Dark matter makes up another 27 percent. In essence, all the matter you've ever seen—from your first love to the stars overhead—makes up less than five percent of the universe. All rights reserved. Origins of the Universe Aftermath of cosmic inflation As time passed and matter cooled, more diverse kinds of particles began to form, and they eventually condensed into the stars and galaxies of our present universe. Nature - Bowman et al. Share Tweet Email. Why it's so hard to treat pain in infants.
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When cosmic inflation came to a sudden and still-mysterious end, the more classic descriptions of the Big Bang took hold. This all happened within just the first second after the universe began, when the temperature of everything was still insanely hot, at about 10 billion degrees Fahrenheit 5.
The cosmos now contained a vast array of fundamental particles such as neutrons, electrons and protons — the raw materials that would become the building blocks for everything that exists today.
This early "soup" would have been impossible to actually see because it couldn't hold visible light. Over time, however, these free electrons met up with nuclei and created neutral atoms, or atoms with equal positive and negative electric charges. Sometimes called the "afterglow" of the Big Bang, this light is more properly known as the cosmic microwave background CMB. It was first predicted by Ralph Alpher and other scientists in but was found only by accident almost 20 years later.
At first, they thought the anomaly was due to pigeons trying to roost inside the antenna and their waste, but they cleaned up the mess and killed the pigeons and the anomaly persisted. Simultaneously, a Princeton University team led by Robert Dicke was trying to find evidence of the CMB and realized that Penzias and Wilson had stumbled upon it with their strange observations. The two groups each published papers in the Astrophysical Journal in Because we can't see it directly, scientists have been trying to figure out how to "see" the Big Bang through other measures.
In one case, cosmologists are pressing rewind to reach the first instant after the Big Bang by simulating 4, versions of the current universe on a massive supercomputer. With what is known about the universe today, the researchers on this study compared their understanding of how gravitational forces interacted in the primordial universe with their thousands of computer-modeled universes. If they could predict the starting conditions of their virtual universes, they hoped to be able to accurately predict what our own universe may have looked like back at the beginning.
In a study, researchers did so by investigating the split between matter and antimatter. In the study, not yet peer-reviewed, they proposed that the imbalance in the amount of matter and antimatter in the universe is related to the universe's vast quantities of dark matter, an unknown substance that exerts influence over gravity and yet doesn't interact with light.
They suggested that in the crucial moments immediately after the Big Bang, the universe may have been pushed to make more matter than its inverse, antimatter, which then could have led to the formation of dark matter. Read more: What came before the Big Bang? The CMB has been observed by many researchers now and with many spacecraft missions.
Planck's observations, first released in , mapped the CMB in unprecedented detail and revealed that the universe was older than previously thought: Answering this question has been a major focus of cosmologists ever since the debate about which model of the Universe was the correct one began. With the acceptance of the Big Bang Theory, but prior to the observation of Dark Energy in the s, cosmologists had come to agree on two scenarios as being the most likely outcomes for our Universe.
In the first, commonly known as the "Big Crunch" scenario, the universe will reach a maximum size and then begin to collapse in on itself. This will only be possible if the mass density of the Universe is greater than the critical density.
Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. In this scenario, known as the "Big Freeze", the Universe would go on until star formation eventually ceased with the consumption of all the interstellar gas in each galaxy. Meanwhile, all existing stars would burn out and become white dwarfs, neutron stars, and black holes. Very gradually, collisions between these black holes would result in mass accumulating into larger and larger black holes.
The average temperature of the universe would approach absolute zero, and black holes would evaporate after emitting the last of their Hawking radiation. Finally, the entropy of the universe would increase to the point where no organized form of energy could be extracted from it a scenarios known as "heat death". Modern observations, which include the existence of Dark Energy and its influence on cosmic expansion, have led to the conclusion that more and more of the currently visible universe will pass beyond our event horizon i.
The eventual result of this is not currently known, but "heat death" is considered a likely end point in this scenario too. Other explanations of dark energy, called phantom energy theories, suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn apart by the ever-increasing expansion.
This scenario is known as the "Big Rip", in which the expansion of the Universe itself will eventually be its undoing. The earliest indications of the Big Bang occurred as a result of deep-space observations conducted in the early 20th century. In , American astronomer Vesto Slipher conducted a series of observations of spiral galaxies which were believed to be nebulae and measured their Doppler Redshift.
In almost all cases, the spiral galaxies were observed to be moving away from our own. In , Russian cosmologist Alexander Friedmann developed what are known as the Friedmann equations, which were derived from Einstein's equations for general relativity. Contrary to Einstein's was advocating at the time with his a Cosmological Constant, Friedmann's work showed that the universe was likely in a state of expansion. In , Edwin Hubble's measurement of the great distance to the nearest spiral nebula showed that these systems were indeed other galaxies.
At the same time, Hubble began developing a series of distance indicators using the inch 2. And by , Hubble discovered a correlation between distance and recession velocity — which is now known as Hubble's law.
And then in , Georges Lemaitre, a Belgian physicist and Roman Catholic priest, independently derived the same results as Friedmann's equations and proposed that the inferred recession of the galaxies was due to the expansion of the universe. In , he took this further, suggesting that the current expansion of the Universe meant that the father back in time one went, the smaller the Universe would be.
At some point in the past, he argued, the entire mass of the universe would have been concentrated into a single point from which the very fabric of space and time originated. These discoveries triggered a debate between physicists throughout the s and 30s, with the majority advocating that the universe was in a steady state.
In this model, new matter is continuously created as the universe expands, thus preserving the uniformity and density of matter over time. Among these scientists, the idea of a Big Bang seemed more theological than scientific, and accusations of bias were made against Lemaitre based on his religious background. Other theories were advocated during this time as well, such as the Milne Model and the Oscillary Universe model.
Both of these theories were based on Einstein's theory of general relativity the latter being endorsed by Einstein himself , and held that the universe follows infinite, or indefinite, self-sustaining cycles. After World War II, the debate came to a head between proponents of the Steady State Model which had come to be formalized by astronomer Fred Hoyle and proponents of the Big Bang Theory — which was growing in popularity.
Ironically, it was Hoyle who coined the phrase "Big Bang" during a BBC Radio broadcast in March , which was believed by some to be a pejorative dismissal which Hoyle denied.
Eventually, the observational evidence began to favor Big Bang over Steady State. The discovery and confirmation of the cosmic microwave background radiation in secured the Big Bang as the best theory of the origin and evolution of the universe. From the late 60s to the s, astronomers and cosmologist made an even better case for the Big Bang by resolving theoretical problems it raised. These included papers submitted by Stephen Hawking and other physicists that showed that singularities were an inevitable initial condition of general relativity and a Big Bang model of cosmology.
In , physicist Alan Guth theorized of a period of rapid cosmic expansion aka. The s also saw the rise of Dark Energy as an attempt to resolve outstanding issues in cosmology. In addition to providing an explanation as to the universe's missing mass along with Dark Matter, originally proposed in by Jan Oort , it also provided an explanation as to why the universe is still accelerating, as well as offering a resolution to Einstein's Cosmological Constant.
Significant progress was made thanks to advances in telescopes, satellites, and computer simulations, which have allowed astronomers and cosmologists to see more of the universe and gain a better understanding of its true age. Today, cosmologists have fairly precise and accurate measurements of many of the parameters of the Big Bang model, not to mention the age of the Universe itself. And it all began with the noted observation that massive stellar objects, many light years distant, were slowly moving away from us.
At the same time, galaxies were crashing and grouping together. As new stars were being born and dying, then things like asteroids, comets, planets, and black holes formed! How long did all of this take? That is a very long time. Because it got so big and led to such great things, some people call it the " Big Bang.
Have you heard the name Hubble before? He has a spacecraft named after him: the Hubble Space Telescope. It orbits Earth and takes amazing pictures of our universe.
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