
Unsolved problems in physics - rms
http://en.wikipedia.org/wiki/Unsolved_problems_in_physics
======
BobNeumann
"Why did the universe have such low entropy in the past, resulting in the
distinction between past and future and the second law of thermodynamics?[7]"

I die laughing at this one. "I know that my theory of the origin of the
universe doesn't align with the laws of physics. SO THE LAWS OF PHYSICS MUST
HAVE CHANGED SOMEWHERE ALONG THE WAY!"

ROFLLMAO

~~~
Maro
What are you talking about?

------
cool-RR
Physicists are ridiculous. Here's an unsolved problem for you:

Given the positions, velocities, masses and charges of a set of macroscopic
bodies moving in vacuum, (in speeds which may be relativistic,) calculate the
position of each of these bodies after a specified amount of time `t` has
passed. (Neglect gravity.) (All quantities are given numerically, and the
answers should be numeric too, allowing for a specified margin of error.)

\---------

Until physicists can solve a problem like this, they can take their time with
quantum gravity and string theory.

~~~
jlefo7p6
I think you were referring to the n-body problem
(<http://en.wikipedia.org/wiki/N-body_problem>). If so, I suggest not
neglecting gravity.

Without gravity (and either assuming these guys don't run into each other or
can somehow pass through each other), the position of each body is
independent, and can be found through the following equation:

Position = Initial + (Velocity * Time)

Blah blah vector components blah blah, but you get my point.

~~~
ars
He included "charge" which (mathematically) is identical to gravity.

Plus he said relativistic, so the very concept of "position" (and time) is not
so simple.

~~~
trjordan
If you're assuming a fixed viewer, it's actually pretty easy to define
position and time. There are just relativistic corrections to a bunch of the
terms.

~~~
ars
Only if you assume no acceleration on the objects. But he said charge, so they
do accelerate.

You'd have to figure out the position and velocity of each one relative to the
others to figure would what the effect of the charge will be. And don't forget
to include the propagation delay of the charge field.

This is by far not a simple problem. Much much harder than the N-body problem.

If the top poster had only left out "Physicists are ridiculous." it would have
been quite an insightful post, instead it was an inciteful one.

Look up <http://en.wikipedia.org/wiki/Einstein_field_equations> \- add in
<http://en.wikipedia.org/wiki/Stress-energy_tensor> and you'll see that the
motion of relativistic bodies is barely understood.

I'm upmoding him, because I think -7 is more than enough.

