I have seen below statement, and it doesn't sound right:

The Sun and Moon seem to have the same size because of this amazing coincidence: the moon is 400 times smaller than the Sun and 400 closer than the Sun.

Checking 400 from this source:

The Moon's distance from the Earth: 384,000 km and diameter: 3,480 km
The Sun's distance from the Earth: 149,000,000 km and diameter of 1,392,000 km

Distance: 149,000,000 / 384,000 = 388.02, OK almost 400
Size: 1,392,000 / 3,480 = 400 spot on.

Does being X times further make it look X times smaller?

I have seen this post but not sure it answer my question: Can the apparent equal size of sun and moon be explained or is this a coincidence?

Note: First time post, let me know if the post is suitable.

  • $\begingroup$ The link you provide seems a duplicate of your question, imo $\endgroup$
    – user140606
    Jan 16, 2017 at 12:50
  • 3
    $\begingroup$ Ah, the silent downvoters... $\endgroup$
    – zx8754
    Jan 16, 2017 at 13:16
  • 3
    $\begingroup$ Yes the apparent equal size can be "explained" (as in the answer), and Yes, it is a coincidence. The earth's moon is HUGE relative to the size of the earth, compared with the moons of every other planet in our solar system. $\endgroup$
    – alephzero
    Jan 16, 2017 at 13:29

1 Answer 1


enter image description here

Also called the intercept theorem.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.