Significance of equal Sun and Moon apparent sizes?

In summary, the Moon's distance from the Earth has changed over time, and this has affected mythology.
  • #1
Loren Booda
3,125
4
How has the near equality of the Sun's and Moon's apparent size (as seen from Earth) affected our planetary history (vs transient phenomena like eclipses)?
 
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  • #2
I believe its principal effect has been on mythology. As far as the physics of the earth, unlikely.
 
  • #3
As the Moon's distance from the Earth has, over our double planet's history, changed quite a lot - and as the Earth's distance from the Sun has been pretty much constant - the apparent near-equality we see today is a curious coincidence in time.

Anyone got a reference (or want to do a calculation) on how the average angular size of the Moon (as seen from the Earth's surface) has changed in the last 500 million to 3 billion years?
 
  • #4
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  • #5
If we assume that the moon is receding at a constant rate of .038 m/yr, 1 million years ago, the moon was 38,000 meters closer. Compared to it's present distance of 3.84x10^8 m, the moon was closer only by a factor of 1.00009896. If today, the moons average apparent size is only 30 arc minutes, 1 million years ago, it would have subtended an additional .18 arc seconds.

A billion years ago, it would have been 38 million meters closer. A factor of about 1.1 times closer. It's apparent size would have been larger by about 3 arc minutes.

These calculations are probably wildly inaccurate in reality.
 
  • #6
Originally posted by mathman
I believe its principal effect has been on mythology. As far as the physics of the earth, unlikely.

e.g., ancient astronomer's/astrologer's ability to predict eclipses was a source of political power. Maybe I can come up with some examples, L.B...
 

1. What is the significance of the equal apparent sizes of the Sun and Moon?

The equal apparent sizes of the Sun and Moon have significant implications in astronomy and ancient cultures. This phenomenon, known as a total solar eclipse, occurs when the Moon passes directly between the Earth and the Sun, blocking the Sun's light and casting a shadow on the Earth.

2. How rare is it for the Sun and Moon to appear to be the same size?

The Sun and Moon appearing to be the same size is quite rare, as it only happens during a total solar eclipse. This phenomenon usually occurs once every 18 months, but the location and duration of the eclipse can vary.

3. Why do the Sun and Moon appear to be the same size during a total solar eclipse?

This apparent size equality is a result of the Moon being approximately 400 times smaller than the Sun, but also being about 400 times closer to the Earth. This coincidence in size and distance creates the perfect alignment for a total solar eclipse to occur.

4. How does the equal apparent size of the Sun and Moon impact ancient cultures?

Many ancient cultures, such as the Egyptians, Greeks, and Chinese, viewed solar eclipses as significant events and often associated them with supernatural or divine powers. Some cultures even developed myths and legends to explain the phenomenon.

5. What scientific discoveries have been made as a result of studying the equal apparent sizes of the Sun and Moon?

Studying the equal apparent sizes of the Sun and Moon has allowed scientists to better understand the Earth-Moon-Sun system and make predictions about future eclipses. It has also helped scientists gather data on the Sun's corona, which is only visible during a total solar eclipse.

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