Plus, incredibly massive meteorites and asteroids frequently slammed onto the surface — creating even more heat. Heavier material sank to the bottom, lighter stuff rose to the top. This transformation created the Earth's layered core and mantle, crust, and atmosphere. Shifting, sliding, and colliding tectonic plates "surf" atop its semi-molten mantle.
This relentless drifting speeds along at the rate of fingernail growth, yet causes mountains to rise, volcanoes to erupt, and earthquakes to strike. These questions burned and plagued astronomers for millennia.
Earth was at a center of a series of concentric spheres containing the Moon, the planets, the Sun, and a final sphere of fixed stars.
By measuring the amount of time between the fluctuating brightness levels of variable stars, Leavitt discovered that it would be possible to estimate their distance away from the Earth, and possible to map the Universe.
After 10 to 100 million years of this banging, eight spherical, stable planets remained. Forces flatten a young solar system and it begins swirling as a protoplanetary disk of gas and dust.
The central stellar embryo may still "feed" off the material collapsing around it and continue to grow.Ever since the Big Bang, the Universe has been drifting and expanding.The birth and death of stars leave an aftermath of galaxies, planets, and even living organisms.Over millions of years, they gradually shaped themselves into solid planetesimals, and later protoplanets with their own unique orbits.Astronomers call all this smashing and joining together accretion.By calculating how bright it appeared from Earth and comparing this to its intrinsic brightness, Astronomers could estimate how much of the star's light had been lost while reaching Earth, and how far away the star actually was. Different elements joining, colliding, breaking apart, and joining again is a very ferocious stage in the life of any planet.In the scale of the Universe, light would take eight minutes to reach the Sun. Even after the Earth formed, when the atmosphere began to stabilize, it was under siege.The tiny bit of heavier elements that remained made up the rockier Mercury, Venus, Earth, and Mars.Through a combination of gentle collisions and gravity these atoms and molecules began attracting other like-sized material.It took billions of years for the Earth to form and settle into orbit around the Sun. To study the movements of heavens back then, you would look up into the sky.You would see the Sun and stars revolve around the very spot where you were standing, the Earth — just as Ptolemy did some 1,900 years ago.