As far as humans can tell, space is infinite; it has no end or borders. Scientists believe that space will always seem infinite to humans for two reasons. First, our investigation of space has never found an edge (or any indications of an edge). Second, measurements show that space is expanding faster and faster, which pushes the edges of the universe ? if there are any ? ever farther out.Know More
Space is continuing to expand (meaning that all the galaxies are speeding away from the center of the universe) because of the Big Bang's momentum and because of a substance called dark energy. Dark energy occupies the seemingly empty parts of the universe, but it has a strong negative pressure, pushing things away from each other even faster than they would move as a result of the Big Bang. This makes it difficult for humans to measure the farthest reaches of space.
In addition, anything traveling through space ? including humans' investigative tools, techniques and measurements ? is limited to the fastest possible speed: the speed of light. Because nothing can travel faster than light, there is a limit to how far scientists can explore or understand the universe. The size of the observable universe (the part astronomers could potentially study) is approximately 45.7 billion light-years across.Learn More
As of 2014, the size of the universe is unknown. Clues to its size can only be found within the limits of the observable universe, which is a sphere with a diameter of about 92 billion light-years.Full Answer >
Depending on the size of the star before it explodes as a supernova, the core of the star either shrinks back into a tiny neutron star or becomes a black hole. If the star is only a few times bigger than the sun, the core becomes a tiny neutron star. If the star is much bigger than the sun, the chances of it becoming a black hole are much greater.Full Answer >
Gravity holds the universe together by keeping the large bodies that make up the universe together. It keeps the Earth in orbit around the sun, the sun in orbit around the center of the Milky Way and the Milky Way bound to other nearby galaxies known as the Local Group.Full Answer >
In astronomy, the term "diurnal motion" refers to the movement of stars around the Earth's celestial poles due to the planet's rotation on its axis. This movement is called a diurnal circle.Full Answer >