- #1
neo143
- 29
- 0
Why the Earth keeps on spinning?
Why Does the Earth Keep Spinning?
Click For Summary
Discussion Overview
The discussion revolves around the reasons behind the Earth's continuous rotation and the origins of this motion. It covers theoretical aspects of rotational inertia, atmospheric effects, and the initial conditions of the Earth's formation.
Discussion Character
- Exploratory
- Technical explanation
- Conceptual clarification
- Debate/contested
Main Points Raised
- One participant suggests that the Earth keeps spinning due to rotational inertia, referencing Newton's 1st law as applicable to rotational motion.
- Another participant questions the impact of atmospheric friction on the Earth's rotation.
- A response argues that atmospheres rotate with their planets and that atmospheric winds are internal phenomena, not affecting the planet's overall motion.
- A participant raises a further question about what initiated the Earth's rotation during its formation.
- Another participant explains that the conservation of angular momentum during the coalescence of matter leads to the Earth's rotation, stating that the Earth was already rotating as a cloud of particles before its formation.
- This participant elaborates on a hypothetical scenario involving two particles in space, discussing how their random velocities and gravitational interactions could lead to cumulative rotation upon collision.
Areas of Agreement / Disagreement
Participants express differing views on the factors influencing the Earth's rotation, particularly regarding the role of atmospheric friction and the origins of the initial rotational motion. The discussion remains unresolved with multiple competing perspectives.
Contextual Notes
Participants have not reached consensus on the effects of atmospheric dynamics on rotation or the precise mechanisms behind the initial rotation of the Earth.
- #2
Doc Al
Mentor
- 45,583
- 2,457
Because it has rotational inertia. 
It's just Newton's 1st law applied to the rotational motion of a solid object. (In other words: It doesn't need a reason to keep spinning--that's what things do. But it would need a reason (a torque) to change its spinning.)
It's just Newton's 1st law applied to the rotational motion of a solid object. (In other words: It doesn't need a reason to keep spinning--that's what things do. But it would need a reason (a torque) to change its spinning.)- #3
neo143
- 29
- 0
What about friction due to atmosphere??
- #4
Danger
Gold Member
- 9,805
- 251
Atmospheres are part of the planets that they're associated with, and as a basic rule rotate with them. There's nothing in space for the atmosphere to drag against. Winds are 'internal' phenomena of the system, caused by convection, and aren't reflective of the planet's motion.
- #5
vaishakh
- 334
- 0
Better the question-What initiated the Earth to be in a state of spinning? Why did Earth start rotating around its axis when it was formed? Can anyone here clear my doubt?
- #6
DaveC426913
Gold Member
2025 Award
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- 8,736
The coalescence of matter into a body will conserve the angular momentum of its individual parts. The Earth did not "start rotating", the Earth was a cloud of particles, rocks and gas, in a loose orbit around a cloud of particles rocks and gas that was to become the Sun and the rest of the Solar System. It was already rotating before it formed.
Where does the rotation come from in the first place?
1] Take two particles in empty space.
2] Give them each a random velocity in a random direction.
3] Place them close enough so that they gravitationally interact.
4] When they eventually collide, they will not exactly cancel each others' motion out (There is only a single, astronomically small chance of this happening - it requires both particles to collide with each other in a direct line, with no tangential motion relative to each other i.e. they were on a collision course to begin with). So, when they collide, they will stick together. They will retain any residual tangential motion that doesn't completely cancel out. This effect is cumulative.
Where does the rotation come from in the first place?
1] Take two particles in empty space.
2] Give them each a random velocity in a random direction.
3] Place them close enough so that they gravitationally interact.
4] When they eventually collide, they will not exactly cancel each others' motion out (There is only a single, astronomically small chance of this happening - it requires both particles to collide with each other in a direct line, with no tangential motion relative to each other i.e. they were on a collision course to begin with). So, when they collide, they will stick together. They will retain any residual tangential motion that doesn't completely cancel out. This effect is cumulative.
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