Earth's rotation(s) & duration

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This is what determines a day on Earth. In summary, the Earth and moon rotate around their common center of gravity, known as the barycentre. It takes about 27.3 days for the Earth to make one revolution around the barycentre, taking into account its orbit around the sun. The Earth also rotates around its own axis, determining a day, which is approximately 24 hours.
  • #1
freedom6446
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The question is about the Earth's rotation and duration.

It is my understanding that the Earth and moon rotate around the earth-moon system common center of gravity (also known as the barycentre).

Question #1. How long does it take for the Earth to complete one full turn around the earth-moon system barycentre?

Question #2. In addition to the Earth rotating around the earth-moon system barycentre, does the Earth also rotate about its own center axis?

Any feedback would be greatly appreciated. Thanks in advance!
 
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  • #2
The answer to question 2: it's called a day.
 
  • #3
And the answer to #1 --To a first approximation-- is a lunar month...

Then you must decide what a 'full turn' represents given the Earth/Moon system orbits Sun, and the orbits are slightly elliptical etc etc...
 
  • #4
freedom6446 said:
The question is about the Earth's rotation and duration.

It is my understanding that the Earth and moon rotate around the earth-moon system common center of gravity (also known as the barycentre).

Question #1. How long does it take for the Earth to complete one full turn around the earth-moon system barycentre?

Question #2. In addition to the Earth rotating around the earth-moon system barycentre, does the Earth also rotate about its own center axis?

Any feedback would be greatly appreciated. Thanks in advance!

1. From wikipedia on the moon: The Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days (its sidereal period). However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show the same phase to Earth, which is about 29.5 days

So the time it takes for the Earth AND the moon to make one revolution around their barycenter is about 27.3 days.

2. Yep. It rotates around its own axis approximately once every 24 hours.
 
  • #5


I can provide answers to your questions about the Earth's rotation and duration.

Question #1: The Earth takes approximately 27.3 days to complete one full rotation around the earth-moon system barycentre. This is known as the sidereal month.

Question #2: Yes, the Earth also rotates about its own center axis. This rotation takes approximately 24 hours to complete, which is known as the solar day. This is what causes day and night on Earth.

I hope this answers your questions. If you have any further inquiries, please let me know. Thank you for your interest in the Earth's rotation and duration.
 

1. How long does it take for the Earth to make one full rotation?

The Earth takes 23 hours, 56 minutes, and 4.0916 seconds to make one full rotation on its axis, also known as a sidereal day.

2. Does the Earth's rotation ever change or vary?

Yes, the Earth's rotation is constantly changing due to factors such as tidal forces, atmospheric winds, and the distribution of mass on the planet. However, these changes are very small and not noticeable to humans.

3. What is the difference between the Earth's rotation and its revolution?

The Earth's rotation refers to the spinning of the planet on its axis, while its revolution refers to its orbit around the sun. The Earth completes one revolution around the sun in approximately 365.24 days, which is known as a solar year.

4. How does the Earth's rotation affect our daily lives?

The Earth's rotation is what causes day and night, as well as the changing of seasons. It also affects the Earth's magnetic field, which helps protect us from solar radiation. Additionally, our concept of time is based on the Earth's rotation, with one day being equal to 24 hours.

5. Is the Earth's rotation slowing down?

Yes, the Earth's rotation is slowing down at a rate of about 17 milliseconds per century. This is due to the tidal forces of the moon, which are gradually causing the Earth's rotation to decrease in speed.

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