He found that these were revolving in orbits round the body of the planet, and, with transport, recognized that they presented a miniature representation of the Copernican system.
The announcement of these wonders at once attracted universal attention.
The spiritual authorities were not slow to detect their tendency, as endangering the doctrine that the universe was made for man.

In the creation of myriads of stars, hitherto invisible, there must surely have been some other motive than that of illuminating the nights for him.
It had been objected to the Copernican theory that, if the planets Mercury and Venus move round the sun in orbits interior to that of the earth, they ought to show phases like those of the moon; and that in the case of Venus, which is so brilliant and conspicuous, these phases should be very obvious.

Copernicus himself had admitted the force of the objection, and had vainly tried to find an explanation.

Galileo, on turning his telescope to the planet, discovered that the expected phases actually exist; now she was a crescent, then half-moon, then gibbous, then full.

Previously to Copernicus, it was supposed that the planets shine by their own light, but the phases of Venus and Mars proved that their light is reflected.