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Tetraneutron Discovered
Caid Raspa writes "According to this
Press Release the French have (accidentally) produced six nuclei of tetraneutron (nucleus with four neutrons and no protons). Theoreticians have previously thought that tetraneutron does not exist. As there is no electric charge in these nuclei, they allow better studies of the nuclear forces. The scientific article is also available at
arXiv.org."
This was a big concern when the Large Hadron Collider was about to go into action. Some feared that the energies would be high enough to create mini black holes, which would promptly fall out of the chamber and begin eating the Earth. Eventually someone realized that higher energy collisions from cosmic rays take place above the Earth every day, and we haven't gotten eaten, yet.
In other words, whatever we can do is already being done in that great laboratory in the sky. Literally in the sky - a few hundred miles over our heads.
The living have better things to do than to continue hating the dead.
One recurring theme is where you cross the line between quantum and classical behavior. How many Fe atoms to you need before it behaves like the Iron we all are familiar with.
This appears to be another case. At some point of glomming neutrons together you get a neutron star, though that's still an odd beast. Where do you cross the line between Tetra/Penta/Hexa-neutrons and a teeny-tiny neutron star? (I suspect this one's easy to figure, in terms balancing gravity against residual strong and weak forces, but I don't know how to do it.)
The living have better things to do than to continue hating the dead.
No... (and I know penicillin was found, not really created, but my point stands)
I see no problem with 'creating' forms of matter, accidentally or on purpose, particularly as it can be argued that, like penicillin, these forms aren't really being created but are being discovered. They might exist elsewhere in the universe, or might have existed. And they're not really making new forms of matter - they're taking matter that already exists (neutrons) and putting them together in a way they haven't seen before (tetraneutrons). Kinda like molding sugar into cubes.
-T
For all you SF fans, "spin-polarized tetraneutrons" were used in the book "Martian Rainbow" by Robert L. Forward.
Yup, absolutely right. The half life of a neutron is about 12 minutes. More interestingly, here is a test for anyone who is feeling brave: Why is the half life of a neutron 12 minutes and not 10 nanoseconds like it should be considering it decays via the weak interacation? I was asked that on my PhD oral qualifying exam...
*whacks forehead*
I told you it's been too long; of course the energy level structure is why you'd expect it to decay to 4He if it held together long enough.
We used to do 2-neutron correlation out of heavy ion collisions, and even that required a good timing signal on when the beam pulse arrived on target so we could eliminate detections clearly not from the reaction (eg, if it arrived such that its speed was greater than c, we knew it wasn't from the reaction). This "time of flight" was also how we energy callibrated.
The detectors we used (for the unitiated reading this) were big jars of napthalene. Large organic molecule=lots of protons for neutrons to hit---then the smacked protons gave off light as they moved, which gets collected. Never break one of these; you smell for weeks. Take it from one who knows.
We've got two lives, one we're given, and the other one we make. --Mary Chapin Carpenter
So far, this reasoning applies to 4He just as much as it applies to a tetraneutron. So why would 4He be so much more stable? Well, the Pauli exclusion principle says that in a tetraneutron, the first two neutrons can both go in the lowest energy level, with their spins in opposite direction, but the third and fourth have to go in a higher energy level.
By this reasoning, we'd expect 2n to be much more stable than 4n. Has this construct been produced and studied?
Lastly, what could we expect for 3n, 5n, and 6n? Would the odd number of nucleons make 3n less stable (vs. the strong force) than 4n due to some shell-filling rule? Ditto 5n vs. 6n? Would 6n be more or less stable (vs. the strong force) than 4n? (more particles to mutually attract, but more of them in the higher energy shell).
My apologies for being a pest, but I've been interested in the subject for quite a while, but lack the background to derive the numbers for myself (went into engineering, not physics).