The Universe, as we know it today, is full of countless stars and galaxies spread across the cosmic immensity. Of all the great mysteries that exist in it, perhaps the greatest of all is this: where did all this come from?
For countless millennia, we have told stories about our cosmic origin: a fiery birth, a separation between light and darkness, an order emerging from chaos, the emergence from a dark, empty, formless state.
Some stories involved the presence of a creative entity, others relied on the unique intervention of nature itself. With the rise of modern science, however, we have gained an entirely new perspective.
Representation of cosmic history from the Big Bang to today.Source: NASA/WMAP
One of the greatest discoveries in Physics and Cosmology that began in the 20th century was that the Cosmos did, in fact, have its origins in a cosmic event known as the Big Bang, which occurred around 13.8 billion years ago. The idea, told in a simplified way, originated from the observation that the Universe was expanding, becoming less dense and cooling over time. The logical step that followed was, then, to go back in time, to imagine a Universe in the past that was increasingly closer, denser and hotter.
Although the Big Bang is today considered fundamental information in major cosmological models, the theory, when first proposed, was immensely debated and even ridiculed by proponents of competing theories. However, future evidence was conclusive in deciding that the Big Bang was, in fact, a key event in the origin of our Universe.
Artistic representation of the Big Bang.Source: GettyImages
However, this event is still little understood by the general public and is surrounded by several mistaken ideals that cause misunderstanding and confusion. Here are the top 3 myths people believe about the Big Bang.
Discover the main myths about the Big Bang
The Big Bang was an explosion
When looking at distant galaxies in the Universe, we see, in general, the same behavior emerging: the further away the galaxy is, the faster it moves away from us. It makes a lot of sense, then, to think that more distant objects are moving away from us at faster speeds and that we could trace every galaxy we see today back to a single point in the past: a huge explosion. But this is a misconception about what the Big Bang really is.
It's not that these galaxies are moving through the Universe, but rather that the structure of space that makes up the Universe itself is expanding.
A simple way to understand this is to imagine an empty birthday balloon that has been marked with a pen, with dots painted on it. As someone fills this bladder with air, the drawn balls will move away from each other in proportion to their initial distance, not because they are moving in the bladder, but because the bladder itself is inflating.
Points on a balloon move away from each other when the balloon is filled with air.Source: NASA
In short, it was not an initial explosion that caused the galaxies to move away from each other, but rather the physics of the expanding Universe, governed by Einstein's General Relativity, that causes space – and the galaxies contained within it – to fall apart. expand. There was no explosion, just a rapid expansion that has evolved based on the matter and energy content that is contained in our Universe.
The Big Bang occurred in the middle of the Universe
The Universe did not emerge at a “central point” in space. Although you might initially think that if everything appears to be expanding away from everything else, then we can extrapolate back in time to when they all originated in the same location, like a grenade that has a central location from where all the shrapnel originates. .
In the Big Bang, all points expand together in space.Source: BBC
However, again, The Universe didn't explode, it just expanded. In an expanding Universe, all places in space look the same when considering a large enough volume.
On the large-scale average, the Universe appears to have the same density, the same temperature and the same number of galaxies everywhere. And if you extrapolate back in time, it will appear hotter and denser, but that's because space itself is also evolving and expanding.
Therefore, the Big Bang did not happen at a single point, but occurred at all points in space at the same time, and it happened a finite period of time ago. When we look at the most distant regions of the Universe, we are looking back in time, and so are all other observers from every other perspective the Universe offers.
The Big Bang occurred at a point of infinite density and temperature
If the Universe is expanding and cooling today, then it must have been infinitely smaller, denser and hotter in the past. By testing this hypothesis by observing and measuring the micro-temperature fluctuations we see in the cosmic microwave background today, cosmologists realized that the Universe never passed a certain specific temperature level.
Temperature fluctuations (different colors) in the Cosmic Microwave Background.Source: ESA
The observed temperature fluctuations are significantly lower than those predicted by an infinitely hot Big Bang state. The only possible conclusion for this result is that the Universe had a temperature cut in the past, never exceeding a critical limit.