New York Review of Books, June 14, 2021
All Things Great and Small
The origins and fates of atoms and galaxies are closely intertwined.
by Priyamvada Natarajan
Reviewed:
Neutron Stars: The Quest to Understand the Zombies of the Cosmos
by Katia Moskvitch
Harvard University Press, 296 pp., $29.95
The End of Everything (Astrophysically Speaking)
by Katie Mack
Scribner, 226 pp., $26.00; $17.00 (paper)
Fundamentals: Ten Keys to Reality
by Frank Wilczek
Penguin Press, 254 pp., $26.00
The physicist Richard Feynman, in a lecture to undergraduates at the
California Institute of Technology in 1961, posed a question and then
answered it:
If, in some cataclysm, all of scientific knowledge were to be destroyed,
and only one sentence passed on to the next generations of creatures,
what statement would contain the most information in the fewest words? I
believe it is the atomic hypothesis (or the atomic fact, or whatever you
wish to call it) that all things are made of atoms.
The profound insight that the entire material world can be described
succinctly as composed of fundamental building blocks is at the
foundation of all theories about the nature of matter, from ancient
inquiries into its properties, to medieval and early modern attempts to
transmute base metals into precious gold, to modern efforts to
understand atomic structure, harness the power of the atom with fission
and fusion, and create artificial materials in laboratories.
Three new books examine our current understanding of matter’s origin and
qualities, and chronicle our continuing quest to probe beyond atoms.
Neutron Stars: The Quest to Understand the Zombies of the Cosmos by
Katia Moskvitch, a science writer, explores recent research into the
super-dense remains of stars ten times more massive than our Sun, whose
precise material composition has eluded us. The astrophysicist Katie
Mack’s The End of Everything (Astrophysically Speaking) shows how the
contents of our universe—matter and energy—determine its destiny and,
ultimately, its demise. In Fundamentals: Ten Keys to Reality, the
physicist Frank Wilczek, who was awarded the Nobel Prize in Physics in
2004, addresses new discoveries that are leading to a reassessment of
the atomic hypothesis. He explains how notions of matter have changed
over the past decades from “all things are made of atoms” to “all things
are made of elementary particles”—the expanding list of which includes
quarks, gluons, muons, and the recently discovered Higgs boson.
Atomism in the West is first attributed to the fifth-century-BCE Greek
philosophers Leucippus and his pupil Democritus. (The word “atom”
derives from the Greek atomos, meaning “without parts.”) While none of
their original writings have survived in complete form, fragments and
quotations attributed to Democritus give us an idea of his atomic
theories. The most famous text influenced by Democritus is De rerum
natura (On the Nature of Things), the didactic poem in six books by
Titus Lucretius Carus (99 BCE–55 BCE), a poet of the late Roman Republic
and a follower of the Greek philosopher Epicurus, who had taken up
Democritus’s atomic theory. Lucretius—who did not use the term “atom,”
opting instead for “first things” and “the seeds of things”—declared
that the fundamental units of matter were infinite, immutable, and
invisible; constantly in motion; and subject to an occasional and
unpredictable small “swerve,” endlessly combining or splitting apart and
reconstituting themselves to take on new forms. According to Lucretius,
while objects in the universe, ranging from the distant stars to life
forms crawling on the Earth, are transient, their constituents—the
fundamental seeds that make them up—are eternal.
In the first two books of De rerum natura, which focus on the material
world, Lucretius compares these fundamental particles to letters in an
alphabet, a finite set that can form an infinite variety of sentences.
Just as there are letter combinations that are not permitted in a
language, not all seeds can combine with all others; moreover, Lucretius
asserted, there is a code that governs the permitted combinations. His
account of matter, which sounds strikingly like a description from a
modern-day physics or chemistry textbook, was utterly radical. Though
Lucretius didn’t claim that he knew the code dictating how these seeds
could arrange and rearrange themselves, he did suggest that it was
knowable through investigation. This is, of course, the goal of modern
science—to uncover, via observation and investigation, the laws of
nature that govern the regularities and patterns in phenomena.
The concept of atoms was not confined to esoteric discussions in natural
philosophy but garnered broad acceptance and percolated into the larger
culture, cropping up in unlikely places, for instance in Shakespeare’s
description of the fairy prankster Queen Mab in Romeo and Juliet:
She is the fairies’ midwife, and she comes
In shape no bigger than an agatestone
On the forefinger of an alderman,
Drawn with a team of little atomies
Athwart men’s noses as they lie asleep.
With his use of the phrase “little atomies,” Shakespeare reveals that by
the 1590s, his world was well acquainted with the atomistic view of matter.
Atomic theories appear in other philosophical traditions too. The notion
that all matter is composed of small, indivisible particles is found in
the teachings of the ancient Indian analytic Vaisesika philosophical
school, which dates back to the third century BCE. According to
Vaisesika atomism, the four elements (earth, water, air, and fire) each
come in two variations: atomic—that is, invisible, indivisible, and
indestructible; and composite—that is, visible and perceptible. A
Vaisesika text called The Manual of Reason argued that if there were no
fundamental unit of matter, a mountain and a mustard seed would be the
same size, since they would each contain an infinite number of parts.
With the development of quantum physics in the early twentieth century,
scientists established that the atoms that make up all visible
matter—which physicists call baryons—are composed of subatomic units:
protons and neutrons, which form the atom’s nucleus, and electrons. It
was soon discovered that the properties of atoms determined which
elements could bond together to make new molecules, and that in certain
conditions atoms could be transformed into others through fusion and
fission, nuclear processes that release enormous amounts of energy.
More recently, cosmology has provided us with an inventory of the
material content of the universe, and what a bizarre one it is. Every
one of the ninety-four elements found naturally on Earth was created
elsewhere in space, and all but three—hydrogen, helium, and lithium,
which were synthesized within the first three minutes of the birth of
the universe at the Big Bang—were formed in the cores of distant stars,
where extreme conditions cause nuclei to collide and fuse, creating
elements of greater atomic mass.
At the end of their life cycles, stars explode, dispersing carbon,
silicon, sulfur, magnesium, calcium, and iron into space, enriching the
hydrogen clouds from which the next generation of stars eventually
forms. These elements may have arrived on Earth via meteors, or possibly
were present in the matter that coagulated into our solar system 4.5
billion years ago. The calcium that our bones are made of and the iron
that permeates every red blood cell in our bodies come from stars.
Clichés aside, we are literally made of stardust.
In 1930 the Indian astrophysicist Subrahmanyan Chandrasekhar calculated
that the birth mass of a star determines its ultimate fate: depending on
its initial size, it will become either a white dwarf, a neutron star,
or a black hole. A star the size of our Sun has an interior with a
temperature of about 15 million degrees centigrade—so hot that atomic
nuclei are stripped of their encircling electrons. These subatomic
particles—electrons and nuclei—constantly collide with one another,
generating pressure inside the core of the star. This internal pressure
prevents gravity from causing the star’s collapse.
Pressure is also generated when hydrogen nuclei, which each have one
proton, fuse with other hydrogen nuclei to form helium, which has two
protons. Once all the available hydrogen in the core is exhausted,
gravity starts to prevail. This causes the core of the star to contract
and heat up, leading to the formation by fusion of heavier elements,
such as carbon, oxygen, and silicon. Our Sun will run out of hydrogen in
another five billion years or so. As its core contracts, its outer
layers will expand, passing into what is referred to as the red giant
phase. At this point, its radius will have grown so large that it
engulfs the orbit of Mercury. It will continue to collapse, ultimately
leading to the formation of a dim remnant, a white dwarf, with fusion no
longer supplying energy in the core.
In 1933 the Swiss astronomer Fritz Zwicky proposed that stars more
massive than our Sun would die by imploding—that is, by collapsing in on
themselves due to gravity—and that this process would cause protons,
which carry a positive electric charge, to capture negatively charged
electrons, leading to the production of neutrons. The energy released in
this process would power dramatic supernova explosions, leaving behind
the neutron-rich, super-dense core—a neutron star. Moskvitch dedicates
her book to Zwicky, does justice to his ideas, and gives him credit for
predicting and detecting supernovae—cosmic beacons that have been
important in shaping our view of the cosmos. Supernovae serve as
standard rulers for measuring distances and were instrumental in the
1998 discovery of dark energy, which is believed to power the
accelerating expansion of the universe.
Zwicky was also the first to propose the existence of dark matter, in
order to explain why some galaxies appear to move faster than expected.
Dark matter, believed to be crucial for the formation of galaxies, is
composed of an as yet undetected particle that likely formed in the
infant universe. Like every other kind of matter, it exerts and responds
to gravity, but it does not interact with light, rendering it invisible
and therefore extremely challenging to detect. Cosmologists estimate
that dark matter makes up about 24 percent of all the stuff in the
universe. By comparison, the ordinary atoms that we are made of account
for a mere 4 percent. To add to the mystery, the dominant constituent of
our universe is yet another invisible and immaterial entity, dark
energy, comprising about 70 percent of the overall cosmic inventory. We
know how both dark energy and dark matter manifest in our universe—but
not quite what they are.
Neutron stars are the densest form of matter currently known, with about
1.4 times the mass of the Sun packed into a radius of just six miles. A
teaspoon of neutron star material would weigh 10 million tons. Like
their more enigmatic cousins, black holes, neutron stars are stellar
corpses, but they come in many types: there are pulsars, which spin at
extremely rapid rates, close to a thousand times per second; and
magnetars, which are the strongest magnets known in nature. Unlike black
holes, neutron stars possess surfaces, suffer starquakes that we can
detect, and are also thought to be the source of gamma-ray bursts, the
most energetic explosions in the universe.
Moskvitch offers riveting explanations of what astronomers have learned
so far using radio telescopes, starting with Jocelyn Bell’s discovery in
1967 of the first pulsar, and what puzzles remain in the tantrums as
well as quiet murmur of neutron stars. She opens with a wonderful
account of the first-ever observation, in August 2017, of the collision
of two neutron stars, by researchers working with the gravitational wave
detectors LIGO in the US and Virgo in Italy. Unlike the dark collisions
of two black holes and the resulting tremors in space-time—gravitational
waves—that LIGO first recorded in 2016, the neutron-star collision was
accompanied by visible fireworks: a bright flash of gamma radiation
arrived seconds after the gravitational waves, reaching Earth after a
130-million-year journey. Researchers used this alert signal to observe
the crash in other ways, using radio, optical, near infrared, X-ray, and
gamma ray telescopes—opening up the new field of multi-messenger astronomy.
These multiple sets of eyes, spanning different wavelengths of light,
captured the collision’s debris cloud in vivid, unprecedented detail and
recorded the production of heavy elements—including an estimated 236
sextillion tons, or forty times the Earth’s mass, of pure gold. This was
the first time we witnessed this process unfold. The conditions inside a
neutron star are not powerful enough to create elements heavier than
iron; only the collision of two neutron stars can do so. All the gold we
know of, including the gold wedding ring on your finger or the chain
adorning your neck, was created by collisions of two neutron stars in
the distant universe.
Moskvitch closes with a description of the current frontier—recently
detected fast radio bursts (FRBs) that most believe to be emitted by
neutron stars, though we don’t yet have a conclusive theory to explain
them. The ultimate mystery, though, pertains to the equation that
describes the state of matter packed into neutron stars. As Moskvitch
observes, this fundamental question is one that brings together fields
in physics that developed largely in parallel—nuclear physics,
condensed-matter physics, and astrophysics. In this incredibly compact
state, matter and its behavior hold many more secrets. For example, the
density at the center of a neutron star is thought to be so high that
neutrons themselves are crushed out of existence, freeing the three
quarks inside each of them. The core would then consist of a liquid of
quarks, called quark matter. Quark matter might have even more peculiar
properties: it is expected to be similar to the state of electrons in a
metal, and perhaps even exhibit a type of superconductivity.
Contrary to Lucretius, our material world is not really indestructible
or eternal. So how will it all end? In The End of Everything
(Astrophysically Speaking), Katie Mack explains the possible fates, each
terrible in its own way, that await our universe. The equations derived
from Einstein’s theory of general relativity connect the contents,
shape, and destiny of the universe. The past, present, and future are
therefore determined by its evolving material and immaterial
constituents. What may seem surprising, she writes, is that “much as
modern cosmology informs our understanding of the very, very small,
particle theories and experiments can give us insight into the workings
of the universe on the largest scales.” The complex interplay of the
microscopic and macroscopic determines cosmic eschatology.
As Mack points out, only one thing is certain: the universe will end. It
simply cannot persist unchanged forever. The universe has been expanding
since its birth about 13.8 billion years ago. As its composition has
changed from being dominated by radiation for the first 30,000 years of
its existence to being dominated by matter and then by dark energy (for
the past 4 billion years), the expansion rate has also changed. Further
transitions will determine the universe’s ultimate fate. This is a
challenging question that several large teams of cosmologists are
probing with observational surveys and experiments.
The five possible cosmic catastrophes that Mack discusses are the Big
Crunch, in which our current cosmic expansion reverses and the universe
condenses into a black hole—a singularity; the Heat Death, in which the
universe expands forever, getting darker and more desolate; the Big Rip,
a dark-energy driven, violent fate in which gravity is overpowered and
eventually everything, including atoms, are ripped apart; Vacuum Decay,
the least likely scenario, in which a rogue bubble of “true vacuum”
would run amok and essentially cancel the universe; and the bounce—the
most speculative of these possibilities—a cyclic cosmology where birth
and death alternate repeatedly.
Though I am drawn by temperament to a cyclic universe that has no
beginning and no end, the possibility that fires my imagination is the
Big Crunch. The sequence would start with a slowdown of the current
accelerating rate of expansion before reversal. Having flipped course, a
contracting universe would become an extreme place—heating up to
incredibly high temperatures and densities, beyond anything we can
produce in the laboratory. None of our current theories, quantum
mechanics and general relativity included, offer any guidance to the
behavior of matter at such high densities. Mack writes that what “you’d
encounter when the entire observable universe is collapsing into a
subatomic dot are all kinds of incalculable.” Nothing material that we
know of would survive; eventually it all would hurtle rapidly into a
singularity. There is a strange symmetry to this fate, in which
everything may end up as it was before the Big Bang—in ashes, as it were.
A book that outlines the grim fates that await our universe might seem
pessimistic, but we humans are unlikely to bear witness to any of these
catastrophic outcomes, as they will not manifest for billions of years.
Even as Mack manages to simplify, with a disarmingly colloquial style,
many complex and abstract physical concepts while explicating cosmic
doom, she leads us to dream of the end without agonizing about it.
By classifying matter into “particles of construction, particles of
change, and bonus particles” in Fundamentals, Frank Wilczek offers an
authoritative update to Democritus’s atomic hypothesis. He shares ten
profound ideas that he believes describe all of physical reality and our
experience of it. As with his previous books, Wilczek deftly blends
contemplative elements with a clear exposition of basic physics, adding
cautious speculation about future experiments likely to reveal deeper
facets of reality. Fundamentals is divided into two main sections,
titled “What There Is” and “Beginnings and Ends,” with alluring chapter
titles in the former section that include “There’s Plenty of Space,”
“There’s Plenty of Time,” “There Are Very Few Ingredients,” “There Are
Very Few Laws,” and “There’s Plenty of Matter and Energy.”
Wilczek explains the three primary properties of elementary particles
from which all others can be derived—mass, charge, and spin—noting “that
they are things you can define and measure precisely.” Yet although they
can be measured, “the connection of the primary properties—the deep
structure of reality—to the everyday appearance of things is quite
remote.” While the mass and charge of the building blocks of matter are
easy to understand, spin is a challenging concept for the nonphysicist.
Wilczek elegantly explains how elementary particles are essentially like
tiny spinning tops or gyroscopes. He summarizes “four (deceptively) easy
principles” that govern how the world works, as far as we know—the basic
laws of physics describe change, are universal, local, and precise.
Wilczek then outlines three big questions pertinent to our understanding
of the physical world and beyond. What caused the Big Bang? Are there
even more meaningful patterns hidden in the sprawling landscape of
fundamental particles and forces that we have not uncovered so far? And
what is the nature of consciousness—did mind emerge from matter, and if
so, how? While his philosophical speculations on the nature of
consciousness and the emergence of complexity meander, he is especially
crisp about the mysteries that remain to be solved in physics.
In particular, he introduces axions—hypothetical subatomic particles
whose name he coined—as the link that may help unlock two mysteries that
appear unrelated: the unknown nature of dark matter and the near-exact
temporal symmetry of known physical laws. Physical laws appear to almost
retain their form independent of the direction of the flow of time—this
is a real puzzle as we live in a universe in which time moves in only
one direction. Physicists suspect that this signals the existence of a
new kind of particle—the axion—that formed in the early universe and has
the right properties to be dark matter. Wilczek is enthusiastic about
the many experimental efforts currently underway to detect the axion.
With so much known and understood about the nature of ordinary atoms, we
still eagerly await the discovery of new classes of subatomic particles
that might hold the key to many vexing theoretical problems.
I write this soon after the announcement from the Fermi National
Accelerator Laboratory in mid-April of a tantalizing development in the
subatomic realm: a mismatch between theoretical computations and
experimental measurement of the wobble of a subatomic particle—the muon,
a heavier cousin of the electron—in a magnetic field. If this holds up,
it portends the existence of a fifth fundamental force in nature—along
with gravity, electromagnetism, and the strong and weak forces—as well
as the existence of new subatomic particles. This would completely shake
up our understanding of matter. The remarkable thing about the era we
live in, which Wilczek aptly characterizes as a time when “technology
has already given us superpowers, and there is no end in sight,” is that
radical, transformative discoveries like this one, which could
dramatically alter our concept of the universe, might be just around the
corner.
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#9179): https://groups.io/g/marxmail/message/9179
Mute This Topic: https://groups.io/mt/83531387/21656
-=-=-
POSTING RULES & NOTES
#1 YOU MUST clip all extraneous text when replying to a message.
#2 This mail-list, like most, is publicly & permanently archived.
#3 Subscribe and post under an alias if #2 is a concern.
#4 Do not exceed five posts a day.
-=-=-
Group Owner: [email protected]
Unsubscribe: https://groups.io/g/marxmail/leave/8674936/21656/1316126222/xyzzy
[[email protected]]
-=-=-=-=-=-=-=-=-=-=-=-
