Origins: Fourteen Billion Years of Cosmic Evolution (27 page)

Thus we remain in a familiar human condition, poised at the edge of events that may not occur. The most important news in human history could arrive tomorrow, next year, or never. Let us go forth into a new dawn, ready to embrace the cosmos as it surrounds us, and as it reveals itself, shining with energy and replete with mystery.

CODA

The Search for
Ourselves in the Cosmos

Equipped with his five senses, man explores the universe around him and calls the adventure science.

—Edwin P. Hubble, 1948

H
uman senses display an astonishing acuity and range of sensitivity. Our ears can record the thunderous launch of the space shuttle, yet they can also hear a male mosquito buzzing in the corner of a room. Our sense of touch allows us to feel the crush of a bowling ball dropped on our big toe, or to tell when a one-milligram bug crawls along our arm. Some people enjoy munching on habanero peppers, while sensitive tongues can identify the presence of food flavors at a few parts per million. And our eyes can register the bright sandy terrain on a sunny beach, yet have no trouble spotting a lone match, freshly lit hundreds of feet away, across a darkened auditorium. Our eyes also allow us to see across the room and across the universe. Without our vision, the science of astronomy would never have been born and our capacity to measure our place in the universe would have remained hopelessly stunted.

In combination, these senses allow us to decode the basics of our immediate environment, such as whether it’s day or night, or when a creature is about to eat you. But little did anybody know, until the last few centuries, that our senses alone offer only a narrow window on the physical universe.

Some people boast of a sixth sense, professing to know or see things that others cannot. Fortunetellers, mind readers, and mystics top the list of those who claim mysterious powers. In doing so, they instill widespread fascination in others. The questionable field of parapsychology rests on the expectation that at least some people actually harbor this talent.

In contrast, modern science wields dozens of senses. But scientists do not claim that these are the expression of special powers, just special hardware that converts the information gleaned by these extra senses into simple tables, charts, diagrams, or images that our five inborn senses can interpret.

With apologies to Edwin P. Hubble, his remark quoted on page 291, while poignant and poetic, should instead have been

Equipped with our five senses, along with telescopes and microscopes and mass spectrometers and seismographs and magnetometers and particle detectors and accelerators and instruments that record radiation from the entire electromagnetic spectrum, we explore the universe around us and call the adventure science.

Think of how much richer the world would appear to us, and how much sooner we would have discovered the fundamental nature of the universe, if we were born with high-precision, tunable eyeballs. Dial up the radio-wave part of the spectrum and the daytime sky turns as dark as night, except for some choice directions. Our galaxy’s center appears as one of the brightest spots on the sky, shining brightly behind some of the principal stars of the constellation Sagittarius. Tune into microwaves and the entire universe glows with a remnant from the early universe, a wall of light that set forth on its journey to us 380,000 years after the big bang. Tune into X rays and you will immediately spot the locations of black holes with matter spiraling into them. Tune into gamma rays and see titanic explosions bursting forth from random directions about once a day throughout the universe. Watch the effect of these explosions on the surrounding material as it heats up to produce X rays, infrared, and visible light.

If we were born with magnetic detectors, the compass would never have been invented because no one would ever need one. Just tune into Earth’s magnetic field lines and the direction of magnetic North looms like Oz beyond the horizon. If we had spectrum analyzers within our retinas, we would not have to wonder what the atmosphere is made of. Simply by looking at it we would know whether or not it contains sufficient oxygen to sustain human life. And we would have learned thousands of years ago that the stars and nebulae in our galaxy contain the same chemical elements as those found here on Earth.

And if we were born with big, sensitive eyes and built-in Doppler motion detectors, we would have seen immediately, even as grunting troglodytes, that the entire universe is expanding—that all distant galaxies are receding from us.

If our eyes had the resolution of high-performance microscopes, nobody would have ever blamed the plague and other sicknesses on divine wrath. The bacteria and viruses that made you sick would have been in plain view as they crawled on your food or slid through open wounds in your skin. With simple experiments, you could easily tell which of these bugs were bad and which were good. And the carriers of postoperative infection problems would have been identified and solved hundreds of years earlier.

If we could detect high-energy particles, we would spot radioactive substances from great distances. No Geiger counters necessary. You could even watch radon gas seep through the basement floor of your home and not have to pay somebody to tell you about it.

The honing of our five senses from birth through childhood allows us as adults to pass judgment on events and phenomena in our lives, declaring whether or not they “make sense.” Problem is, hardly any scientific discoveries of the past century have flowed from the direct application of our senses. They came instead from the direct application of sense-transcendent mathematics and hardware. This simple fact explains why, to the average person, relativity, particle physics, and eleven-dimensional string theory make no sense. Add to this list black holes, wormholes, and the big bang. Actually, these concepts don’t make much sense to scientists either, until we have explored the universe for a long time with all senses that are technologically available. What eventually emerges is a newer and higher level of “uncommon sense” that enables scientists to think creatively and to pass judgment in the unfamiliar underworld of the atom or in the mind-bending domain of higher dimensional space. The twentieth-century German physicist Max Planck made a similar observation about discovery of quantum mechanics: “Modern physics impresses us particularly with the truth of the old doctrine which teaches that there are realities existing apart from our sense-perceptions, and that there are problems and conflicts where these realities are of greater value for us than the richest treasures of the world of experience.”

Each new way of knowing heralds a new window on the universe—a new detector to add to our growing list of nonbiological senses. Whenever this happens, we achieve a new level of cosmic enlightenment, as though we were evolving into supersentient beings. Who could have imagined that our quest to decode the mysteries of the universe, armed with a myriad of artificial senses, would grant us insight into ourselves? We embark on this quest not from a simple desire but from a mandate of our species to search for our place in the cosmos. The quest is old, not new, and has garnered the attention of thinkers great and small, across time and across culture. What we have discovered, the poets have known all along:

We shall not cease from exploration

And the end of all our exploring

Will be to arrive where we started

And know the place for the first time . . .

                              —T. S. Eliot, 1942

Glossary of Selected Terms

absolute (Kelvin) temperature scale
:
Temperature
measured on a scale (denoted by K) on which water freezes at 273.16 K and boils at 373.16 K, with 0 K denoting absolute zero, the coldest theoretically attainable temperature.

acceleration
: A change in an object’s speed or direction of motion (or both).

accretion
: An infall of matter that adds to the mass of an object.

accretion disk
: Material surrounding a massive object, typically a
black hole
, that moves in orbit around it and slowly spirals inward.

AGN:
Astronomical shorthand for a
galaxy
with an active
nucleus
, a modest way of describing galaxies whose central regions shine thousands, millions, or even billions of times more brightly than the central regions of a normal galaxy. AGNs have a generic similarity to
quasars
, but they are typically observed at distances less than that of quasars, hence later in their lives than quasars themselves.

amino acid
: One of a class of relatively small
molecules
, made of thirteen to twenty-seven
atoms
of
carbon
,
nitrogen
,
hydrogen
,
oxygen
, and
sulfur
, which can link together in long chains to form
protein molecules
.

Andromeda galaxy
: The closest large
spiral
galaxy
to the Milky Way, approximately 2.4 million
light-years
from our own galaxy.

antimatter
: The complementary form of matter, made of
antiparticles
that have the same mass but opposite sign of
electric charge
as the particles that they complement.

antiparticle
: The
antimatter
complement to a particle of ordinary matter.

apparent brightness
: The brightness that an object appears to have as an observer measures it, hence a brightness that depends on the object’s
luminosity
and its distance from the observer.

Archaea
: Representatives of one of the three domains of life, thought to be the oldest forms of life on Earth. All Archaea are single-celled and thermophilic (capable of thriving at temperatures above 50–70º Celsius).

asteroid
: One of the objects, made primarily of rock or of rock and metal, that orbit the Sun, mainly between the orbits of Mars and Jupiter, and range in size from 1,000 kilometers in diameter down to objects about 100 meters across. Objects similar to asteroids but smaller in size are called
meteoroids
.

astronomer:
One who studies the
universe
. Used more commonly in the past, at a time before spectra were obtained of cosmic objects.

astrophysicist:
One who studies the
universe
using the full toolkit enabled by the known laws of physics. The preferred term in modern times.

atom
: The smallest electrically neutral unit of an
element
, consisting of a
nucleus
made of one or more
protons
and zero or more
neutrons
, around which orbit a number of
electrons
equal to the number of protons in the nucleus. This number determines the chemical characteristics of the atom.

Bacteria
: One of the three domains of life on Earth (formerly known as prokaryotes), single
-
celled organisms with no well-defined
nucleus
that holds genetic material.

barred spiral
galaxy
: A
spiral galaxy
in which the distribution of stars and gas in the galaxy’s central regions has an elongated, barlike configuration.

big bang:
The scientific description of the origin of the
universe
, premised on the hypothesis that the universe began in an explosion that brought space and matter into existence approximately 14 billion years ago. Today the universe continues to expand in all directions, everywhere, as the result of this explosion.

black hole
: An object with such enormous
gravitational force
that nothing, not even light, can escape from within a specific distance from its center, called the object’s
black hole radius
.

black hole radius
: For any object with a mass M, measured in units of the Sun’s mass, a distance equal to 3M kilometers, also called the object’s
event horizon
.

blue shift:
A shift to higher
frequencies
and shorter
wavelengths
, typically caused by the
Doppler effect
.

brown dwarf:
An object with a composition similar to a star’s, but with too little mass to become a star by initiating
nuclear fusion
in its core.

carbohydrate
: A
molecule
made only of
carbon
,
hydrogen
, and
oxygen atoms
, typically with twice as many hydrogen as oxygen atoms.

carbon
: The element that consists of
atoms
whose
nuclei
each have six
protons
, and whose different
isotopes
each have six, seven, or eight
neutrons
.

carbon dioxide
: Molecules of CO
2
, which each have one
carbon atom
and two
oxygen
atoms.

Cassini-Huygens
spacecraft
: The spacecraft launched from Earth in 1997 that reached Saturn in July 2004, after which the
Cassini
orbiter surveyed Saturn and its moons and released the
Huygens
probe to descend to the surface of Titan, Saturn’s largest satellite.

Celsius
or
Centigrade temperature scale:
The
temperature
scale named for the Swedish astronomer Anders Celsius (1701–1744), who introduced it in 1742, according to which water freezes at zero degrees and boils at 100 degrees.

carbon dioxide
(CO
2
): A type of
molecule
containing one
carbon
and two
oxygen atoms
.

catalyst
: A substance that increases the rate at which specific reactions between
atoms
or
molecules
occur, without itself being consumed in these reactions.

CBR
: See
cosmic background radiation
.

cell
: A structural and functional unit found in all forms of life on Earth.

chromosome
: A single
DNA
molecule, together with the
proteins
associated with that molecule, which stores genetic information in subunits called
genes
and can transmit that information when cells
replicate
.

civilization
: For SETI activities, a group of beings with interstellar communications ability at least equal to our own on Earth.

COBE
(
COsmic Background Explorer
)
satellite
: The satellite launched in 1989 that observed the
cosmic background radiation
and made the first detection of small differences in the amount of this radiation arriving from different directions on the sky.

comet
: A fragment of primitive solar system material, typically a “dirty snowball” made of ice, rock, dust, and frozen
carbon dioxide
(dry ice).

compound
: A synonym for
molecule
.

constellation
: A localized group of stars, as seen from Earth, named after an animal, planet, scientific instrument, or mythological character, which in rare cases actually describes the star pattern; one of eighty-eight such groups in the sky.

cosmic background radiation (CBR)
: The sea of
photons
produced everywhere in the
universe
soon after the
big bang
, which still fills the universe and is now characterized by a
temperature
of 2.73 K.

cosmological constant
: The constant introduced by Albert Einstein into his equation describing the overall behavior of the
universe
, which describes the amount of energy, now called
dark energy
, in every cubic centimeter of seemingly empty space.

cosmologist:
An
astrophysicist
who specializes in the origin and large-scale structure of the
universe
.

cosmology
: The study of the
universe
as a whole, and of its structure and evolution.

cosmos
: Everything that exists; a synonym for
universe
.

dark energy
:
Energy
that is invisible and undetectable by any direct measurement, whose amount depends on the size of the
cosmological constant
, and which tends to make space expand.

dark matter
: Matter of unknown form that emits no
electromagnetic radiation
, that has been deduced, from the
gravitational forces
it exerts on visible matter, to comprise the bulk of all matter in the universe.

decoupling
: The era in the
universe
’s history when
photons
first had too little energy to interact with
atoms
, so that for the first time atoms could form and endure without being broken apart by photon impacts.

DNA (deoxyribonucleic acid)
molecule
: A long, complex
molecule
consisting of two interlinking spiral strands, bound together by thousands of cross links formed from small molecules. When DNA molecules divide and
replicate
, they split lengthwise, splitting each pair of small molecules that form their cross links. Each half of the molecule then forms a new replica of the original molecule from smaller molecules that exist in the nearby environment.

Doppler effect
: The change in
frequency, wavelength,
and
energy
observed for
photons
arriving from a source that has a relative velocity of approach or recession along an observer’s line of sight to the source. These changes in frequency and wavelength are a general phenomenon that occurs with any type of wave motion. They do not depend on whether the source is moving or the observer is moving; what counts is the relative motion of the source with respect to the observer along the observer’s line of sight.

Doppler shift
: The fractional change in the
frequency, wavelength,
and
energy
produced by the
Doppler effect
.

double helix
: The basic structural shape of
DNA molecules
.

Drake equation
: The equation, first derived by the American astronomer Frank Drake, that summarizes our estimate of the number of
civilizations
with interstellar communications capability that exist now or at any representative time.

dry ice
: Frozen
carbon dioxide
(CO
2
).

dust cloud:
Gas clouds in interstellar space that are cool enough for
atoms
to combine to form
molecules
, many of which themselves combine to form dust particles made of millions of atoms each.

dynamics
: The study of the motion and the effect of
forces
on the interaction of objects. When applied to the motion of objects in the solar system and the universe, this is often called celestial mechanics.

eavesdropping
: The technique of attempting to detect an extraterrestrial
civilization
by capturing some of the
radio
signals used for the civilization’s internal communications.

eccentricity
: A measure of the flatness of an
ellipse
, equal to the ratio of the distance between the two “foci” of the ellipse to its long axis.

eclipse
: The partial or total obscuration of one celestial object by another, as seen by an observer when the objects appear almost or exactly behind each other.

electric charge
: An intrinsic property of
elementary particles
, which may be positive, zero, or negative; unlike signs of
electric charge
attract one another and like signs of electric charge repel one another through
electromagnetic forces
.

electromagnetic force
: One of the four basic types of
forces
, acting between particles with
electric charge
, and diminishing in proportion to the square of the distance between the particles. Recent investigations have shown that these forces and
weak forces
are different aspects of a single
electro-weak force
.

electromagnetic radiation
: Streams of
photons
that carry energy away from a source of photons.

electron
: An
elementary particle
with one unit of negative
electric charge
, which in an
atom
orbits the atomic
nucleus
.

electro-weak forces
: The unified aspect of
electromagnetic forces
and
weak forces
, whose aspects appear quite different at relatively low energies but become unified when acting at enormous energies such as those typical of the earliest moments of the
universe
.