Tropic of Cancer, latitude approximately 23°27′ N of the terrestrial Equator. This latitude corresponds to the northernmost declination of the Sun’s ecliptic to the celestial equator. At the summer solstice (in the Northern Hemisphere), around June 21, the Sun attains its greatest declination north and is directly over the Tropic of Cancer. At that time the Sun appears in the constellation Gemini, but much earlier in history, it lay in the constellation Cancer, thereby resulting in the designation Tropic of Cancer. Because of the gradual change in the direction of Earth’s axis of rotation, the Sun will reappear in the constellation of Cancer in approximately 24,000 years.
Answer by Mimiwhatsup: These 'rocks' are actually called fossils they are originally called sedimentary rocks as they are the only rocks that can undergo the certain process. Besides fossils regular rocks can be used to show how long they have been around there are these machines that show how long something has been around and what happened to it.
