Why Hasn't the Moon Crashed into the Earth?

In summary, the Rings of Saturn would be little affected if the planet were to suddenly stop rotating about its axis. This is because the rotation of the planetary disk is what created the rings in the first place. However, if Saturn's rotation were to gradually slow down, the rings may be affected by the changing tidal forces. Additionally, the use of the word "centripetal" and the rock-on-a-string analogy should be avoided in explaining this concept, as they may not fully capture the complexity of the situation. It is important to continually test and evaluate scientific ideas based on new observations and evidence.
  • #1
Inductor
3
0
please don't mention the word centripetal or use the (misguided) rock-on-a-string analogy.
clue: there is no "balance of forces"

in a similar vein - please answer the following orbital skills question ... were the planet Saturn to stop rotating about it's axis - what would happen (if anything) to the Rings of Saturn? Would they fling out into deep-space? Would they glom into a big ball and catch fire? Would they come crashing down and burn up (ionize) in the Saturnian atmosphere? What exactly would happen to them?
 
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  • #2
Inductor said:
please don't mention the word centripetal or use the (misguided) rock-on-a-string analogy.
What's misguided about it? And what do you have against the word centripetal? (It's kind of important.)
clue: there is no "balance of forces"
That's true. F = ma.
 
  • #3
Inductor said:
in a similar vein - please answer the following orbital skills question ... were the planet Saturn to stop rotating about it's axis - what would happen (if anything) to the Rings of Saturn? Would they fling out into deep-space? Would they glom into a big ball and catch fire? Would they come crashing down and burn up (ionize) in the Saturnian atmosphere? What exactly would happen to them?

If Sat stopped rotating its gravity would be same. The rings would be little affected.
 
  • #4
The Moon as going sideways fast enough to always keep missing the Earth as it falls towards it.

Also, what DocAl said. What's wrong with centripetal force?

Actually, let me try and read your mind.
You're probably thinking of the equation:
Fc=Fg
and reason that this is a bunch of baloney, because not only gravity is the only force acting(hence, why for is the other one there?), but if the two forces were equal, then Newton's first law of motion would apply(the Moon would have to either stand still or move in a straight line.

The trick is, this equation is not an equation of motion.
It merely says that for a body(e.g.the Moon) to keep moving in circles, the force acting on that body(here Fg) must have a very specific magnitude, which is described as Fc.

Fc is not a real force, it's just a mathematically derived value that you need your force to be for your body to have it's velocity vector constantly changing its direction, but not its magnitude(aka moving in circles).
 
  • #5
ImaLooser said:
If Sat stopped rotating its gravity would be same. The rings would be little affected.

This would depend on what stopped Saturn from spinning. Conservation of momentum means the angular momentum from Saturn's rotation has to go somewhere. Whatever stopped Saturn's rotation would probably have a drastic affect on the rings, as well.

And if Saturn had never been spinning in the first place, then you wouldn't have rings, either. The rotation of the planetary disk created both.

But, given the unrealistic conditions that Saturn violated the known laws of physics and stopped spinning for no reason at all, the rings wouldn't be affected since they're motion is independent of the planet's rotation once the rings after the rings have been formed.

Or, the change could happen gradually, as with the Earth and Moon. Because of tidal forces, the Earth's rotation gradually slows and the Moon's orbit gradually increases in size. This wouldn't stop the Earth's rotation, however. Once the Moon's orbit and the Earth's rotation reached the point where the same face of the Earth always faced the Moon, the Earth's rotation would stabilize.

And, it would be hard for this to happen to Saturn. There's more than one moon, plus you have the rings. In other words, the forces are pulling from many directions. Whatever the imbalance in tidal forces, it would seem like it would have to be much smaller than the imbalance created by the Earth's Moon.
 
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  • #6
Doc Al said:
What's misguided about it? And what do you have against the word centripetal? (It's kind of important.)

I agree completely. The moon's orbit's elliptical, but otherwise, once you know a little about Newtonian gravitation, the Rock-on-a-string Analogy is pretty much perfect.

And maybe it's centrifugal, not centripetal, you want us to avoid?
 
  • #7
Um, let's see. Why is it you want us to avoid using standard explanations that work well for the past several hundred years? Do you have a source of some new revelation?

You do understand that Science works by repeatedly testing ideas (hypotheses) and adding new observations that either support or reject existing ideas. Do you have some new obserations?
 
  • #8
if we are talking about moon and earth. the moon was constructed of the accretion of fragments after a giant collision of the embryo Earth with another giant object.
so if the moon was going to fall towards the Earth it would not have time to form in the first place.
as to the present state of affairs, the moon is drifting out by about 3cm a year
 

1. Why hasn't the moon crashed into the Earth?

The moon has not crashed into the Earth because of its orbit and the Earth's gravitational pull. The moon is constantly moving in a circular path around the Earth, while the Earth's gravity keeps the moon in its orbit. This balance of forces prevents the moon from crashing into the Earth.

2. Can the moon ever crash into the Earth?

While it is unlikely, there is a small chance that the moon could crash into the Earth in the distant future. This could happen if the moon's orbit is disrupted by a large external force, such as a collision with a large asteroid. However, the chances of this happening are extremely low.

3. How far away is the moon from the Earth?

The average distance between the moon and the Earth is about 238,855 miles (384,400 kilometers). This distance varies slightly due to the moon's elliptical orbit around the Earth.

4. What would happen if the moon crashed into the Earth?

If the moon were to crash into the Earth, it would have catastrophic effects on both the Earth and the moon. The impact would cause massive earthquakes, tsunamis, and volcanic eruptions. It would also alter the Earth's rotation and potentially destroy all life on the planet.

5. Will the moon ever stop orbiting the Earth?

Yes, eventually the moon will stop orbiting the Earth. This is due to the phenomenon known as tidal locking, where the moon's rotation and orbit are synchronized. As a result, the moon's orbit will slow down until it becomes stationary, always facing the same side towards the Earth. However, this is estimated to happen in billions of years, so it is not a concern for our lifetime.

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