Universe
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Universe A-Z. (2023). In Q-files Encyclopedia, Space, Universe. Retrieved from
https://www.q-files.com/space/universe/universe-a-z
"Universe A-Z." Space, Universe, Q-files Encyclopedia, 17 Nov. 2023.
https://www.q-files.com/space/universe/universe-a-z.
Accessed 19 Mar. 2024.
Universe A-Z 2023. Space, Universe. Retrieved 19 March 2024, from
https://www.q-files.com/space/universe/universe-a-z
Space, Universe, s.v. "Universe A-Z," accessed March 19, 2024.
https://www.q-files.com/space/universe/universe-a-z
Universe A-Z
Accelerating Universe A theory that the Universe is expanding at an increasing speed. This may be caused by a force called dark energy, which could overcome the gravitational force that pulls galaxies towards one another.
Cosmic inflation A theory that the Universe expanded to trillions of trillions of times its size in the first billionth of a trillionth of a second of its existence, before continuing to expand at a slower rate.
Cosmology The study of the Universe. A person who studies the Universe is called a cosmologist.
Cosmos Another word for Universe. It comes from the Greek word kosmos, meaning both “order” and “world”.
Critical density The density that all of the matter in the Universe would need to have in order for the Universe to stop expanding. At exactly the critical density the Universe will stop expanding and stay the same size. If the Universe has less than the critical density then it will continue to expand forever. If the Universe has more than the critical density then it will eventually be collapsed by its own gravity.
Dark energy A form of energy of an unknown type which is causing the expansion of the Universe to accelerate.
Dark matter Scientists think that dark matter makes up 90% of the Universe. Dark matter cannot be seen, but it can be detected by observing the effects of its gravity on other objects.
Einstein, Albert (1879–1955) German-born physicist who is famous for his theories about space, time, matter, gravity and light. Einstein is most famous for his theories of relativity. In 1921, he was awarded a Nobel Prize for Physics.
Electromagnetic Spectrum A group of different types of radiation (energy that travels as particles called photons, which have no mass and which sometimes behave like waves). Radio waves, microwaves, light and X-rays are all forms of electromagnetic radiation. In a vacuum they all travel at the same speed, but have different amounts of energy per photon.
Hubble’s Law Edwin Hubble’s theory that the farther away a distant galaxy is from the Earth, the faster it is moving away from the Earth. The observation that clusters of galaxies are moving away from each other is used (along with the existence of Cosmic Microwave Background Radiation or CMBR) as evidence of the Big Bang.
Multiverse Theory The theory that there may be other universes than our own, sometimes called “parallel universes”.
Observable Universe The parts of the Universe that we can, at least in theory, observe from Earth (with telescopes). We can see these distant regions because the light they emit has had time to reach us since the Big Bang.
Redshift Light travels as particles, but also behaves like waves. Red light has a longer wavelength (the distance between wave crests) than other colours. When a light source moves away from you, its wavelength stretches and it appears more red. This is redshift. All galaxies outside the Local Group show redshift. This indicates that they are moving away from us and that the Universe is expanding.
Supercluster A group of clusters of galaxies. Superclusters tend to be stretched into long “strings”, called filaments, that stretch across the Universe.
Universe The Universe is made up of everything we know, from the tiniest grain of sand to the most gigantic star. It even includes empty space. Nearly all the matter in the Universe is contained in galaxies, which are grouped into giant patterns called superclusters. These are spread round the Universe like a net. The “holes” between matter are empty spaces, called voids. Scientists think that the Universe began in a sudden hot expansion about 13.8 billion years ago, known as the Big Bang.
Void A region of space that is completely empty of matter, even dark matter.
Consultant: Mike Goldsmith