
IAmA theoretical physicist. Ask me anything (via reddit) - d4ft
http://www.reddit.com/r/IAmA/comments/cba5t/iama_theoretical_physicist_ama/
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Jach
I stopped reading after it appeared he was advocating collapse theory. About
the only non-confusing quantum mechanics I've read so far that's been light on
math has been Feynman's stuff like QED and this series:
<http://lesswrong.com/lw/r5/the_quantum_physics_sequence/>

On a meta-note, I don't really think this is anything but noise. If you want
to really, really understand the physics, you have to do the math, and if you
just want a high-level concept I don't see how in the space of a single reddit
post you could take away loads of confusion or adequately explain a concept
without cheating the person. Here's Feynman's take on magnets (really, on
answering 'why' questions): <http://www.youtube.com/watch?v=wMFPe-DwULM>

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Maro
Check out Dirac's classic 'The Principles of Quantum Mechanics':

[http://www.amazon.com/Principles-Quantum-Mechanics-
Internati...](http://www.amazon.com/Principles-Quantum-Mechanics-
International-
Monographs/dp/0198520115/ref=sr_1_3?ie=UTF8&s=books&qid=1275651696&sr=8-3)

I was shocked how much clearer (and more useful) the exposition is compared to
textbooks.

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pfedor
I strongly second this recommendation, but it's not exactly "light on math".
It's light on calculations, but you need to have had some contact at the very
least with linear algebra and calculus. Now that I think about it, that
probably makes it a perfect book for software engineers, who know the
mathematical concepts from studying computer science, but have not much
experience actually doing calculations, so typical QM textbooks may be off-
putting for them.

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tca
There's no relevant physics without mathematics, one has to work out the math
before trying to answer the 'why' questions. There are no short cuts. (Note:
I'm also a theoretical physicist :) )

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Confusion
The math follows from the basic assumptions made about nature. Assume
translational, rotational and time invariance, add the finite speed of light
and some less obvious assumptions and all of classical physics (for those non-
phycisists: this includes special and general relativity) follows.

Assume charged fundamental particles and EM follows. Assume quantized
fundamental units and quantum mechanics follows. Lots of relevant physics can
be described and shown with hardly any mathematics at all.

The idea that nature is mathematical in essence is a notion that primarily
physicists entertain. They mistake intelligence for knowledge and
philosophers, that have actual _knowledge_ of the philosophical problems
involved, know better. The idea that nature is mathematical in essence, and
that we have discovered this fundamental essence, is both hubris and usually
utterly devoid of any philosophical sophistication.

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tca
You could invert the phrase and still make a lot of sense: 'Nature follows
from the basic mathematical assumptions.'

But you are quite right: Philosophers know better, could know...

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Confusion
_You could invert the phrase and still make a lot of sense: 'Nature follows
from the basic mathematical assumptions._

It's not just that. It's also that a lot of physics can readily be explained
and understood without mathematics. It's just that with mathematics, it's
easier to demonstrate the consequences. It's important to remember that
Einstein got at relativity by understanding the right assumption to be made.

Just to be clear on this: I fully agree that in advanced physics, you
sometimes you have to blindly 'do the math' and can determine the physical
interpretation of the result only afterwards. However, that doesn't mean that
there _is_ no physics without mathematics, it doesn't mean that there isn't a
lot of physics that can be understood without mathematics and it certainly
doesn't mean nature is mathematical in essence. Hell, it isn't even physical
in essence, unless you can reduce our minds to physics.

The notion that 'nature is mathematical in essence' is not logically seperated
from assumptions about the object/subject and mind/matter dualities (and about
whether they are dualities in the first place) that I doubt most of the
phycisists espousing these notions are willing to support, because they are
rather incompatible with other parts of their worldview.

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pwhelan
I like what you say, but I am conflicted. As I understood it, math is the
language that physics uses for us to understand/manipulate reality. Just as
one understand "coffee" without the word coffee, one can understand projectile
motion without understanding derivatives -- however in the absence of a
language to describe it, the concept remains difficult to build upon.

I do not understand about it not being logically separated from assumptions
about dualities (Platonic forms?) and their respective worldview. Could you
explain more please.

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lmkg
Some guy by the name of Hartry Field claims to have successfully generated a
logical axiomitization of Newtonian mechanics, without using math, only
qualitative concepts like "betweenness."[1] Math can extend this model and is
consistent with it, but it's not necessary in principle. Of course, this does
not mean that you don't need math in practice, in the same way that
continuations are the only control structure you need in principle but in
practice you use loops and function calls and switches or whatever. What it
does mean, from a philosophical view, is that math isn't necessary the
quintessential 'language of the universe' that we thought it was.

As far as advanced mathematical physics goes, our problem is that we stop
being able to easily understand what the math represents when you go deep
enough. A first derivative is understandable as velocity, the second as
acceleration, and multiplying that by mass to get force has some intuitive
notion. If you look in the middle of a bunch of scribblings, it's possible to
put the equation into words and it will make sense and have a physical
interpretation. Special relativity and the beginnings of quantum mechanics
came about because we had intuitive concepts, and were able to fit math around
them. In modern physics, the math has come first, and the intuition later or
not at all. Quantum phenomena still have competing interpretations
(probability fields, many-worlds), which may not even be mutually exclusive.
Once we figure out what in the hell is going on, the math _may_ prove to be
unnecessary, but right now the math is all we have to go on, and we sort of
have to treat it like a literal truth in order to get anything done.

[1]
[http://en.wikipedia.org/wiki/Philosophy_of_mathematics#Ficti...](http://en.wikipedia.org/wiki/Philosophy_of_mathematics#Fictionalism)

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pwhelan
Thanks. This is kinda difficult to wrap my head around though. I found this
passage interesting:

"By this account, there are no metaphysical or epistemological problems
special to mathematics. The only worries left are the general worries about
non-mathematical physics, and about fiction in general. Field's approach has
been very influential, but is widely rejected. This is in part because of the
requirement of strong fragments of second-order logic to carry out his
reduction, and because the statement of conservativity seems to require
quantification over abstract models or deductions."

I will admit that I have a problem when fictionalism requires that we regard
"2 + 2 = 4" as false (also from wikipedia). All in all an interesting idea.

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Jun8
There should be more people like him/her who are willing to put time in
answering questions about their specialty, although some may be unexplainable
to the general public. For another excellent example of such a guy, see
Terence Tao.

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dhimes
+1 for Tao

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mbh2000
Help me with a thought experiment. What do you think the result would be if a
target, heated by the National Ignition Facility were to encounter a partical
stream from 2 sides such as provided by the LHC.

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mbh2000
Help me with a thought experiment. What do you think the result would be if a
target, heated by the National Ignition Facility were to encounter a partical
stream from 2 sides such as provided by the LHC.

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tjmaxal
Whoa this is long!

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vrode
When did you start actively pursuing you goal? Do you think someone less
exposed to science and math in particular can achieve the same level as you?

