- Basics of 4D Spacetime in an animation
- How fast are you moving?
- How big is the universe?
- Why is our visible universe 14B light-years wide while the universe started about 14M light years back?
- Can you travel faster than speed of light?
- Sunlight hitting the earth is very old - approx 170,000 years old!
- How many universes are there? - 0 to infinity predicted by String theory.
- How will the universe end? - thanks to dark energy
1. Understanding 4d space time and the world line https://www.youtube.com/watch?v=ScdLqAA_64E
2. Lorentz transformation https://www.youtube.com/watch?v=aeCsS6PjhK8
3. Gravity and space time - how does it bend? https://www.youtube.com/watch?v=NAXHHBUY9_E
How fast are you moving?
Some motions are relative while others are not. Acceleration and rotation are absolute, while steady motion is relative. Always depends on the frame of reference https://www.youtube.com/watch?v=wIzvfki5ozU
How big is the universe?
If the space is flat or hyperbolic, it is infinite. If it is closed (like a sphere) it is no lesser than 250 times the size of the visible universe.
Why is our visible universe 14B light-years wide while the universe started about 14M light years back?
This is purely because of the expansion of space after the big bang. The background radiation that is measured was still given out at the time of the big bang. However, space has been expanding.
Can you travel faster than speed of light?
In some cases you can, e.g.
1. When light enters some other medium and slows down, other particles may not. So those can travel faster than light.
2. If you are in the part of the universe that is expanding faster than the speed of light, you can. This is outside of the visible universe and this effect is because the space is expanding.
3. In case of quantum coupling - where the two particles being coupled are at large distances from each other. So no matter how fast the observer checks, it looks like the two particles are connected at a speed faster than light
Video ref: https://www.youtube.com/watch?v=BhG_QZl8WVY
Sunlight hitting the earth is very old - approx 170,000 years old!
Generated in the core of the sun, it has to do a random walk to get to the surface of the sun. The random walk depends on how many times a photon collides with protons and get deflected. Based on simulations, the calculated time is about 170,000 years + 8mins (to get from the surface of the sun to the earth).
Ref: https://www.youtube.com/watch?v=Z-UO-RZBQ3U
How many universes are there? - 0 to infinity predicted by String theory.
https://www.youtube.com/watch?v=a1bWKZFP2Tc
How will the universe end?
The universe is proven to be almost flat. It consists of 5% of visible mass - which we touch and feel and the remainder is the dark universe. This dark universe consists of dark matter and dark energy
Video ref: https://www.youtube.com/watch?v=BhG_QZl8WVY
Sunlight hitting the earth is very old - approx 170,000 years old!
Generated in the core of the sun, it has to do a random walk to get to the surface of the sun. The random walk depends on how many times a photon collides with protons and get deflected. Based on simulations, the calculated time is about 170,000 years + 8mins (to get from the surface of the sun to the earth).
Ref: https://www.youtube.com/watch?v=Z-UO-RZBQ3U
How many universes are there? - 0 to infinity predicted by String theory.
https://www.youtube.com/watch?v=a1bWKZFP2Tc
How will the universe end?
The universe is proven to be almost flat. It consists of 5% of visible mass - which we touch and feel and the remainder is the dark universe. This dark universe consists of dark matter and dark energy
Dark energy is the biggest component and it is pushing our universe apart. Thus eventually, everything will be spread apart and burn out of fuel - leaving a cold dark empty expanse. https://www.youtube.com/watch?v=mSzCS_5qtVY
