[Theory] Quantum Mechanics Thread [Physics] (6)

1 Name: Mad Scientist 2005-09-06 10:29 ID:Wk1VOLmk

itt Quantum Mechanics!

Quantum mechanics is a fundamental physical theory that extends, corrects and unifies Newtonian mechanics and Maxwellian electromagnetism, at the atomic and subatomic levels. It is the underlying framework of many fields of physics and chemistry, including condensed matter physics, quantum chemistry, and particle physics. The term quantum (Latin, "how much") refers to the discrete units that the theory assigns to certain physical quantities, such as the energy of an atom at rest

Scanned pages from Albert Einstein's notes on quantum theory:

Note: Quantum mechanics are very whacky and delightful!

2 Name: !WAHa.06x36 2005-09-06 11:39 ID:JYIx8JLp

There are two quotes going around attributed to Richard Feynman: "If you think you understand quantum theory, you don't understand quantum theory" and "You don't understand quantum theory, you just get used to it". I don't know if either of those are genuine - they're too widely quoted for me to dig up a definite source on them - but they are none the less very relevant, the latter especially so.

The gist of the latter quote is really that most of quantum mechanics is just a thicket of mathematics that happen to describe how nature works. These mathematics are very, very different from how we normally think of nature, and there's nothing in our experience to really connect them to. All attempts to describe the workings of quantum mechanics in terms of similes, metaphors or reference to anything in our intuitive world tend to end up failing for the exact reason, because while you may be able to describe some small subset of phenomena in an understandable way, any attempts to extrapolate from this understanding will go wrong, because the description is not the mathematics, and the mathematics do not care about our attempts to intuit them.

A lot of popular understanding of quantum mechanics suffers from this - people are extrapolating from simplified descriptions in ways that are not actually supported by the theory. The only real understanding of quantum mechanics ends up coming from sitting down and doing the maths. This is really quite unfortunate, because knowledge shouldn't be limited to the small elite who are actually capable of doing this, but it seems our universe is so fundamentally perverse, there is no way around this.

3 Name: Mad Scientist 2005-09-06 17:18 ID:lvSFa3qs

May i had that all the mathematics' tools used to describe quantum physics are not yet proved to be right.What i mean is that some of the feynman path integrals may diverge (or strictly diverge) if you try to understand them with mathematics knowledge.

4 Name: Mad Scientist 2006-01-19 17:32 ID:84sLadbf

Any high schooler can grasp e=mc^2 without too much handholding. But the pages upon pages of math that back those little characters up is beyond most people's reach.

And that's okay.

Eventually, some brilliant, persistant, signifigant physicist will boil down all of the reams of paper with mortally-unintelligible maths on them into something as simple to grasp as that famous little equation. And it won't matter that they don't grast the heavy math behind it, since they'll be able to put that little quantum equation to work anyway.

As for the only real understanding being based on actually looking at the numbers, buffalo bagels. If it can be expressed mathematically, it can be expressed in any number of other, more easily grasped ways.

5 Name: !WAHa.06x36 2006-01-20 13:03 ID:Heaven

> If it can be expressed mathematically, it can be expressed in any number of other, more easily grasped ways.

So you claim, but I've never seen this done. All the non-mathematical descriptions of quantum mechanics I've seen have been simplified to the point of being essentially meaningless. I've been interested in it for a long time, but until I really did the maths, I really didn't understand any of it.

6 Name: YeahLove : 2011-09-22 00:11 ID:KiRg5kq+

Yeah I'm not sure if you're right about that.


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