Evolution

Our universe got created 13.7 billion years ago. Consider the following data point to get a sense of how big our universe is. From Earth, light takes

1.29 seconds to reach Moon
8 minutes to reach Sun
322 minutes to reach Pluto
93 billion years to reach the edge of Universe

Where did everything come from? Recently I completed the big history project course and it answered a lot of questions about who we are and where we came from. In this post I will be writing about my understanding from the course.

Big Bang

Around 13.7 billion years ago, everything (matter + energy) in the universe was squashed into a tiny space smaller than an atom. Nobody knows who squashed all matter and energy into a tiny space. But we know that an extreme condition like this will create enormous amount of heat. The temperature was around 10 billion degrees. In order to get a sense of how hot the conditions were, water boils at 100 degrees. This tiny space started expanding so fast and it looked like an explosion which is called as big bang. Under these extreme conditions matter and energy are interchangeable. Einstein’s theory of relativity already proved this.

Energy = Mass * Speed of Light²

As the universe expanded the temperature started to come down and four forms of energy appeared (1) Gravity (2) Electro magnetism; positive and negative charges (3) Strong nuclear forces (4) Weak nuclear forces. Nuclear forces are responsible for binding the center of nucleus in an atom.

Quarks where the first forms of matter. They quickly combined in triplets to form protons and neutrons. Protons are positively charged and neutrons had no charge. They together formed the nucleus. Then electrons appeared and it had a negative charge. Since universe had too much of energy and heat, electrons did not get attracted to protons. Hence there were no atoms. All these happened in a second or two after the big bang. This state is called as the plasma universe.

After 380,000 years since the birth of the universe, the temperature dropped to less than 3000 degrees. At this temperature protons and electrons got attracted to each other and they formed atoms. Hydrogen and Helium atoms were thus formed. At that time 75% of universe contained hydrogen atoms and around 25% contained helium atoms. There were traces of Lithium, Beryllium, and Boron.

Why did universe had more hydrogen and helium atoms? Hydrogen atoms has an atomic number of 1 which means it has 1 proton and 1 electron. Helium has an atomic number of 2 which means it has 2 protons and 2 electrons. Since few proton-electron pairs are needed to make hydrogen and helium atoms the universe had more quantities of them.

Birth Of Stars

After 200 million years since the birth, the universe was dark and cold. It was filled with hydrogen and helium atoms. These atoms were almost evenly distributed in the universe with tiny differences in their distributions. This means some regions had more matter compared to the other regions.

Gravity got to work on these tiny differences. Gravity is the force of attraction between objects. The more massive an object, the stronger its gravitational pull. The region with more matter started pulling in the regions with less matter. This resulted in bigger region growing bigger and bigger. All the atoms in the bigger region started banging into each other and generated enormous amounts of heat.

When the temperature rose above 3000 degrees protons cannot hold on to electrons and the electrons flew apart. The temperature rose steadily and the banging of protons continued violently. The temperature reached its peak of 10 million degrees. At this high temperature, the protons overcome their repulsion (like charges repel; unlike charges attract) and fused together. This resulted in the release of enormous energy and thus stars were born. The entire universe got lit up by these stars.

Take a look at the periodic table given below. Most of the universe is made up of hydrogen and helium elements. Where did the other elements came from? All the remaining elements came from dying stars.

The nearest star to our planet Earth is Sun. The outer surface of the Sun is 5,800 degrees and the center is 15 million degrees. At this temperature stars fuses protons of hydrogen nuclei into helium nuclei i.e it converts a nucleus with 1 proton into nucleus with 2 protons. Stars convert hydrogen to helium nuclei for 90% of its life time. When it runs out of hydrogen nuclei the center of the star loses stability. At that moment gravity kicks in and collapses the star. This produces enormous temperature of around 200 million degrees.

At this temperature it fuses helium nuclei with 2 protons into Carbon nuclei with 6 protons. When it runs out of helium nuclei the center of the star loses stability. At that moment gravity kicks in and it collapses the star. This process continues until it produces Iron nuclei with 26 protons at 3 billion degrees. Cesare Emiliani an Italian-American scientist wrote

A star 25 times more massive than the sun will exhaust the hydrogen in its core in a few million years, will burn helium for half a million years, and—as the core continues to contract and the temperature continues to rise—will burn carbon for 600 years, oxygen for 6 months, and silicon for 1 day.

Once iron is formed the star explodes. This is called as super nova and it results in extremely high temperatures. At this very high temperature all the remaining elements in the periodic table comes out.

Planet Earth

Our nearest star Sun was formed 4.6 billion years ago. It formed in the same manner as other stars – a great cloud of gases pulled ever more tightly together by gravity. Eventually a spinning protostar grew at the center of the cloud and finally lit up with nuclear fusion. The Sun took in 99.9% of all the elements into it. The remaining 0.1% elements spun around the Sun. For millions of years these leftovers crashed together, combined, and formed new bodies through the process called accretion. These bodies along with Sun is called as the solar system. One such body is our planet Earth.

98% of the universe contains hydrogen and helium elements. In Earth they make up only 10%. The remaining 90% contains other elements like Iron, Oxygen, Silicon, Magnesium, Copper, Sodium, Aluminum, and Nitrogen. These elements are responsible for creating all the objects that we see around us including you and me.

If you want to create anything interesting then atoms needs to combine together to form molecules. All living and non-living organisms are made up of molecules. For atoms to form molecules three things are needed.

Diversity of elements – If you want to form a variety of molecules you need to have diverse elements like Carbon, Nitrogen, Oxygen, Phosphorus, Sulphur, and Hydrogen. Earth has all of them. Also these elements are the building blocks for living organisms. Without them you and me will not exist.

Energy – For atoms to link up together you need energy. Sun is the source of energy for Earth. If there is a lot of energy then it will blast all the complex molecules. If there is a too little then atoms will not combine. You need the right amount of energy. Earth receives the sufficient amount of energy due to its perfect location from Sun.

Liquid – In gas, atoms move very fast and hence they do not link up to form molecules. In ice they are stuck up to form grid and hence they will not link up. In liquids atoms cruise along freely and combine with other atoms to form molecules. Water is the ideal liquid and Earth contains plenty of water. The first simple organic molecules appeared in the deep oceanic vents around 3.5 billion years back. These simple molecules are made up of 10+ atoms. Amino acids (basis of proteins) and Nucleotides (basis of DNA) were some of the simple molecules.

Replicators (DNA)

At some point a remarkable molecule got formed by accident. Let us call it as the Replicator. This molecule had an extraordinary property of being able to create copies of itself. In the book The Selfish Gene – Richard Dawkins writes

This may seem a very unlikely sort of accident to happen. So it was. It was exceedingly improbable. In the lifetime of a man, things that that are that improbable can be treated for practical purposes as impossible. That is why you will never win a big prize on the football pools. But in our human estimates of what is probable and what is not, we are not used to dealing in hundreds of millions of years. If you filled in pools coupons every week for a hundred million years you would very likely win several jackpots.

There is another strange property of replicators. It makes few mistakes while copying. These mistakes sowed the seeds for evolution. Richard Dawkins explains this concept beautifully.

But imagine the days before printing, when books such as the Gospels were copied by hand. All scribes, however careful, are bound to make a few errors, and some are not above a little willful ‘improvement’. If they all copied from a single master original, meaning would not be greatly perverted. But let copies be made from other copies, which in their turn were made from other copies, and errors will start to become cumulative and serious.

DNA is the advance form of replicators. All organisms have DNA in their cells. The make up of DNA determines whether you are a banana, dog, or a human. The common ancestor of all organisms that are now living on earth is called as LUCA. Because of the mistakes done during copying process there are millions of species on earth. Here is one fact to prove this – Chimpanzee and Humans share 98% of their genes.

Natural Selection

Charles Darwin was twenty-two years old when he went on the voyage of HMS Beagle to the South American coast. The voyage lasted for five years from 1831 to 1836. In the Galapagos Islands Darwin found finches that differed from one island to the next. Upon his return to England, Darwin wondered what drove the variations in species he had seen on his voyage. He know that farmers and pigeon breeders could deliberately cultivate favorable variations. Why would that occur in nature?

Darwin came out with a break through idea and he called it as natural selection. In the book Seeking Wisdom – Peter Bevelin explains this concept beautifully.

After a mutation changes an individual, the environment determines if the change gives the individual an advantage. If the new trait is helpful, the mutated individual is more likely to survive, reproduce and pass the new trait to his children. Take a poisonous spider as an example. Assume that a population (a group of individuals belonging to one species that occupy the same geographic/ecological niche at the same time) of black widows differs in how toxic their venom is. If some spiders (mutants) are born with more toxins than others, two things could happen over time. If more toxins give an advantage in the spiders’ environment, more toxins might be “selected” for and the “more-toxins” characteristic might be passed to children. If the more toxic black widow spiders survive and reproduce better than the less toxic ones, then black widow spiders, will, over time, evolve more toxic venom. The frequency of the “more-toxic” spiders in the population increases over time. If there is no advantage, the trait disappears and the population of less toxic spiders increases.

Closing Thoughts

Big history project is one the best courses I have ever taken. I really enjoyed it and it changed the way I perceive life around me. I am ending this post with an excerpt from the book The Black Swan by Nassim Taleb

I am sometimes taken aback by how people can have a miserable day or get angry because they feel cheated by a bad meal, cold coffee, a social rebuff or a rude reception. We are quick to forget that just being alive is an extraordinary piece of good luck, a remote event, a chance of occurrence of monstrous proportions. Imagine a speck of dust next to a planet a billion times the size of earth. The speck of dust represents the odds in favor of your being born; the huge planet would be the odds against it. So stop sweating the small stuff. Don’t be like the ingrate who got a castle as a present and worried about the mildew in the bathroom. Stop looking at the gift horse in the mouth – remember you are a Black Swan.