How small?

  • Thread starter Gary_J
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Hello all, I'm an uneducated layman (physically and mathematically uneducated) new to the forum and to the whole concept of quantum physics, so apologies in advance if I sound stupid! :P

I was listening to a talk recently where the speaker was trying to explain how small an atom was, he was using analogies that had pretty precise numbers (a thousand billion, billion atoms in a 1mm grain of sugar; a '1' followed by 21 '0's', or as many stacked sheets of paper as it would take to get to the height of the Empire State Building) and it just got me wondering how much of quantum physics is actually empirical and how much of it is theoretical? Surely there is no way we can empirically observe something so small?

Do we arrive at these figures by following mathematics that have been formulated to explain what we so far understand of atoms and their components?

Yours inquisitively,

Gary
 

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how much of quantum physics is actually empirical and how much of it is theoretical? Surely there is no way we can empirically observe something so small?

Do we arrive at these figures by following mathematics that have been formulated to explain what we so far understand of atoms and their components?
We've formulated some mathematics, and have found that it is extremely successful at predicting the properties of atoms and other stuff of that size. For example from quantum mechanics we can calculate with great precision the colors of light that hydrogen should emit when you pass an electric current through it (that is one simple way to observe a process that is going on at very tiny length scales). We believe the mathematics because it predicts so many things so well. No one would pay attention to the theory if it hadn't been empirically confirmed so thoroughly.
 
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G01
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...and it just got me wondering how much of quantum physics is actually empirical and how much of it is theoretical? Surely there is no way we can empirically observe something so small?

Ah but it is possible to observe and measure many quantum effects!

Like previously mentioned, light emitted by excited hydrogen atoms is predicted extremely well by quantum mechanics. Also superconductivity, the photoelectric effect, and the properties of semiconductors are all macroscopic effects or observations, yet are governed entirely by quantum mechanics. (Classical physics cannot explain the properties of semiconductors or superconductors or the photo electric effect.)

It is the great predictions for phenomena like these that make quantum physics not just "theoretical" as you say.
 
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good introduction here:
http://en.wikipedia.org/wiki/Quantum_physics

Like much of physics, we can only measure theoretical effects rather indirectly.....but are pretty confidentin the theory.
 
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f95toli
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Worth noting is also that there are plenty of macroscopic systems where we can observe quantum phenomenon. We can now build "artificial atoms" using microelectrinic circuitry that behave exactly as natural atoms, but are much much larger.
Google "circuit-QED" for some good examples.
 

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