If the moon stopped orbiting the earth

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Discussion Overview

The discussion explores the theoretical scenario of the moon stopping its orbit around the Earth and the subsequent effects on both celestial bodies. Participants consider the implications of such an event, including gravitational interactions and potential impacts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant posits that if the moon stopped moving, Earth's gravity would pull it toward the Earth, likely resulting in a collision.
  • Another participant compares the scenario to a plane stopping mid-flight, suggesting it would fall due to gravity.
  • A participant questions whether the moon would enter a stable orbit again as it falls, indicating uncertainty about the dynamics involved.
  • Another participant clarifies that for the moon to achieve a stable orbit, it would need to change direction to move parallel to the Earth's surface.
  • One participant raises the idea that the moon's gravitational force would also affect the Earth, suggesting mutual attraction between the two bodies.
  • Another participant confirms that both the Earth and moon would be attracted to each other if the moon fell.
  • A question is posed about calculating the force of impact and the time it would take for the moon to hit the Earth, with some expressing doubt about the complexity of such calculations.
  • One participant suggests using Newton's laws and mentions that it would take several days for the moon to collide with the Earth.
  • A request is made for more detailed guidance on the calculations involved, including the specific equations to use.

Areas of Agreement / Disagreement

Participants generally agree that if the moon stopped orbiting, it would be pulled toward the Earth, but there is no consensus on the specifics of the dynamics involved or the feasibility of calculating the impact force and time.

Contextual Notes

Some assumptions about gravitational interactions and orbital mechanics are not fully explored, and the discussion includes varying levels of detail regarding calculations and physical principles.

lisa1234
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I know this is impossible, but theoretically speaking what would happen if the moon was stopped, so that it stopped orbiting the Earth and "stood still"? Would it hit Earth or what impact would it have on earth?
 
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If the moon momentarily stopped moving with respect to the Earth, then the Earth's gravity would pull the moon toward it. After a short time they would crash together. (It's likely that tidal forces would start pulling both the Earth and moon apart before they actually hit)
 
It's similar to if a plane somehow stopped mid-flight, it would just fall.
 
Thank you!
But since it gains speed as it falls closer to Earth wouldn't it again go into a stable orbit? Or doesn't it work that way?:S
 
No. Think about which direction the moon would be moving. It would be gaining speed toward the earth, which would just cause it to keep coming. In order to go into a stable orbit, it would need to change direction and start moving parallel to the Earth's surface.
 
Okey! But if the moon fell shouldn't the moon's force of gravity have an impact on Earth as well, so that they both were attracted towards each other and the Earth would "move"?
 
Yep, that's exactly what would happen.
 
Is there anyway to calculate with what force the moon would hit Earth and/or how long it would take? Or would such calculations be too complicated..? Is there in that case any simpler way to estimate the force and time?
 
You can use Newton's laws, plugged into a spreadsheet. It isn't too difficult. It would take several days for the moon to hit the earth.
 
  • #10
Could you show me more precisely how i could do that? What kind of equations would i use etc?
Thanks!
 

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