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betterthanwell comments on What was your biggest recent surprise? - Less Wrong Discussion

11 Post author: DataPacRat 09 June 2012 11:57PM

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Comment author: betterthanwell 10 June 2012 06:49:08PM *  18 points [-]

A very salient moment of surprise was when I realized that my mental model of a simple three-quark proton was deeply (or simply) wrong:

You may have heard that a proton is made from three quarks. Indeed here are several pages that say so. This is a lie — a white lie, but a big one. In fact there are zillions of gluons, antiquarks, and quarks in a proton. The standard shorthand, “the proton is made from two up quarks and one down quark”, is really a statement that the proton has two more up quarks than up antiquarks, and one more down quark than down antiquarks. To make the glib shorthand correct you need to add the phrase “plus zillions of gluons and zillions of quark-antiquark pairs.” Without this phrase, one’s view of the proton is so simplistic that it is not possible to understand the LHC at all.

http://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/

What still surprises me, whenever I think of it, is how we live in a such a big world, even on the smallest scales we are able to probe. And also that things like nuclei happen to be stable over long enough timescales for things like chemistry and life to occur.

Comment author: Luke_A_Somers 12 June 2012 12:54:31PM 3 points [-]

All of those gluons and quark-antiquark pairs are every bit as stable as the Earth's gravitational field. They're elements of the ground state for a quark.

The process of finding the ground state for a particle from its interactions, including dragging in virtual pairs to screen high field intensities around the singularity, is called Renormalization.

Comment author: betterthanwell 11 June 2012 09:05:51AM *  1 point [-]

I realized that my mental model of a simple three-quark proton was deeply (or simply) wrong.

For an explanation using more showing and less telling: Checking what's inside a proton

You’ve heard the famous statement that “a proton is made from two up quarks and a down quark”. But in this basic article, and this somewhat more advanced one, and in a recent post where I went into some details about what we know about proton structure, I’ve claimed to you that protons are chock full of particles, most of which carry a tiny fraction of the proton’s energy, and most of which are gluons, along with a substantial number of of quarks and antiquarks.

What I want to do in this article is show you evidence that the statements made about proton structure in this post are true. After all, why should you have to take my word for such things? Let’s look at some LHC data, and see how it confirms these notions.

(The author is blooking high-energy physics.)

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