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I was hoping for some questions about general relativity. Those are always fun.

Does a orbit of a planet change due to gravity getting weaker ?
Believe that falls under general relativity

I think that's probably better answered using Kepler's Third Law (Newtonian gravity). Newtonian gravity is equivalent to GR in weak gravitational fields with speeds much less than that of light. Kepler's Law is:

T[SUP]2[/SUP] = 4π[SUP]2[/SUP]R[SUP]3[/SUP] / GM

where:
π = pi
T = the time is takes for a planet to complete one orbit
R = the planet's maximum distance from the sun
G = the gravitational constant
M = the mass of the sun

The gravitational potential field (gravity's "strength") is given Φ = GM / R. Substituting this into Kepler's law gives us:

T[SUP]2[/SUP] = 4π[SUP]2[/SUP]R[SUP]2[/SUP] / Φ

So as you can see, the stronger the field is the faster planets will orbit the sun. (As Φ gets larger, T gets smaller.)


I'm not sure whether or not that answered your question. If not, feel free to ask a more specific one.

Why are planets round? Like, why not square or triangles? It would be pretty cool is Mars was square.

Or if Mars was a giant chocolate bar.

And with a somewhat realistic question - What is quantum? I always use the word, I have no idea what it actually means.

Please go Barney style with me, I don't need a foreign language course.

Nature, in general, likes low-energy configurations. For example, if you lift a ball to some height above the ground then you are bringing it from a low-energy state to a higher-energy state (you put energy into it). When you let go, the ball falls back to its low-energy state - the ground. Spheres are the lowest possible energy configuration of a large object, which is why nearly all large celestial objects are roughly spherical.



"Quantum physics" means that the properties of particles (energy, charge, etc) must occur in discrete values. This is a break from familiar classical physics, in which these values can follow a continuous distribution. For example, you can lift a ball to any height above the ground that you want. This means that the energy of the ball can have any value. The energy of the ball could be 1, 12.9, 3.1416, 0.001, etc. This is a continuous distribution. Electrons, on the other hand, can only occupy a set number of energy levels. It could have an energy value of 1, 2, 3, etc., but it cannot possibly have an energy in between.

You overshot the Barney bit. I had to use a dictionary for half of that.

Continuous distribution just means that like...say, for every meter a ball is lifted it gains like 12.5 joules of [potential] energy (just some random numbers).

And with quantum physics and discrete values it's like...no .5 and for every meter a ball gains like 12 joules because that's how electrons work or something?

Why is it that every time we look at women, we see their boobs first?

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The graph on the left shows discrete values. The one on the right shows continuous values.

Another example would be an analog vs. a digital clock. An analog clock can show any time. The minute/hour hand can point at any spot on the clock. A digital clock, on the other hand, can only display a discrete set of numbers. It can show 12:01 and 12:02, but it can't show any number in between.


Subatomic particles can only have a discrete set of energies, charges, spin, etc. Physics that deals with particles with these properties is called quantum physics.



Boobs emit "boobonic fields" which attract the photoreceptors of people with Y chromosomes.