Sticky Quarks

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Sticky quarks - a comic strip

Sticky Quarks

Yup, OK. Terrible joke. Pretty accurate, though: quarks are indeed “sticky.” So sticky, indeed, that they can’t separate themselves from each other. It is physically impossible to observe a single quark: they come in pairs or in threes (less often, in groups of four or even five) but, unlike the forever alone meme, they will never know loneliness.

The Strong Force

Quarks are sticky because of the strong force. This is just a force, just like gravity or the electromagnetic force. The messenger particle for the electromagnetic force is the photon; the messenger for the strong force is the gluon. However, the strong force is different from all the other forces in that it doesn’t decrease with distance. Gravity, for example, gets weaker as you get further from its source. This is the reason why we don’t all rush towards the Sun and instead just stick to good old Earth. But the strong force is always equally strong. If you try to pull two quarks apart, you will have to continue to push with exactly the same amount of force for all eternity.

Mass and Energy

So what? You may think. Just pull enough. Eventually, they will be separated enough that we can see them. But things aren’t so simple, thanks to Einstein’s E = mc2. As we pull the two quarks away, we are giving them energy, in the same way that pulling on a rubber band gives it energy. But energy can be turned into mass, which means it can be used to create new particles! So, as we pull and pull, we give the system more energy and the energy is used to create more quarks, which again will be as close as they can possibly be. So then we can start pulling on the new quarks, but this will only have the effect of creating yet more quarks in a never-ending cycle. Long story short, we will never, ever, get two quarks far enough.

There you have it: quarks are sticky and cannot be unstuck. They are forever doomed to spend their lives surrounded by their fellow quarks. Whether that’s a good thing, you should probably ask them. Oh and, in case anyone wants to know, this pesky phenomenon is called confinement.

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