By Victoria Hristova, Year 12
Apologies for the misleading title. The Big Bang is not a scam, and my goal is not to refute the theory, for it has been justified time and time again by a plethora of evidence over the course of nearly a century. I am merely going to elaborate on the nature of our cosmic origins, a question whose answer has proven rather elusive, even for great minds such as Einstein. As we go back in time, closer and closer to the first moments of existence, the laws of physics break down, giving place to chaos and singularity, which leads one to wonder how far we can actually turn back the clock.
First and foremost, no, the Big Bang was not an explosion. Ironically, the term “Big Bang” was coined by Fred Hoyle, an English astronomer who famously disliked the theory and strongly believed in an unchanging but dynamic Universe (Steady State theory). It clearly stuck with both scientists and the wider audience, which over time led to the common misconception that the beginning of our Universe was some sort of spontaneous combustion. So, if not that, what was it?
Fundamentally, the Big Bang marked the beginning of time in our Universe, quite literally. It isn’t a point in space but a moment in time, the first one, for that matter. Time simply did not “exist” before it. Hard to imagine, right? Think of it as traveling to the North Pole on Earth: Once you reach it, you can only go South from there, regardless of which direction you take. Same here, from the Big Bang, you can only go “South” in temporal terms, in other words, forward. Once the cosmic clock began ticking, the singularity—where all the matter in the Universe, visible and invisible, was packed in an infinitely dense point—expanded faster than the speed of light in a fraction of a fraction of a fraction of a fraction…… of a second. If you thought picoseconds were small (10-12), then bear in mind that this happened in less than 10-37 seconds. From then on, everything was a blazing primordial soup of matter, antimatter, plasma, and radiation, according to the words of Neil DeGrasse Tyson. In the minutes that followed, the astronomically high temperatures entailed nucleosynthesis, creating the first atomic nuclei. However, those temperatures did not allow the protons and neutrons to capture the electrons needed to form proper atoms, which left the youthful Universe an opaque fog through which light was scattered. Ultimately, when it finally cooled enough from expansion, some 380’000 years later, collisions between particles decreased, and the nuclei attracted the zooming electrons to themselves, forming atoms of hydrogen, helium, and some lithium and beryllium, albeit very few.
You may, understandably so, be wondering how we discovered this celestial shenanigan if we cannot even see it. The fact is, anything before the “clearing up” of the electron-plasma fog is purely theoretical, based on models that fit our current understanding of the cosmos’s expansion. Essentially, instead of working from past to present, we wind the clock backward. Edwin Hubble, once he discovered that the Universe was expanding—and by expansion, I mean that each point is moving away from everything simultaneously, not from a “center”—suggested that logically it all began in a singularity. However, in the late 1920s, that theory had not yet been experimentally proven. It was totally by accident, in 1964, that two American scientists, Penzias and Wilson, picked up a mysterious background noise with their radio telescope that they initially mistook for bird excrement.1 The signal was persistent, coming from every direction in the sky, day and night, summer and winter. It turned out to be just the proof Hubble had been predicting: the cosmic microwave background (CMB), the initial burst of free light from when atoms assembled and became neutral a mere 380’000 years after the Big Bang. Light, as we know, is an electromagnetic wave whose frequency decreases proportionally to the distance it’s traveled (Doppler effect). Seeing as the signals received were in the microwave spectrum, stretched by the cosmic expansion, scientists deduced that the Universe had over time cooled to a temperature that emitted that specific wavelength, which in turn allowed us to approximately age the Universe to 13.8 billion years, give or take. However, the CMB brought more to the table, arguably the greatest proof for the Big Bang theory.
The radiation from the CMB was omnipresent, and cosmologists measured the distribution of energy at different wavelengths, the temperature, if you will. What came out was a surprise: The overall temperature of the CMB was almost entirely uniform, the fluctuations being no more than 1/10’000 K. Such an infinitesimal variation suggested that the Universe must have been in thermal contact with itself at some point, aka the pre-expansion period singularity; otherwise, such an isotropic temperature would not be possible. Essentially, this is the most credible proof we have ever gathered on the inflationary model of the Universe.
Phew. That was dense, yet we barely even skimmed the surface of this intriguing and mind-bending topic. This is the well-known part; just imagine how much deeper we can go digging. Of course, as you may have also guessed, there is only so much we can actually know with our current technologies, only so much we can predict, extrapolate, and observe. But who knows? The answer is always there somewhere, simply waiting for a curious enough mind to find it.
(Image credit: Planck’s view of the cosmic microwave background, ESA/Planck collaboration)
Bibliography
- Copeland, Edmund. “Your Universe – the Past, the Present, and the Future.” 7 Nov. 2024, Université de Genève, Genève. Lecture.
- “Cosmic History.” NASA Science, NASA, science.nasa.gov/universe/overview/#big-bang. Accessed 28 Nov. 2024.
- Tyson, Neil deGrasse. Cosmic Queries: StarTalk’s Guide to Who We Are, How We Got Here, and Where We’re Going. National Geographic, 20
- From here comes Wilson’s famous quote: “We’ve either detected a pile of bird shit or the origin of the Universe.” ↩︎
