Author: Neil de Grasse Tyson
ASIN: B01MAWT2MO
Great book to get the sense of vastness of our universe and our insignificance. If you're looking for better understanding of base reality, search for others in my "science" category.
EXCERPTS
In the beginning, nearly fourteen billion years ago, all the space and all the matter and all the energy of the known universe was contained in a volume less than one-trillionth the size of the period that ends this sentence.
Einstein’s general theory of relativity, put forth in 1916, gives us our modern understanding of gravity, in which the presence of matter and energy curves the fabric of space and time surrounding it. In the 1920s, quantum mechanics would be discovered, providing our modern account of all that is small: molecules, atoms, and subatomic particles. But these two understandings of nature are formally incompatible with one another, which set physicists off on a race to blend the theory of the small with the theory of the large into a single coherent theory of quantum gravity.
The clash between gravity and quantum mechanics poses no practical problem for the contemporary universe. Astrophysicists apply the tenets and tools of general relativity and quantum mechanics to very different classes of problems. But in the beginning, during the Planck era, the large was small, and we suspect there must have been a kind of shotgun wedding between the two.
Later still, the electroweak force split into the electromagnetic and the “weak nuclear” forces, laying bare the four distinct forces we have come to know and love: with the weak force controlling radioactive decay, the strong force binding the atomic nucleus, the electromagnetic force binding molecules, and gravity binding bulk matter.
All the while, the interplay of matter in the form of subatomic particles, and energy in the form of photons (massless vessels of light energy that are as much waves as they are particles) was incessant.
Shortly before, during, and after the strong and electroweak forces parted company, the universe was a seething soup of quarks, leptons, and their antimatter siblings, along with bosons, the particles that enable their interactions. None of these particle families is thought to be divisible into anything smaller or more basic, though each comes in several varieties. The ordinary photon is a member of the boson family. The leptons most familiar to the non-physicist are the electron and perhaps the neutrino.
Within the chemically rich liquid oceans, by a mechanism yet to be discovered, organic molecules transitioned to self-replicating life.
What happened before all this? What happened before the beginning? Astrophysicists have no idea. Or, rather, our most creative ideas have little or no grounding in experimental science. In response, some religious people assert, with a tinge of righteousness, that something must have started it all: a force greater than all others, a source from which everything issues. A prime mover. In the mind of such a person, that something is, of course, God. But what if the universe was always there, in a state or condition we have yet to identify—a multiverse, for instance, that continually births universes? Or what if the universe just popped into existence from nothing? Or what if everything we know and love were just a computer simulation rendered for entertainment by a superintelligent alien species?
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 will never go to the Moon.” What they have in common is that no established law of physics stood in their way. The claim “We will never outrun a beam of light” is a qualitatively different prediction. It flows from basic, time-tested physical principles.
Another class of universal truths is the conservation laws, where the amount of some measured quantity remains unchanged no matter what. The three most important are the conservation of mass and energy, the conservation of linear and angular momentum, and the conservation of electric charge.
It happens that 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.
For ordinary household gravity, Newton’s law works just fine. It got us to the Moon and returned us safely to Earth in 1969. For black holes and the large-scale structure of the universe, we need general relativity. And if you insert low mass and low speeds into Einstein’s equations they literally (or, rather, mathematically) become Newton’s equations—all good reasons to develop confidence in our understanding of all we claim to understand.
The power and beauty of physical laws is that they apply everywhere, whether or not you choose to believe in them. In other words, after the laws of physics, everything else is opinion.
After the big bang, the main agenda of the cosmos was expansion, ever diluting the concentration of energy that filled space. With each passing moment the universe got a little bit bigger, a little bit cooler, and a little bit dimmer.
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.
If all mass has gravity, does all gravity have mass? We don’t know. Maybe there’s nothing wrong with the matter, and it’s the gravity we don’t understand.
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.
Particle physicists are confident that dark matter consists of a ghostly class of undiscovered particles that interact with matter via gravity, but otherwise interact with matter or light only weakly or not at all. If you like gambling on physics, this option is a good bet.
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. The tally: night and day, a hundred billion neutrinos from the Sun pass through every thumbnail square of your body, every second, without a trace of interaction with your body’s atoms. In spite of this elusivity, neutrinos are nonetheless stoppable under special circumstances. And if you can stop a particle at all, you’ve detected it.
Dark matter particles may reveal themselves through similarly rare interactions, or, more amazingly, they might manifest via forces other than the strong nuclear force, weak nuclear force, and electromagnetism. These three, plus gravity, complete the fab four forces of the universe, mediating all interactions between and among all known particles. So the choices are clear. Either dark matter particles must wait for us to discover and to control a new force or class of forces through which their particles interact, or else dark matter particles interact via normal forces, but with staggering weakness.
As if you didn’t have enough to worry about, the universe in recent decades was discovered to wield a mysterious pressure that issues forth from the vacuum of space and that acts opposite cosmic gravity. Not only that, this “negative gravity” will ultimately win the tug-of-war, as it forces the cosmic expansion to accelerate exponentially into the future.
If a physicist’s model intends to represent the entire universe, then manipulating the model should be tantamount to manipulating the universe itself. Observers and experimentalists can then go out and look for the phenomena predicted by that model. If the model is flawed, or if the theorists make a mistake in their calculations, the observers will uncover a mismatch between the model’s predictions and the way things happen in the real universe. That’s the first cue for a theorist to return to the proverbial drawing board, by either adjusting the old model or creating a new one.
General relativity [GR] outlines the relevant mathematical details of how everything in the universe moves under the influence of gravity.
GR regards gravity as the response of a mass to the local curvature of space and time caused by some other mass or field of energy. In other words, concentrations of mass cause distortions—dimples, really—in the fabric of space and time. These distortions guide the moving masses along straight-line geodesics, though they look to us like the curved trajectories we call orbits.
In my opinion best representation of curvature of space-time fabric (Source: ESA)
“Matter tells space how to curve; space tells matter how to move.”
As Hubble was the first to show, the expanding universe makes distant objects race away from us faster than nearby ones.
The most accurate measurements to date reveal dark energy as the most prominent thing in town, currently responsible for 68 percent of all the mass-energy in the universe; dark matter comprises 27 percent, with regular matter comprising a mere 5 percent.
The shape of our four-dimensional universe comes from the relationship between the amount of matter and energy that lives in the cosmos and the rate at which the cosmos is expanding.
Since both mass [mass is basically a highly condensed energy] and energy cause space-time to warp, or curve, omega tells us the shape of the cosmos. If omega is less than one, the actual mass-energy falls below the critical value, and the universe expands forever in every direction for all of time, taking on the shape of a saddle, in which initially parallel lines diverge. If omega equals one, the universe expands forever, but only barely so. In that case the shape is flat, preserving all the geometric rules we learned in high school about parallel lines. If omega exceeds one, parallel lines converge, and the universe curves back on itself, ultimately recollapsing into the fireball whence it came.
So what is the stuff? Nobody knows. The closest anybody has come is to presume dark energy is a quantum effect—where the vacuum of space, instead of being empty, actually seethes with particles and their antimatter counterparts. They pop in and out of existence in pairs, and don’t last long enough to be measured. Their transient existence is captured in their moniker: virtual particles. The remarkable legacy of quantum physics—the science of the small—demands that we give this idea serious attention. Each pair of virtual particles exerts a little bit of outward pressure as it ever so briefly elbows its way into space.
A remarkable feature of lambda and the accelerating universe is that the repulsive force arises from within the vacuum, not from anything material. As the vacuum grows, the density of matter and (familiar) energy within the universe diminishes, and the greater becomes lambda’s relative influence on the cosmic state of affairs. With greater repulsive pressure comes more vacuum, and with more vacuum comes greater repulsive pressure, forcing an endless and exponential acceleration of the cosmic expansion.
As a consequence, anything not gravitationally bound to the neighborhood of the Milky Way galaxy will recede at ever-increasing speed, as part of the accelerating expansion of the fabric of space-time. 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.
In a trillion or so years, anyone alive in our own galaxy may know nothing of other galaxies. Our observable universe will merely comprise a system of nearby, long-lived stars within the Milky Way. And beyond this starry night will lie an endless void—darkness in the face of the deep.
Behold my recurring nightmare: Are we, too, missing some basic pieces of the universe that once were? What part of the cosmic history book has been marked “access denied”? What remains absent from our theories and equations that ought to be there, leaving us groping for answers we may never find?
Every second of every day, 4.5 billion tons of fast-moving hydrogen nuclei are turned into energy as they slam together to make helium within the fifteen-million-degree core of the Sun.
There’s a variation of the ever-popular multiverse idea in which the multiple universes that comprise it are not separate universes entirely, but isolated, non-interacting pockets of space within one continuous fabric of space-time—like multiple ships at sea, far enough away from one another so that their circular horizons do not intersect. As far as any one ship is concerned (without further data), it’s the only ship on the ocean, yet they all share the same body of water.
Newton’s formula specifically prescribes that, while the gravity of a planet gets weaker and weaker the farther from it you travel, there is no distance where the force of gravity reaches zero. The planet Jupiter, with its mighty gravitational field, bats out of harm’s way many comets that would otherwise wreak havoc on the inner solar system. Jupiter acts as a gravitational shield for Earth, a burly big brother, allowing long (hundred-million-year) stretches of relative peace and quiet on 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. The more massive the planet, the larger the star’s response must be, and the more measurable the jiggle gets when you analyze the star’s light.
Our galaxy contains more than a hundred billion stars, and the known universe harbors some hundred billion galaxies.
Latest estimates, extrapolating from the current catalogs, suggests 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.
But who gets to think that way? Who gets to celebrate this cosmic view of life? Not the migrant farmworker. Not the sweatshop worker. Certainly not the homeless person rummaging through the trash for food. You need the luxury of time not spent on mere survival. You need to live in a nation whose government values the search to understand humanity’s place in the universe. You need a society in which intellectual pursuit can take you to the frontiers of discovery, and in which news of your discoveries can be routinely disseminated. By those measures, most citizens of industrialized nations do quite well.
When I track the orbits of asteroids, comets, and planets, each one a pirouetting dancer in a cosmic ballet, choreographed by the forces of gravity, sometimes I forget that too many people act in wanton disregard for the delicate interplay of Earth’s atmosphere, oceans, and land, with consequences that our children and our children’s children will witness and pay for with their health and well-being.
Passport to the Universe, he wrote, elicited the most dramatic feelings of smallness and insignificance he had ever experienced.
In all fairness to the fellow, powerful forces in society leave most of us susceptible. As was I, until the day I learned in biology class that more bacteria live and work in one centimeter of my colon than the number of people who have ever existed in the world. That kind of information makes you think twice about who—or what—is actually in charge.
From that day on, I began to think of people not as the masters of space and time but as participants in a great cosmic chain of being, with a direct genetic link across species both living and extinct, extending back nearly four billion years to the earliest single-celled organisms on Earth.
Need more ego softeners? Simple comparisons of quantity, size, and scale do the job well. Take water. It’s common, and vital. There are more molecules of water in a cup of the stuff than there are cups of water in all the world’s oceans. Every cup that passes through a single person and eventually rejoins the world’s water supply holds enough molecules to mix 1,500 of them into every other cup of water in the world. No way around it: some of the water you just drank passed through the kidneys of Socrates, Genghis Khan, and Joan of Arc. How about air? Also vital. A single breathful draws in more air molecules than there are breathfuls of air in Earth’s entire atmosphere. That means some of the air you just breathed passed through the lungs of Napoleon, Beethoven, Lincoln, and Billy the Kid. Time to get cosmic. There are more stars in the universe than grains of sand on any beach, more stars than seconds have passed since Earth formed, more stars than words and sounds ever uttered by all the humans who ever lived.
The cosmic perspective is spiritual—even redemptive—but not religious.
The cosmic perspective opens our minds to extraordinary ideas but does not leave them so open that our brains spill out, making us susceptible to believing anything we’re told.
The cosmic perspective opens our eyes to the universe, not as a benevolent cradle designed to nurture life but as a cold, lonely, hazardous place, forcing us to reassess the value of all humans to one another.
The cosmic perspective enables us to see beyond our circumstances, allowing us to transcend the primal search for food, shelter, and a mate.
The cosmic perspective not only embraces our genetic kinship with all life on Earth but also values our chemical kinship with any yet-to-be discovered life in the universe, as well as our atomic kinship with the universe itself.
At least once a week, if not once a day, we might each ponder what cosmic truths lie undiscovered before us, perhaps awaiting the arrival of a clever thinker, an ingenious experiment, or an innovative space mission to reveal them. We might further ponder how those discoveries may one day transform life on Earth.
Absent such curiosity, we are no different from the provincial farmer who expresses no need to venture beyond the county line, because his forty acres meet all his needs. Yet if all our predecessors had felt that way, the farmer would instead be a cave dweller, chasing down his dinner with a stick and a rock.
