Quote:
Originally Posted by Nereid
There are a couple of things that have nothing much to do with 'cycles', directly, but sometimes get mixed in.
Take a nice, pure crystal of atoms, at an appropriately low temperature.
Leave aside (for now) quantum uncertainty.
The atoms in the crystal are at fixed positions in space, and those positions are periodic.
Let's now excite the crystal, in a precise (but gentle!) way. The lattice will now vibrate - waves of a precise frequency will travel through the crystal, a frequency that can be derived from physical properties of crystal*.
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And then there's the Sun, merrily oscillating away in thousands of p, f, and (we expect) g modes.
To use a single label ('cycles') for all these is, I think, very confusing.
For starters, it mixes up discrete (e.g. atomic spacings in a crystal, the 133Cs atomic transition) and continuous phenomena.
It also, as tusenfem points out, obscures the explanatory power of the relevant physics - you get planetary orbital 'cycles' because (Newtonian) gravity is inverse square; you get solar oscillation 'cycles' because (ultimately) gravity is inverse square and the constituent particles the Sun's plasma is composed of collide (lots of details omitted); you get crystal 'cycles' because of the Pauli exclusion principle; you get the quartz crystal vibration 'cycles' (that your watch depends upon to tell you the time) from that same principle (ultimately); and so on.
To be sure, the various epiphenomena are hugely interesting and valuable, but once you have GR and QED (and, for nuclear transitions and particle physics, QCD and electroweak theory), all the various 'cycles' fall out when you turn the handle^.
So is the compiling of long lists of 'cycles' just a form of stamp collecting?
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As I mentioned in my preceding post, the study of cycles can lead to discoveries that were not made in some other way.
There is the the question of resonance also which can cause seemingly unconnected things to move together. The discovery that pendulum clocks on a wall may get perfectly tuned was a wonderful moment in physics history. And yet resonance works regardless of the supposed law of physics involved. You can say that it is common to them all, but in a sense it is deeper than the various departments of physics.
Discoveries concerning how weather works including in recent times space weather have been assisted by the study of cycles. Cycles researchers knew the decades before astronomers did the measurement of solar irradiance variations measured by satellites that the "solar constant" was not constant. The presence of 11 year cycles and related variations in Earth weather systems meant that space weather was a worthwhile study. More recently, 11 year fluctuations in cosmic rays has meant that this is understood as a possible intermediary between solar variations and cloud formation on Earth.
It is not a question of either / or. Cycles is an extra tool that assists a scientist to make connections.
Someone found the 9.6 year cycle in the Canadian Lynx interesting. There are some dozen or more different species that have 9.6 year cycles of population, and many of them have no contact with each other. So there has to be a common cause. The only clue so far is a weak variation in ozone with the same period. This is still a largely unresolved situation. In the 1930s there were several conferences held by leading scientists from different fields (with many biologists) to look at these type of issues and eventually that lead to the formation of the Foundation for the Study of Cycles.