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Feb
9
comment How Much Weight Would This Put On The Legs Of A Desk?
It's symmetric, so 17.5 pounds will be on the left two legs of the top desk, 17.5 pounds on the right two legs of the top desk, 17.5 pounds on the left two legs of the bottom desk, 17.5 pounds on the right two legs of the bottom desk. ie, if you put a scale under any one of the (total eight) legs it will read 17.5lbs.
Feb
8
comment Why the 3D heat equation is $\frac{\partial u}{\partial t}=\alpha\nabla^2u$
What is insufficient about the Wikipedia article on the heat equation? en.wikipedia.org/wiki/Heat_equation
Jan
28
comment Symmetry and Group theory book
I think you need to specify what field you're interested in to get good answers! If you're interested in symmetry in crystallography, you'll need a different answer than for symmetry in particle physics. Or, you could be talking about how conservation of energy/momentum/angular momentum follow from symmetry laws in classical and quantum mechanics, which is a fact that requires almost no group theory!
Jan
20
comment Why is there “ringing” at the violet end of a rainbow but not the red end?
Oh towards the center of it! I was looking at either end.
Jan
20
comment Why is there “ringing” at the violet end of a rainbow but not the red end?
I see: Before violet it looks to me like the rainbow colors blend into the background colors. After violet the rainbow stops. Could you elaborate on what seems weird?
Jan
11
awarded  Self-Learner
Jan
10
reviewed Edit Stacking lenses for higher magnification (a DIY microscope)
Jan
10
revised Stacking lenses for higher magnification (a DIY microscope)
improved formatting
Jan
10
comment How far away from the Sun does space start to be cold?
I like the answer but a perfect spacesuit would still radiate like a blackbody!
Dec
31
revised Does Quantum Mechanics say that anything is possible?
added 17 characters in body
Dec
31
comment How do I describe the order of events in spacetime?
@StanShunpike I mean you can transform the vector $(0,1)$ into the vector $(\gamma \beta,\gamma)$ under a Lorentz transformation. Since $\gamma>0$ and $\beta$ can be positive or negative, you can let the timelike coordinate be positive of negative. The time coordinate of $(0,1)$ can change sign depending on your reference frame. The time coordinate of $(1,0)$ cannot change sign depending on your reference frame. You should prove this for general timelike/spacelike/lightlike vectors.
Dec
29
comment How do I describe the order of events in spacetime?
@StanShunpike Yep, I should have said "timelike or lightlike". I think you should figure out the answer on yourself though. Hit ${\bf x-y}$ with a Lorentz transformation and figure out when the time coordinate can change sign.
Dec
29
revised How do I describe the order of events in spacetime?
added 13 characters in body
Dec
29
comment Does Quantum Mechanics say that anything is possible?
@Shing You meant to comment on aquidturtle's post.
Dec
29
answered How do I describe the order of events in spacetime?
Dec
21
revised Does Quantum Mechanics say that anything is possible?
edited body
Dec
21
answered Does Quantum Mechanics say that anything is possible?
Dec
19
comment Initial wave function for a particle in an infinite square well
The solution you worked out does not have the property that $|\psi|^2=(\mathrm{constant})$ everywhere, so it doesn't meet the supposition of the problem.
Dec
15
comment Can you break causality if you are able to instantaneously perceive a distant system?
Assuming you meant: "He assumes that it had been sent time $D/c$ before", that sounds like exactly the OPPOSITE situation of what the original poster cares about.
Dec
14
reviewed Approve Calculate the applied force associated with uniform distortion of an area