reading not enough learning books knowledge blog charlie sanabria Cosmos depths space history universe book Carl Sagan veil nebula
reading not enough learning books knowledge blog charlie sanabria summary cosmos carl sagan

Date posted: December 29th 2016

Book Title: Cosmos (continued)

click here to start from the beginning

back to contents

Chapter 10: The early universe

The universe is quite old, and a lot can happen in 13.85 billion years. Thanks to the limited speed of light we can look back in time and come to the conclusion that the universe is expanding. We can also realize that hundreds of millions of years ago, the universe was much hotter and brighter than it is today. One of the reasons that we think this is the case, is because of the way quasars look. Quasars are really far! Remember that the closest one is 2.3 billion light years away—compared to for example the andromeda galaxy which is 2.5 million light years away (with an m not a b). Yet, being that far, quasars still look pretty bright from here. We have calculated that for them to have such observable brightness, their actual brightness must be (or must have been) as bright as a thousand supernovas exploding at once. We suspect that quasars are the explosions that lead to the formation of galaxies. Of course there are many things that we don't know for sure, but we are learning so much from the Cosmos—and the answers are slowly coming.

back to contents

Chapter 11: The replicators

Inside such a big universe, a very common question we ask is: Are we alone? And this unfolds other questions such as: How did we come to be? To answer the first question may require only one word, yes or no (although we don't know it). But to answer the second question requires a much more complex answer. Seriously, how did we come to be?

One of the ways in which we came to be as complex as we are today is through the passing of information. That is, via replication of DNA.

sketch DNA being split replicated

A sketch of DNA being split and replicated

Image by Madprime under Creative Commons BY-SA 3.0 license via Wikimedia Commons

To have an offspring means to pass on all the information required to make another living organism of the same kind. This is called reproduction and we owe our existence to the process. However this replication is not perfect, small errors can occur by outside influences like radiation, or even simple replication mistakes. They are called mutations, and if those mutations manage to get passed down to future generations, over a long period of time they can transform a fish into a reptile. This is called evolution, and as funny as it sounds is the result of mistakes—very subtle replication mistakes every few generations—that when added through the eons made every single organism on Earth.

cartoon Darwin chimp

A cartoon of Darwin’s face on a chimp’s body

Image under Public Domain via Wikimedia Commons

The anatomy of our brain is perfect evidence for evolution. The R‑complex, at the base of our brain (sometimes called the reptilian brain), is responsible for our most primal instincts such as aggression, territoriality, and social hierarchy. An almost identical structure is also observed in reptiles, and it seems to have evolved hundreds of millions of years ago in our reptilian ancestors. Surrounding the R‑complex is the limbic system, or mammalian brain, which seems to have evolved tens of millions of years ago. This Limbic system is a major source of our moods and emotions—of our concern and care for the young. Then, surrounding all of this, we find the cerebral cortex (found only in a few mammals).

So if we look closely, our brain is a timeline. Shaped by evolution, and built on top of preexisting versions.

Now, as mentioned before, the DNA contains a lot of information. It is the code required to make a dog for example, a tree, or a human. Animals without an advanced cerebral cortex, base most of their behavior on the information provided by the DNA. They fear certain things and behave in certain ways “by instinct”—by obeying their DNA and the information that was given to them at birth. Some smart animals however, may learn other things here and there, they may store additional information throughout their lives. For example, wolves know how to walk from the day they are born, they know how to whine, and they know how to drink milk. That information is in their DNA. But they don't know where the deer are, or when their home is. Such information is taught and learned by circumstances and can make an regular animal do outstanding things—think of all the amazing things dogs can do!

Furthermore, this additional information can overrule some of the things our DNA tells us. That is the amazing thing of the cerebral cortex, it can overtake what our reptilian brain tells us, and replace it with useful practices such as kindness, curiosity, honesty, and good judgement (which seem so valuable nowadays). But unfortunately we have not found a high fidelity replication system (like the DNA) for all that good information we learn in our lifetimes. We teach our offsprings some of that information, and some people reach out through writing, but a lot of it gets lost.

Nonetheless, writing is perhaps the greatest of human inventions. It is an excellent way to pass down useful information to other generations—just like DNA does. If passing down useful information for millennia made amazing creatures all around the world, imagine what we could accomplish if we established a system that could replicate (down to the last detail) ALL the useful information learned by the most outstanding individuals of our advanced civilization.

back to contents

Chapter 12: Are we alone?

This chapter talks about how to calculate the probability of life elsewhere in the universe. It is a little too mathematical for my taste, so I don't want to go into the details. Besides there has been a lot of new discoveries and hypotheses in this field. So I’ll let you google about it and you will find out that the probability of us being alone is very [very] slim. We are not alone. It’s only a matter of time we find intelligent life elsewhere. Check out Wait But Why’s post on the Fermi Paradox1

  1. Also, do yourself a favor and read his Elon Musk series on Tesla and SpaceX

  2. Check out my post on the 7 habits of highly effective people in which I talk about how overcoming our instinctive reactions can make us better

back to contents

Chapter 13: Will we make it?

This chapter closes with another awakening perspective, but unlike that on Chapter 1, it focuses on us. The human species has been running around the Earth for about 200,000 years, and it was not until the last tenth of a percent of our existence that we found out the Earth was not flat. We owe this finding to science—and pretty much every other finding that has advanced our species. Science works, it’s as simple as that. One could say that it was invented during the Ionian awakening, however its effects were delayed by religion and slavery during the dark ages. Nonetheless, our curiosity managed to free us from the boundaries of mysticism—and once the Europeans crossed the atlantic, adventure and discovery were unleashed by science.

time line cosmos carl sagan

Made with public domain images from this post.
Ever since I read this book I’ve been making a timeline of the universe. If you want to check it out click here

Image under Creative Commons Attribution-ShareAlike 4.0 International license via

A couple hundred years after Columbus sailed to America we had already invented calculus, the telescope, the microscope, and many other devices that triggered more questions and more invention. Then the industrial revolution took place in the 1800—and globalization a hundred and fifty years later. Then the internet... We are learning exponentially!

But Carl’s concern in this chapter is whether we will be able to prevent our own destruction. I assume he included this chapter because the book was written in the middle of the Cold War, and an imminent nuclear disaster was in everyone’s mind. Nonetheless I think some of his concerns are relevant even today—given our inability to address global warming or eliminate terrorism.

Carl mentions that one of the characteristics that has led humans to be so good at surviving is the fact that we care for the young and those immediately around us. This is a behavior we owe to our Limbic system (our mammalian brain) which has evolved precisely for that reason, it helped us survive. The problem is that our reptilian brain is still there, and it often conflicts with the more caring mammalian brain.2

As I mentioned before, this R‑complex is very reactive and acts purely on instinct. This is where aggression and other characteristics that could be classified as “savage” can arise. And if stimulated enough it can create violent outcomes in human societies—some of which have stained our recent history. Today we still have certain cultures where this R‑complex is stimulated in the young through violence at home and crime in the streets. In such cultures, slavery, torture, mutilation of enemies, and repression of women are ubiquitous. Moreover, such cultures often believe in one or more supernatural beings, and claim they intervene in everyday life.

Carl calls upon everyone reading this book to pay more attention to the things that makes societies unite, care for others, and advance together. He says that it all starts by tenderly loving our children and encouraging their curiosity. He also says that “the percent likelihood of a society becoming physically violent if it is physically affectionate towards its infants and tolerant of premarital sexual behavior is 2 percent.”

Unfortunately at the moment humans seem to be more fond of barriers, and we like to separate ourselves by nationality, ethnicity, social status, etc. But such barriers only prevent the union and love necessary for the eradication of hostile behaviors.

mythical creature donald trump very fond barriers labels overcome hostility

This mythical creature is very fond of barriers and labels. Not precisely the way to overcome hostility

Image by gageskidmore under Creative Commons Attribution-ShareAlike 2.0 Generic License via Flickr

This book is really special. The information in it is so breathtaking yet so easy to forget. The only reason I am now very familiar with all the things written here, is because since I read it, I’ve submerged myself in this kind of information. I’ve watched a lot of shows, listened to lots podcasts, and read a ton of articles that talk about the universe and our place in it—over and over again.

The average Cosmos reader will most likely forget all these things within a year—or only be able to talk about them in a very abstract way, no details, no numbers, no names. But if this content gives you goosebumps (like it happens to me), don't be like the average reader. Get involved, read more, write about it, surround yourself with the Cosmos—your home.


Why is it that people all around the world still believe in things like superstition, ghost stories, the horoscope, karma, etc. despite these things always failing scientific tests, and having never given anything useful to humanity? Please answer in the comments below, or tweet about it using #comsosquestion

I have added here a list of quotes and useful things to remember in case you want to check them out. And that is it! Thank you so much for reading, and don't forget to read more. But don't read books to say you did. Read them consciously! And write about them, for it is the only way for them to stay solid in the mind.

1  2  3  4  5    

back to contents