Answer:
See below.
Step-by-step explanation:
A lot of the evidence is related to the fact that light takes time to travel, one of the core principles underlying relativity.
- Space itself is expanding
Light has characteristics resembling waves, particularly the wavelength (or frequency), which humans see as color. The doppler effect occurs when an object emits light while moving, compressing or stretching the wavelength and altering the color of the light. The light from a galaxy traveling away from us will look "stretched out," or redshifted, to observers on Earth. A moving object's light is either compressed or blueshifted. This nomenclature is based on the fact that blue light has the largest wavelength and red light has the smallest wavelength for visible light. More frequently than not, invisible light like x-rays or radio waves are used to measure the impact of galaxies.
When we do gaze up at the galaxies in the sky, we notice something unsettling: it seems as though everything in the cosmos is frantically attempting to get away from the planet. Everything is far more redshifted than we would anticipate if galaxies were just randomly cruising through space. It is highly improbable that the earth is at the heart of a galaxy explosion that spans the entire universe in the post-Copernican era of science. Instead, we come to the conclusion that space itself is expanding and that the redshift effect would apply everywhere in the cosmos, not only on Earth.
The fact that space is expanding implies that everything was more compacted in the past. Theoretically, there must have been a time in the past when everything was maximum compressed if space has always been increasing.
- We can see the remnants of the big bang
Since light travels slowly, whenever we gaze into the remote reaches of the cosmos, we are also doing so in the past. By the turn of the 20th century, technology had evolved to the point where humanity had seen everything inside the observable universe. We discovered that a thick plasma "fog" of stuff from the early cosmos surrounds us on all sides in the form of cosmic background radiation. This suggests that the cosmos did not always exist in its current form. Stars and galaxies were created from a sort of primordial soup that subsequently cooled and concentrated.
We can learn some details about the characteristics of the cosmic background radiation, which will help us understand what the early cosmos was like. The evidence suggests that it was extremely hot and that stable stuff, such atoms and molecules, needed some time to form.
- It can be used to explain known phenomena
One of the best tests for a theory is if it can explain a well-known but yet unrecognized phenomena that is unrelated to the original motivation behind its development. Because the first nucleosynthesis only produced the lightest atoms, the big bang hypothesis, for instance, explains why there is a considerably greater abundance of hydrogen and helium in the universe than heavier elements.
- Appendix: Problems and open questions
The fact that both quantum and relativistic physics apply to the big bang is one of the challenges in researching it. These two models don't work well together, as you may be aware. One issue is that gravity is fundamentally weaker than the other forces, making it very hard to measure gravitational effects at the quantum level. As a result, there is no known quantum explanation of gravity.
Dark matter and dark energy are further issues. Simply put, dark matter is "additional" stuff with gravity but no other interactions. Since dark energy is in charge of space's perpetually accelerating expansion, it is much more intimately associated with the big bang idea.
The baryon asymmetry, an issue with antimatter, is another issue. When matter and antimatter come into contact, they completely destroy one another and transform into energy. When the great bang happened and subatomic particles first started to form, there was only a tiny bit more matter than antimatter; as a result, all that was left was matter. The galaxies are currently made up of this small amount of additional stuff. It is not understood why different amounts of matter and antimatter are produced.
However, the big bang theory is by far the most reliable hypothesis for the early universe's development. It is at the leading edge of contemporary science, therefore it's critical to grasp what evidence is actually being given and to accept new discoveries with a grain of salt.