What is the impact of the moon's disappearance on Earth's rotation?

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SUMMARY

The disappearance of the moon would lead to a gradual increase in Earth's rotation speed, potentially reverting to a historical average of six-hour days. The moon currently exerts a significant tidal braking effect, which slows Earth's rotation. While the Sun also influences tides, its effect is weaker than that of the moon. Therefore, without the moon, Earth's spin would continue to decelerate, but at a slower rate due to the Sun's tidal braking.

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  • Understanding of tidal forces and their effects on planetary rotation
  • Basic knowledge of celestial mechanics and orbital dynamics
  • Familiarity with the concept of tidal braking
  • Ability to differentiate between 'break' and 'brake' in a scientific context
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  • Research the effects of tidal braking from the Sun on Earth's rotation
  • Explore historical data on Earth's rotation periods before the moon's formation
  • Learn about the mathematical modeling of tidal forces using relevant equations
  • Investigate the role of celestial bodies in influencing planetary rotation
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Astronomers, physicists, students studying planetary science, and anyone interested in the dynamics of Earth's rotation and tidal interactions.

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What if the moon disappeared??

Homework Statement


I am doing a project answering this question: what if the moon disappeared? I was looking up how the moon was affecting Earth's rotation around its axis and noticed how the moon pulls Earth backward, slowing down Earth's rotation. One of the websites says that one day on Earth used to be six hours before the moon was created, but the moon in its orbit started extending it as it receded away from Earth.

My question is, does this mean that if the moon were to disappear (destroyed by aliens or something) Earth would start spinning faster? (back to 6 hours days?) The website says its impact on Earth would be insignificant because the days are still extended due to tidal braking of the Sun. But wasn't Sun there with Earth before the moon was created? Why wasn't Earth's spin affected by Sun back then and one day only lasted 6 hours? (It will be really helpful if you could also explain to me about solar tidal braking!)

Homework Equations



http://theness.com/roguesgallery/index.php/evolution/what-if-the-moon-disappeared/
here is the website if you wanted to have a look.

The Attempt at a Solution

 
Last edited:
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At least learn the difference between 'break' (to smash or damage) and 'brake' (to slow down or retard).

Since this is HW, you must at least try to answer your questions. If their is something you don't understand about the answers you develop, you can ask someone to clarify with what you are having problems. These are the rules for PF.
 
Sonya36 said:
The website says its impact on Earth would be insignificant because the days are still extended due to tidal braking of the Sun. But wasn't Sun there with Earth before the moon was created? Why wasn't Earth's spin affected by Sun back then and one day only lasted 6 hours?
Yes, the Sun also contributes to Earth's tides, but the effect is weaker than the moon's.
So if the moon were to vanish, the Earth's spin would continue to slow, but more gradually.
As to how much the tidal braking from the Sun contributes to the current slowing, that's a tricky question. Remember that the two effects are sometimes in phase (spring tides) and sometimes out of phase (neap tides). Can you suggest some suitable equations to model that?
 

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