The slow ________ of Mercury was first determined using radar ...

[tsand2]

The slow ________ of Mercury was first determined using radar signals sent from Earth.
 
  Fill in the blank(s) with correct word

Question 2

Of the Ptolemaic and Copernican models, who wins the battle of Occam's Razor for the simplest explanation of retrograde motions?
 
  What will be an ideal response?

[kilada]

Answer to Question 1

rotation

Answer to Question 2

Copernicus simply had retrograde motion resulting from the different speeds of the planets, with retrograding occurring any time one planet overtook another. Ptolemy by contrast needed complex deferents, epicycles, and equants to handle the complex planetary motions.

[tsand2]

Thanks for the timely response, appreciate it

[steff9894]

Wow, this really help