Likelihood of moon and sun appearing equal in size (Earth, solar, universe)

[RaveOnn]

What is the likelihood (chance) that the sun and moon always both appear as the same size in our sky?

That is one of the unique aspects of a solar eclipse.

[hikernut]

The apparent size of the sun varies, over the course of a year, from 0.524 degrees to 0.5418 degrees.

The apparent size of the moon varies, over the course of a roughly a month, from 0.49 degrees to 0.559 degrees.

So there's two times during each month (more accurately, from one new moon to the next new moon) when the sun and the moon appear the same size.

[rjshae]

Since the Moon was formed, its relative size has steadily decreased over time due to tidal influences. It's just a happy coincidence that the Moon and Sun happen to be about the same angular size when we appeared.

[RaveOnn]

Coincidence is the official explanation then?

[hikernut]

Originally Posted by RaveOnn

Coincidence is the official explanation then?

Sure, it's a pure coincidence that the sun and moon are more or less the same apparent size.

[rokuremote]

Originally Posted by hikernut

Sure, it's a pure coincidence that the sun and moon are more or less the same apparent size.

And that our planet during the span of humanity was located in relation to the sun and moon that such a phenomenon was observable.

[rjshae]

Originally Posted by RaveOnn

Coincidence is the official explanation then?

It's the simplest explanation. Occam's razor applies. Anything else would require extraordinary circumstances, for which there is no evidence.

[roodd279]

They don't have to be the same size for an eclipse. If the moon appeared larger than the sun - any amount larger - then eclipses would still be a thing. The moon moves nearer - and farther - from the earth regularly, and is only (apparently) as large (or larger) than the sun some of the time.



But on the overall - I see your point that dumb luck has it they are "about" the same size. Why? Yep, just dumb luck. You think there's another explanation?



Why not ask where our other moons are? Why don't we have two or six of various sizes? If the earth were closer to the sun (neverminding the frying) - the sun would appear larger, while the moon remained the same size. No eclipse.


Lots of "what ifs" and "whys." This universe we're in is, well, the way it is. Sometimes, it's just coincidence.

[james112]

I think it's coincidence, although I think I read the moon is slowing moving closer to the Earth.


Also fascinating about the moon. Even though the moon is rotating, only one side faces the Earth while it rotates. The other is the 'dark' side. This has an easy explanation. Also I read that the moon helps keep the Earth's tilt of axis in place.

[rjshae]

Originally Posted by james112

I think it's coincidence, although I think I read the moon is slowing moving closer to the Earth.

Also fascinating about the moon. Even though the moon is rotating, only one side faces the Earth while it rotates. The other is the 'dark' side. This has an easy explanation. Also I read that the moon helps keep the Earth's tilt of axis in place.

The Lunar Laser Ranging experiments have directly demonstrated that the Moon is receding from the Earth at the rate of about 3.8 centimeters per year.