Science questions not worth a thread I: I'm a moron!

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The Imp

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Post your science questions not worth a thread here.


I'll start it off, why doesn't light travel faster or slower then 299 792 458 m/s ?
 
It does travel slower. That's the speed of light in a vacuum.
 
I'll start it off, why doesn't light travel faster or slower then 299 792 458 m/s ?

What Paradigm says +
-Maxwells equations demand 299 792 458 m/s propagation speed for electromagnetic waves in a vacuum
-the invariant mass of a photon is zero
 
How much energy does a photon have?

If it has no mass does it mean by e = mc^2 it has no energy?
 
The constant nature of speed of light is an observed fact established by the [wiki]Michelson–Morley experiment[/wiki].

Einstein's theories take that fact as a premise.
 
How much energy does a photon have?

E=h*f

h is the Planck's constant and f is the frequency.


If it has no mass does it mean by e = mc^2 it has no energy?

That formula is only half of the story. The full formula is:

E^2 = m^2c^4 + p^2c^2

There are two extreme cases. The first is a resting particle. In that case the particle has no momentum (p=0) and thus the formula reduces to E=mc^2. For any particle with a mass greater than zero (and which is not accelerated) it is possible to find the resting frame in which E=mc^2 is valid.

However as photons have no mass, there is no resting frame and and E=mc^2 is not valid. This is the second extreme case of the above formula when a particle has no mass and thus: E=p*c.

with p=h/(2 Pi) * k; k=(2 Pi) / lambda; lambda = c/f you get to E=h*f
 
:):):):)ing magnets, how do they work?

Short answer: Electrons have spins, which have a magnetic moment. Usually either the electrons occur in pairs and have opposing spin and cancel each other out, or the spin points in a random direction and the average over many spins results in a magnetic moment close to zero.

But under certain conditions, the spins can align to each other, so that together they have one big magnetic moment. A magnetic moment creates a magnetic field which attracts (or repels, depending on orientation) other magnetic moments.

The long answer would involve a lot of complicated quantum mechanics.
 
So, Uppi, does that mean that protons have no magnetic moment, but positrons (the anti-particle mate of electrons) do?

Or do all charged particles (protons & anti-protons, positrons & electrons) have magnetic moments?

And does that mean that neutrons don't have spin?? Or do neutrons have spin, but no magnetic moment?

I'm sure it's easily wiki-able, but I prefer this format :p
 
So, Uppi, does that mean that protons have no magnetic moment, but positrons (the anti-particle mate of electrons) do?

Protons also have a magnetic moment, but they usually don't play a role in ferromagnetism, because the short-range exchange interaction mainly affects electrons, which are far more delocalized than the nucleus.

Or do all charged particles (protons & anti-protons, positrons & electrons) have magnetic moments?

All charged particles with spin have a magnetic moment.

And does that mean that neutrons don't have spin?? Or do neutrons have spin, but no magnetic moment?

Neutrons do have spin, and as they are not charged they should have no magnetic moment. But they have a small magneic moment, because it contains charged quarks with spin that have a magnetic moment. As the charge is unevenly distributed among the quarks (-1/3,-1/3 and 2/3) these magnetic moments do not cancel each other out.
 
The constant nature of speed of light is an observed fact established by the [wiki]Michelson–Morley experiment[/wiki].

Einstein's theories take that fact as a premise.

Yes, I know this, but why is the speed of light what it is, and can it be faster or slower unobstructed in vacuum?
 
Yes, I know this, but why is the speed of light what it is, and can it be faster or slower unobstructed in vacuum?
Nope. As to why? I'm not really sure that's a sensible question. That's just the way it is.
 
Nope. As to why? I'm not really sure that's a sensible question. That's just the way it is.

Forgive me if I am not satisfied with that answer. :)
 
Well my point is not to belittle your question, but to a certain extent remind that every scientific construct has core values that really don't have theoretical justification, they just are that way. Of course, we might postulate something more fundamental, but that too will have said core values.

But I think I should point out that in the case of the speed of light the question isn't so much why the speed of light is 299,792,458 m/s rather why every other speed is X fraction of the speed of light? The speed of light is the most fundamental speed in the universe.
 
I really hope I get the English terms right here...

Anyway, symmetrical convex polyhedron, assuming it is made of material with equal and uniform density, should be stable on any of its faces (when placed on flat surface etc).

Now, what is the smallest possible number faces any convex polyhedron (still of uniform density) can be stabilized on? A hunch says me it should be three, but can anyone prove it?
 
A polyhedron with curved faces? 2 in that case I reckon (a sphere wouldn't be stable) like a boat shape?

Flat faces - 4 (a tetrahedron).
 
Flat faces.

But I am quite sure it is possible to construct a tetrahedron that can not be stabilized on one of its four faces - that's why I said three...
EDIT: or maybe it's not possible :S

Maybe I was not clear enough: it does not have to be symmetrical any more.
 
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