How do we know things don’t just get infinitely smaller? If a quark is the smallest particle we know of, what makes up a quark? And so on?

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It also makes me wonder if everything is actually the same? I know it’s a silly question, but are all quarks the same (composition wise) if so, does that mean that at our smallest core, we are made up of the same thing? Does this also mean that if not, that there is always going to be variance even to our smallest level? I suppose this question is asking more about what exactly is the composition of the smallest possible particle, and is there really an end?

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Anonymous 0 Comments

Two points seem worth making.

Firstly, if you were to keep going to smaller and smaller particles, you’d eventually hit the Planck length*, below which it’s fundamentally not possible to measure things, and it’s questionable how much sense it starts to make saying that “This thing is made of smaller components” once “smaller” no longer has a useful meaning.

Secondly, once we get down to quark level we seem to be at the point where virtual particles are constantly popping in and out of existence, and it’s getting a little tricky to say precisely what something is made of anyway. For example, when we look at what’s inside a proton, we apparently sometimes find things that only make sense if they’re virtual particles with extremely short lives (for example we sometimes find a charm quark – which has more mass than the proton itself).

Both of those seem to suggest that there are fundamental limits to how far you can keep pushing a neat, ordered heirarchy of “THIS is made up of THESE”. There’s a limit to how far you can go, plus reality seeems rather messier anyway. So even if quarks are made up of smaller things, sooner or later things are going to break down.

There’s a recent [PBS Space Time video](https://www.youtube.com/watch?v=TbzZIMQC6vk) on the structure of the proton that’s accessible, interesting and relevant. Well worth a watch.

*We’re still a LONG way from that – the Planck length compared to the size of a quark is on the scale of a grain of sand compared to the Sun – but the point still applies.

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