In the introduction to his book great astronomers, robert stawell ball states, “the history of astronomy thus becomes inseparable from the history of the great men to whose labours its development is due.” based on what you read in the ptolemy section, how does ball develop and refine this central idea in his book?

banquo is a great foil

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.