Explore the Universe With This History of Cosmology Quiz

Cosmic microwave background (CMB) is leftover radiation from the Big Bang, which helps astronomers learn how the universe formed. Researchers Arno Penzias and Robert Wilson found CMB by accident while creating a radio receiver for Bell Telephone Laboratories in 1965. The receiver picked up a strange noise all over the sky, which turned out to be the evidence of CMB that astronomers were looking for.

In 1543, Nicolaus Copernicus published a mathematical model that proved the sun, not the Earth, lay at the center of the solar system. His heliocentric model kicked off the Copernican Revolution in astronomy, which initiated the gradual replacement of Ptolemy’s geocentric model. Copernicus’ ideas were controversial at the time, and it took 200 years to fully overturn the Ptolemaic model.

Until 1924, many astronomers thought the Milky Way galaxy made up the entirety of the universe. But when Edwin Hubble measured the distance from Earth to the Andromeda Nebula, he found Andromeda was much too far away to belong in the Milky Way, and was a separate galaxy all together. His observation was the first evidence of other galaxies in the universe.

Dark matter is an unknown form of matter that makes up about 80% of the matter in the universe. Although experts don’t know what exactly dark matter is, astronomer Vera Rubin and her colleagues were the first to find evidence of its existence, in the rotation of spiral galaxies in the 1970s. Dark matter is believed to keep stars from flying apart from each other when galaxies rotate.

Before Albert Einstein proved otherwise, physicists thought there was no limit to how fast an object could travel through space. However, Einstein showed that the universe has a speed limit of 186,000 miles per second, equal to the speed of light in the vacuum of space. Currently, massless particles such as photons are the only known objects to travel at the speed of light.

The Voyager spacecraft launched in 1977, and it left our solar system and crossed into interstellar space in 2012. A second Voyager spacecraft crossed into interstellar space in 2018. The mission of the two spacecraft is to explore space beyond the solar system and outer planets. Their plutonium-fueled energy supply is expected to last until 2025.

Edwin Hubble discovered that the universe is expanding when he observed distant galaxies drifting away from each other, and found the galaxies farthest from Earth were moving the fastest. This discovery is considered the most important revelation in astronomy in the 20th century. Universe expansion also supports the Big Bang model, since a massive central explosion could force such an expansion.

Albert Einstein’s 1915 Theory of General Relativity argued that space and time are unified in a continuum called space-time. He based his theory on the fact that the speed of light is the same everywhere. He further argued that the gravity of massive objects distorts space-time without breaking it. Astronomers use this theory to understand phenomena such as gravitational waves and black holes.

On his popular 1980s TV show “Cosmos,” Carl Sagan famously said, “We are made of star stuff.” He was referring to the fact that all humans are composed of elements that were first created in stars that died over 4.5 billion years ago. When a star dies, it reaches supernova, sending an explosion of material that disperses throughout the universe, some of which ultimately created human life on Earth.

Scientific consensus holds that the universe was created in a single massive explosion, dubbed a “big bang” by astrophysicist Fred Hoyle in 1949. Even though there have been other proposed origins of the universe, the Big Bang model is the current leading cosmological model accepted by astronomers.