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Comment Re:Nuclear propulsion. (Score 1) 662

The reason we don't have a lot of production is no one has put together a system dedicated to making antimatter.

But we do, the Fermilab Antiproton Source. By my calculations, it currently has about an order of magnitude higher production rate than the parent's prediction (which originally comes from an un-sourced section of the wikipedia article on antimatter).

Comment Re:Nuclear propulsion. (Score 1) 662

Using the current process it would take 2 billion years to produce 1 gram of anti-hydrogen

We are much better at making anti-protons. Fermilab's Antiproton source can regularly do 25*10^10 antiprotons an hour, with rates topping out at 28*10^10 per hour (sustained).

So you could probably manage one gram in 'only' 250 million years with what we have built today. However, the best antiproton storage machine has only held 540*10^10 antiprotons at the same time, so there'd need to be an improvement in storage.

Comment Re:Nice pix (Score 4, Informative) 67

The "star filters" you mention are actually diffraction spikes caused by the rods that support the secondary mirror of the telescope. They are an intrinsic quality of the telescope. If you look at the left side of this image of the Hubble under construction you can see three (of the four) black spokes that connect the outer cylindrical support to the cylinder in the middle (this is where the secondary mirror is mounted to). It is the light diffracting off of these spokes that cause the starburst pattern that you noticed.

Comment Re:I'm dumb, I think. (Score 2, Informative) 194

There's a few things going on here that are related in different ways.

1) The single-top isn't the only quark being produced, it's actually produced with a bottom quark at the same time. Usual top quark production is in pairs, one top quark one anti-top quark, but single-top is different; a top quark is produced with a anti-bottom quark.
2) The top quark decays before it can hadronize. That is, it decays before it can pick up a partner quark. This is completely allowed in the Standard Model, but I'm a bit sketchy on the details. I think it behaves as though it was attached with the other quark it was produced with.

Comment Re:Explanation wanted (Score 4, Informative) 194

The fine article says that this results limits the number of possible quarks. Can someone give an explanation (or even the outline of one) at a level that someone with a B.S. in physics can understand?

One of the things single-top is sensitive to is the coupling strength of the top and bottom quarks via the weak force. The value of this coupling is tightly constrained if one assumes that there are only six quarks (ie. there are three generations of matter). The fact that they measured it and it's within the six quark ballpark means that it is very likely that there isn't another pair of quarks waiting to be discovered.

The basic idea is that if the top and bottom coupling strength is measured to be less than the value we expect for six quarks then that means that some of that coupling strength actually goes to a different, seventh or eighth, quark. But I'm grossly simplifying things here for the general slashdot crowd.

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