I think physicists do not understand gravity at all,
But they can describe and predict it very precisely.
I disagree with the first and present the second quote as proof, since the second is exactly what "understanding" means to a physicist... and really to any else. If you understand something, that means you a) know it's facts (describe) b) well enough to use those facts to create new ones (predict).
Put another way, pick any of the following:...
1. mental process of a person who comprehends; comprehension; personal interpretation: My understanding of the word does not agree with yours.
2. intellectual faculties; intelligence; mind: a quick understanding.
3. superior power of discernment; enlightened intelligence: With her keen understanding she should have become a leader.
4. knowledge of or familiarity with a particular thing; skill in dealing with or handling something: an understanding of accounting practice.
5. a state of cooperative or mutually tolerant relations between people: To him, understanding and goodwill were the supreme virtues.
6. a mutual agreement, esp. of a private, unannounced, or tacit kind: They had an understanding about who would do the dishes.
7. an agreement regulating joint activity or settling differences, often informal or preliminary in character: After hours of negotiation, no understanding on a new contract was reached.
...and you will see that physicists DO understand Gravity.
