Expanding Universe

Universe is 13 billion years old and yet expanding! It is expanding at a decent pace and it is believed that galaxies will evaporate in the coming 1019 to 1020 years. It has been learnt from a number of theories by different Physicists worldwide that only White Dwarfs (a type of star) would be able to survive as their lifetime is more than 1032years.

Black holes are not black.

They’re very dark, sure, but they aren’t black. They glow, slightly, giving off light across the whole spectrum, including visible light. This radiation is called “Hawking radiation”, after the former Lucasian Professor of Mathematics at Cambridge University Stephen Hawking, who first proposed its existence. Because they are constantly giving this off, and therefore losing mass, black holes will eventually evaporate altogether if they don’t have another source of mass to sustain them; for example interstellar gas or light.

Time is relative

Time is relative

This is one of the most astounding facts I have come across while studying physics. The passage of time is different for people moving at different velocities, ie. we each have our own sense of time. Time progresses slower at speeds approaching the speed of light.

The first picture is a stationary light clock with the beam moving up and down. The second is a moving light clock and as you can see the trajectory of the light beam is longer when moving. A longer path means it takes more time to cross it. This is called time dilation. Time dilation takes place in our everyday lives only we don't notice it, because the speeds we are used to are nowhere near the speed of light. It is estimated that astronauts at the ISS experience time more slowly, at a rate of roughly 1 second ‘lost’ every 747 days. If this isn't amazing, you may not have understood completely, but if you have, take a minute to soak it in

If sun was made up of ice cubes, it'll be as hot as it is now!

The reason sun has high temperature is its huge mass and the huge exerted gravity! Even if it was made up of ice cubes and had the same mass, it would have exerted same amount of gravity on the electrons around and cause the pressure to increase and pressure increment will cause the temperature of electron gas to increase just same as any ideal gas.

However, in such case, because of absence of hydrogen fuel, the sun will cool down a lot faster and won't remain burning for billions of years as it is doing today!

Things can travel faster than light; and light doesn’t always travel very fast

In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them.

When this happens, they cause a blue glow, known as “Cherenkov radiation”, which is (sort of) comparable to a sonic boom but with light. This is why nuclear reactors glow in the dark.

Incidentally, the slowest light has ever been recorded travelling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate.

MIND BENDING PHYSICS WITH FACTS.

If you forced all the atoms together, removing the space between them, crushing them down, a single teaspoon or sugar cube of the resulting mass would weigh five billion tons; about ten times the weight of all the humans who are currently alive.
Incidentally, that is exactly what has happened in a neutron star, the super-dense mass left over after a certain kind of supernova.