The Big Bang Theory is the leading explanation about how the universe began. At its simplest, it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today.
Because current instruments don't allow astronomers to peer back at the universe's birth, much of what we understand about the Big Bang Theory comes from mathematical formulas and models. Astronomers can, however, see the "echo" of the expansion through a phenomenon known as the cosmic microwave background.
While the majority of the astronomical community accepts the theory, there are some theorists who have alternative explanations besides the Big Bang — such as eternal inflation or an oscillating universe.
The phrase "Big Bang Theory" has been popular among astrophysicists for decades, but it hit the mainstream in 2007 when a comedy show with the same name premiered on CBS. The show follows the home and academic life of several researchers (including an astrophysicist).
The first second, and the birth of light
In the first second after the universe began, the surrounding temperature was about 10 billion degrees Fahrenheit (5.5 billion Celsius), according to NASA. The cosmos contained a vast array of fundamental particles such as neutrons, electrons and protons. These decayed or combined as the universe got cooler.
This early soup would have been impossible to look at, because light could not carry inside of it. "The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds," NASA stated. Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.
This early light — sometimes called the "afterglow" of the Big Bang — is more properly known as the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948, but was found only by accident almost 20 years later. [Images: Peering Back to the Big Bang & Early Universe]
Arno Penzias and Robert Wilson, both of Bell Telephone Laboratories in Murray Hill, New Jersey, were building a radio receiver in 1965 and picking up higher-than-expected temperatures, according to NASA. At first, they thought the anomaly was due to pigeons and their dung, but even after cleaning up the mess and killing pigeons that tried to roost inside the antenna, 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. The teams each published papers in the Astrophysical Journal in 1965.
Determining the age of the universe
The cosmic microwave background has been observed on many missions. One of the most famous space-faring missions was NASA's Cosmic Background Explorer (COBE) satellite, which mapped the sky in the 1990s.
Several other missions have followed in COBE's footsteps, such as the BOOMERanG experiment (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck satellite.
Planck's observations, first released in 2013, mapped the background in unprecedented detail and revealed that the universe was older than previously thought: 13.82 billion years old, rather than 13.7 billion years old. [Related: How Old is the Universe?] (The research observatory's mission is ongoing and new maps of the CMB are released periodically.)
The maps give rise to new mysteries, however, such as why the Southern Hemisphere appears slightly redder (warmer) than the Northern Hemisphere. The Big Bang Theory says that the CMB would be mostly the same, no matter where you look.
Examining the CMB also gives astronomers clues as to the composition of the universe. Researchers think most of the cosmos is made up of matter and energy that cannot be "sensed" with conventional instruments, leading to the names dark matter and dark energy. Only 5 percent of the universe is made up of matter such as planets, stars and galaxies.
Gravitational waves controversy
While astronomers could see the universe's beginnings, they've also been seeking out proof of its rapid inflation. Theory says that in the first second after the universe was born, our cosmos ballooned faster than the speed of light. That, by the way, does not violate Albert Einstein's speed limit since he said that light is the maximum anything can travel within the universe. That did not apply to the inflation of the universe itself.
In 2014, astronomers said they had found evidence in the CMB concerning "B-modes," a sort of polarization generated as the universe got bigger and created gravitational waves. The team spotted evidence of this using an Antarctic telescope called "Background Imaging of Cosmic Extragalactic Polarization", or BICEP2.
"We're very confident that the signal that we're seeing is real, and it's on the sky," lead researcher John Kovac, of the Harvard-Smithsonian Center for Astrophysics, told Space.com in March 2014.
But by June, the same team said that their findings could have been altered by galactic dust getting in the way of their field of view.
"The basic takeaway has not changed; we have high confidence in our results," Kovac said in a press conference reported by the New York Times. "New information from Planck makes it look like pre-Planckian predictions of dust were too low," he added.
The results from Planck were put online in pre-published form in September. By January 2015, researchers from both teams working together "confirmed that the Bicep signal was mostly, if not all, stardust," the New York Times said in another article.
Separately, gravitational waves have been confirmed when talking about the movements and collisions of black holes that are a few tens of masses larger than our sun. These waves have been detected multiple times by the Laser Interferometer Gravitational-Wave Observatory (LIGO) since 2016. As LIGO becomes more sensitive, it is anticipated that discovering black hole-related gravitational waves will be a fairly frequent event.
Faster inflation, multiverses and charting the start
The universe is not only expanding, but getting faster as it inflates. This means that with time, nobody will be able to spot other galaxies from Earth, or any other vantage point within our galaxy.
"We will see distant galaxies moving away from us, but their speed is increasing with time," Harvard University astronomer Avi Loeb said in a March 2014 Space.com article.
"So, if you wait long enough, eventually, a distant galaxy will reach the speed of light. What that means is that even light won't be able to bridge the gap that's being opened between that galaxy and us. There's no way for extraterrestrials on that galaxy to communicate with us, to send any signals that will reach us, once their galaxy is moving faster than light relative to us."
Some physicists also suggest that the universe we experience is just one of many. In the "multiverse" model, different universes would coexist with each other like bubbles lying side by side. The theory suggests that in that first big push of inflation, different parts of space-time grew at different rates. This could have carved off different sections — different universes — with potentially different laws of physics.
"It's hard to build models of inflation that don't lead to a multiverse," Alan Guth, a theoretical physicist at the Massachusetts Institute of Technology, said during a news conference in March 2014 concerning the gravitational waves discovery. (Guth is not affiliated with that study.)
"It's not impossible, so I think there's still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously."
While we can understand how the universe we see came to be, it's possible that the Big Bang was not the first inflationary period the universe experienced. Some scientists believe we live in a cosmos that goes through regular cycles of inflation and deflation, and that we just happen to be living in one of these phases.
Essay on The Big Bang Theory
First there is nothing - no time, no space, not even emptiness for there is no space to be empty. Then from this void suddenly explodes a universe far smaller than the tiniest speck of dust. And from this speck of dust, this infinite darkness will emerge all of creation.
The entire cosmos began as an incredibly dense primitive atom. Approximately 15 billion years ago this atom exploded with an intense force. This was not a usual blast, but rather an explosion filling all space with all of the particles of the developing universe charging away from each other. In 1927, the same year he got his PhD from MIT, Georges LeMaitre, a Belgian Jesuit priest and cosmologist proposed the theory in which he stated the expanding universe was the same in all directions (Big Bang 1). LeMaitre had no data to substantiate his theory; so many scientists ignored his theory.
Two years later in 1929, Edwin Hubble discovered that galaxies were moving away at high speeds. Imagine the galaxies hurrying away as in a movie; run the movie backwards and after a time all those galaxies will rush together. Hubble’s discovery showing the universe was expanding supported LeMaitre’s theory of 1927. An expanding universe, much like the after effects of an explosion, must have at one time been “unexploded,” a single mass in space and time (Hubble 1)
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The Big Bang symbolizes the instant the universe began, when time and space came into existence and all matter in the cosmos launched into expansion. Prior to this all four fundamental forces (gravity, electromagnetism and the strong and weak nuclear forces) were combined. The explosion was one of space within itself. It was not like the explosion of a bomb where fragments are thrown outward (LaRocco 1). The galaxies were not clumped together. During the first second or so of the universe large amounts of energy, known as photons, smashed together and changed their energy into mass. This caused the four forces to split into their separate identities. As the universe continued to cool, protons and neutrons combined to form helium and other light nuclei. It was not until around one million years after the Big Bang, nuclei and electrons were cool enough to unite to form atoms. The universe did not start to look as it does today until small deviations in the matter distribution were able to squeeze to form the stars and galaxies as they are known today.
The Big Bang Theory does a remarkable job of describing the universe, as it is known today. It explains the development of the universe, predicting the correct profusion of hydrogen and helium (the most common elements in the universe) and it accounts for the cosmic background radiation. Though it was very successful and few scientists doubt its validity, the Big Bang Theory was too simple to be complete.
Despite the name “Big Bang,” the big bang premise is not really a theory of a bang at all. It describes the aftermath of the bang. The theory expresses how the early, hot dense universe expanded and cooled. Light chemical elements were synthesized during the expansion and matter clotted to form galaxies and stars (Guth 1).
Yet, there is further evidence for the Big Bang. In 1964, two astronomers, Arno Penzias and Robert Wilson, in an effort to detect microwaves from outer space, accidentally discovered a noise of an extraterrestrial source. The noise did not seem to originate from one location but came from all directions at once (LaRocco 1). What Penzias and Wilson heard was radiation from the outermost reaches of the universe, which had been left over from the Big Bang. These radioactive leftovers from the initial explosion gave credibility to the Big Bang Theory.
In 1990 NASA’s Cosmic Explorer Background satellite took a detailed spectrum of microwave background radiation. These studies showed the radiation is in nearly perfect agreement with the Big Bang Theory. Two years later, the same instrument was used to discover tiny deviations in the background radiation, the earliest known proof of the structure of the universe (Big Bang Confirmed 1)
The Big Bang attempts to clarify the origin and structure of the universe. It includes the talents of many individuals through the course of more than 150 years of study. The Big Bang Theory offers a feasible solution to one of the most pressing questions of all time --- how did the universe begin. It is vital to understand, though, that the theory itself is continually being adjusted. As more observations are made and more research is conducted, the Big Bang becomes more complete and our knowledge of the origins of the universe more significant.
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