Category Dreams of Other Worlds

On Planets and Dwarfs

Somewhere in the twilight between stars and planets lie objects called brown dwarfs. Below about 8 percent of the Sun’s mass, physical conditions will never allow the fusion of hydrogen into helium, as happens in the Sun. There may be a flickering of en­ergy from the fusion of hydrogen into deuterium, but lower mass objects don’t have a sustainable source of energy. When they’re young, brown dwarfs are easy to observe in the infrared because they generate a lot of heat during their gravitational collapse. As they age, they get cooler and fainter. For example, a puny star 10 percent of the mass of the Sun would have a temperature of 3000 K and a luminosity 1/10,000 that of the Sun. By contrast, a brown dwarf 5 percent of the mass of the Sun would be three times cooler and a further 100 times dimmer. It would take a million of these feeble objects to equal the light of the Sun. Some astronomers con­sider Jupiter a failed star or a brown dwarf. Models indicate that brown dwarfs likely host moons like those of Jupiter and Saturn, worlds replete with weather systems, geysers, volcanoes, moun­tain ranges, and oceans—even if, as on Europa, the oceans are frozen over.

Set on a moon orbiting a gas giant planet in the nearby Alpha Centauri star system, James Cameron’s film Avatar (2009) mes­merized audiences with its rendering of Pandora orbiting a Jupiter- like world whose swirled and rippled clouds resemble those of Ju­piter and its Great Red Spot. Cameron’s Pandora (one of Saturn’s moons also happens to be named Pandora) abounds in colorful flora and fauna evocative of Earth’s ocean environments, like the giant Christmas Tree Worms that suddenly retract when touched, the seeds of the sacred tree that float with the pulses of a jelly­fish, and the photophores that dot the plants, animals, insects, and human-like inhabitants of Cameron’s adventure tale.58 That the Na’vi have blue skin seems no accident or random artistic choice. In ocean waters, blue light is least absorbed and can penetrate into the depths so that most deep-sea animals see solely in blue light. With the announcement in October 2012 of an exoplanet with a similar mass to Earth detected in the Alpha Centauri triple star system, Cameron’s fictional depiction seems even more plausible.59

In part, what captivated film audiences was the bioluminescence with which Cameron painted his Pandoran forests. Having ex­plored and documented deep ocean fauna in the film Aliens of the Deep (2005), Cameron is familiar with myriad bioluminescent sea life and readily projects similar plants and animals onto his imagi­nary world. Draped with waterfalls alight with bioluminescence, Pandora’s forests teem with glowing fireflies and whirling fan liz­ards. The forest floor is carpeted with illuminating moss, while its streambeds are lit with the equivalent of sea anemones. In effect,

Cameron anticipates how life might be adapted on an exomoon of a gas giant planet or a brown dwarf star. On such worlds, we might expect to find luminous biota highlighted with photophores as Cameron predicts or species with eyes better adapted to night or low-light conditions. Even as felines have dark-adapted vision superior to humans, the Na’vi have feline features and navigate the night-t ime forest with far better facility than the character Jake. Cameron’s bioluminescent world may have been inspired by Jules Verne’s 20,000 Leagues Under the Sea, in which the char­acters, strolling on the ocean floor, encounter bioluminescent jel­lyfish and note their “phosphorescent glimmers.” Actually, nearly all jellies in the deep sea are luminescent. Verne’s voyagers likewise chance upon corals, the tips of which glow. In stark contrast to the nineteenth-century perception that the ocean floor was devoid of life, Verne imagined the seafloor abounding in bioluminescence. An engraved illustration for 20,000 Leagues titled “On the ocean floor” depicts a kelp forest with large corals, crustaceans, and a flotilla of giant jellyfish whose bodies and tentacles radiate light (figure 9.6). Cameron’s vision of bioluminescent organisms flour­ishing on a nearby exomoon is similarly prescient.

Back on Earth, the first brown dwarf was discovered in 1995. Spitzer has contributed to this research by detecting some of the coolest and faintest examples known, including eighteen in one small region of sky sifted from among a million sources detected.60 Despite their extreme faintness, Spitzer can detect the coolest brown dwarfs out to a distance of one hundred light-years. The outer layers of these substellar objects are cool enough that they’re rich in molecules. The composition of the gas, and so the appear­ance of narrow lines that act as chemical “fingerprints” in the spec­trum, changes as the brown dwarf evolves. Most of the eight hun­dred cataloged brown dwarfs have atmospheres with temperatures in the range 1200°C to 2000°C. The next category, with tempera­tures from 1200°C down to 250°C, has strong methane absorp­tion in their atmospheres. There’s overlap (and often confusion) between planets and brown dwarfs because some giant exoplanets are larger and hotter than some brown dwarfs. The very coolest category of the brown dwarf, and the end point of their evolution, has recently been discovered. NASA’s Wide Field Infrared Survey

On Planets and Dwarfs

Figure 9.6. An original illustration from Jules Verne’s 20,000 Leagues Under the Sea depicting bioluminescence. A more modern media representation is in James Cameron’s 2009 motion picture Avatar, where bioluminescent creatures inhabit the exomoon Pandora, where the action takes place. On Earth, thousands of species of sea creatures of all sizes employ bioluminescence (Jules Verne’s 20,000 Leagues Under the Sea).

Explorer (WISE), which was launched in 2009, has finished a scan of the entire sky at infrared wavelengths. In 2011, astronomers reported six of the coolest stars ever found, one of which has a sur­face at no more than room temperature.61 The WISE data have the potential to reveal brown dwarfs closer than Proxima Centauri, the nearest star to our Sun.

Another promising mission in the search for dwarf stars and transiting exoplanets is headed by Harvard astronomer David Charbonneau and was designed largely by Philip Nutzman, an as­tronomer at the University of California, Santa Cruz. The MEarth Project is focusing eight small robotic telescopes on 2,000 M dwarf stars.62 The project targets particularly M dwarfs as they are smaller than the Sun and transiting planets would block out a greater portion of the star’s light, making them easier to detect. Studying nearby transiting exoplanets could afford astronomers a better sense of whether Earth-like planets are common and ad­ditionally allow astronomers to discriminate the chemistry of their atmospheres. Within six months of launching their project, the team detected their first transiting planet, a super-Earth named GJ 1214b in orbit around a star 13 parsecs from Earth.63 In 2010, the journal Nature reported that the atmosphere of GJ 1214b was found to be comprised either of water vapor, or of thick clouds or haze as on Saturn’s moon Titan.64 Infrared investigations are planned to determine which of these options exist on the planet. With resources like Zooniverse. org, in the coming decade the pub­lic will likely contribute to the search for biomarkers such as ozone or water vapor in the atmospheres of these other worlds.

Awash as it is in newborn stars and exoplanets, the universe may be teaming with life. Perhaps in some far future humans will have physical, robotic, or other means of virtual presence on a nearby exoplanet or one of its moons that, similar to Cameron’s Pandora, teems with bioluminescent life. Astronomer Carole Haswell cau­tions, “If any of this is to happen, however, we need to use our collective ingenuity to understand and repair the effects that our industrial activity and our burgeoning population are having on our own planet.”65 What we learn from exoplanets, Haswell sug­gests, might be invaluable in understanding Earth’s climate evolu­tion and in ensuring our own survival and that of our companion species. In the meantime, NASA and the astronomical community welcome the public’s contribution to one of humankind’s greatest adventures—locating possible habitable planets and, in time, the signatures of life in some dark and overlooked corner of the vast and silent wastes of interstellar space.

On Planets and Dwarfs

Celestial Harmonies

The correlation between music and exploration of outer space is deeply rooted in the human psyche. The Greek mathematician Pythagoras was purportedly the first to show that musical notes, octaves, chords, and their harmonics were the product of simple mathematical ratios and whole numbers. The Pythagoreans real­ized that a string attached to an instrument produces a fundamen­tal tone when plucked. Halve the string and the tone will be an octave higher. Other harmonics, or overtones, occur at the third, fourth, fifth, seventh, and ninth divisions or intervals of the string. The Pythagoreans further posited that the universe itself could be understood in terms of this basic mathematics of music, and that the planets, for instance, would be distanced from the Sun in inter­vals similar to the intervals along a string that produce harmon – ics.43 By the early 1600s, German astronomer Johannes Kepler was also captivated by Pythagoras’s notion of a “music of the spheres.” He theorized in Harmonices Munde (The Harmony of the World) that musical harmonies could be seen in the motion of planetary bodies. As physicist Amedeo Balbi explains, “Building on ideas by Pythagoras and Plato. . . Kepler was trying to give a scientific foundation to the concept of the ‘music of the spheres’, the idea according to which each planet moving around the Sun produces a definite sound.”44 Kepler suggested their orbits would be deter­mined by the mathematics of musical harmonics.

Stars, galaxies, even planets naturally produce electromagnetic energy, or low-energy radio emission, as they rotate and move through space. Several planets in our Solar System generate strong electromagnetic emissions from their powerful magnetospheres. In the 1970s, the Voyager spacecraft recorded Jupiter’s radio emis­sions. Of course, the human ear cannot detect sound in the empty vacuum of space. However, we can “hear” the whine of Earth and the eerie sounds of Saturn’s radio emissions via satellite recordings translated by computer programs that render measured frequen­cies as audible sound.45

Far more impressive are the acoustic tones of the Sun, as we learned in the chapter on SOHO. Astrophysicists are learning a great deal about the interior composition and physics of the Sun via helioseismology, by which astronomers track acoustic sound waves that travel through the entire body of the Sun. Amazingly, the Sun resonates with myriad sound waves that can be measured like musical notes that are directly analogous to fundamental tones and complex harmonic overtones. Turbulence at the top of the Sun’s convective zone segments the photosphere into granules, thousands of kilometers across, that pulse up and down. These pulses send sound waves careening through the body of the Sun and reveal a characteristic acoustic imprint at various internal boundaries like that between the convective and radiative zones.46 By recording the acoustic waves traveling through our Sun, astro­physicists have a far better understanding of the internal struc­ture of stars, the abundance of helium in our Sun revealing its age, the Sun’s rate of rotation, and how temperatures at the core compare to its million-degree corona. These internal acoustic waves also are associated with storms on the solar surface and are being used to predict future sunspots by detecting disturbances inside the Sun.47

Synesthesia is the experience of one sense being rendered as an­other so that you can taste a color or hear visual phenomena. Just as musicians were experimenting with electronic and psychedelic explorations of outer space, astronomers were documenting the Sun’s acoustic waves and experiencing their own synesthesia. In the case of the tonal resonances generated by the Sun’s pulsing surface, scientists can hear what they visually detect of this reso­nance. The first phase of helioseismology, launched from 1960 to 1979, interestingly emerged during the same period as the rise of electronic space music.

Hunting Dark Matter and Dark Energy

Chandra has also weighed in on two of the profound mysteries of cosmology: the nature of dark matter and dark energy. These two components of the universe account for 95 percent of its be­havior, yet the physical basis for them is not known and is not part of standard physics. Dark matter outweighs normal matter by a factor of six and binds galaxies and clusters and stops them from flying apart, as well as causing the expanding universe to decelerate for most of the first two thirds of its existence. Dark energy dominates dark matter by a factor of three and has caused the cosmic expansion to accelerate in the most recent third of the universe’s existence.67

Dark matter and dark energy don’t interact strongly with nor­mal matter like the atoms in our bodies, so stealth and cunning must be used to ensnare them and measure them. In both cases the laboratories used are rich clusters of galaxies, consisting of thousands of galaxies moving swiftly under the action of gravity and a huge cloud of superhot gas, so energetic that it emits X – rays. In 2006, an object called the Bullet Cluster was used for a convincing demonstration that dark matter actually exists. In the Bullet Cluster, a bullet-shaped cloud of hundred-million-degree gas is produced by a high-speed collision between a large cluster and a smaller one. The hot gas was slowed by the collision, due to a drag force analogous to air resistance. By contrast, the dark mat­ter hardly interacted at all and sailed through during the collision, ending up on either side of the hot gas.68 This result would not have occurred unless weakly interacting dark matter dominated the mass of both clusters. In particular, alternate theories of grav­ity, conjured up to avoid needing dark matter, fail to explain the observations. It seems we have to live with dark matter.

Dark energy is even more ephemeral, announcing its presence (and ubiquity) only by the effect it has on the cosmic expansion. The long and hard search for independent evidence of its existence settled on clusters of galaxies. In a study that took nearly a de­cade to complete, researchers showed that rich clusters suffer from “arrested development.”69 It’s more difficult for clusters to grow when space is being stretched. By comparing the size and age of clusters with simulations of how they should grow under differ­ent conditions of cosmology, the results cement the interpretation of dark energy as a universal repulsive agent. They also rule out alterations to gravity theory and confirm that general relativity is a good description of the behavior of matter and radiation on large scales. The enigma of dark energy has not been solved, but its status as the biggest challenge in both physics and cosmology has been enhanced. Whether it is a black hole devouring a companion, massive black holes causing mayhem in the centers of galaxies, or clusters being pulled apart by the accelerating expansion of space, Chandra has provided data to illustrate the violence of the uni­verse we inhabit.

A result of these insights is a new sense of the power of gravity. Stars are powered by gravity, and gravity also governs the nature of the most compact and energetic objects we’ve ever discovered. Dark forces even govern the expansion of the universe. When we think of other worlds, we think of planets illuminated by stars, where any life that exists is beholden to the energy from the star. But in a fundamental sense, starlight is just the inefficient leakage of radiation from mass-energy conversion by fusion. The true source of the starlight is gravity—a star is a gravitational engine. Black holes and neutron stars have no light but they have intense gravity. While they seem alien and utterly different from our world, given suitable protection or adaptation living creatures might be able to live near these compact stellar husks, using gravity to power their dreams.

Completing Hubbles Work

The Hubble Deep Field and the Ultra Deep Field images would have fascinated Edwin Hubble perhaps most of all, since they plumb the depths of space near the edge of the observable universe and reveal our universe as it was 400 million years after the big bang. In current cosmological models based on the big bang, the universe has an edge in time rather than space. Looking out, we look back in time due to the finite speed of light. At the limits of Hubble’s vision, no edge in space has been detected. Rather, we’ve looked so far back in cosmic time that we’re seeing the epoch where the first small galaxies were created and began merging into the larger and mature galaxies we see around us now. The edge in time corresponds to “first light,” but beyond that was an early period called the “dark ages” when there were no stars and galax­ies. Hubble has been so successful that it has almost completed the fundamental task of seeing the entire population of galaxies in the visible universe over all cosmic time. The Ultra Deep Field images provide new information regarding how highly structured spi­ral galaxies are formed. Astronomers now understand that large spiral galaxies represent mergers, over eons, of fragments of the young, chaotic galaxies seen at the faintest levels of brightness.52 “To some degree, we can follow the stages of galaxy formation right into the fog bank of the Dark Ages and beyond, even toward the big bang itself,” writes Jeff Kanipe, who describes the Hubble Space Telescope “as both a pathfinder and a plumb line into the vast depths of our cosmic origins.”53 The Deep Field images repre­sent humankind’s first glimpse of those origins.

The Hubble Space Telescope is named in recognition of Edwin Hubble, an observational astronomer who in the 1920s and 1930s worked at Mount Wilson Observatory with the Hooker 100-inch telescope, then the largest reflecting telescope in the world. Dur­ing his lifetime Hubble was accepted as “the world’s preeminent observational astronomer,”54 in part because the 100-inch reflector allowed Hubble to seek answers to some of the then fundamen­tal questions of astronomy—whether there were galaxies beyond the Milky Way, how to create an accurate distance ladder to such galaxies, and what could be known at the limits of the observ­able universe. In 1923, Hubble determined a distance to the An­dromeda galaxy of roughly 800,000 light-years. Though today we know it lies about 2.2-2.3 million light-years from our gal­axy, Hubble’s calculation settled once and for all the debate over whether anything existed beyond the Milky Way galaxy. It was a monumental find. Hubble accomplished this through Henrietta Leavitt’s research into the regular periodicities of Cepheid variable stars. Upon discovering and charting a Cepheid variable in An­dromeda, Edwin Hubble could determine its intrinsic brightness to calculate a distance to the galaxy.55 Later, in 1929, he used the 100-inch reflector, and the inestimable skills of Milton Humason as an observer and photographer, to determine that galaxies are racing away from each other at remarkable speeds. Hubble didn’t use the phrase when he published his result, but this marked the discovery of the expanding universe.56

Perhaps it was Grace, Edwin Hubble’s wife, who dubbed him “the mariner of the nebulae.” She was an eloquent writer whose memoirs of Hubble are archived at the Huntington Library in San Marino, California. Gale Christianson’s biography, which draws upon Grace’s unpublished memoirs of Hubble, vividly recreates the scene of the astronomer at work at his telescope: “Like a captain on the bridge of a great ship, the master mariner barked out his or­ders—so many hours and so many degrees. Then came the metallic whining of the traverse, a series of loud clicks, a final heavy clang of the Victorian machinery as the 100-inch was clamped” into place for viewing far-flung galaxies, or nebulae as Hubble referred to them. Christianson extends the metaphor, characterizing Hubble as a sentinel mariner “[s]lipping, night after night, silent and alone, past the distant shoals, of the nebulae.”57 Hubble himself wrote of astronomical exploration in the terms of oceanic exploration. He spoke of the 100-inch reflecting telescope as performing reconnais­sance at the “dim boundary—the utmost limits of our telescopes,” as Hubble in the cold early morning hours would “search among ghostly errors of measurement for landmarks that are scarcely more substantial.”58


When we dream of other worlds, our dreams may be vivid and real and colorful, but they’re subject to the limitations of our senses. To visualize something, even if in our mind’s eye, we use the visual sense. For most of the history of astronomy we learned about the universe exclusively through visible light. Tens of thousands of years of naked-eye observations were followed by the first night time use of the telescope by Galileo in 1610, followed by a steady march of successively larger telescopes, culminating with the 8-11 meter behemoths of the present day, with dreams of even larger ones to come.1

The historical focus on visible light was natural, since the most powerful human sense evolved to match the peak energy output of our life-giving star. The cool outer envelopes of stars emit most of their radiation in the visible range, and galaxies are just assem­blages of stars. The night sky is visually rich. About 6,000 stars are visible to the naked eye at a dark site, but they are just an infini­tesimal sliver of the stellar plentitude of the universe. We live in a system of 400 billion stars, and the observable universe contains roughly 100 billion stellar systems, for a staggering total of 1023 stars.2 Also, the spectral transitions that are the fingerprints of dif­ferent types of atoms fall mostly in the visible wavelength range. Cosmic chemistry is practiced with telescopes that gather light and disperse it into its constituent wavelengths.

Nevertheless, just over two hundred years ago experiments showed there are wavelengths longer than the reddest waves of light and bluer than the bluest waves of light. A hundred years later, Wilhelm Rontgen performed the first systematic experiments to understand the nature of mysterious radiation that was gener­ated by high-energy particles moving in the vacuum of a sealed glass tube. In 1895, he announced the discovery of “X rays.” The details of the discovery are poorly documented because Rontgen had his lab notebooks burned when he died. X-rays electrified the scientific community and within a year their potential for medical imaging was realized. It was a lot longer before anyone discovered that they could be used for astronomy. Rontgen received the first Nobel Prize ever awarded for Physics in 1901.3

Just as X-rays provided a window into the human body, they now provide a window in space onto worlds barely imagined. X – ray telescopes have revealed the nature of black holes and neutron stars for the first time, they’ve discovered sizzling hot plasma in the centers of galaxy clusters and in the diffuse space between galax­ies, and they’ve let us make great strides in probing extraordinary black holes that lurk in the centers of all galaxies, ranging from a few million up to a few billion times the mass of the Sun. Their high energy relative to visible light means they’re often created by events of unimaginable violence, phenomena unknown to us fifty years ago (figure 10.1).

Grooves in the Cosmic Pond

As early as 1937, James Jeans observed that “the tendency of mod­ern physics is to resolve the whole material universe into waves, and nothing but waves. These waves are of two kinds: bottled-up waves, which we call matter, and unbottled waves, which we call radiation or light.”48 WMAP’s image of the early universe would seem to confirm Jeans’s observation that the universe might be un­derstood in terms of waves. Even as sound waves traveling through the Sun’s plasma reveal information about its structural composi­tion, fluctuations in the plasma that comprised the very early uni­verse reveal critical data about its matter density and structure. Amedeo Balbi, a member of ESA’s Planck mission, the successor to WMAP, writes, “The primordial plasma resonated like an enor­mous bell, and the mechanism which started the vibrations could plausibly only be one: a period of inflation that occurred a tiny fraction of second after the big bang.”49

Balbi points out that galaxies are clustered throughout space and they have a very slight preference for spacings that can be thought of as corresponding to sound waves. These galaxy sepa­rations designate grooves or “acoustic peaks,” as in a wave, and represent gravity and temperature variations on the cosmic micro­wave background, which evolved into a subtle imprint on the dis­tribution of galaxies. One wave that’s clearly detected in the galaxy distribution has a scale of 300 million light-years.50 Astrophysicist Jean-Pierre Luminet likewise claims that the early universe “‘rang’ like a musical instrument.” He explains that the variations or peaks and troughs we see in the cosmic microwave background reveal details of the universe’s mass and density in much the same way acoustic waves reverberating through a drum reveal its struc­tural properties. “If you sprinkle sand on the surface of a drum,” writes Luminet, “and then gently vibrate the drum skin, the grains of sand will assemble into characteristic patterns” that reveal data regarding “the size and shape of the drum” or “the physical nature of the drum skin.”51 Similarly, in analyzing the variation in clusters and superclusters of galaxies, we are gathering details about the matter density of the primeval universe.

University of Virginia astronomer Mark Whittle likewise char­acterizes the variations in the microwave background as similar to the crest and trough of sound waves: “The waves are actually very long; they’re many thousands of light years, and so they cor­respond to frequencies, pitch which is very, very low by human standards, roughly 50 octaves below human ears.”52 Whittle has produced a sound file simulating what the big bang would sound like if modulated for the human ear. Describing his recreation of the acoustic peaks in the cosmic microwave background as a “sort of a raw, deep roaring sound,” Whittle is quick to note that there’s “actually musicality present.”53 He describes WMAP’s image of the microwave background as “a microscope. . . a telescope. . . a time machine, all rolled into one, and stored in it is enough infor­mation to kind of diagnose what the character of the universe is today, what its future will be and what its birth was.” Of this “ex­traordinary document,” Whittle reminds us that embedded in the image is the primeval narrative of the universe “written by nature in nature’s own language.”54 COBE and WMAP (and now Planck) have given nature a voice.

Amedeo Balbi observes in The Music of the Big Bang, “Ripples in the matter density of the early Universe had to leave a perma­nent imprint in the ancient cosmic light—as a seal impressed into wax.”55 Cosmologists theorize that etched into the primordial plasma at the beginning of time were density and heat variations that became the galaxy clusters we observe today. Balbi’s meta­phor of matter density fluctuations imprinted on the cosmic mi­crowave background as indentations in wax brings to mind an early method of creating phonograph records by etching grooves in wax. Early sound recordings involved “engraving” data into a wax overlay of a zinc record. Music or voice data were recorded by tracing with a sharp stylus a spiral onto beeswax coating the zinc record. The disc was then treated with chemicals that pre­served the grooves where the stylus had removed the wax, after which the phonograph record could be played.

As early as 1931, Georges Lemaitre apparently wondered whether information about the universe had been recorded in the primordial quantum, even as information is preserved in the grooves of a phonograph record. Lemaitre observed that “the whole story of the [universe] need not have been written down in the first quantum like the song on the disc of a phonograph.”56 However, the WMAP results suggest that, in fact, it was. From Lemaitre to Balbi, the technology of the grooved record and the shape of an acoustic wave served as apt metaphors for peaks in the cosmic microwave background.57 Had we some other technology for recording sound in the time of Lemaitre, perhaps astronomers would have characterized these acoustic peaks in other terms. On the other hand, scientists find that acoustic and electromagnetic waves are means by which the universe, the stars, and planets tell their story. Astronomers and cosmologists, since Pythagoras, have never given up on finding music in the cosmos. And now they have.


Above all scientific projects, the Hubble Space Telescope encapsulates and recapitulates the human yearning to explore distant worlds, and understand our origins and place in the universe. Its light grasp is 10 billion times better than Galileo’s best spyglass, and many innovations were needed for it to be realized: complex yet reliable instruments, the ability for astronauts to service the tele­scope,1 and the infrastructure to support the projects of thousands of scientists from around the world. The facility and its supporters experienced failure and heartache as well as eventual success and vindication.

Hubble’s legacy has touched every area of astronomy, from the Solar System to the most distant galaxies. In the public eye, it’s so well known that many people think it’s the only world-class astronomy facility. In fact, it operates in a highly competitive land­scape with other space facilities and much larger telescopes on the ground. Although it doesn’t own any field of astronomy, it has made major contributions to all of them. It has contributed to Solar System astronomy and the characterization of exoplanets, it has viewed star birth and death in unprecedented detail, it has paid homage to its namesake with spectacular images of galaxies near and far, and it has cemented important quantities in cosmology, including the size, age, and expansion rate of the universe.2

Ranked by size of the mirror, Hubble wouldn’t make it into the top fifty largest optical telescopes.3 Its preeminence is based on three factors associated with its location in Earth orbit. The first

is liberation from the blurring and obscuring effects of the Earth’s atmosphere. Ground-based telescopes typically make images far larger than their optics would allow because turbulent motion in the upper atmosphere jumbles the light and smears out the im­ages. Hubble gains in the sharpness of its vision by a factor of ten relative to a similar-sized telescope on the ground. Earth orbit also provides a much darker sky, which affects the contrast and depth of an image. The difference you might see in going from a city cen­ter to a rural or mountain setting is only part of the story; natural airglow and light pollution affect even the darkest terrestrial skies. A vacuum can’t obfuscate. The last feature of a telescope in Earth orbit is its ability to gather wavelengths of radiation that would be partially absorbed or even quenched by the Earth’s atmosphere. Hubble has taken advantage of this by working at infrared and ultraviolet wavelengths.

The Hubble Space Telescope (HST) is well into its third decade of operations, and it’s easy to take for granted the beautiful images that are released almost weekly. But it was not an effortless jour­ney for NASA’s flagship mission.

Cosmic Voyages

The characterization of Edwin Hubble maneuvering the 100-inch reflector like a mariner upon a vast sea evokes another celebrated captain who navigated the depths of space in the science fiction television series Star Trek launched in September 1966. As noted in the chapter on the Voyager mission, Captain James T. Kirk of the starship Enterprise, portrayed by William Shatner, commanded a fictional five-year mission to explore the far reaches of our galaxy.

When Gene Roddenberry began producing Star Trek, the world’s attention was turned toward space as the final frontier and the dream of traveling vast distances across our galaxy was at a fever pitch. The Apollo missions of the late 1960s and early 1970s cap­tivated audiences around the world, who watched with trepidation as Neil Armstrong, and through him humankind, stepped onto the surface of another world for the first time. We delighted in watch­ing the astronauts skipping and hopping across the lunar surface, and bounding lazily over cratered terrain in the lunar rover. The final episode of the original Star Trek series was broadcast in June 1969, just a month before Neil Armstrong and Buzz Aldrin stood on the lunar surface. Many in that generation came away from the truncated Apollo program wistful that the limits of money and politics prevented NASA from further manned lunar exploration.

One effect of Star Trek first airing in the runup to the moon landing was that the series inspired the first space-faring genera­tion, including many at NASA. William Shatner writes of the origi­nal series that “every time [NASA] launched a manned rocket our ratings went up, meaning people were very interested in space: and when our ratings went up Congress voted more money for the space program.” Even if we don’t assign causation, this is interest­ing. The perceived interconnection between Star Trek and NASA extended to NASA itself. Shatner recalls:

NASA officials often invited us to launches, and finally I decided to go to one of them. They treated me as space royalty, eventually allowing me to sit in the LEM, the moon landing module, with an astronaut. I was lying in the hammock like seats. . . looking out of the small win­dows at the universe displayed as the astronauts would see it. The astronaut, who was teaching me how to fly this craft, told me to look at a certain section of the star system—and as I did, flying beautifully across the entire horizon came the Starship Enterprise.59

That model of the Enterprise was assembled, Shatner points out, by some of the same engineers who built the Apollo spacecraft that landed on the Moon.

So compelling was Roddenberry’s vision that in the late 1970s, the space agency recruited Nichelle Nichols, who played commu­nications officer Lieutenant Uhura in the original series, to help in attracting young people to NASA’s program. In 1977, NASA had received roughly 1,600 applications for new hires, but fewer than one hundred from women, and far fewer from minorities. Within four months of Nichols’s recruiting, applications rocketed up to 8,400, with approximately 1,650 from women and 1,000 from minority candidates.60 Years later, in 1992, during the STS 47 mission, Space Shuttle astronaut Mae Jemison, the first Afri­can American woman in space, made it her practice, in honor of Nichelle Nichols, to begin each of her shifts with “Hailing frequen­cies open,” an often scripted line for Nichols.61 That same year, in 1992, in recognition of Star Trek’s contribution to the popular fas­cination with space exploration, a portion of Roddenberry’s ashes were flown aboard Space Shuttle Columbia.

Fred Hoyle predicted over sixty years ago that when “the sheer isolation of the Earth [had] become plain to every man whatever his nationality or creed. . . a new idea as powerful as any in his­tory will be let loose.” Hoyle optimistically expected “this not so distant development may well be for the good, as it must in­creasingly have the effect of exposing the futility of nationalistic strife” and would inevitably reconfigure “the whole organization of society.”62 Hoyle’s point about a new understanding of Earth in the context of the vastness of space is in part why Star Trek and, later, the Hubble Space Telescope, garnered such global interest. Both NASA and Star Trek contributed to a deep cultural narrative about the possibilities of exploring the universe through interna­tional collaboration. Only twenty-four men traveled to the Moon, but unimaginable surveys of deep space have been realized via the Hubble Space Telescope. The telescope continues to capture and convey stunning images of galaxies and nebula and inspire a new generation who dreams of a time when not just a handful of care­fully selected astronauts, but they themselves can explore worlds within our galaxy and beyond. That powerful cultural dream has been realized as Hubble’s cameras extend our vision to the very limits of the observable universe.

When the Apollo 8 astronauts toured the world upon return from the Moon, command module pilot Michael Collins recalls that regardless of which nations they visited, people congratulated them on the fact that “we,” humankind, made it to the Moon.63

Collins noted that people around the world embraced the Moon landing as a collective human achievement. The Hubble Space Telescope, an international effort between NASA and the Euro­pean Space Agency (ESA), is similarly embraced and loved globally as a shared human achievement. Hubble’s remarkable images have forever altered our understanding of the cosmos and demonstrate how far humankind has reached across the universe in our as yet most palpable survey of the intergalactic abyss.

X-rays in Popular Culture

News of Rontgen’s discovery of X-rays rippled around the world. “When Rontgen discovered X-rays in November of 1895 by plac­ing his hand between a Crookes Tube and a florescent screen, the medical applications of the technology were immediately appar – ent.”4 By January 1896, Rontgen had issued a report regarding his experiments to media in Europe and the United States. The public was immediately fascinated by the possibility of seeing through seemingly solid objects or inside the human body, and the topic made headlines in newspapers and weeklies. Apparently, X-r ay

X-rays in Popular Culture

Figure 10.1. At the end of the nineteenth century, X-rays were harnessed for medical imaging, where dense material like bones cast a shadow in X-rays. In the astronomical realm, a very hot gas or plasma emits X-rays, as do regions near compact objects like black holes. The X-rays may also be absorbed by intervening material, and they can only be detected by a satellite above the Earth’s atmosphere (NASA/CXC/M. Weiss).

“mania” swept through the public sphere but at a level far sur­passing a simple cultural fad, explains Nancy Knight, who notes that “X-rays appeared in advertising, songs, and cartoons.”5 John Lienhard similarly reports, “Seldom has anything taken hold of the public imagination so powerfully and completely. . . . Right away, magazine cartoons celebrated the idea. A typical one showed a man using an X-ray viewer to see through a lady’s hat at the theatre.”6

Edwin Gerson has investigated the speed with which X-rays were incorporated into the branding of products in the United States, and he explores why so many marketers used the term X – ray to appeal to consumers. Being a medical doctor, Gerson began collecting household products dating back to the 1890s, none of which have anything whatsoever to do with X-rays. One could purchase Sniteman’s X-Ray Liniment for horses and cattle, and Patt’s X-Ray Liniment for people. X-Ray Golf Balls, ostensibly to improve the accuracy of one’s game, were sold by John Wana – maker of New York. There was the D-cell X-Ray flashlight battery, X-Ray Stove Polish, X-Ray Cream Furniture Polish manufactured in New York, and X-Ray Soap made in Port Huron, Michigan. X-Ray Blue Double Edge razor blades were touted as “the fin­est blade known to science,” while drinking fountains for chicken houses were marketed by the X-Ray Incubator Company in Wayne, Nebraska. Housewives could purchase an X-ray Coffee Grinder or the X-Ray lemon squeezer, and the X-Ray Raisin Seeder was available as early as November 1896. A company from Baltimore, Maryland, sold boxes of X-Ray headache tablets, with 8 pills for ten cents promising relief in just fifteen minutes.7 Clearly, adver­tising by means of non sequitur is not just a phenomenon of the modern age.

The popular fascination with X-rays continued for decades. By 1924, an X-ray shoe fitter was deployed by shoe vendors to image both feet inside a new pair of shoes. David Lapp reports that in the United States “there were approximately 10,000 of these fluo – roscopes in use, being made by companies such as Adrian X-Ray Shoe Fitter,” and that by the early 1950s most shoe stores were using the devices.8 As Gerson points out, “The public was simply astonished with X rays, and advertisers played off this spellbound attention by adding the name to almost any type of product. . . . Not only did the image of the X ray convey a sense of cutting-edge technology, it also functioned as a metaphor for ‘powerful unseen truth and strength.’”9

Researchers and medical personnel working with X-rays were frequently exposed to dangerous or fatal levels of radiation, in­cluding Elizabeth Fleischmann, who at age 28 read a news article on how to build an X-ray device and by 1900 became the best medical radiologist in the United States. But in ten years’ time, Fleischmann had been so badly overexposed to radiation by im­aging her patients and developing the films that she did not sur – vive.10 At the time, the effect of exposure to radiation was poorly understood and this ignorance played out in dangerous exposure for both medical practitioners and those working with the new technology for purposes of entertainment. Nancy Knight, for in­stance, indicates that “papers reported daily” on Thomas Edison’s efforts to X-ray a person’s brain in order to figure out how the brain functions.11

Allen Grove reports that some speculated at the time that the new technology might afford a kind of X-ray vision that might make it possible to capture on film the images of ghosts, appar­ently a popular notion in England. He also comments that within months of Rontgen’s announcement, theaters were headlining performances inspired by the popularity of X-rays.12 Piano sheet music for American composer Harry L. Tyler’s “X Ray Waltzes” from 1896 depicted on its cover a man holding his hand under an X-ray tube. Beneath the man’s hand appears a skeletal X-ray image. In fact, in 2010, Tyler’s waltzes were dusted off and fea­tured in a BBC broadcast titled “Images that Changed the World.” And, any discussion of X-rays in popular culture must recall that in the 1930s, when writer Jerry Siegel and artist Joe Shuster in­vented the prototypical superhero, it was inevitable that Superman would be gifted with X-ray vision. Though Superman didn’t have such ability at the outset, in later adventures he is able to see in multiple wavelengths of the electromagnetic spectrum, including radio waves, infrared, ultraviolet, and eventually X-rays.13

Rontgen’s discovery had a deep shaping effect on the arts. This was because X-rays were an entree into a hidden world, the “world within the world” represented by the interior structure of atoms and molecules. In 1912, less than twenty years after the initial dis­covery, physicist Max von Laue showed that X-rays were a form of electromagnetic radiation because they diffracted when inter­acting with matter. A year later, the father and son team of William Henry and William Lawrence Bragg described mathematically how X-rays scattered within a crystal, winning the Nobel Prize in Physics for their work in 1915. This opened the door to X-ray crystallography, a powerful tool for measuring the spacing and arrangement of atoms within a solid. The impact of this discovery was particularly strong in the visual arts, which were undergoing their own revolution with the onset of Fauvism, Cubism, and Fu­turism. The X-ray was liberating because to artists it “proved that the external is not valid, it’s just a false layer.”14

Art historian Linda Dalrymple Henderson contends that X-rays suggested the possibility of stepping into the fourth dimension. She writes, “From the 1880’s to the 1920’s, popular fascination with an invisible, higher dimension of space—of which our famil­iar world might be only a section or shadow—is readily apparent in the vast number of articles and the books. . . published on the topic.” Henderson has demonstrated that modern artists read­ily embraced X-rays, and their ability to expose realities and per­spectives not perceptible to the human eye, as suggestive of four­dimensional space.15 Cubist paintings, with their simultaneous depiction of all sides of a seemingly transparent object, and their suggestion of interior planes, explains Henderson, “are testaments to the new paradigm of reality ushered in by the discovery of X – rays and interest in the fourth dimension. Such paintings are new kinds of ‘windows’—in this case, into the complex, invisible reality or higher dimensional world as imagined by the artist.”16 The in­spiration was sometimes very direct. According to historian Arthur Miller, “Picasso’s Standing Female Nude” (1910) was inspired by the power of X-rays to glimpse beyond the visible: what you see is not what you get. In this case, the inspiration was X-ray photo­graphs taken to diagnose the illness of Picasso’s mistress, Fernande Olivier. Superposed on a background of planes, her body lies open to reveal pelvic hip bones made up of geometrical shapes: forms reduced to geometry—the aesthetic of Cubism, inspired by mod­ern science.”17 From the arts, to medicine, and particularly through astronomy and space exploration, X-rays have profoundly altered human culture.

Precision Cosmology

WMAP has not only put us “in tune” with the cosmos; it has re­fined and sharpened our view of the extraordinary event that cre­ated all matter and energy 13.8 billion years ago.

WMAP has taken quantities that were poorly known or only hinted at and turned them into well-measured cosmological param – eters.58 The temperature is measured to a precision of a thousandth of a degree. Since space can be curved according to general relativ­ity, the universe can act as a gigantic lens. To do this vast optics experiment we look at the microwaves that have been traveling across space for billions of years. The fundamental harmonic of the microwave radiation sets the size of the “spot.” Radiation from that typical spot size travels through space and the angular size can be magnified or de-magnified depending on whether space has positive or negative curvature, which is like the universe acting as either a convex or a concave lens. WMAP has shown that the spot size doesn’t change so the universe is behaving like a smooth sheet of glass. The inference is that space is not curved; the universe is flat to a precision of 1 percent.59 This is just as expected from inflation.

WMAP has measured the mass and energy of the universe with unprecedented precision. The ratio of fundamental to first harmonic powers depends on the baryonic or normal matter con­tent of the universe. Ordinary atoms only make up 4.6 percent of the universe, to within 0.1 percent. The strength of the second harmonic is sensitive to dark matter, and shows that dark matter is 23 percent of the universe, to within 1 percent.60 Knowing the mass and energy content of the universe, General Relativity can be used to calculate the current age. It’s 13.73 billion years with a precision of 1 percent or 120 million years, though that precision depends on assuming that space is exactly flat (which is a good assumption). These numbers have been refined and slightly altered by Planck. The cosmic “pie” has dark slices and just a sliver of vis­ible stuff (figure 12.4).

We’ve also been able to learn about the epoch when the first stars and galaxies formed using the WMAP data. If stars formed soon enough after recombination, they would have ionized the still-diffusing gas. That would have recreated the conditions where photons bounce off electrons, as was routinely the case before re­combination. This late scattering imprints polarization on the mi­crowave radiation, analogous to sunlight being polarized when it bounces off a water surface. Polarization requires a special direc­tion, and that can only be seen if photons travel relatively freely before interacting. Before recombination no polarization is ex­pected. WMAP saw a polarization indicating that 20 percent of the photons were scattered by a sparse fog of ionized gas a couple of hundred million years after the big bang. This is surprising because astronomers didn’t expect the first stars to form that quickly.61

The sum of all WMAP’s improvements leaves little doubt that the universe began with a hot big bang. The model is described quite precisely and any competing idea would have to clear some very high bars of evidence to be viable. It’s extraordinary that we can know some attributes of the overall universe better than we know attributes of the Earth.

Precision Cosmology

Figure 12.4. Observations of the microwave background radiation combined with ground-based observations determine the contents of the universe. Most of the universe is in the form of enigmatic dark matter and dark energy, with just a small component of the normal matter that comprises all stars, planets, and people (NASA/WMAP Science Team).