What is the Big Bang?

Everyone who ever attended a science class knows that the universe originated with the Big Bang. It is the leading and the simplest explanation of how the universe began. At it’s simplest, it says that the universe started with a small singularity, that inflated over the next 13.8 billion years and formed the cosmos that we know today.

Since our current instruments do not let just peek beyond the time when the big bang occurred, whatever we understand about the Big Bang comes from mathematical formulas. Astronomers can see an echo of the Big Bang that is known as the cosmic microwave background.

The majority of the astronomical community accepts this theory but there are other alternatives, such as an oscillating universe, or an eternal inflation. The phrase “Big Bang Theory” has been quite common amongst the astronomers and the scientific community but reached the mainstream when a comedy show started at CBS from 2007.

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, according to NASA. The cosmos contained a large number of fundamental particles – electrons, neutrons and protons, and these combined to form atoms once the universe got cooler. This early soup is impossible to study as the light would not carry the 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. But over time, as neutral atoms formed with electrons combining with the nuclei, light formed. The light that we can study from the Big Bang is 380,000 years younger than the Big Bang.

This early light has been changed by the expanding nature of the universe into a microwave radiation. This is known as the cosmic microwave background or the 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]

Determining the age of the universe

The cosmic microwave background has been observed in many missions. One of the most famous was the Cosmic Background Explorer or COBE satellite imaging which mapped the sky in the 1990s. There were several other missions following this. These include 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.

Plank’s observation gave us unprecedented details of the map of the universe. It also showed that the universe is older than what we originally thought it to be. It was 13.82 billion years old instead of 13.7 billion. Also, the southern hemisphere of the map appears to be warmer than the northern hemisphere. This contradicts the initial theory that CMB would be same no matter in which direction we look at.

Examining the CMB also gives astronomers the clues of what the universe is made of. Researchers think that most of the cosmos is made out of matter and energy that cannot be sensed using conventional instruments. These are called Dark Matter and Dark Energy. Only 5% of the universe is made of observable mass and energy such as the stars and planets.

Gravitational waves controversy

Chandra data (above, graph) on J0806 show that its X-rays vary with a period of 321.5 seconds, or slightly more than five minutes. This implies that the X-ray source is a binary star system where two white dwarf stars are orbiting each other (above, illustration) only 50,000 miles apart, making it one of the smallest known binary orbits in the Galaxy. According to Einstein’s General Theory of Relativity, such a system should produce gravitational waves – ripples in space-time – that carry energy away from the system and cause the stars to move closer together. X-ray and optical observations indicate that the orbital period of this system is decreasing by 1.2 milliseconds every year, which means that the stars are moving closer at a rate of 2 feet per year.

While astronomers can see the beginning of the universe, they also started looking for proofs of the rapid expansion of the universe. 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.

Later, astronomers found evidence in CMD that pointed towards 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.

Gravitational waves separately were confirmed while talking about the movements and collisions of black holes that were ten times 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 just expanding, but it is also getting faster as it is expanding. This means, that with time, nobody will be able to spot galaxies from earth or from any other point of our galaxy.

While we have understood how the universe was formed, the Big Bang may not have been the first inflationary event in the universe. Some scientists believe that the universe undergoes regular cycles of inflation and deflation. We just happen to be living in one of these phases.

Source: Space.com

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