Distilled: Astrophysics for People in a Hurry

Astrophysics for People in a Hurry

Author: Neil deGrasse Tyson

Imagine a world in which everyone, but especially people with power and influence, holds an expanded view of our place in the cosmos. With that perspective, our problems would shrink (or never arise at all) and we could celebrate our earthly differences while shunning the behaviors of our predecessors who slaughtered one another because of them.

Review & Thoughts

If astrophysics seems like an esoteric field of science irrelevant to the average man or woman, think again. There’s no need for everyone to become an expert, but a basic competence with the knowledge we have about our universe is arguably a necessity for human progress. Discussions about these kinds of things need to become more commonplace if significant progress is going to be made. Scientists will continue to work and discover and theorize, but our species as a whole will be held back by the widespread ignorance of people who refuse to believe or understand basic principles of cosmic science.

The last chapter talks about the “cosmic perspective.” If nothing else, this alone is a gift to all those upon whom it is imparted. If you already have natural curiosity and perspective, then it can only be strengthened by education. For many others, still wrapped up in the perceived significance of the minutiae of their ephemeral existence, this newfound perspective can be a life-changing wake up call. It’s a source of discomfort and depression only to those who do not fully understand and appreciate the universe. If you feel uncomfortable contemplating your own cosmic insignificance, you simply need to learn more. This perspective has always been a strong source of motivation, inspiration, and comfort for me, and it has only been made even more so by this book.

It’s written in plain English, and is expertly structured to simplify larger-than-life concepts. A little prior knowledge helps, but you don’t need to know anything about the universe in order to read and benefit from this book. I chose to intermittently pause and do deeper research on some of the topics, the fruits of which appear in my notes. However, the top-level information provided in the book is plenty to serve as a foundation and context for understanding new scientific discoveries as they unfold.

I finished this book in two days, and I’m a slow reader. It’s an incredibly small time investment for priceless knowledge. It would be hard for me to justifiably give this book any less than a perfect score, given the importance of the subject matter and the prowess of the author, but it is genuinely deserving of this esteem.

Rating: 10/10

Excerpts & Notes

The Greatest Story Ever Told

Unlike protons, each with an electric charge of +1, and electrons, with a charge of -1, quarks have fractional charges that come in thirds. And you’ll never catch a quark all by itself; it will always be clutching other quarks nearby. In fact, the force that keeps two (or more) of them together actually grows stronger the more you separate them.

Without the billion-and-one to a billion imbalance between matter and antimatter, all mass in the universe would have self-annihilated, leaving a cosmos made of photons and nothing else. [This is what people refer to when talking about the asymmetry of matter in the universe.]

What was true for quarks, and true for hadrons, had become true for electrons: eventually only one electron in a billion survives. The rest annihilate with positrons, their antimatter sidekicks, in a sea of photons.

As the cosmos continues to cool, dropping below a hundred million degrees, protons fuse with other protons as well as with neutrons, forming atomic nuclei and hatching a universe in which ninety percent of these nuclei are hydrogen and ten percent are helium, along with trace amounts of deuterium (“heavy” hydrogen), tritium (even heavier hydrogen), and lithium.

These elements would be stunningly useless were they to remain where they formed. But high-mass starts fortuitously explode, scattering their chemically enriched guts throughout the galaxy.

Within the chemically rich liquid oceans, by a mechanism yet to be discovered, organic molecules transitioned to self-replicating life. Dominant in this primordial soup were simple anaerobic bacteria; life that thrives in oxygen-empty environments but excretes chemically potent oxygen as one of its byproducts. These early, single-celled organisms unwittingly transformed Earth’s carbon dioxide-rich atmosphere into one with sufficient oxygen to allow aerobic organisms to emerge and dominate the oceans and land.

People who believe they are ignorant of nothing have neither looked for, nor stumbled upon, the boundary between what is known and unknown in the universe.

We are stardust brought to life, then empowered by the universe to figure itself out, and we have only just begun.

On Earth as In the Heavens

Spectra are not only beautiful, but contain oodles of information about the light-emitting object, including its temperature and composition. Chemical elements reveal themselves by their unique patterns of light or dark bands that cut across the spectrum.

Further analysis of the Sun’s spectrum revealed the signature of an element that had no known counterpart on Earth. Being of the Sun, the new substance was given a name derived from the Greek word helios (“the Sun”), and was only later discovered in the lab. Thus, helium became the first and only element in the chemist’s Periodic Table to be discovered someplace other than Earth.

We cannot see, touch, or taste the source of eighty-five percent of the gravity we measure in the universe. This mysterious dark matter, which remains undetected except for its gravitational pull on matter we see, may be composed of exotic particles that we have yet to discover or identify. [Seeing is not believing!]

To the scientist, the universality of physical laws makes the cosmos a marvelously simple place. By comparison, human nature — the psychologist’s domain — is infinitely more daunting. [Remember this during encounters with people who express disinterest in attempting to understand the universe, yet clearly enjoy analyzing and explaining human behavior.]

Let There Be Light

As the temperature drops, particles move more and more slowly. And so right about then, when the temperature of the universe first dipped below a red-hot 3,000 degrees Kelvin, electrons slowed down just enough to be captured by passing protons, thus bringing full-fledged atoms into the world. This allowed previously harassed photons to be set free and travel on uninterrupted paths across the universe.

As the cosmos continued to cool, the photons that had been born in the visible part of the spectrum lost energy to the expanding universe and eventually slid down the spectrum, morphing into infrared photons. [And, eventually, cooled even more and morphed into microwaves; thus, the cosmic microwave background. Someday, when the universe is even colder, it will become the cosmic radio wave background.]

When something glows from being heated, it emits light in all parts of the spectrum, but will always peak somewhere. For household lamps that stull use glowing metal filaments, the bulbs all peak in the infrared, which is the single greatest contributor to their inefficiency as a source of visible light. Our sense detect infrared only in the form of warmth on our skin.

Being the remnant of something that was once brilliantly aglow, the [cosmic microwave background] has the profile we expect of a radiant but cooling object: it peaks in one part of the spectrum but radiates in other parts of the spectrum as well. [Also gives off radio waves and vanishingly small number of photons.]

The precisely measured temperature of these microwaves [CMB] is 2.725 degrees. [This is the general temperature of the cosmos in Kelvin, or about -500 degrees Fahrenheit.]

Because light takes time to reach us from distant places in the universe, if we look out in deep space we actually see eons back in time.

The universe was opaque until 380,000 years after the big bang. [As explained in earlier chapters, this is because before the universe dropped below 3,000 Kelvin, electrons were freely bouncing around space, knocking into photons and scattering them all over the place.]

Ordinary matter is what we are all made of. It has gravity and interacts with light. Dark matter is a mysterious substance that has gravity but does not interact with light in any known way. Dark energy is a mysterious pressure in the vacuum of space that acts in the opposite direction of gravity, forcing the universe to expand faster than it otherwise would.

Between The Galaxies

We have probed [intergalactic space] and revealed all manner of hard-to-detect things: dwarf galaxies, runaway stars, runaway stars that explode, million-degree X-ray-emitting gas, dark matter, faint blue galaxies, ubiquitous gas clouds, super-duper high-energy charged particles, and the mysterious quantum vacuum energy. [Quantum vacuum energy is another name for dark energy.]

Where there is mass there is gravity. And where there is gravity there is curved space, according to Einstein’s general theory of relativity. And where space is curved it can mimic the curvature of an ordinary glass lens and alter the pathways of light that pass through.

Intergalactic space is regularly pierced by super-duper high-energy, fast-moving, charged, subatomic particles. We call them cosmic rays. Their origin continues to be a mystery, but most of these charged particles are protons, the nuclei of hydrogen atoms, and are moving at 99.9999999999 percent of the speed of light.

Perhaps the most exotic happenings between (and among) the galaxies in the vacuum of space and time is the seething ocean of virtual particles — undetectable matter and antimatter pairs, popping in and out of existence. This peculiar prediction of quantum physics has been dubbed the “vacuum energy,” which manifests as an outward pressure, acting counter to gravity, that thrives in the total absence of matter. The accelerating universe, dark energy incarnate, may be driven by the action of this vacuum energy.

Dark Matter

Dark matter is our frenemy. We have no clue what it is. It’s kind of annoying. But we desperately need it in our calculations to arrive at an accurate description of the universe.

Unlike sound waves, which consist of air vibrations, light waves were found to be self-propagating packets of energy requiring no assistance at all.

We’re not inventing dark matter out of thin space; instead, we deduce its existence from observational facts.

The worst that can happen is we discover that dark matter does not consist of matter at all, but of something else. [This is cool because we won’t need to change how we account for dark matter in our mathematical formulas, leaving established canon intact. Only our understanding of the substance will change.]

Science is not just about seeing, it’s about measuring, preferably with something that’s not your own eyes, which are inextricably conjoined with the baggage of your brain. That baggage is more often than not a satchel of preconceived ideas, post-conceived notions, and outright bias.

The copious flux of neutrinos from the Sun (two neutrinos for every helium nucleus fused from hydrogen in the Sun’s thermonuclear core) exit the Sun unfazed by the Sun itself, travel through the vacuum of space at nearly the speed of light, then pass through Earth as though it does not exist. [Neutrinos are awesome! These “ghost particles” have almost no mass and do not interact with most other matter, passing through just about anything. Billions of neutrinos from the Sun are passing through every centimeter of your body every second! They are only stoppable under certain circumstances.]

If you can stop a particle at all, you’ve detected it.

For now, we must remain content to carry dark matter along as a strange, invisible friend, invoking it where and when the universe requires it of us.

Dark Energy

For the most mind-warping ideas of twentieth-century physics, just blame Einstein.

Concentrations of mass cause distortions (dimples, really) in the fabric of space and time. [This warping of space-time is gravity.]

You cannot assert that the entire universe is a special case that happens to be balance forever and ever, Nothing ever seen, measured, or imagined has behaved this way in the history of science, which makes for powerful precedent.

The expanding universe makes distant objects race away from us faster than nearby ones. [This is one method in the “cosmic distance ladder” for determining the distance of objects far, far away.]

The most accurate measurements to date reveal dark energy as the most prominent thing in town, currently responsible for 68 percent of all mass-energy in the universe; dark matter comprises 27 percent, with regular matter comprising a mere 5 percent.

Whatever dark energy turns out to be, we already know how to measure it and how to calculate its effects on the past, present, and future of the cosmos.

Without a doubt, Einstein’s greatest blunder was having declared that lambda was his greatest blunder. [Lambda was a variable used by Einstein in his general theory of relativity to represent the “cosmological constant”, later retracted as a mistake after Hubble’s discovery of the expanding universe, and then later reinstated and renamed “dark energy” when it was found to be necessary to explain the acceleration of the universe’s expansion.]

Distant galaxies now visible in the night sky will ultimately disappear beyond an unreachable horizon, receding from us faster than the speed of light. A feat allowed, not because they’re moving through space at such speeds, but because the fabric of the universe itself carries them at such speeds. No law of physics prevents this.

The Cosmos on the Table

Only three of the naturally occurring elements were manufactured in the big bang. The rest were forged in the high-temperature hearts and explosive remains of dying stars, enabling subsequent generations of star systems to incorporate this enrichment, forming planets and, in our case, people.

Helium is the second simples and second most abundant element in the universe.

How about life based on the element silicon? Silicon sits directly below carbon on the Periodic Table, which means, in principle, it can create the same portfolio of molecules that carbon does. [May be unlikely, according to Scientific American, because silicon doesn’t form many compounds with a characteristic called “handedness” which would make it difficult to interact with other compounds to perform useful functions.]

On Being Round

Using freshman level calculus you can show that the one and only shape that has the smallest surface area for an enclosed volume is a perfect sphere.

The cosmic mountain-building recipe is simple: the weaker the gravity on the surface of an object, the higher its mountains can reach. [On Earth, mountains wouldn’t be able to reach much higher than Mount Everest without collapsing under their own weight.]

The stars of the Milky Way galaxy trace a big, flat circle. With a diameter-to thickness ratio of one thousand to one, our galaxy is flatter than the flattest flapjacks ever made. [I always imagined the Milky Way to be thicker, but it is actually similar in proportion to a vinyl record!]

This general flattening of objects that rotate is why Earth’s pole-to-pole diameter is smaller than its diameter at the equator. [A result of centrifugal force. Earth is also actually widest just below the equator, giving it more of a pear shape. This is why spherical cosmic bodies are referred to more correctly as “spheroids”.]

There’s a variation of the ever-popular multiverse idea in which the multiple universes that comprise it are not separate universe entirely, but isolated, non-interacting pockets of space within one continuous fabric of space-time. [Beyond certain distance, objects in the universe are moving away from us faster than the speed of light. This makes it impossible for anything beyond that distance to affect our part of the universe, giving plausibility to this theory.]

Invisible Light

Filling out the entire electromagnetic spectrum, in order of low-energy and low-frequency to high-energy and high-frequency, we have: radio waves, microwaves, infrared, ROYGBIV, ultraviolet, X-rays, and gamma rays. [ROYGBIV represents the red, orange, yellow, green, blue, indigo, and violet spectra.]

Between The Planets

Interplanetary space is so not-empty that Earth, during its 30 kilometer-per-second orbital journey, plows through hundreds of tons of meteors per day, most of them no larger than a grain of sand.

The asteroid belt’s total mass is less than five percent that of the Moon, which is itself barely more than one percent of Earth’s mass. [Nonetheless, most of these will hit Earth eventually and some are totally capable of wreaking major havoc on the global ecosystem.]

If we had eyes that could see magnetic fields, Jupiter would look ten times larger than the full Moon in the sky.

Jupiter’s moon Europa has enough H2O that its heating mechanism (the same one at work on Io) has melted the subsurface ice, leaving a warmed ocean below. If ever there was a next best place to look for life, it’s here. [This heating mechanism is from structural stress imposed by the tug and pull of nearby gravitational fields.]

The Sun loses material from its surface at a rate of more than a million tons per second. We call this the “solar wind,” which takes the form of high-energy charged particles. [We are protected from this stuff by Earth’s magnetic poles.]

Exoplanet Earth

Contrary to what most people suppose, a planet does not orbit its host star. Instead, both the planet and its host star revolve around their common center of mass. [Same applies to moons and their respective planets, and all other orbiting bodies. For this reason, orbital paths are not perfectly elliptical but rather wobbly.]

We’re ablaze in long-frequency waves; spectacular evidence that something unusual is going on here, because in their natural state, small rocky planets emit hardly any radio waves at all. [Basically, intelligent life elsewhere would most likely detect our presence by the abnormal abundance of radio and microwaves emanating from Earth.

Every element, every molecule, no matter where it exists in the universe, absorbs, emits, reflects, and scatters light in a unique way. Pass that light through a spectrometer, and you’ll find features that can rightly be called chemical fingerprints.

Latest estimates, extrapolating from the current catalogs, suggest as many as forty billion Earth-like planets in the Milky Way alone. Those are the planets our descendants might want to visit someday, by choice, if not by necessity.

Reflections on the Cosmic Perspective

Sometimes I forget that every day, every twenty-four-hour rotation of Earth, people kill and get killed in the name of someone else’s conception of God, and that some people who do not kill in the name of God, kill in the name of needs or wants of political dogma.

Part the curtains of society’s racial, ethnic, religious, national, and cultural conflicts, and you find the human ego turning the knobs and pulling the levers.

Imagine a world in which everyone, but especially people with power and influence, holds an expanded view of our place in the cosmos. With that perspective, our problems would shrink (or never arise at all) and we could celebrate our earthly differences while shunning the behaviors of our predecessors who slaughtered one another because of them.

If small genetic differences between us and our fellow apes account for what appears to be a vast difference in intelligence, then maybe that difference in intelligence is not so vast after all.

Imagine a life-form whose brainpower is to ours as ours is to a chimpanzee’s. To such a species, our highest mental achievements would be trivial.

If a huge genetic gap separate us from our closest relative in the animal kingdom, we could justifiably celebrate our brilliance. We might be entitled to walk around thinking we’re distant and distinct from our fellow creatures. But no such gap exists. Instead, we are one with the rest of nature, fitting neither above nor below, but within.

It’s conceivable that life began on Marts and later seeded life on Earth, a process known as panspermia. So all Earthlings might, just might, be descendants of Martians.

Enjoy this edition of Distilled?

Pick up Astrophysics for People in a Hurry on Amazon here.

Distilled is an edition of the Side Effects blog that I publish upon completion of a new book. My reviews are an account of my personal, subjective experience of the book. I do my best to describe the impact it had on me, and any lessons I’ve taken away from it. The included excerpts and notes are sections that I highlighted and noted while reading, and represent what I feel to be the most poignant pieces of information. By publishing these reports here publicly, it is my hope that others will be able to receive the best of the knowledge and lessons from my literary journey.