The Big Bang Theory is a hypothesis, and certainly a guess. However, compared with other theories of the origin of the universe, the Big Bang theory is currently the most complete and the hypothesis with the most evidence. Other origin theories don’t even have any evidence, just mere hypotheses.
At the same time, I would like to emphasize that, strictly speaking, any scientific theory is a hypothesis (hypothesis), because any scientific theory is first put forward by means of a hypothesis, and then continuously demonstrated to test its universality, and finally formed and accepted by the public (of course it may be denied) science. The so-called bold assumption, careful verification.
Let’s briefly talk about how the Big Bang Theory came into being.
In the 1920s, the famous astronomer Hubble observed the motion of distant galaxies through astronomical telescopes and accidentally discovered that the light emitted by distant galaxies had a redshift phenomenon, which indicated that the distant galaxies were moving away from our earth.
Through continuous efforts, Hubble summed up the famous Hubble’s law, indicating that the universe has been expanding, rather than a steady universe.
After that, Hubble specially invited Einstein to come to the observatory to observe the fact that distant galaxies were moving away. Einstein was also ashamed to announce that his “cosmological constant” was a mistake, because the cosmological constant was what Einstein wanted to do. “steady-state universe”.
Since the universe has been expanding, then if time goes backwards, the universe will definitely become smaller and smaller, and eventually return to the infinitely dense singularity. This is the singularity of the Big Bang.
So what is the evidence for the Big Bang theory?
The most direct evidence is the redshift phenomenon of light just mentioned, which is also the earliest evidence. Here we only need to mention Hubble’s law, which is expressed by the formula: Vf = Hc×D.
Vf represents the speed of the celestial body moving away, Hc is the Hubble constant, D is the distance between the celestial body and the earth, and the Hubble constant is 67.80±0.77(km/s)/Mpc.
The second piece of evidence is the cosmic microwave background radiation.
The cosmic microwave background radiation, or “the afterglow of the Big Bang,” still exists today, and it exists in every corner of the universe. The first ray of light generated after the Big Bang took 13.8 billion years. In addition, the expansion of the universe has been stretching the light. Today, the light has long been stretched into microwaves that we cannot see.
But we can perceive the presence of microwaves. When I was a child, the black and white TV at home usually had snowflakes when there was no signal, which was actually caused by the influence of microwaves on the TV signal.
There is other evidence, such as elemental abundance. Astronomers have long discovered gas clouds without heavy elements in the universe, only the lighter elements of hydrogen and helium, which are the original gas clouds produced after the Big Bang.
Of course, the Big Bang is not a perfect theory, nor does any perfect theory exist. Since the Big Bang Theory was proposed, it has been questioned, which is normal. After all, how could an infinitely dense little point (singularity) suddenly expand into the vast universe today?
There are various other questions, such as, what happened before the Big Bang? Why did the Big Bang happen? What is a singularity?
All of the above problems need to be explained by scientists, and they may never be explained. Maybe the Big Bang Theory itself is wrong. After all, the mysteries of the universe that humans understand are too limited. But in any case, the Big Bang Theory is the best “hypothesis” at present. It is not like other theories that can be figured out, but a hypothesis based on a large number of observational studies!
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