Short answer: the strange quark is one of the six kinds (“flavours”) of quark. It is heavier than the up and down quarks that make up everyday matter, and it only shows up in unusual, short-lived particles.
The basics
- Symbol: s
- Electric charge: minus one third (the same as a down quark)
- Weight: much heavier than up and down quarks, but far lighter than charm, bottom and top
- Lifespan: very short. It quickly turns into lighter quarks.
Why is it called “strange”?
In the 1940s and 1950s, scientists found new particles in cosmic rays and in early machines. These particles were made very easily, but they took a surprisingly long time to fall apart. That did not match what people expected, so the odd behaviour was called “strangeness”. Later, when quarks were proposed, the quark that carried this strangeness got the name strange quark. The name stuck, even though the quark itself is not that mysterious anymore.
Where do we find strange quarks?
You will not find one in a table, a tree or your own body, at least not for long. Strange quarks appear in:
- Kaons: light particles made of two quarks. Each kaon has either a strange quark or a strange antiquark, paired with an up or down quark (or antiquark).
- Lambda and sigma particles: heavier cousins of the proton that include a strange quark.
- Inside protons, for a blink: even a normal proton has pairs of quarks popping in and out of existence, and a few of them are strange.
Scientists make strange quarks on purpose in particle accelerators and watch what they turn into.
Strange matter: a big “what if”
Some scientists ask whether a lump of matter made of up, down and strange quarks together could be steady. This idea is called strange matter. It has never been found, and it is still only a theory. It is also behind the idea of a quark star.
Quick recap
- The strange quark is one of six quark flavours.
- It is heavier than the quarks inside normal atoms.
- It lives for a tiny moment and is found in particles like kaons.
Next: read what is smaller than a quark, or return to the science section on the home page.