An amazingly simple, and ridiculously useful and successful mechanism that converts linear motion to rotational motion. It’s basically what allows us to take a force produced by, say, steam, or an explosion, and make a wheel turn. Stick a few of these together and time the rotation of each correctly, carefully controlling the explosions and the exhaust and you have an internal combustion engine that powers our cars. There’s a lot amazing to me about it, but I am still impressed with how effectively it takes something moving back and forth, and makes something spin round, and vice versa.

The piston

The data vary, but for a medium-sized adult you can probably expect half of the caffeine from that 3pm cup of coffee to still be doing half of its thing about 7pm, 4 hours later. Apparently smokers deal with caffeine quicker and caffeine sticks around in children much longer.

You can expect about 10 minutes before it first kicks-in which, I suppose, is why if you’re feeling tired while driving it’s a decent plan to take a break and drink a coffee, then have a 15 minute nap. See tiredness can kill, take a break. Once it starts to kick-in you might hit peak caffeine any time from 45 minutes to 2 hours later.

Caveat: that chart visualisation is extrapolated from reported data, so the shape is approximate only.

Some references say longer, and some say, from 3-9 hours or so. My source which seemed pretty comprehensive was:

Bertil B. Fredholm, Karl Bättig, Janet Holmén, Astrid Nehlig and Edwin E. Zvartau, Actions of Caffeine in the Brain with Special Reference to Factors That Contribute to Its Widespread Use, Pharmacological Reviews March 1999, 51 (1) 83-133;

The half-life of caffeine.

For a closer look next time you’re at the beach. Pay close attention to whether you find one with a dextral or sinistral aperture.

Gastropods are the largest class of molluscs which includes limpets, snails and sea slugs. For those who weren’t sure.

Info from Discovering Sea Shells by Barry Charles

Typical gastropod anatomy