A telescope design that uses a lens and no mirrors is a refractor.

The simplest telescope design is the prime focus reflector.

Grazing incidence optics are critical to focusing __________ .

It is diffraction that limits the ________ of a telescope of a given objective diameter.

When Earth overtakes Mars, the outer planet retrogrades near __________ .

A fatal flaw with Ptolemy’s model is its inability to predict the observed phases of:

According to Newton’s third law, when the Voyager probes passed Jupiter in 1979, they exerted exactly the same force on Jupiter as the giant planet did on them.

The __________ blows out of the coronal holes.

At its current rate of consuming hydrogen, the Sun can stably shine for__________ .

A total solar eclipse will only occur when the new moon is both on the ecliptic and at its greatest distance from Earth.