72 lines
3.3 KiB
HTML
72 lines
3.3 KiB
HTML
<h2>What is color?</h2>
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<p>Color has the nice property that you need three different colors:
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red, green and blue, to get back something neutral, white, - which is
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very similar to what we observe in the proton, where we also need
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three different "colors" to form something that is going to be neutral
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in the end: A red quark, a green quark and a blue quark. </p>
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[Picture: Intersecting Color plains]
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<p>[READ MORE: In fact, protons and neutrons are not really white, or
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color-neutral. The nuclei of atoms consist solely of positively
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charged protons and sometimes also neutrally charged neutrons. Hence
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the electromagnetic interactions cannot hold the nucleus together, but
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would tear them apart instead. Thus, there must be some very strong
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force to keep them together, which is where the name of the strong
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force came from in the first place. The strong force affects both the
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neutrons and the protons, because they are so close to each other that
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they will not only "see" the charge of the others as a whole, but also
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the partial color-charges of the quarks.]</p>
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<p>The mediators of the strong force are called the gluons (because
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they bind particles together very tightly, just like some kind of
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super-glue). But the strong force is very different from the
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electromagnetic one in various aspects. Speaking-of the mediators
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instead of the forces, this means that the gluons are different from
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the photons in a very fundamental way: they carry color, unlike
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photons, which aren’t electrically charged themselves. This means that
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gluons can participate in their own interaction, which makes the
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strong interaction very special.</p>
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<h2>The strong force is special!</h2>
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<p>One consequence of this is that the strong interaction does not
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decrease with distance. Two electrically opposite charged objects will
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attract each other less when their distance increases. The strong
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interaction of two particles of different color, on the other hand,
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will increase rapidly as you tear them apart, and eventually grows so
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strong that the energy you needed to remove the particle any further
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would be sufficient to create new colored particles instead (due to
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Einstein’s famous relation E=mc², allowing us to transform energy into
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mass).</p>
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[Cool animation showing color string snapping and quark pair creation]
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<p>This process is the reason why we have up to now never observed an
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isolated quark - they only appear in groups of three or two (as in the
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animation, although we have not explained how this happens for pairs
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yet, and this will have to wait until we explain antimatter). The
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property of quarks to stick together so tightly and to never show up
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alone is called “confinement”.</p>
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<h2>Outlook</h2>
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<p>We have come pretty far. We know how the protons and neutrons are
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made from quarks, and we know what holds together the protons and
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electrons to form atoms. This is a great achievement, as it allows us
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to explain about everything that holds together the building blocks of
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natures. But it is not the whole story.</p>
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<p>Sometimes, thinks break apart - and it was only in the 20th century
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that radioactivity was discovered - the breaking apart of nuclei,
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emitting highly energetic and dangerous radiation. We cannot explain
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this kind of thing happening until now, and this will be what the next
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chapter is about.</p>
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