Expert: Philip Stahl - 6/15/2010

Question
Your question was

without using telescopes or satellites what are the observations that early astronomers made that convinced them that:
1.the earth rotates on it's axis
2.that the earth rotates around the sun
3.that the moon rotates around the earth

Sorry, but I don't answer homework questions.

This is not a homework assignment I'm 48 years old. I have an open mind and am willing to except new concepts, but if I were alive 2000 years ago and  someone told me they thought, the earth rotates on it's axis, the earth rotates around the sun, and the moon rotates around the earth, I would want to know why they thought that. Would you have been able to figure any of these basic concepts out if you lived 2000 thousand years ago.
do you want to help me? sometimes the most basic concepts are the most difficult to explain clearly.

Thank you

Expert: Philip Stahl

Answer
Hello,

Okay, no need for snark. I had to ask because the question fit the profile of numeros others that have been asked from university students taking Introduction to Astronomy, or History of Astronomy courses.

In addition, the issue isn't that the questions engage "most basic concepts that are difficult to explain clearly" but that to address them accurately (especially as you've posed THREE, not just one) would take a lot of megabytes! We are often, in the case of these landmark early discoveries, talking of multiple personae, multiple methods, then the reasoning of how it was all put together to arrive at the putative discovery. (I can attest this in respect of just dealing with the first two, having written a History of Astronomy supplement text for the Caribbean Examinations Council).

For example, the last question to do with uncovering the lunar revolution around the Earth can easily be traced to Isaac Newton, in terms of the proximate methods - and the application of his law of universal gravitation. But in fact many more players and their roles were involved, such as those who also detected aberrations in the lunar orbit.

The best thing, therefore, is probably for you to go to a decent standard textbook, where answers are given in detail, and where the required logical connections to the process of discovery are made. As opposed to me doing it and using understandable short cuts (given what you're asking).

One of the best texts is Michael Zeilik's 'Astronomy: The Evolving Unverse' which can probably be obtained at reduced cost at Amazon. The relevant Chapters are 2, 3 and 4, which range from early Greek models and observations (Ch. 2) to Copernicus' and Tycho Brahe's observations (leading to the heliocentric theory for Earth's revolution about the Sun), to Galileo and Newton's contributions (CH. 4).

Sorry, I can't be more directly helpful, but the questions you've asked aren't "unanswerable" - they just demand more time and space than I'm prepared to give right now....as a lowly unremunerated expert!