Criteria to be classified as a planet

Why did Pluto lose its status as a planet in 2006? Its old news, but I hope it helps!
There are 3 criteria that determines a planet.
1: The object must have sufficient mass for its self-gravity to overcome its 'rigid body forces' and assume a hydrostatic equilibrium shape. Hence becoming round.
2: It must orbit around a star, hence our moon cannot be considered as one.
3: It must have 'cleared its neighbourhood around its orbit' of everything except much smaller objects. This rules out Pluto as a planet as its orbit which has Neptune, which is much larger, being in close proximity due to their unique orbits that seem to overlap each other on a 2 dimensional plane.
Source: David A Rothery

Solidification of eggs

We all know that when eggs are cooked over a long period of time it becomes hard boiled. Why is it so when liquid water boils and solid ice melts but liquid eggs turn solid?
Actually in eggs, it contains proteins such as Ovalbumin. In proteins, the basic unit of amino acid forms a chain of polypeptide which then coils to form a 3 dimensional shaped protein. Its shape is held in place by weak hydrogen bonds that can break under heat. When we cook, the hydrogen bonds that keep the protein in its 3 dimensional shape breaks causing the protein to lose its original shape and become denatured. The denatured protein in the eggs would then be long coils of polypeptide that ends up forming an interconnected mass with each other becoming a solid. A hard boiled egg is then formed.

Great oxygenation event

Disclaimer: The stuff I share is from what I've read and learned. It may be extremely vague. I only hope to present the things I learned in a more simple manner for understanding.(if it even helps) and maybe to discuss. 


The great oxygenation event is the point where oxygen became a permanent part of our atmosphere that happened about 2.4billion years ago. Before that, oxygen is produced by photosynthesis, but quickly combines with elements (such as iron), and organic matter and does not stay in the atmosphere. The great oxygenation event happened when there are not enough of those reactants on the surface to react with the oxygen since they were already reacted to form compounds. This cause oxygen to remain in the atmosphere and accumulate over time.
Oxygen is produced by cyanobacteria which can carry out photosynthesis. The word 'cyano' refers to the colour of the bacteria, which is actually blue-green algae.
Note: Another reason for the fact that oxygen did not immediately accumulate in the atmosphere is that it reacted with methane first, which was present due to other bacteria at that time, to give carbon dioxide.