How did the universe begin?

Main topic: Tech

Other topics: Existential AI questions

Short answer:

• As suggested by the Big Bang theory, the universe came into existence during a period of inflation that started around 13.8 billion years ago. Within a microsecond, it ballooned from a size too small than an electron to roughly its current size.
• The Big Bang hypothesis incorporates the mainstream theories of elementary particles and the general theory of relativity that Albert Einstein developed.

File:Bigbang.png

Bigbang

The Big Bang Theory is now the most popular theory for how the universe came into existence. It states that the universe began as an infinitely extremely dense single point (the Singularity or the Planck Era) that expanded and stretched, at first at unimaginable speeds, and then proceeded at a much more quantifiable rate over the subsequent 13.8 billion years to become the still-expanding universe that is known today.

According to NASA, all of this occurred within the first second after the universe came into being when the temperature of everything was still very high. At the time, the temperature of everything was around 10 billion degrees Fahrenheit (5.5 billion degrees Celsius). The entire universe now contained a massive array of elementary particles such as electrons, protons, and neutrons, the building resources that would become the foundations for everything which exists today. This process is known as "reheating," It started when an overflow of matter and energy began compiling in our universe.

Is it feasible to gaze back in time and see the universe's beginning? - Not precisely

Since the available technology does not let astronomers physically see back in time to the moment the universe was formed, most of what we know about the Big Bang comes from mathematical calculations and models. However, astronomers can observe the "echo" of the universe's expansion due to the cosmic microwave background (CMB) phenomenon. This phenomenon is sometimes called the "afterglow" of the Big Bang. Ralph Alpher and some other scientists made the first prediction of it in 1948, but it wasn't discovered until an accident happened 20 years later.

Galaxies greater than 13 billion years old and originated shortly after the Big Bang may be seen by the Hubble Space Telescope due to its advanced imaging capabilities. The cosmic microwave background has been seen, which is the faint light left over after the Big Bang. These observations assist in creating an image of what the early universe resembled, particularly before those first stars appeared. The Andromeda galaxy, the primary galaxy closest to our own, is seen not as it is now but as it was more than two million years ago. This is because of the time it took for the light from the galaxy to travel across space and arrive on Earth.

Because it is not possible for humans to see the Big Bang directly, scientists have been focusing their efforts on devising methods that would allow them to "observe" it indirectly. In one scenario, cosmologists are "pushing rewind" to reach the first moment after the Big Bang. To do this, they are using a gigantic supercomputer to simulate 4,000 different versions of the universe we live in today.

While most astronomers believe in the big bang hypothesis, some propose eternal inflation or an oscillating universe

The Oscillating Universe Theory is a cosmological model that integrates both the Big Bang and the Big Crunch. This event is referred to as the oscillation of the universe. To put it another way, if this hypothesis is correct, then the portion of the universe in which we exist lies between the Big Bang and the Big Crunch. In other words, our world may be the first in a sequence of conceivable universes or the N^th in the series.

After the Big Bang, there was a short period referred to as inflation, during which the universe expanded at a very high rate. According to the notion of eternal inflation, inflation has never ceased and has continued for an infinitely long time. Within the enormous structure known as the multiverse, brand-new universes are being formed somewhere out there in space. The physical principles governing these worlds could be different in these realms. The oscillating model of the universe postulated a never-ending cycle of Big Bangs, followed by Big Crunches that began the process all over again.

The presence of dark energy, which is still one of the biggest mysteries in all science is responsible for the universe's accelerated expansion

Expanding Universe

Edwin Hubble, an astronomer, discovered that the universe was not stationary in the 1920s. Instead, it expanded, leading researchers to conclude that the universe must have begun with a Big Bang.

As it expands, continuous measurements of the universe are carried out by NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope. Whether the universe will continue to expand indefinitely or if it will one day come to a halt, turn around, and collapse in a "Big Crunch" has been one of the aims.

For a long time, scientists believed that the gravitational pull of the cosmos' many forms of matter would slow down the universe's expansion. Then, in 1998, measurements made by the Hubble Space Telescope of supernovae located very far away indicated that an extremely long time ago, the rate at which the universe was expanding was slower than it is now. In other terms, the expansion of the cosmos was not occurring at a slower rate as a result of gravity; instead, it was happening at a mysteriously faster rate. Dark energy is the term given to the mysterious factor that is thought to be responsible for this accelerated expansion, and it continues to be one of the biggest mysteries in scientific research.