not gain as much energy--true, nuclear attraction energy is released, but energy must be invested to bring close together many protons, which repel each other electrically. The break-even point is reached in iron--see graph in http://www.phy6.org/stargaze/Sun7enrg.htm --and beyond that, energy must be given to a nucleus to make it accept more protons. (These elements exist because they were created in supernova collapses in our galaxy, before the solar system existed). Very heavy nuclei--like uranium and thorium--even break up spontaneously (by alpha radioactivity), because of this repulsion of positive charge. Even heavier nuclei (created artificially) can break up by spontaneous fission into two nuclei of about 1/3 and 2/3 the mass, a process which releases even more energy than radioactivity. Our nuclear reactors and bombs operate by inducing fission artificially, which is just barely possible in some heavy nuclei bombarded by neutrons. See http://www.phy6.org/stargaze/Snuclear.htm
This is the one case where nuclear breakup liberates energy. Jets from high-energy collisions don't do it.