Pale Blue Dot – by Carl Sagan

Pale Blue Dot – by Carl Sagan

‘A vision of the human future in space’


This offering from Carl Sagan, an astronomer, cosmologist, astrophysicist and astrobiologist who popularised science takes us on a journey of space exploration. It seriously puts our Earth into perspective and shows us that really, in the grand scheme of things, we’re not that important.


Grab a copy of the book here:


Here is a dot point summary of the book!


A Wanderers Introductions


  • We were wanderers from the beginning
  • For 99.9% of the time since our species came to be, we were hunters foragers, wanderers on the savannahs and the steppes
  • There were no border guards then or customs officials
  • The frontiers were everywhere
  • We were bounded only by the Earth the ocean and the sky


  • The zest to explore and exploit has clear survival value
  • These days there seems to be nowhere left to explore, at least on Earth



  • Out planet and our solar system are surrounded by the new world ocean, the depths of space
  • Maybe it’s not the time quite yet, but those other worlds – promising untold opportunities beckon


  • We have uncovered wonders undreamt by our ancestors who speculated on the nature of those wandering lights in the night sky
  • We have probed the origins of the planet and ourselves


  • Life is a comparative rarity, you can survey dozens of planets and find that on only one of them does life arise and evolve and persist






Chapter 1: You are here


  • A spacecraft in Early 1990 took a picture of Earth 3.7 billion miles away from Earth
  • It took 5.5 hours travelling at the speed of light to reach us


  • From our here, there is no signs of humans in this picture
  • Not the remaking of the Earths surface, not our machines, not ourselves
  • From here, our obsession with nationalism is nowhere in evidence


Any pic of Earth from outer space

  • The pictures convey to multitudes something very well known to astronomers, on the scale of the worlds – to say nothing of the stars or galaxies – humans are inconsequential, a thin film of life on an obscure and solitary lump of rock and metal





Chapter 2 – Aberrations of light


  • Look back at the pale blue dot of the previous chapter, take a good look at it from this vantage point
  • Then try and convince yourself that God created the world for one of the 10 million species of life that inhabit that speck of dust
  • Now take it a step further, imagine that everything was made just for a  single shade of that species, or gender, or ethnic or religious subdivision
  • If this doesn’t strike you as unlikely, then pick another dot. Imagine it to be inhabited by a different for of intelligent life.
  • They too cherish the notion of a God who has created everything for their benefit. How seriously do you take their claim?


  • And after the Earth dies, 5 billion years from now, after it is burned to a crisp or swallowed by the sun, there will be other worlds and stars and galaxies
  • into being and they will know nothing of the Earth
  • Too many it still seems fitting that because of an accident of birth, our group (whichever that is) should have a central position on the social universe


Debates over the centuries

  • Many of the debates in the history of science seem to be, at least in part contests over which humans are special
  • Almost always the going in assumption is that we are special
  • After the premise is closely examined, though it turns out – in dishearteningly many cases – that we are not


You might imagine an uncharitable extraterrestrial observer looking down and see us excitedly chattering

  • “The universe is created for us! And concluding that our pretentions are amusing, our aspirations pathetic, that this must be the planet of the idiots




The princes of the Church threatened the aged astronomer with torture if he persisted in teaching the abominal doctrine that the Earth moved

  • The debate started to conclude in 1837 not due to better debate but by better instruments

God made in the image of us

  • The conceit of religion is brought closer to culmination in the notion that we are created in Gods image: The creator and the ruler of the entire universe looks just like you and me.. My, what a coincidence! How convenient and satisfying
  • The Ethiopians make their gods black and snub nosed
  • The Thracians say theirs have blue eyes and red hair
  • If horses could paint, they would paint the forms of God like horses


Modern science has been a voyage into the unknown with a lesson in humility at every step


The Great Demotions

  • In the 17th century there was still hope that the Earth may be the center of the universe
  • It might be the only world, but Galileos telescope revealed that the moon certainly does not possess a smooth and polished surface and other worlds look similar to the Earth
  • After millennia of philosophical debate they concluded the plurality of worlds


This was the start of a series of Great Demotions


Well then some hoped even if the Earth isn’t at the center, then the sun is. The sun is our sun. So the Earth is approximately at the center of the universe. Perhaps some pride can be salvaged

  • But by the 19th century observational astronomy had made it clear that the sun is the but one lonely star in a great self gravitating assemblage of stars called the milky way galaxy
  • Far from being the center our Sun with its entourage of dim tiny planets lies in an undistinguished sector of an obscure spiral arm


Well then our milky way is the only galaxy

  • Then it turned out that the milky way is one of billions if not hundreds of billinos of galaxies


Well then, our galaxy is at the center of the universe

  • It turns out the universe is expanding in all directions and in fact, there is no center of the universe


Well then, even if there are hundreds of billions of galaxies each with hundreds of billions of stars, no other star has planets

  • Turns out there are thousands with the right conditions for life


According to standards of Jewish, Christian and Muslims the Earth is 6000 years old

  • But then there is an awkward question, how is it that there is astonmical objects more than 6000 light years away
  • The only plausible conclusion is that God made all of the photons of light arriving on the Earth in such a coherent format as to mislead generations of astronomers into the misapprehension that there are such things as galaxies
  • Intentionally driving them to the conclusion that the universe is vast and old



Perhaps that the search for an unmerited privileged position for humans that will never be wholly abandoned is what in physics and astronomy we call the anthropic principle 


The weak principle

  • Merely notes that if the laws of nature and the physical constants – such as speed of light, the electrical charge of the electron, the Newtonian gravity constant or Planks quantum mechanical content had been different, then the course leading to humans would never transpire


  • If you changed the laws of nature at all, then very different things emerge and the universe is incompatible with life


The strong anthropic says that the physical constants are established so humans would eventually come to be


Sagan says – “We have not been given the lead in the cosmic drama. Perhaps someone else has. Perhaps no one has. In either case, we have good reason for humility”


Ch4 – A universe not made for us

  • We have tended in our cosmologies to make things familiar, despite all our best efforts we have not been very inventive
  • In the west, heaven is placid and fluffy, hell is the inside of a volcano
  • To which whatever group we are born, we owe passionate love and loyalty


  • Science has carried human self-consciousness to a higher level. This is surely a rite of passage, a step towards maturity


Science v Religion (in a way)


  • In some respects, science has surpassed religion in delivering awe
  • How is it that hardly any religion has looked at science and concluded, “This is better than we thought. The universe is bigger than the prophets had said! God must be greater than we dreamed”
  • They say, my God is a little god and we want him to stay that way


  • We were kept ignorant but we couldn’t  ourselves
  • We were starving for knowledge created hungry
  • It is no longer why we live in a garden, we found out too much
  • So as long as we were incurious and obedient, I imagine, we could console ourselves with our importance and centrality
  • And tell ourselves we were the reason the universe was made
  • We could not happily remain ignorant forever


  • If we crave cosmic purpose, then let us find ourselves a worthy goal


Chapter 5 – Is there intelligent life on Earth


You’re an alien explorer entering the solar system

  • After a long journey through interstellar space you examin some planets looking for something interesting
  • As you approach Earth


  • Your first impression is white clouds, brown continents with a blueish substance covering most of the Earth
  • You also observe it is 1/5 oxygen and has an ozone layer, implying  photosynthetic plants. A high level of intelligence is still not implied
  • You inspect methane, it is a sign of life
  • Radio transmissions start hitting due to the technology on Earth
  • You know at least one species on Earth has achieved radio technology, but which one?
  • To find this out you search at a higher resolution
  • You start seeing a checkerboard geometry in some regions near water
  • These are the planets cities with only a few patches of green
  • At last you detected the source of all the technology and the dominant life forms of the planet
  • The streets of the cities are built for their benefit


You park and watch it year by year

  • You may look closely at the center of the South American continent, which you know by now is a vast rain forest
  • In the daytime you see it covered by smoke and over the years there is less and less forest
  • The top soil of Madagascar is washing out to sea
  • But no topsoil means no agriculture? In another century, what will they eat? What will they breathe? How will they cope with the changing environment?


Having noticed what’s happening.. Are they oblivious to their fate?

Are they unable to work together on behalf of the environment to sustain them all?

.. Perhaps you think its time to reassess the conjecture that there is intelligent life on Earth


Ch 21 – to the sky!

“When my grandparents were children, the electric light, the automobile, the airplane, and the radio were stupefying technological advances, the wonders of the age


  • Our machines, increasingly competent and autonomous are speeding through the solar system discovering new worlds, examining them closely and comparing them to Earth


Extraordinary moment on Earth

  • Due to our own actions or inactions and misuse of technology, we live in an extraordinary moment, for the Earth at least
  • For the first time our species has become capable of wiping ourselves out
  • But this is the first time we have been able to journey to the planets and the stars
  • If you were dropped randomly at any moment in the past or the future, the chance of arriving at this critical moment is less than 1 in 10 million
  • Our leverage on the future is high just now


  • Our short term prospects are quite bleak, but if we survive the short term, our long term chances of survival are great


Ch22 – tiptoeing through the milky way

  • Science cuts two ways, its products can be used for both good and evil, but there is no turning back from science
  • In the long run, putting all our eggs in the single stellar basket no matter how reliable the solar system has been lately, may be too risky
  • In the long run, we need to leave the solar system
  • If this is true for us , why not for others also.. Why aren’t they here?
  • Space is vast  and even if there are older civilizations expanding onward and outward takes a long time


  • For the group who leaves Earth.. In successive generations as they go outward, the Earth would fade from bright star to pale dot to invisibility
  • The sun would appear dimmer until it was no more than a vaguely yellow point of light, among the thousands of others
  • Perhaps all contact with them will be lost, their exitance forgotten


  • So after a brief only partially successful sedentary experiment, we may become wanderers again – more technological than last time


  • Even a modest extrapolation of our recent advances in transportation suggests in only a few centuries we will be able to travel close to the speed of light


  • I do not imagine that it is precisely we , with our present customs and social conventions who will be out there
  • If we continue to accumulate only power and not wisdom, we will surely destroy ourselves
  • Our very existance in that distant time requires that we will have changed our institutions and ourselves
  • It will not be we who reach Alpha Centauri and the other nearby stars
  • It will be a species very like us, with our strenghts and less of our weaknesses


  • We may discover outlets for ambitions far grander and more worthy than merely populating an unlimited number of worlds


Humans capable of greatness

  • There are people who were born before there was such thing of an airplane
  • And who in old age saw four ships launched to the stars
  • For all our failings, we humans are capable of greatness


  • This is true for science and some other areas of technology
  • What new wonders undreamt of in our time will have we wrought in another generation?
  • And another? And the next millennium?
  • Two billion years ago our ancestors were microbes and constantly evolving


  • I believe that it is healthy and essential to keep our frailty and fallibility firmly in mind
  • I worry about the people who aspire to be god like
  • But for a long term goal and a sacred project, there is one before us
  • Something worthy and larger than ourselves, a crucial act on the behalf of humanity


Enter Sagan? Final page

  • After the brief sedentary hiatus, we will resume our nomadic way of life
  • These descendants travelling through the solar system will gaze up and strain to find a blue dot in their skies
  • They will marvel at how vulnerable the repository of all our potential once was
  • How perilous our infancy, how humble our beginnings, how many rivers we had to cross before we found our way


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