Chapter 3: The Expanding Universe!

If you didn't know before...The universe is actually expanding. I can't really blame you for not knowing this though. In fact our "accurate" view of the universe only surfaced after Edwin Hubble observed our solar system, milky way galaxy and a variety of other galaxies through his very good telescope. The Sun is just a normal yellow star and the solar system is slowing rotating around the centre of the galaxy. 

Since the universe is so big with many other galaxies and systems just like our solar system. A problem arises as astronomers need a way to distinguish between billions of different stars in space. The technique of analyzing the light spectrum of each individual star. Since different elements have a different spectrum of light that they release(due to the election orbitals releasing specific amount of energy when collide). By focusing on the spectrum of a single star we can learn the composition of this star. 

When analyzing the different stars, astronomers also notices another pattern and trend. They discovered the fact that most stars seem to be red-shifted and moving away from us (thus the universe is expanding). In order to understand this, we must first learn the Doppler effect. Imagine a stationary radio sending out music. It sends its sound wave (the music) in a concentric pattern (in circles radiates outward). Therefore, everyone will hear the sound wave at the same frequency (same pitch). However, imagine the sound of an alarm on a fire trunk moving towards you. Although the frequency of the alarm (the source) is constant, as the fire trunk moves towards you, the speed of the fire trunk causes the (perceived) frequency of the alarm sound to increase (the alarm's frequency is not changed) this way, you perceive the alarm to be in high frequency or high pitch. But, as the fire trunk moves away from you, the (perceived) frequency of the alarm sound to decrease, this way, you perceive the alarm to be in low pitch. This works with sound but also applies to light (since it belongs to the electromagnetic spectrum). The term red-shift means that the star is moving away since the red colour is lower on the electromagnetic spectrum, and the term blue-shift means that the star is moving close since the blue colour is higher on the electromagnetic spectrum. 

How to know the shift of star

The doppler effect

The expanding universe made it no longer static and allowed general relativity to work better. Also anything is the universe that gives off light, the light will eventually reach us, but it will be an "old light" and not the current light produced by the source. (This is because light is only fast enough to travel through space) Interestingly, the sun we see is not the sun currently it is the sun 8 minutes ago. 

(although Hubble discovered the expanding universe, Alexander Freidmann, a Russian physicist, tried to explain the expanding universe years before Hubble). His two assumption of universe are: the universe looks identical in whichever direction we look, and that this would also be true if we were observing the universe from anywhere else. This is unexpectedly very accurate.

Freedman's hypothesis is proven by other physicists working on microwaves in the Bell Telephone research labs and other scholars working in Preston University. They observed microwaves in every direction and believed that these microwaves must have come from space. Every direction only has very slight change in the microwave amount. Therefore, theory is proven. 

Also the expanding universe suggested the beginning of universe as a big band, an intensely dense sphere explode. 

The big bang theory is full of energy and explosion, even today we can still see it as the cosmic background radiation. These are electromagnetic spectrums left behind from big bangs that travelled to us. But since they are so far away from where we are (and a long period of time has passed), they become the low frequency and long wavelength waves.
Another question is that what will the universe end up - the future of the universe. And this answer will be told tomorrow...