5 interesting facts about the Big Bang, the theory that defined the history of the universe

The term “Big Bang” was thrown around so casually that it became the title of one of the most beloved sitcoms of all time. But while we all understand this basic idea—that the universe was once small, hot, and dense—many people still have big misconceptions about the theory. Here are five interesting facts about the theories that define our universe.

1. A Catholic priest first thought of this

Albert Einstein (left) and Georges Lemaitre in 1900. (Image credit: Getty)

In 1915, Albert Einstein published his general theory of relativity, which initially stated that the universe expands or contracts naturally. But Einstein, and the vast majority of astronomers and physicists at the time, thought the universe was static, so he added some extra terms to the equation to balance everything out.

Years later, Edwin Hubble discovered that galaxies, on average, were moving away from us. As astronomers continued to debate the implications of this observation, Belgian physicist and Roman Catholic priest Georges Lemaïtre was the first to take both Einstein’s and Hubble’s results at face value , who believes we live in an expanding universe that was once smaller, hotter, and denser than it is today. He called this origin the “primitive atom”.

2. Accidental verification

A researcher sits in front of a high-power microwave receiver receiving information from orbiting satellites. (Image credit: Getty/Universal Historical Archives)

Most physicists are skeptical of Lemaitre’s idea, especially since his theory seems a little too close to the Genesis story. But all other attempts to explain Hubble’s results have failed observational scrutiny for decades. Still, the “Big Bang” theory is considered an interesting but less plausible idea.

In 1964, two radio engineers at Bell Laboratories, Arno Penzias and Robert
Wilson is testing a new microwave receiver. No matter how hard they tried, they couldn’t get rid of the stubborn background hiss they kept hearing in the instrument—they even tried wiping all the pigeon droppings off the receiver. While searching around for an explanation, they stumble upon a team of theoretical physicists who are raising money to build what they have. It turns out that the background hiss is due to radiation left over from the universe’s transition from hot, dense plasma to slightly cooler, neutral gas. It’s called the cosmic microwave background, and it remains the cornerstone of our understanding of the Big Bang.

3. This is not creationism

An image of the Helix Nebula, also known as the Eye of God Nebula. (Image credit: NASA/JPL-Caltech/University of Arizona)

The Big Bang is the theory of the history of the universe, especially its early moments. We can say, with extreme confidence based on multiple independent pieces of evidence, that our entire observable universe – every mote of dust, every star and every galaxy – was once packed into a volume no bigger than a peach, at a temperature in excess of 1 trillion degrees .

What the theory doesn’t tell us, however, is where the universe came from — or even if that question makes sense. Our current understanding of physics can only take us so far into the past before all our theories, including our knowledge of how space and time work, collapse. In other words, we don’t know how the universe “began”. We only know what happened afterwards.

4. We can (almost) see it

An image of the cosmic microwave background taken by ESA’s Planck mission. (Image credit: NASA)

The cosmic microwave background is a big deal. Not only did it cement the Big Bang as the only theory capable of explaining all observational data, but it also served as a window into our distant past. When our universe was a million times smaller than its present size, it was hotter than 10,000 Kelvin (over 17,000 degrees Fahrenheit) and in a state of plasma. As it expands and cools, the plasma transforms into a neutral gas as the first atoms are formed. The event released a huge amount of radiation that remains today as the cosmic microwave background, or CMB. The CMB is responsible for more than 99.999 percent of the radiation in the universe.

The CMB formed about 380,000 years ago in the universe. Compared to your current age of 13.77 billion years, that’s equivalent to taking baby pictures when you were 10 hours old.

5. It’s everywhere

An image of the Rosette Nebula. (Image credit: ESA and PACS, SPIRE and HSC alliance, F. Motte AIM Saclay, CEA/IRFU – CNRS/INSU – U.Paris Didedrot for HOBYS key program)

One of the craziest things about discussing the universe is that our normal notions of objects simply don’t apply. For example, the universe has no edge, and no exterior—because the concept of a “universe” expands to encapsulate everything that exists.

Likewise, the Big Bang was not a space explosion, but a space explosionexplode. The Big Bang happened to everything in the universe at the same time. It happens not at a particular location in space, but at a particular location in time. It’s hard to think about, but that’s why we have math: to help us with concepts we don’t usually understand.

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