Astrophysics for People in a Hurry by Neil deGrasse Tyson

Although title of the book says Astrophysics for People in a Hurry but believe me the book has more depth than the label interprets. Neil deGrasse Tyson is an epitome of masterly skill at explaining complex scientific concepts into the most elementary and comprehensible manner. He makes astrophysics so interesting that even a person who has no inclination towards the subject will surely gravitate towards the space and evolutionary history after listening to his talks. His enthusiasm is contagious indeed.

It took me quite a time to finish this masterpiece. My daily bed-time ritual that I looked forward to with great awe.

The book is simple, I thoroughly loved the way, Tyson explained and joined the threads. As a matter of fact, reading this was more like listening to him.

This is my first book from Tyson and now am looking forward to grab another creative spill from the genius.  

(Spoiler alert!)

Remarkable symmetry

One of the foremost interesting things of this book is his idea of “remarkable symmetry”. To understand this, let’s start from the beginning of what we call matter formation. Initially, temperature was extremely high, which enables matter to go between “matter” and “energy”.

The equation E= mc^2 means, energy equals mass times the speed of light squared. It also implies energy (E) and mass (m) are interchangeable. This forms the recipe for the formal conversion formula of matter and energy.

c^2 is the speed of light squared. Again, it’s a very huge number.

Current energy is not high enough to allow matter to go back and forth between “matter” and “energy”. 

We do not experience E= mc^2 in real life (material world) because energy in which we are emersed is not high enough to enable the interchanging of matter into energy and vice-versa continuously.

E= mc^2 the most profound equation

Tyson calls the Einstein’s mass – energy equivalence as one of the most profound equation that manifest before the beginning of time to the future of universe but not in our life’s experience. Therefore, universe is what we measure to be and not what we feel it to be.

In Tyson’s words, “The universe is under no obligation to make any sense to you”.

Senses need to be different to grasp the essence of universe and that is reality. The five senses that we have are different than what is required to understand the universe.

Energy-matter-energy cycle under huge temperature

Energy decides to morph into matter, spontaneously and it depends on temperature.

For instance, in equation E= mc^2, if we take electron. It has very low mass. The amount of energy required to create particle out of it would be very very high. If that much energy is not around, it will never become a particle.

So, early universe had so much of energy that every particle could be made. Therefore, each packet of energy morphed into mass.

How are we so sure of it?

Tyson explains that we happen to know particles that were the product of intense heat, that is,

  • Particles and anti – particles
  • Matter and anti – matter
  • Electron and positron (anti- electron)
  • Neurons and anti – neutrons

All types of particles spewed out, opposite pairs in every possible measurable way.

Matter and anti-matter annihilate to give out pure energy

Matter and anti-matter are identical to each other. The only difference is they carry opposite charge and spin. So, when both combine, they immediately annihilate and become pure energy. And matter disappears. By pure energy, it also means photons because they carry energy.

Sun is the “living” proof of this process. Nuclear fusion reactions happen all the time in the center of the sun. And same thing happened during the early universe as well.

Packet of energy is equal to photon. Photon turns into matter and anti – matter pair. Matter and anti – matter pair come together and they make a photon. This is how remarkable symmetry is achieved.

Matter without the anti-matter pair

As temperature in the universe drops, a point is reached where one cannot make particles with the energy that is left.

Out of million reactions, one photon did not make matter and anti-matter pair. It only made a matter particle without the anti-matter pair. This single matter particle got frozen out of the universe and eventually it became all matter that we know and interact with today.

Therefore, the concept of multi-universe could exist. And all laws of physics do not need to be same in each universe.

Newton’s equation of gravity

Tyson then talks about planets and stars going retrograde and loop to loop. Initially, this phenomenon was not fully understood. Thus, the idea or evidence of divinity seep in. However, at this point in time, Newton steps in and wrote down the equation of gravity and laws of motion.

This paved a new way for exploring the universe. Gravity explained the controlling forces of nature from the planets orbiting around Sun to the oceanic tides on planet Earth.

Newton’s equation of gravity demonstrated why and how the planets are moving. His equations were so potent that it also worked for the moons of Jupiter orbiting Jupiter and not just planets orbiting sun.

Galactical cannibalism

Next, Tyson moves on to galaxies, the grand tally of cosmic constituents.  In the observable universe nearly hundred billion galaxies have estimated. In these, there are dwarf galaxies. Typically, small galaxies orbit bigger galaxies. And in due course of time, these smaller stellar bodies are eaten or merged within the bigger bodies, thus, a form of “galactical cannibalism” is observed within the universe.

In the earlier time, milky way, our own spiral shaped galaxy, had dwarf galaxies around it, which was then hard to detect. However, things became slightly observable with the inventions of visible light telescope, x-ray light telescope and infra-red-light telescope.

Dark matter

Dark matter is a mysterious thing in the galaxy clusters. It does not consist of ordinary matter neither does it resides in black hole. Existence of any black cloud is also ruled out.

If we look at the cosmic finger print of early universe, we find, during the nuclear fusion after the big bang, nearly one helium nucleus for every ten hydrogen nuclei was left. Hydrogen nuclei are simply protons.

If dark matter had involved, more helium nucleus with respect to hydrogen should be in the picture but this is not the case. This means, dark matter did not participate in nuclear fusion. Therefore, dark matter is not the matter that we are made up of or we interact with.

It does not interact with strong and weak nuclear force. So, we can decipher, it cannot make nuclei. Neither does it interact with electromagnetic force, which means, it does not make molecules and neither form dense balls of (dark) matter.

Expanding universe

Einstein did not perform most of his experiments in lab but his laws were the product of his thought experiments.

Newton postulated that things fall back due to the pull of earth’s gravity. However, Einstein in his Theory of General Relativity concluded that gravity is the response of a mass to the local spacetime curvature caused by some other mass or field of energy. In other words, space and time act like a mesh or a fabric on which mass of an object creates distortions. This is why we see planets revolving around the sun. The distortions give curved trajectories.

Einstein’s concept summed up by John Archibald Wheeler “Matter tells space how to curve; space tells matter how to move”.

Two types of gravity via theory of relativity

Theory of relativity concluded two kinds of gravity. First, attraction between sun and planets, between objects thrown in air and earth. And second, anti- gravity pressure associated with vacuum of spacetime.

Physicists believed that universe is static, however, astrophysicist Edwin P. Hubble in 1929 discovered otherwise. With the observations of distant supernova, the community concluded that universe is ever expanding. And what’s surprising was, Einstein’s the equation for general relativity still fit-in perfectly in new state of expanding universe.

Dark energy

The next entity that came under the radar of astrophysicists was dark energy. Scientists are still not clear with what exactly it is but one thing is sure, dark energy is a quantum effect.

As per this hypothesis, vacuum is not empty but seethes with particles and their anti-matter counterparts. These virtual particles pop in and out of existence and are extremely transient by nature, they cannot be measured.

One of the remarkable features of expanding universe is the repulsive force that arises within vacuum and not from any material. As vacuum increases, density of matter and energy within the universe diminishes.

Thus, dark energy is even more subtle than dark matter.

Universe has a spherical edge

Right from the cosmic entities till objects on earth, energy and gravity conspire to turn all objects into spheres. Force of gravity causes collapse of objects from all sides.

Gravity has shaped cluster of galaxies into sphere, best example is that of Coma Cluster.

If we look at the observable universe, we will find galaxies go back from us and the speed is directly proportional to their distance. Of course, this is also a sign of expanding universe.

And in due course of time, if observed, light from all luminous objects loses its energy before it reaches us, thus astrophysicists concluded that as far as knowable margins are concerned, the universe has a spherical edge.

Invisible light

Human beings finally sensed that they couldn’t see that there is a rainbow of colors that we all can see which are waves of different lengths.

Isaac Newton performed the first experiment on rainbow colors using glass prism. He allowed white light to pass through a prism and then observed the seven visible colors or the visible spectrum, ROYGBIV.

When these lights are again passed through the prism, it gives white color upon reflection.

Then came William Herschel. He was curious to know the temperature of colors. Thus, he placed thermometer next to violet, blue, green, yellow, orange, and red light of visible spectrum, after directing sunlight through a glass prism. Finally, he observed that the region above red has the highest temperature of all. Thus, he discovered infrared (IR) radiation through his experiment.

Nearly after one year, scientist Johann Wilhelm Ritter who was intrigued by Herschel’s discovery, decided to look beyond the violet end of the spectrum. He experimented with chemicals that reacted to exposure with sunlight and thus, he discovered ultra-violet (UV) light.  

Eventually, with the discovery of UV and IR, astrophysicists build telescopes that were able to see those bands from cosmic sources.

Gravitational sling shot

According to Newton’s law of gravity, the gravitational force of a planet may get weaker the father one travel from it, however, it will never reach to level zero.

Jupiter’s gravitational field has protected solar system from many comets or huge debris that otherwise would have caused havoc.

We have used the gravity of planets to explore other planets within our solar system. For instance, the Cassini probe that was launched for exploring Saturn took gravitational sling shot twice by Venus, once by Earth and once by Jupiter.

Even with all our tech, we look puny in front of solar system, be it energy or speed. And to explore other areas of our solar system, we have taken gravitational trajectories from planet to another.

Universe is a ship in gigantic cosmic ocean

Our galaxy encompasses more than a hundred billion stars and the known universe has around hundred billion galaxies. The number is too huge to understand and it is not the end.

More than three thousand exoplanets have been discovered since 1995. These exoplanets are occupying a small pocket of the Milky Way around the solar system.

Some of these exoplanets resemble Earth, though not in detail but in overall properties. This suggests that there could be possibility of life in different forms maybe if not human.

The space is like one gigantic cosmic ocean, with many universes drifting on its surfaces. Our universe is one just ship floating on it.

Takeaway

Reading this masterpiece is certainly an enriching experience. Everyone, at least once, should try reading this book. It’ll take your mind to the next level and we will look at the same sky with a new perspective.

As its mentioned in the book, it indeed is “a conduit to the cosmos”.

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