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Do Strangelets Pass Through Earth?
Weirdolet writes: "Ananova are reporting that ultra-dense, pollen sized strangelets (aka nuggets of strange quarks) travelling at 900,000 miles per hour hit the earth, violently pass through it and have done on at least two occasions already. It's also reported, allegedly, in the Sunday telegraph but I haven't found it there yet :P
Coming to a particle accelerator near you soon ... ?" Another reader has found the story at the Telegraph.
For those of you freaking out, here's a link Strangelets are strange but not dangerous
The speed of light is about 185,000 miles per second, or 11,100,000 mph, so these things are moving at 0.1c. Still not inconsiderable, mind you, considering their mass...
Ceci n'est pas une sig
Given the surface area of the planet that is not water, and then the area of land that is habitable, and the area of habitable land that people actually live on, you end up with a percentage so low (I'm too lazy to go number crunching, it's late) that the probability of one of these things coming down on LA, New York, London, etc, is so low that it's not even really worth spending time to think about it.
So many replies... Let me be the first to give the *exact* speed of light in vacuum:
670,616,629.3843951324266284896206... mph
(= 936851431250/1397 mph)
This is exact because the mile is defined in terms of meters, and the meter is defined as the distance travelled by light in vacuum during 1/299,792,458 of a second.
"Two Seismic Evens with the Properties for the Passage of Strange Quark Matter Through the Earth"
Primordial black holes face similar problems; a 1-ton black hole will evaporate due to Hawking radiation in about 85 nanoseconds, so we're unlikely to measure any hitting us if they're that light.
The big bang is not an explosion with a epicenter -- a common misconception perpetuated by the popular media. It started everywhere, and the results of the explosion are going outwards from every point. The diagrams at the Cosmology FAQ help:
http://www.astro.ucla.edu/~wright/nocenter.html
"Cosmic Separation of Phases".
"Uplets and downlets" are what we call "protons" and "neutrons. :-)
All quarks have charges which are \pm 1e/3 or \pm 2e/3. Doesn't stop normal matter being stable. I think the suggestion is that the strangelets contain enough up and down quarks and (presumably) electrons to make the aggregate close to zero charge.
Paul
Lasciate ogne speranza, voi ch'intrate
To explain a bit more, a system is only stable, if it can't get to a lower energy state without breaking some rule. Since one kind of quark can turn into another pretty freely, this favours systems made up to the lowest energy quarks, namely up. However, two things combine to make the proton stable (uud) rather than the particle with three up quarks, whose name I can't recall:
One is ordinary electrostatics. up quarks have positive charge (2/3 of a unit, as it happens), down quarks negative (-1/3) so cramming three u quarks together involves overcoming more electrostatic repulsion that forming a proton.
The other is a litle subtler. Many of you will be familiar with the idea of "shells" of electrons inside an atom, representing groups of possible energy levels for an electron, each able to hold just one electron. Something similar goes on in any compact collection of quarks: isolated baryon, atomic nucleus, strangelet or neutron star core. Each energy level can be occupied by at most one quark <emph>of each flavour</emph>. This favours structures with reasonably equal balances between the types of quarks. So a proton, uud with the us in the two lowest energy states and the d in the lowest state, ends up with lower total energy than uuu, which would have to use three enegry states.
OK. Now what happens when we try and compute the stable options for clusters of quarks.
With small numbers of quarks, we have to strike a balance between the fact that u are lighter and the goal of balancing u & d to keep the energy levels low and the electrostatic problems to a minimum. Solutions to this make up all the stable atomic nuclei from 1H (uud) to lead nuclei with 250--300 quarks of each type.
Somewhat larger stable clusters do not form, the electrostatic repulsion and the high energy states into which the quarks would be forced mean that they can lose energy by splitting into two smaller clusters, so they do, hence nuclear fission.
When cluster sizes get very large, then gravity starts to play a role. Solar mass sized clusters of u and d quarks (2 downs to 1 up, so the whole thing is neutral) can be stablized, despite the energy cost of all the down quarks, by the mutual gravitational attraction. The result is a neutron star. The fact that quarks are in different spatial locations also helps with the energy level problem.
It is suggested that collections of quarks intermediate in mass between nuclei and neutron stars may be stable, if they contain a significant portion of strange quarks. Although basically heavier and so more energetic than u and d quarks, they would be free to occupy the lowest energy levels. Estimates of how massive these clusters would need to be to be stable vary wildly. One the one hand people are looking for extra-compact neutron-star like objects on the other hand for "stranglets" a few microns across and massing tons.