The universe began with the Big Bang around 13.6 billion years ago. The Big Bang was a rapid expansion of the universe from a tiny single point. This hot expansion has continued since then, resulting in the expansion of the universe in every direction.Continue Reading
At the time of the Big Bang, the universe and all of its matter was concentrated in a single point. As the Big Bang started, this matter was heated to very high temperatures and expanded rapidly.
Several scientific observations have convinced astronomers that the Big Bang theory is correct. One of the strongest pieces of evidence is called the cosmic microwave background, or CMBR. This is the remaining heat from the Big Bang that can be seen in all directions when looking into the universe. As the universe has expanded, the initially hot material has cooled, so that it now emits light as microwaves.
By looking at distant galaxies and stars, scientists have also discovered that everything seems to be moving away from the Earth. The further away a galaxy is, the faster it appears to be moving. This shows that the universe is still expanding, although there is debate as to whether this expansion will continue forever.Learn more about Universe
Ptolemy's model of the universe was geocentric, containing the Earth at the center with a series of circles, called deferents, moving outward from the Earth, containing the moon, Mercury, Venus, the sun, Mars, Jupiter and Saturn. Ptolemy placed fixed stars and the Primum Mobile in the spheres after Saturn.Full Answer >
The universe has been known to be expanding since 1929, when Edwin Hubble measured the speed at which distant galaxies appear to be receding from Earth's position in space. In the early 21st century, astronomers measured the rate of expansion and discovered that it is increasing.Full Answer >
Nicolaus Copernicus was a Polish scientist who is credited with the early 16th-century discovery that the sun is the center of the universe and that Earth and several other planets orbit it. Copernicus' discovery, which subsequent astronomers expanded on, has become known as the heliocentric solar system.Full Answer >
The universe contains three different categories of black holes: stellar, supermassive and miniature, which are further divided according to whether they are spinning. Non-spinning black holes are always spherical, while spinning black holes tend to be more oblate. The degree of equatorial bulge is determined only by the rotational velocity of the object.Full Answer >