Final answer:
An ellipse is a curve that is symmetric about its center and is defined by the sum of the distances from its foci to any point on the curve. The heliocentric theory, proposed by Nicolaus Copernicus, suggests that Earth is a planet that orbits the Sun. Galileo made important observations that supported the heliocentric theory and convinced others of the reality of the Copernican theory.
Step-by-step explanation:
An ellipse is a type of curve that is symmetric about its center. It is defined as the set of all points in a plane such that the sum of the distances from two fixed points, called the foci, to any point on the curve is constant. In other words, an ellipse is a stretched out circle.
The heliocentric theory, which suggests that the Sun is at the center of the solar system, was introduced by Nicolaus Copernicus in his book De Revolutionibus. He challenged the geocentric view that had been held by the ancient Greeks and proposed that Earth is a planet that orbits the Sun.
Galileo, on the other hand, made significant contributions to the fields of experimental physics and telescopic astronomy. He observed the moons of Jupiter, the phases of Venus, and the nature of the Milky Way and the Moon, among other things. His observations provided evidence in support of the heliocentric theory and helped convince his scientific contemporaries of the reality of the Copernican theory.