Universe

The Universe is the name that we use to describe all of space and its contents. It comprises billions of stars and planets and enormous clouds of gas separated by a gigantic empty space.

PHYSICAL PROPERTIES AND COMPOSITION

There are close to 50 billion galaxies in the observable universe, each comprising somewhere around 100 billion stars orbiting the galaxy's center of mass.

2014 Hubble Team Unveils Most Colorful View of Universe Captured by Space Telescope 

There are ten times more stars in the night sky than grains of sand in the world's deserts and beaches.

It is estimated that the diameter of the Universe is at least 93 billion light years, or 8.80 ×1026 metres

The universe is expanding, with the galaxies moving apart from each other (as revealed by the red shift in their light).

Humans can only see about 4% of the matter in the Universe. The rest (about 23%) is made up of invisible matter (called Dark Matter) and a mysterious form of energy (73%) known as Dark Energy.

The brightest things in the universe are quasars, which can be over 4,000,000,000,000 times brighter than our sun.

GRB 080319B was a gamma-ray burst (GRB) detected by the Swift satellite at 06:12 UTC on March 19, 2008. The explosion occurred about 7.5 billion years ago setting a new record for the farthest object that was observable with the naked eye. It remained visible to human eyes for approximately 30 seconds.

ESO artist's impression of gamma-ray burst GRB 080319B

A galaxy 13.4 billion light years away was spotted by the Hubble Space Telescope in 2016 breaking the record for the furthest thing that humans had seen. The light from the galaxy, named GN-z11, came just 400 million years after the universe began.

Approximately 73% of everything in the universe is in the form of hydrogen. Helium makes up about 25% of the mass, and everything else represents only 2%.

The average color of the universe is "Cosmic latte," a light beige.

The cosmological constant governs the expansion rate of the universe. If it varied from its actual value by one part in ten to the power of 120 (1 with 120 zeros after it) then the universe would have expanded too rapidly for anything to form or collapsed back on itself.

The hottest place in the universe is a cluster of galaxies called RXJ1347; it was discovered in 2009 by the Japanese telescope Suzaku and has a constant temperature of 300 million Celsius degrees.

A cloud of gas and dust formed from a dying star, called the Boomerang Nebula, is the coldest place in the universe, at minus 272c (minus 457.6f). Also known as the bow tie nebula, it is 5,000 light years away from Earth and was discovered in 1995.

Scientists searching for an explanation for an unusually cool area of sky instead discovered a 'supervoid'; an empty spherical blob 1.8 billion light years across that is the largest object in the known universe. The supervoid is not an actual vacuum, as its name suggests, but has about 20% less stuff in it than our part of the universe – or any typical region. An estimated 10,000 galaxies were “missing” from the part of the sky it sits in.

The lowest musical note in the known universe is caused by the rumbling of a black hole in the Perseus galaxy - 57 octaves below middle C.

HISTORY

The universe is thought to have originated in an immense explosion called The Big Bang.

After the big bang only hydrogen and helium along with trace amounts of lithium and beryllium were created. The other 86 elements found in nature were all created by nuclear reactions inside stars.

The ancient Egyptians regarded the spherical onion bulb as a symbol of the universe.

Some ancient Greeks believed that the Universe has infinite space and has existed forever. They thought it had a set of spheres which corresponded to the fixed stars, the Sun and various planets. The spheres circled about a spherical but unmoving Earth.

Aristarchus's 3rd century BC calculations on the relative sizes of, from left to right, the Sun, Earth, and Moon

Aristotle, the Greek philosopher was the first western man to argue that the universe owes its existence to an intelligent being, that is to say God.

Nicolaus Copernicus maintained in his revolutionary book On the Revolutionary of Heavenly Bodies that the Earth revolves round the Sun rather than the then established teaching that the Earth is at the center of the universe. Published in 1543, it was hugely controversial at the time, and was fought long and hard by authorities of the Christian church.

In 1632 Galileo Galilei published Dialogue on Two Chief World Systems, which updated Copernicus' theories about the Earth not being at the center of the universe. The following year, The Inquisition summoned Galileo to Rome where he was cross-examined and threatened with torture. The Roman Catholic Church argued "The doctrine that the Earth is neither the center of the Universe, nor immovable, but moves, even with a daily rotation is absurd and both philosophically and theologically false and the least an error of faith".

The French philosopher René Descartes was in the middle of writing The World, a book on the universe in which he accepted the views of Copernicus, when he heard that Galileo had been condemned for believing with Copernicus that the sun was the center of the universe and not the earth. Descartes decided to abandon the work.

Descartes applied certain methods of mathematics to science, teaching that the universe is explainable in mathematical terms. For the French philosopher the universe was a mechanical system activated by God, the first cause of all motion.

Below is a Model of the Copernican Universe by Thomas Digges in 1576, with the amendment that the stars are no longer confined to a sphere, but spread uniformly throughout the space surrounding the planets.

Isaac Newton published Principia Mathmaticia in 1687. The book set out laws which showed the Universe to be divinely ordained and set the foundation of the science of mechanics. Newton explained that gravitational force was responsible for controlling the motions of the celestial bodies.

Albert Einstein's theory of general relativity describes how spacetime is curved and bent by mass and energy (gravity).  In 1919 that prediction was confirmed by Sir Arthur Eddington during the solar eclipse of May 29th.

Einstein later introduced an extra term into his equations, the cosmological constant, to balance out gravity and produce a static universe that is neither expanding nor contracting. However, the German-born theoretical physicist had failed to notice that his theory predicted an expanding universe. Five years later, in 1922,  the Russian mathematician Alexander Friedmann discovered that Einstein had made an elementary algebraic error that caused him to overlook a solution to his own equations. Einstein had divided by zero at one point in his calculations, a mathematical impossibility. Friedmann then introduced the idea of an expanding universe that contained moving matter.

Though Albert Einstein came from a family of non-active Jews, he admitted, "Everyone who is seriously involved in the pursuit of science becomes convinced that a Spirit is manifest in the laws of the universe. A Spirit vastly superior to that of man and one in the face of which we modest powers feel humble."

Once when Albert Einstein was visiting Mount Wilson observatory in California with his wife Elsa, Mrs Einstein pointed to a complex piece of equipment and asked its purpose. The guide said that it was used to determine the shape of the universe. "Oh" she said not at all impressed. "My husband uses the back of an old envelope to work that one out."

The Big Bang theory was formulated in 1927 by Georges Lemaitre (July 17, 1894 – June 20, 1966), a Belgian Roman Catholic priest, In a May 9, 1931 letter to Nature journal Lemaître wrote: "If the world has begun with a single quantum, the notions of space and time would altogether fail to have any meaning at the beginning; they would only begin to have a sensible meaning when the original quantum had been divided into a sufficient number of quanta. If this suggestion is correct, the beginning of the world happened a little before the beginning of space and time."

Georges Lemaitre was also the first to present the idea of an expanding universe, derived from General Relativity and later known as Hubble's law.

Portrait of Georges Lemaître. Wikipedia

American astronomer Edwin Hubble (1889-1953) was the first to confirm that the universe is expanding.

We are currently in the Stelliferous Era, which in the grand scale of the universe is the age where stars are created throughout the universe. Eventually all stars will burn out, and we will enter the Black Hole Era followed by the Dark Era, where there is no longer any light in the universe.