New to Physics. Can you explain?

• consistency
In summary, the conversation discusses the concept of objects in motion remaining in motion unless an external force is applied, using the example of the Earth spinning due to its initial motion and the Sun as an external force. It also explores the idea that only stars can make bodies of mass spin, causing planets like Jupiter to have locked positions for their satellites. The conversation also delves into the question of why the Sun does not keep the Earth in a locked position like the Earth keeps the Moon, and the concept of tidal locking is mentioned. It is suggested that the Earth may eventually stop rotating, but it will take a long time due to its massive size. Finally, the conversation touches on the idea that the Earth does not have the same power as the
consistency
I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

They say the Earth keeps spinning because it started spinning and now there is no external force applied to it to stop it.

The Sun is an external force.

I actually believe that only Stars can make bodies of mass spin. Hence the Earth and other planets like Jupiter have their satellites in a locked position(not spinning).

Why doesn't the Sun keep the Earth in a locked position like the Earth keeps the Moon in a locked position? or like Jupiter keeps its satellites in a locked position?

I am pretty sure that eventually the Earth will stop rotating, but it will take quite a long time. The Earth is quite massive.

The moon isn't quite in a locked position, it rate of rotation coincides with it's rate of orbit, so that the same hemisphere faces the earth, but due to the axis of rotation versus plane of it's orbit, and the elliptical orbit of the moon, (and the position of an Earth observer) over time an Earth bound observer can see 59% of the moons surface due to libration:

http://en.wikipedia.org/wiki/Libration

That wiki article contains a link to tidal locking:

http://en.wikipedia.org/wiki/Tidal_locking

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This is actually a guess on my part, but I think it's because the torque that causes the effect falls off like 1/r which means something with a smaller separation distance (such as the Earth/Moon distance) will fall into tidal locking faster than something with a large separation distance. That's a guess though, I haven't put pen to paper on that one.

khemist said:
I am pretty sure that eventually the Earth will stop rotating, but it will take quite a long time. The Earth is quite massive.

rcgldr said:
The moon isn't quite in a locked position, it's orientation relative to it's orbit oscillates somewhat, allowing an Earth bound observer to see about 59% of the moon's surface over time.

The Moon doesn't spin 100% like the Earth does around the Sun. It oscillates because its fighting to get out of Earth's orbit. 59% isn't much. 59% - 50% = 9% of oscillation.

The Earth doesn't seem to have the "Power" to spin a body of mass like the Sun does.

consistency said:
I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

They say the Earth keeps spinning because it started spinning and now there is no external force applied to it to stop it.

The Sun is an external force.

I actually believe that only Stars can make bodies of mass spin. Hence the Earth and other planets like Jupiter have their satellites in a locked position(not spinning).

Why doesn't the Sun keep the Earth in a locked position like the Earth keeps the Moon in a locked position? or like Jupiter keeps its satellites in a locked position?

This is incorrect. Any spinning object keeps spinning unless a force is applied, like the law states. The Earth and all the planets and moons and everything else are spinning because they were spinning when the gas cloud that formed the solar system first collapsed and formed them. Had there not been enough mass within this cloud to give the Sun enough mass to ignite fusion, and hence it would not have been a star, it would still have been spinning and so would anything else that had formed with it.

The moon is tidally locked to the Earth because of Tidal Locking: http://en.wikipedia.org/wiki/Tidal_locking

The Earth isn't tidally locked to the sun because the gravitational gradiant isn't sufficient enough to cause that effect. If you look at Mercury however, it IS tidally locked in a 3:2 orbital resonance. The eccentricity of its orbit causes this to be stable. The moon is in a 1:1 orbital resonance with the Earth because of its nearly circular orbit with low eccentricity. (And even then it isn't perfectly synced, there is a small shifting back and forth that allows us to view a little bit more than 50% of the moon over the course of its orbit.)

The Earth doesn't seem to have the "Power" to spin a body of mass like the Sun does.

The Earth caused the moon to STOP rotating as fast as it was and become locked. It did not cause the moon to spin.

1. What is physics?

Physics is the scientific study of matter, energy, and their interactions. It seeks to understand the fundamental laws that govern the behavior of the universe.

2. Why is physics important?

Physics is important because it helps us understand the natural world and how everything around us works. It also allows us to develop new technologies and make advancements in various fields such as medicine, engineering, and astronomy.

3. What are the main branches of physics?

The main branches of physics are classical mechanics, electromagnetism, thermodynamics, quantum mechanics, and relativity. These branches cover different aspects of physics, such as the motion of objects, electricity and magnetism, heat and energy, and the behavior of matter at a very small or very large scale.

4. What is the scientific method and how is it used in physics?

The scientific method is a systematic approach to conducting experiments and making observations in order to understand the natural world. In physics, the scientific method is used to formulate hypotheses, conduct experiments, collect data, and analyze results in order to test and refine our understanding of physical phenomena.

5. Can you give an example of a real-world application of physics?

One example of a real-world application of physics is the development of GPS technology, which relies on the principles of relativity to accurately determine the position of objects on Earth. Other examples include the use of electricity and magnetism in various technologies such as electric motors and generators, and the use of thermodynamics in designing more efficient and sustainable energy systems.

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