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Old 24-May-2008, 12:03 PM
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Quote:
Originally Posted by HenrikOlsen View Post
Our situation is actually worse.
We're living in a universe where all we can figure out is that if we look at in at one scale it behaves like apples.
Amazingly like apples, every test we've made on that scale points to apples.
Unfortunately on another scale it acts like oranges.
Amazingly like oranges, every test we've made on that scale points to oranges.
I would not use the words "worse" and "unfortunately".

It can be well argued that the greatest achievement, the what-would-you-take-on-a-desert-island piece of information about Physics, is the understanding that a physical system behaves differently depending the scale (length, time, energy, etc.).

For example, take a glass of water.
If you look at single molecule, you have three nuclei and a bunch of electrons around them; to figure out how it behaves you use Quantum Mechanics.
If you look at a greater length-scale, you see a bunch of molecules, weakly interacting with each other; you can use Classical Electrodynamics with some quantum corrections to figure out how each molecules moves, without bothering about the exact configuration of the electrons in the molecules.
At an even greater length-scale, you see lot and lots of molecules; in this case you can use Statistical Mechanics and forget about the trajectories of the single molecules, and end work out stuff like the temperature of the water.
And when you finally decide to drink the water, you can use classical Fluid Mechanics (where water is a continuum, instead of being composed of discrete particles) to work out how the water will flow into your mouth.
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