Nature's egg timer?
August 15, 2012 5:14 AM   Subscribe

What readily available materials change state at a constant, predictable rate in an easily observable manner?

As I understand it, carbon dating works because we can calculate the decay of carbon 14 fairly accurately (and apologies to any physisists reading this if that's a sloppy attempt at explaining it). I'm after things that work in a similar fashion, but over much shorter timescales and in an immediately observable way. Like an egg timer, but without the mechanical construction. Are there, for example, any materials that oxidise at a steady state (without the need to control environment)?
posted by londonmark to Science & Nature (12 answers total) 2 users marked this as a favorite
What time frame are you looking at? Would ice cubes melting work? Or even melting then evaporating?
posted by Grither at 5:24 AM on August 15, 2012 [1 favorite]

Apparently you can tell the time reasonably well with a calibrated candle, or by burning incense or oil.
posted by A Thousand Baited Hooks at 5:53 AM on August 15, 2012

Human bodies: 'The Glaister equation[1][2] estimates the hours elapsed since death as a linear function of the rectal temperature...'
posted by j_curiouser at 6:11 AM on August 15, 2012

Wikipedia has a really neat page on all sorts of dating methods - including some really awesome ones I would never have thought of in a million years. Clay-fired magnet hearths!
posted by Rallon at 6:16 AM on August 15, 2012

Carbon-14 isn't the only radioactive element. Here's a list of other decay rates, some on the order of seconds. Of course there would be "exponential timers", not linear timers, if that matters, and fundamentally stochastic in nature. But over long enough averages they would give very accurate predictions of time.

The "second" itself is defined in terms of a quantum mechanical process involving the Cesium atom. See here for more detail.
posted by grog at 6:37 AM on August 15, 2012

Clock reactions
posted by Rhomboid at 7:11 AM on August 15, 2012

How about soda going flat?
posted by maryr at 12:57 PM on August 15, 2012

Another thought: Glow in the dark stars.
posted by maryr at 5:01 PM on August 15, 2012

I think radiometric dating works because the rate of decay isn't affected by things like temperature and pressure, it's purely down to the properties of the nucleus. Any process that involves the movement of large numbers of molecules (like melting) probably will be significantly affected by the environment.

Maybe the best solution would be to stick with radioactive material, but use a cloud chamber combined with something with a short half life to make the change more visible.
posted by lucidium at 3:59 AM on August 16, 2012

A flower wilting? An orange peel losing its color? Lots of foods change over a few days.

A receipt losing its ink on a dashboard?

A balloon losing air?

A glowstick? A flashlight left on?

In the other direction, many life forms grow at predictable rates.
posted by at at 5:23 PM on August 16, 2012

Response by poster: Thanks for all your answers folks. Nothing exactly matching what I'm looking for yet but some interesting avenues for further investigation!
posted by londonmark at 8:04 AM on August 18, 2012

Dry ice?
posted by maryr at 8:16 AM on August 18, 2012

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