pixabay.com Since Pluto is no longer considered a planet, the Solar system consists of the Sun and ________ planets that are connected to it by gravitational forces.
wikipedia.org In his "De revolutionibus orbium coelestium" ("On the Revolutions of the Heavenly Spheres"), Nicolaus Copernicus presented research results that challenged the __________ theory which was dominant at that time.
pixabay.com The distance between the Earth and the Sun changes as the Earth moves around the sun: it reaches the perihelion in January and the aphelion in July. The average distance is about 93 million miles (1 astronomical unit). How much time does it take light to travel this far?
