- Around 14 billion years ago, the universe began from a very small region that was extremely hot and dense.
- Then, there was a giant explosion known as the big bang
- This caused the universe to expand from a single point, cooling on expansion and forming the universe as we know it today
- particles formed → atoms → nebulae, stars, galaxies
- no sound as there were no particles, only energy
- energy was converted into particles
- equal amounts of matter and antimatter
- antimatter + matter = photons
- we are left over dust from the big bang
- Each point moves away from each other
- This is seen in galaxies moving away, the further away they are the faster they are moving
- As a result of the initial explosion, the universe continues to expand
- As all galaxies continue to move away from each other, it shows that the universe is continuing to expand
Evidence for the Big Bang
- Galactic red shift
- Cosmic background radiation
(need to have previous knowledge about red shift)
The big crunch (we might not need this)
- It is a theoretical scenario for the ultimate fate of the universe, wherein the big bang would essentially reverse. (the metric expansion of the universe would reverse)
- Instead of the universe expanding outwards, they would accelerate towards a point, and recollapse.
- This would cause the reformation of the universe with another Big Bang
Hubble's law
- As the stars move away, their velocity increases
- Recession speed is the speed at which galaxies move away from us
- Galaxies further away from us are moving faster than galaxies closer to us
(us is basically the earth)
- Hubble’s constant = 45-90 km/sec/Mpc
The most recent precise measurements of the distances and movements of distant, exploding stars suggest a Hubble constant of 69.8 km/s/Mpc, but other reports have pushed the value as high as 74 km/s/Mpc. - https://news.uchicago.edu/explainer/hubble-constant-explained#:~:text=The most recent precise measurements,74 km%2Fs%2FMpc.
- Hubble’s Law: $v = H_0 \times d$