From the Big Bang to the Nobel Prize and on to the James Webb Space Telescope

John C. Mather

Observational Cosmology Laboratory

NASA Goddard Space Flight Center


The Big Bang 13.7 billion years ago started the expansion of our piece of the universe, and portions of it stopped expanding and made stars, galaxies, planets, and people. I summarize the history of the universe and explain how humans have learned about its size, expansion, and constituents. The COBE (Cosmic Background Explorer) mission measured the remnant heat radiation from the Big Bang, showed that its color (spectrum) matches the predictions perfectly, and discovered hot and cold spots in the radiation that reveal the primordial density variations that enabled us to exist. My current project, the James Webb Space Telescope (JWST), is the planned successor to the Hubble Space Telescope (HST) and will extend its scientific discoveries to ever greater distances and ever closer to the Big Bang itself. Its infrared capabilities enable it to see inside dust clouds to study the formation of stars and planets, and it may reveal the atmospheric properties of planets around other stars. Planned for launch in 2013, it is an international project led by NASA along with the European and Canadian space agencies.

INTRODUCTION

From the beginning of time to the end of time, with a few details in between, is the story of cosmology. The journey to the Nobel Prize began long ago and far away, on a small planet around an ordinary star in an ordinary galaxy. And now, humans have the temerity to push beyond, to seek to understand the origins of everything—from the primordial explosion, to the formation of objects (stars?) from the initial material, to the formation of galaxies, stars with planets, and even life. Such is the quest of modern astrophysics, and remarkable steps have been taken while enormous mysteries abound.

My personal career began with childhood on a scientific research station, the Dairy Research Station of Rutgers University, located perhaps 75 miles northwest of New York City as the crow flies but immensely distant for a child. My dad was a professor investigating the breeding and feeding of dairy cattle, a subject at one time of immense commercial importance to the state of New Jersey. The chemistry laboratory was located next to the barn where 20 bulls lived, and there were tanks

FIGURE 1.1 Lusscroft Farm, Sussex County, New Jersey, where I lived. SOURCE: Courtesy of the Heritage and Agriculture Association, Wantage Township, N.J.

FIGURE 1.1 Lusscroft Farm, Sussex County, New Jersey, where I lived. SOURCE: Courtesy of the Heritage and Agriculture Association, Wantage Township, N.J.



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From the Big Bang to the Nobel Prize and on to the James Webb Space Telescope John C. Mather Obserational Cosmology Laboratory NASA Goddard Space Flight Center The Big Bang 13.7 billion years ago started the to the formation of galaxies, stars with planets, and expansion of our piece of the universe, and portions of even life. Such is the quest of modern astrophysics, it stopped expanding and made stars, galaxies, planets, and remarkable steps have been taken while enormous and people. I summarize the history of the universe mysteries abound. and explain how humans have learned about its size, My personal career began with childhood on a expansion, and constituents. The COBE (Cosmic scientific research station, the Dairy Research Station Background Explorer) mission measured the remnant of Rutgers University, located perhaps 75 miles north- heat radiation from the Big Bang, showed that its color west of New York City as the crow flies but immensely (spectrum) matches the predictions perfectly, and dis- distant for a child. My dad was a professor investigating covered hot and cold spots in the radiation that reveal the breeding and feeding of dairy cattle, a subject at one the primordial density variations that enabled us to time of immense commercial importance to the state of exist. My current project, the James Webb Space Tele- New Jersey. The chemistry laboratory was located next scope ( JWST), is the planned successor to the Hubble to the barn where 20 bulls lived, and there were tanks Space Telescope (HST) and will extend its scientific discoveries to ever greater distances and ever closer to the Big Bang itself. Its infrared capabilities enable it to see inside dust clouds to study the formation of stars and planets, and it may reveal the atmospheric proper- ties of planets around other stars. Planned for launch in 2013, it is an international project led by NASA along with the European and Canadian space agencies. INTRODUCTION From the beginning of time to the end of time, with a few details in between, is the story of cosmology. The journey to the Nobel Prize began long ago and far away, on a small planet around an ordinary star in an ordinary galaxy. And now, humans have the temer- ity to push beyond, to seek to understand the origins FIGURE 1.1 Lusscroft Farm, Sussex County, New Jersey, where of everything—from the primordial explosion, to the I lived. SOURCE: Courtesy of the Heritage and Agriculture As- formation of objects (stars?) from the initial material, sociation, Wantage Township, N.J. 

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 FORGING THE FUTURE OF SPACE SCIENCE of liquid nitrogen as well as Geiger counters for civil emitted light, and that can be a long time ago if we defense against the possibility of nuclear attack from are looking at things very far away. The speed of light, the Soviet Union. immense though it is from a human perspective, is still But somehow, the cows were not as fascinating finite. We see the nearest star as it was 4 years ago, the to me as the mysteries of the sky. When I was around center of our galaxy as it was 25,000 years ago, and if we 8, my parents took me and my sister to the American look almost to the edge of the visible universe, we look Museum of Natural History in New York City, and we back almost 13.7 billion years. Geologists look at old saw the planetarium show and the dinosaur and fish rocks, historians look at old documents, but astrono- bones. My parents also read aloud to me and my sister mers really travel back in time with their telescopes. from biographies of Darwin and Galileo. Quite an introduction to science, which looked very important Measuring Distances and a bit dangerous! Jumping ahead many decades, astronomers now Astronomers naturally need to know how far away have a coherent story to tell about the origin of today’s t hings are, and we have two basic methods (see universe. We say there was a Big Bang 13.7 billion Figure 1.3). First, we draw triangles, just as the ancient years ago that started everything, we have a lot of Egyptians did. Given one side and two angles of a mathematics to describe how it worked, and we have triangle, we can compute the other parts. The ancient elaborate computer simulations of how the primordial Greeks, at least some of them, knew how to apply this material would grow into the things we see today. to get the size of Earth and a rough distance to the But until recently, when the COBE satellite flew, we Moon, but everything else was too far away for them did not know the details of the starting point, so we to calculate. The other basic method astronomers use is did not know what computer simulations to run. The the standard candle method: if two objects are known scientific impact of the COBE was to provide that to have the same intrinsic brightness, then the fainter starting point. one is farther away, in accordance with the inverse square law. (In the expanding universe, this law has to be modified a bit.) Surprise! Explosions in the Bathroom Mirror One of the great challenges of modern science has been Measuring Velocities to work out the origins of the chemical elements. When you look in the mirror in the morning, thinking of hair Of course, we also need to know how fast things are and whiskers and the day ahead, you are looking at the moving. The Sun, the Moon, and the planets move remains of exploded stars. The Big Bang gave us only hydrogen and helium and tiny traces of lithium, and everything else has been made since then by nuclear reactions inside stars. The basic idea was explained by Fred Hoyle in 1946, and developed in great detail over the years. However, much is still unknown about this, since the details seem related to the nuclear reactions that take place during the final explosions of superno- vas. Those are very difficult to calculate because the three-dimensional structure of the explosion is highly turbulent. Looking Back in Time Astronomers look back in time in a way that is not open FIGURE 1.2 Looking back in time by looking at things far to anybody else. We see things as they were when they away.

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 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE recently discovered that there are pulsating stars in the galaxy M31, the great nebula in Andromeda. Since he knew about pulsating stars close to home, and he saw similar patterns in these distant stars, he could estimate the distance to the Andromeda Nebula, and then with much more work, even more distant nebulae. The distances were immense, far greater than those within the Milky Way galaxy. And even more surprising, the distant galaxies were almost all going away from us at high speeds. Remarkably, there was a pattern to all this: the galaxies fit close to a straight line on the velocity- distance plot (see Figure 1.4). So it appeared that all of them were together a few billion years ago! Hubble had discovered the expanding universe in the same year that the worldwide economy collapsed. Needless to say, Hubble’s discovery was front-page news around the world. FIGURE 1.3 Measuring distances with triangles, and with standard candles. Why the Surprise, Dr. Einstein? pretty fast across the sky, and we know how far away Back in 1905, Albert Einstein shocked the physics they are, so we can get their velocities very accurately. world, and then the world at large, by proposing that Some stars also move quickly enough to measure. But space and time are inevitably mixed together, and nei- most do not move fast across the sky, but we can still ther one has absolute meaning. He was driven to this spread their light out with a spectrometer. As it hap- by “thought experiments” about synchronizing clocks pens, stars like the Sun emit a wide range of wave- using light signals, then a hot topic in the engineering lengths of light, but at certain wavelengths the light is world. Working in the Swiss Patent Office, he saw a lot brighter or fainter than one might expect. These many patent applications about this, so it turned out special wavelengths are the result of the interactions to be a good thing for him that he was not a professor. of chemical elements and molecules, which absorb or As it happens, this Special Theory of Relativity also emit in very characteristic patterns. That means that we explains why the Michelson Morley experiment could can determine the chemistry and physical properties of not detect the “luminiferous ether” that was supposed distant stars by analyzing their spectra. It also means to be the medium in which light waves would oscillate. The famous E = mc2 came from this work. Then, in that we can use the Doppler effect to measure their velocities. If a star is coming toward us, the light we 1915 and 1916, he developed the General Theory of receive is at shorter wavelengths than if the star is not Relativity, shocking the world further with the asser- moving, and conversely, if it’s going away, the light is at tion that gravitation works by curving space and time. longer wavelengths, i.e., it is redder. Since the chemi- It did not take long for his predictions to be confirmed cal elements have very characteristic patterns, we can by Eddington’s observation of the bending of light by determine the apparent velocity (towards or away from the Sun, during a solar eclipse. Einstein applied his us) very precisely. equations to the universe as a whole, and (assuming that the universe must be static) added a constant of integration to the equations to keep the (theoretical) The Big Surprise: The Expanding Universe! universe from expanding or contracting. Why did Back in 1929, Edwin Hubble was using the biggest Einstein assume that the universe had to be static? It telescope in the world, the 100-inch Hooker telescope was a fair guess, there was no evidence against it, and on Mount Wilson, to study distant galaxies. He had it seemed simple.

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 FORGING THE FUTURE OF SPACE SCIENCE FIGURE 1.4 Edwin Hubble’s plot of speed of galaxies versus distance. SOURCE: Hubble Box 24(1), “Velocity-Distance Relation among Extra-Galactic Nebulae,” Papers of Edwin Powell Hubble, 1900–1989, The Huntington Library, San Marino, California. But it was wrong. In 1922, Alexander Friedmann, a state the Primeval Atom and described in clear terms young mathematician in the Soviet Union, applied Ein- that the universe was expanding from this extraordinary stein’s equations without assuming the universe would event. It was only 2 more years before Hubble found by be static, and showed that the mathematics allowed for measurement that Friedmann and Lemaître were right, an expansion. Einstein heard about it and said that was and Einstein had to apologize for what he termed his wrong. Three years later, Friedmann died. But in 1927, greatest blunder. Georges Lemaître, a Belgian priest and mathematician, came to similar conclusions and was similarly rejected No Center, No Edge! by Einstein, who admitted that the math was OK, but that the physics was terrible. Lemaître named his initial Curiously enough, the pattern of motion that Hubble found says that there is no center and no edge of the ob- servable universe. We can calculate what an astronomer in another galaxy would observe, and he or she would also see distant galaxies receding, with the same shape of diagram found by Hubble. So, we all think we’re in the middle. Therefore, there can not be a middle. As it happens, this also simplifies the mathematics of general FIGURE 1.5 A lexander Fried - relativity immensely, so it’s very convenient to think mann, first to recognize in 1922 that this means the universe is really infinite and almost that Einstein’s General Relativity suggests that there was an initial uniform throughout. But in truth, we’ve only measured compressed state of the universe. a little piece, the part we can see in the 13.7 billion years SOURCE: Courtesy of the Russian that light has been traveling. Quite possibly, the part Federation. we can not see is pretty different.

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 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE FIGURE 1.8 George Gamow, extraordinarily creative physi- cist, initiated work on Big Bang p hysics in 1948. SOURCE: Courtesy of Professor William C. Parke, The George Washing- ton University. team considered first whether the Big Bang could have made the chemical elements in the abundances that we find them today. The answer was tantalizing: neutrons captured by atomic nuclei would make bigger nuclei, with an abundance pattern like what we see. But, there FIGURE 1.6 Georges Lemaître (left) and Albert Einstein (right). is a bottleneck: there is no way to make a carbon nucleus In 1927 Lemaître rediscovered Friedmann’s equations and by attaching neutrons to smaller nuclei, so the Big Bang named the Primeval Atom. SOURCE: New York Times Magazine, can not make all the chemical elements. But the other February 19, 1933. big question was, what happened to the heat in that Big Bang? Alpher and Gamow computed that it should The Power of Thought still exist, and should have an equivalent temperature of about 5 Kelvin (K), not far from the current measured Jumping ahead to the end of World War II, scientists value of 2.7 K. Gamow decided it would be fun to have came back to science and started applying the knowl- Hans Bethe’s name on the paper, so it was the Alpher, edge gained in battle. George Gamow (originally from Bethe, Gamow paper, but it was mostly Alpher’s work. Kiev) came to Washington and started thinking about Alpher eventually got the National Medal of Sci- the Big Bang (it was not called that yet). He had a ence, shortly before his death in 2007. So there was a young postdoc, Robert Herman, and a young gradu- prediction that the universe should be filled with this ate student, Ralph Alpher, and set them to work. This heat radiation, but in 1948 it was either impossible or extremely difficult to measure it. Perhaps in hindsight we would say it could have been done given the motiva- tion of a Nobel Prize, but serious scientists at that time gave up and did not try. It was not until 1965 that another team was moti- vated to try. Robert Dicke at Princeton University was thinking about that Big Bang and the possibility of an eternally oscillating universe that would fill the universe with heat radiation. He thought it might be possible to measure the heat radiation, so he set the Gravity Group at Princeton going to do the measurement. Meanwhile, a few miles away, a pair of scientist-engineers (Arno Penzias and Robert Wilson) at Bell Laboratories were checking out their antenna and found a persistent excess temperature in it. When the two groups were FIGURE 1.7 Three astronomers independently obtain the same put in contact it was immediately clear what the Bell Hubble constant from different locations. None can claim to be Labs group had found: the predicted whisper of the Big at the center, so there is no center.

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 FORGING THE FUTURE OF SPACE SCIENCE particles, antiparticles, quarks, gluons, leptons, photons, gravitational waves, and so on, and so on. Then, skipping many details that have been cal- culated and might even be true, the universe expanded and cooled. When it was a few minutes old, some of the neutrons attached themselves to the protons and made helium nuclei, and traces of lithium. And that is it as far as nuclear reactions went, until the formation of stars. When the universe was about 380,000 years old, FIGURE 1.9 Robert Herman (left) and Ralph Alpher (right) at it reached a temperature of about 3,000 K, and that the launch of the COBE satellite. They worked out the Big Bang physics under Gamow. SOURCE: Courtesy of NASA. was cool enough that the electrons could stick to the atomic nuclei and make neutral gas. That’s an impor- Bang. The companion paper by Dicke, Peebles, Roll, tant day for us, because when that happened, the gas and Wilkinson gave the interpretation of the Penzias became transparent, and the heat radiation became free and Wilson discovery. A few months later the Princ- to move across the universe. This event is called the eton group confirmed the measurement at a different Decoupling, because the radiation and the matter were wavelength. Then the race was on to learn all about the no longer coupled together. Moreover, the radiation cosmic microwave background radiation, or CMB, as was then free to come to us, human observers, almost it came to be called. unchanged. The expansion of the universe stretched out the wavelengths, reducing the temperature of the radiation accordingly, but the brightness pattern we see Inflation, and How Did That Little Ball Make the today was mostly imprinted on the radiation when the W hole Universe? universe was 380,000 years old. There were a lot of mysteries about the Big Bang, and Then, the universe entered a kind of “Dark Ages,” one of them was How could the universe become so when nothing much happened except expansion and completely uniform (as it appears today) if there has cooling. But during this quiet time, gravitation was not been time for the different parts to communicate working, pulling on the denser parts of the universe and with each other? So, scientists were looking for a way reversing their expansion. According to calculations, to make the whole universe erupt from some primordial if the early universe had been completely uniform, we material that was pretty uniform. In 1980, Alan Guth could not ourselves exist, because no part of the uni- found such a theory, now known as Cosmic Inflation. verse would have stopped expanding. So this is a very Guth found a way to apply the theory of elementary interesting question: How did the material begin to particles to imagine a new kind of cosmic energy that move to make stars and galaxies? could take a small volume of space, say 10 centimeters We calculate that the first stars and galaxies could (cm) across, and make it grow exponentially, doubling have formed when the universe was a few hundred mil- in size around a hundred times in the tiniest fraction of lion years old and maybe 1/10 or 1/20 as large as it is a second. So if that is what happened, then the 10-cm today. The first objects might have been very massive ball of primordial material could grow big enough to stars, maybe a few hundred times as massive as the Sun, kick off the expanding universe we see today. and they would have burned very hot (maybe 100,000 Needless to say, the conditions in such a little ball K) for about 3 million years. Then, they would end were extreme, but nevertheless, it seems possible to their lives in supernova explosions, possibly producing calculate many things about it. This is now the favored black holes, as well as liberating the heavier chemical picture of the origin of the universe: a 10-cm blob of elements that make up places like Earth. If stars and primordial material, probably surrounded by other stuff planets had formed from this enriched material, it is that is a bit different, that has a quantum fluctuation conceivable that life might have formed soon after, and starts to expand exponentially, stretching out space in the first hundreds of millions of years after the and time and filling them with the stuff of physics: Big Bang.

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 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE Then, somehow, ordinary galaxies of ordinary stars on Earth capable of supporting life. And in about 5 were formed. This process is a great mystery, though billion years, it is predicted that the great Andromeda numerical calculations are giving us a hint. It seems Nebula will collide with the Milky Way, changing its likely that galaxies evolve by colliding with and absorb- shape beyond recognition. Possibly the Sun will end ing their neighbors, and indeed the Milky Way still has up orbiting around the Andromeda nebula. And then, two small satellite galaxies (the Magellanic Clouds) about 7.6 billion years from now, the Sun will expand that are still falling in. Then, quite recently on a cosmic so much that Earth will orbit inside its surface. Shortly scale, only 4.5 billion years ago, the Sun formed with after, the Sun will go out. Then, over billions of years, the planets, apparently rather abruptly from the isoto- the remaining hydrogen and helium gas will form new pic evidence in various residual bits of the early solar stars, those stars will themselves burn out, and the system. So our solar system is very young, only 1/3 of universe will become mostly dark. If present trends the age of the universe. continue, most of the distant galaxies will continue to recede from us, and the universe will seem small and isolated. But, since we do not know why the universe Very Recent History is expanding now, we do not know if it will continue. We have evidence that life appeared on Earth shortly Perhaps there will be the Big Crunch, a.k.a. the Gib after it became cool and wet enough to support life Gnab. as we now it, but that is a topic for another science. And shortly after a small asteroid made a crater in THE STORY OF COBE, THE COSMIC the Yucatan about 65 million years ago, mammals re- BACKGROUND EXPLORER placed dinosaurs as the dominant large land animals. Only a million years ago or so, the large mammals of In 1970, I was looking for a thesis project at the Uni- today came into their present forms: lions, elephants, versity of California, Berkeley, just 5 years after the and humans (or their ancestors). And in 1609, Galileo discovery of the CMB. At the time there had been pointed his newly improved telescope at the heavens some really wrong measurements of the CMB at short and discovered satellites of Jupiter, craters and moun- wavelengths, around a millimeter, so it was a time to tains on the Moon, and spots on the Sun. Copernicus try a thesis project. Mine involved a ground-based mea- was right, the Protestant Reformation was in full swing, surement at White Mountain with Mike Werner and and science was politicized. But Galileo was buried in Paul Richards, and then a balloon payload with David honor in Santa Croce in Florence, Italy, across the hall Woody and Paul Richards and Norm Nishioka. It was from Michelangelo, and now the Church has admitted tough work, and the balloon payload did not work to a terrible misunderstanding. Moreover, the Vatican right on the first flight. I left Berkeley thinking I would maintains its own observatory and sponsors confer- try something easier as a postdoc in radio astronomy ences on cosmology. with Pat Thaddeus at the Goddard Institute for Space In 1905, Einstein had his Miracle Year of major Studies in New York City. But in 1974, a few months discoveries; we celebrated the International Year of after I arrived in New York, NASA announced an op- Physics in 2005; and in 2009, we will celebrate Galileo’s portunity to propose new scientific satellites, and it discoveries with the International Year of Astronomy. seemed obvious that a better version of my thesis work Just 50 years ago, on October 4, 1957, the Sputnik had to be proposed. My advisor, Pat Thaddeus, gave me launched a new era of the space race. Started as a scien- some names, we called them up and made a team, and tific research project, it had huge effects on the world. we submitted our proposal. In 1976, NASA chose to NASA was founded a year later, on October 1, 1958. make a new team, composed of members of our team and two other teams, to define the new mission. So I moved to Goddard Space Flight Center in Greenbelt, The Future Maryland, to work on it. The new team named it the Perhaps in another 50 years, we will find signs of life Cosmic Background Explorer, or COBE. on other planets. But certainly, in a billion years or so, The hair-raising details of this project are well told the Sun will be so bright that there will be no place in the book The Very First Light, a popular account by

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10 FORGING THE FUTURE OF SPACE SCIENCE John Mather and John Boslough. The project suffered theoretical curve as a solid line (Figure 1.11). All the many perils, and had to be re-designed after the loss of boxes were right on the line. The result was a standing the space shuttle Challenger. But it was finally launched ovation from the audience of about 2,000 astronomers. on November 18, 1989, and almost immediately began I was completely unprepared for this response, since returning data. I had always thought I knew the right answer: the CMB must have the predicted form. But the audience knew that there had been repeated measurements that Proving the Big Bang showed that the spectrum did not match the blackbody You cannot prove the Big Bang. But you can test the predictions. And there were many papers showing that predictions of the theory, and you can compare them it required very implausible theories to explain these with other theories. There were two major predictions: deviations. So it was a huge relief for the crowd that First, the spectrum of the CMB should match that of (a) the Big Bang was now safe, and (b) none of these a perfect black radiator at a temperature of about 2.7 exotic theories were required. K. Second, the CMB should be slightly non-uniform Prior to the discovery of the CMB, the dominant (anisotropic, in Greek), so that some parts of the uni- alternate theory about the universe was the Steady State verse would have enough gravitation to stop expanding theory, which held that the universe has existed for an and turn into galaxies, stars, and people. infinite amount of time and that, although it seems The first experiment to report scientific results was to be expanding, it is continually being refilled by the the FIRAS, the Far Infrared Absolute Spectrophotom- creation of new matter. This theory does allow for the eter. This was my thesis project, grown larger and made existence of a cosmic background radiation, produced to work very well by professional engineers. When I by stars through the infinite history of the universe, presented the first results to the American Astronomi- but it does not predict that the spectrum should match cal Society in January of 1990, I showed them a graph the perfect black radiator. So, in 1965 the Steady State that had the measurements as little boxes and the theory was already dying because of the discovery of the F IGURE 1.10 The COBE satellite in orbit 900 km above Earth. The instrument package is protected by conical shield. The Sun is to the side, and Earth below. SOURCE: Courtesy of NASA.

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11 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE FIGURE 1.11 First public spectrum of the CMB from the COBE FIRAS instrument, shown at AAS meeting in January 1990, received a standing ovation. SOURCE: Courtesy of NASA and the COBE Science Working Group. CMB, and in 1990 it became very difficult to make the Steady State match the CMB spectrum. In the end, we reduced the error bars to about 50 parts per million. The CMB has a spectrum that is as close to the theoretical prediction as we can measure. Why Are We Here? The Pink and Blue Blobs The second major result from the COBE was an- nounced in April 1992. The Differential Microwave Radiometer (DMR) instrument was designed to map the brightness of the CMB and to look for tiny differ- ences in brightness from one place to another. Consid- ering that the differences we found are very, very faint, only 30 micro-K, and that the instrument operates at a temperature of 140 K or 300 K depending on the channel, this is an extraordinary accomplishment, pull- ing tiny signals out of mountains of noise. It depended on making hundreds of millions of measurements and fitting them to a map of the sky using a “least squares fit” on a computer. We found the map in three scientific stages (see Figure 1.12). First, we made the map of the sky, repre- sented as an oval, with the center of the galaxy in the middle. This map shows a small difference between one part of the sky and the other: half of the sky is pink, and half is blue. This is the expected result if Earth is FIGURE 1.12 The first published all-sky maps of the CMB moving relative to the rest of the universe, with a speed fluctuations. SOURCE: Courtesy of NASA and the COBE Science of about 300 km/s toward the constellation of Leo. It’s Working Group.

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12 FORGING THE FUTURE OF SPACE SCIENCE What’s Next with the CMB? not of cosmic significance, but eventually we’d like to know why we have that speed. Second, we subtracted The CMB has been astonishingly informative, con- off that effect, and we got a map that has a lot of pink sidering how difficult it was to measure it. The DMR and blue blobs and a strong reddish band across the map had 6,144 pixels, and there may already be more middle. That’s the Milky Way galaxy, emitting micro- than 6,000 scientific papers citing the DMR work. The wave radiation because there are electrons spiraling WMAP already made far more detailed maps, with far around magnetic fields and bumping into protons. We sharper images and far better sensitivity. Its maps have were expecting that effect too, and we mapped the sky revealed some huge surprises and confirmed others. at three different wavelengths so we could tell what First, the universe is filled with dark matter and dark part of the map came from the electrons and what part energy—that are both far more abundant than ordinary came from the Big Bang. So the third map is all pink matter. According to WMAP and other measures, the and blue blobs, and except for measurement errors, they universe is composed of about 4 percent ordinary mat- all come from the Big Bang. ter, 23 percent dark matter, and 73 percent dark energy. When Steven Hawking saw these maps, he said The dark matter has been suspected for a long time, it was the discovery of the century, if not of all time. going back to Fritz Zwicky in 1933, but now it is clear: At first I thought he was being too generous, but now the pattern of speckles on the microwave map can not I would like to point out that if it were not for these be explained by ordinary matter. Dark matter is not blobs, we could not exist. These blobs map out the den- coupled to the radiation field and is free to move under sity differences in the early universe, and as it happens the influence of gravity, long before the decoupling the cool (blue) blobs come from dense regions. And if event at 380,000 years, so the pattern has a different there were no spots that were dense enough to stop the shape than it would have with ordinary matter alone. expansion, we would not be here to measure them. As it happens, it was also discovered (in 1998) that distant supernovas are too faint, quite a lot too The Nobel Prize faint—about 20 percent or so—way too much to be explained by experimental error. The interpretation was On October 3, 2006, I was awakened by a phone call that the universe is larger than it seems from the veloc- from Sweden, wanting to know if I were the real John ity of expansion, and that would be so if the universe has Mather who worked on the COBE satellite. People been accelerating. This was pretty shocking when it was had been telling us for years that we had done Nobel- discovered by the High Z team and later confirmed by worthy work, and now it was happening! The next the Supernova Cosmology Project, but their discovery months were a whirlwind of preparations for 10 days of has stood the test of time. In particular, the acceleration parties and speeches in Stockholm. The big challenge changes the pattern of speckles on the WMAP image was to arrange for as many as possible of the COBE of the sky in just the way that would be expected if the team members to go to the big event. George Smoot, acceleration determined from the supernovas is really my co-winner, and I each had a quota of 16 invita- there. The big questions now for astronomy are What is tions. I would like to specifically mention that Ned that dark matter doing? How does it relate to ordinary Wright, the data team leader on COBE, was the first matter? and What is causing the acceleration? We call to compute the maps of the pink and blue blobs, and that acceleration force “dark energy” to be able to talk that Chuck Bennett, deputy principal investigator for about something, but in truth it was not expected by the DMR instrument, was crucial for the success of the many theorists, and we see no obvious reason why it measurement. Bennett is also the principal investigator should exist. for the WMAP, the Wilkinson Microwave Anisotropy The CMB also may harbor traces of something Probe, which made a tremendous improvement on even more exotic: gravitational waves in the primordial the DMR measurements, and showed as well that the material. If these waves existed, with the amplitude DMR maps were correct. Without that confirmation, predicted by many theories of inflation, then they perhaps the Nobel Prize would not have been given would produce an imprint of a certain pattern of po- to us.

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1 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE larization of the CMB. The hunt for this polarization really needed. By 2007, we had a list of 10 new tech- has already started, with some preliminary results, but nologies that would be needed, and all of them were the final answer may require an even more sensitive ready, which means that representative designs had satellite mission. been tested in the relevant space-like environment. The JWST Team “MY” NEW PROJECT: THE JAMES WEBB SPACE TELESCOPE The JWST project is led by project manager Phil Sa- In 1995, the COBE mission was done, and I was writ- belhaus at NASA Goddard Space Flight Center and ing a book about it with John Boslough. The HST was includes major contributions from other parts of NASA up and working beautifully after its repair, but it had at Marshall Space Flight Center, the Jet Propulsion been very difficult and costly. I thought NASA might Laboratory, and Johnson Space Center. The observa- never again do something as exciting and challenging tory will be operated by the Space Telescope Science as the COBE or the HST, but one day in October, I Institute in Baltimore, Maryland. received a phone call from Ed Weiler, the new head of NASA held many competitions to choose the team the Origins Theme at NASA Headquarters and the members for the telescope. In the end, the prime con- long-term guiding light for the HST. Weiler knew tract was awarded to TRW. The part of TRW doing that we needed to plan for the successor project after the telescope was then bought by Northrop Grumman the HST and had already started a committee going to and became Northrop Grumman Space Technolo - define what it ought to do. The committee, chaired by gies, located near Los Angeles Airport. Their major Alan Dressler, wrote a beautiful report called HST and subcontractors include Ball Aerospace, ITT (formerly Beyond, which outlined two objectives. First, NASA Kodak), and ATK. should build a new space telescope that is optimized for near infrared wavelengths (1 to 5 micrometers) as The JWST Concept large as possible, at least 4 meters in aperture. Second, NASA should start planning for missions to observe This new telescope does not look much like any tele- Earth-like planets around other stars. In 1995, Michel scope you’ve ever seen (Figure 1.13). First, it has to fold Mayor and Didier Queloz announced that the nearby up, and second, it has to get cold. So it will fly to deep star 51 Pegasi has a big planet orbiting close in; not space, a million miles from Earth, and orbit around exactly Earth-like, but tantalizing. Obviously, NASA the Sun–Earth Lagrange point L2 (Figure 1.14). It (and other space agencies) would have to follow up on will have a folding sunshield, with five plastic layers to this discovery. Now, we know of over 300 exoplanets achieve a Sun Protection Factor of a million, to let the of many different types, mostly found by this radial telescope cool itself down to 40 K. It will not have a velocity technique. protective tube: if it did, it would not be able to radiate So Ed sent a little money to Goddard Space Flight away its heat to outer space. So it ends up looking more Center and we got started on a study, working with the like a solar energy concentrator than like the HST. But Space Telescope Science Institute in Baltimore, with it will be far more powerful, with a mirror collecting industrial partners, and gradually with international area more than 6 times that of the HST, with infrared partners, the European and Canadian space agencies. instruments that the HST can not use because it is Under the leadership of Dan Goldin, NASA was trying too warm, and with advanced camera chips far beyond to reach out far beyond the realm of the currently pos- anything known before. sible, and an extremely ambitious telescope was just the thing. The initial studies said that a telescope 8 meters Naming the Telescope across could be built at an affordable price, even though it would have to fold up like an origami bird to fit into Originally called the Next Generation Space Tele- the rocket. New technologies were needed, but the plan scope (a lot of our colleagues were Star Trek fans), was to develop them all to a high level before they were the new machine was finally named after the second

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1 FORGING THE FUTURE OF SPACE SCIENCE 1.13 jwst 012897.eps bitmap image FIGURE 1.13 James Webb Space Telescope, planned for launch in 2013 as successor for the Hubble Space Telescope. SOURCE: Courtesy of NASA Goddard Space Flight Center. administrator of NASA. Scientists rebelled: Should not every observatory be named for a great scientist? But James E. Webb, the man who built NASA to go to the Moon, did more for science than most people know. He personally persuaded John Kennedy that the science done with the Apollo program would outlast the political statement and have lasting value for the USA. As a result, Webb initiated the creation of space science laboratories at universities around the country. Science owes a lot to James Webb. For more details, consult the fine biography Powering Apollo by Henry Lambright. Folding Mirror! The most obviously difficult part was the giant primary FIGURE 1.14 The 5 Lagrange equilibrium points of the Sun– mirror. It would have to be built in segments and de- Earth system, discovered in 1772. JWST orbits the L2 point, a ployed after launch. Then it would have to be adjusted million miles from Earth, and is overhead at midnight. SOURCE: to the right shape, using the mathematics that we Courtesy of NASA.

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1 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE learned when we had to fix the HST. It would all have to happen by remote control, long after the last human could touch it. We held competitions for the mirror technology, with about a dozen contracts to famous optics companies. In the end, there was a shoot-out between two leading designs. One used a sandwich of ULE® glass sheets bonded to a glass honeycomb for light weight. The other used pure beryllium metal machined to remove 95 percent of the material and polished very carefully. In the end we chose beryllium, because the glass sandwich did not hold its shape when it was cooled down to the low temperatures we needed, around 40 K. But the beryllium is a tough material to use: it’s very strong, very stiff, very light, and very hard, but it can change its shape a little if a rather modest pressure is applied, and powdered beryllium can be quite toxic. Now, we are polishing the mirrors for the flight telescope. It takes about 4 years to get from powdered beryllium to polished hexagons, and we’re about half done with the process. Adjusting the Mirror FIGURE 1.15 The JWST mirror rack. SOURCE: Courtesy of 1.15 JWST.eps Ball Aerospace Corporation. After the HST experience, people are a little touchy bitmap image about telescope mirrors in space, so we have built a testbed telescope, 1/6 scale, to learn everything about adjusting the real one. Our current plan requires 11 by the Apollo astronauts to get ready for the Moon different adjustment methods to get from the initial (Figure 1.16). It’s so old, it’s on the Historic Register. deployment to a nearly-perfect mirror, so all 11 have In the big tank, the telescope will be at the bottom been tried out on the testbed. It takes a computer a day looking up. At the top will be test equipment located at or so to adjust the testbed, but we expect the real space the center of curvature of the primary mirror, as well as telescope to take weeks. (Figure 1.15) 3 autocollimating flat mirrors that will reflect light back into the telescope. A tiny light at the focal point of the telescope will radiate outwards to the flat mirrors, and Testing the Real Telescope their beams will return through the telescope to detec- One of the lessons from the HST was that conserva- tors to create an end-to-end test. The telescope will be tive engineers are right: test as you fly, fly as you test. It cold and in vacuum, but of course not in zero gravity. was believed that a full test of the HST optics was too expensive. But if you do not have time to do it right, Scientific Objectives and Instruments when will you have time to do it over? That’s the title of an inspirational book on time management. So the The JWST will collect light from distant stars and test plan for the new telescope is very carefully designed galaxies, and instruments will spread it out into images to catch every possible kind of error that our engineer- and spectra for transmission back to the ground. There ing teams can imagine and to be ready to catch the are four main scientific topics that will certainly be unimagined errors as well. The big test will be held at investigated by users of the telescope, along with many Johnson Space Center in the same vacuum tank used others that will be proposed by observers:

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1 FORGING THE FUTURE OF SPACE SCIENCE 1. The end of the Dark Ages: first light and reion- The near infrared instruments (NIRCam, NIR- ization of the universe, Spec, FGS, and TFI) cover the wavelength range from 2. The assembly of galaxies, red (0.6 microns) to 5 microns, and the MIRI covers 3. The birth of stars and protoplanetary systems, the range from 5 to 28 microns. The near-infrared de- and tectors are all made with mercury-cadmium-telluride 4. Planetary systems and the origin of life. (HgCdTe) sensing layers and are produced by Teledyne (formerly Rockwell), and the mid-infrared detectors are To enable these investigations, the JWST will carry arsenic-doped silicon produced by Raytheon. four instruments: The End of the Dark Ages 1. The Near Infrared Camera (NIRCam), being produced by the University of Arizona with its major The prime objective in this area is to discover and contract to Lockheed Martin; measure the earliest possible objects that formed after 2. The Near Infrared Spectrograph (NIRSpec), the Big Bang. As described above, theoretical predic- being produced by the European Space Agency (ESA) tions suggest that these were extremely massive stars, with its major contract to Astrium; hundreds of times the mass of the Sun, that would be 3. The Mid Infrared Instrument (MIRI), produced extremely hot and bright, burning out in a few million by a European Consortium led by the United Kingdom years with some kind of spectacular supernova explo- Advanced Technology Center (UKIRT), in partnership sions. If so, individual supernovas could be detectable with the Jet Propulsion Laboratory; and from a time when the universe was only a few hundred 4. The Fine Guidance Sensor (FGS), including million years old. To find them, the JWST would the Tunable Filter Imager (TFI), produced by the survey the sky, returning repeatedly to the same areas Canadian Space Agency, with their major contractor to search for objects that have changed in brightness. COMDEV. Close to home, supernovas rise rapidly to maximum brightness in a few days and then slowly decay over a period of months. The most distant ones will show time dilation, with days stretching into months and months stretching into years. We also imagine that the first objects may have been clustered together because of the way in which the primordial density variations combine to enable gravity to slow and stop the expansion of the original material. If so, we might find proto-galaxies containing thousands of massive stars burning near each other. We would recognize the first objects in several ways. First, they would be extremely hot, as expected from the lack of heavy chemical elements in them. Second, they would be embedded in the primordial hydrogen, so their ultraviolet radiation at rest wave- lengths less than 0.1216 microns would be cut off by absorption by that intergalactic hydrogen. We would use the NIRCam to search for the objects and to determine whether they show the predicted lack of ultraviolet radiation due to the hydrogen. Third, they might be clustered together, with a group all at the FIGURE 1.16 JWST optical system in test chamber at Johnson Space .16 optical test IGY_9_07.eps of chamber. 1 Center, looking up to test apparatus at top same redshift. We would use the TFI to hunt for this bitmap image effect, since it can be set to search for objects emitting The end-to-end test! SOURCE: Courtesy of NASA.

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1 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE hydrogen Lyman-alpha spectra at a specific redshift. and brightness; and then compared with simulated Fourth, their spectra would show no signs of elements galaxies based on theories about how this process is heavier than the primeval hydrogen and helium. Un- supposed to have worked. fortunately, this last step is very difficult, because it requires not only discovering the first objects, but also The Formation of Stars and Planetary Systems obtaining their spectra. We would carry out this step with the NIRSpec, which has been optimized for just Understanding the history of the solar system has this purpose. The NIRSpec is capable of observing 100 always been one of the fascinating challenges of as- candidate objects at the same time, using a remarkable tronomy. Early astronomers had no idea that the solar new technology of microshutter arrays. system was very old, and, indeed, before the discovery According to predictions, these first objects are of nuclear energy and the conversion of mass into en- outside the range of ground-based telescopes and even ergy it seemed the Sun had to be very young. But now, the HST, because the expansion of the universe has we see stars forming before our very eyes in nurseries stretched the original ultraviolet light out into the in- like the Orion Nebula (the fuzzy spot in Orion’s sword). frared by the time we see it. So, we need a giant space Some stars are hot and bright and must be very young, telescope capable of observing the infrared. only a few million years old, otherwise they’d already be burned out. But the process is largely hidden from us now, because the nebulae where birth occurs are The Assembly of Galaxies dusty. The dust itself is a part of the process, because it We would very much like to know how our own home shields the gas clouds from external heat and enables galaxy, the Milky Way, was formed. We now have two the gas to cool and condense into massive knots that small satellite galaxies, as do many other galaxies. We then become stars. Using visible light, the HST gave imagine that the Milky Way has grown by absorbing us the famous pictures of the Eagle Nebula, also called many such small galaxies, and we can check this theory “the Pillars of Creation,” where bright new stars have by observing other galaxies like ours. With the JWST, just been born (Figure 1.17). Using infrared light, the we will look back in time to see how different the early Very Large Telescope in Chile has shown us that we galaxies were in shape, rotational characteristics, color, can see inside the dust clouds. However, most infrared brightness, chemical composition, and temperature. wavelengths do not reach ground-based telescopes, be- In addition, we would pursue one of the great current cause the atmosphere is opaque, so we need an infrared mysteries: Why is there a giant black hole in the middle telescope in space to see better. The JWST MIRI will of almost every galaxy? Did the galaxy make the black be especially important for this task because it observes hole, or did the black hole make the galaxy? Was there wavelengths that pass through the dust clouds very well just one black hole made per galaxy, or were there many and that are emitted by objects far too cool to emit vis- of them, merging together later to make bigger ones? ible light. The MIRI includes both cameras and spec- We currently see that most galaxies are either spiral trographs to detect candidate young stars and stellar in shape, like the Milky Way, or elliptical. We already nurseries and to analyze their temperatures, structures, know that at earlier times, many more galaxies were and compositions. irregular in shape, as though their internal motions had not settled down. We also know that at early times, Planetary Systems and the Origin of Life galaxies collided frequently with one another. It appears that the universe became a much more peaceful place Since the first planets around other stars were dis- around the time that the Sun was formed about 4.5 covered in 1995, the tantalizing possibility that some billion years ago. Curiously enough, that is also when might harbor life has driven intense efforts to learn the expansion started to accelerate. more about them. There are several major topics to In any case, this whole story has to be checked by investigate. measurement. Thousands of galaxies will be observed; First, we have small residual pieces from the for- cataloged; classified by shape, redshift, color, spectra, mation of our own solar system that are orbiting the

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1 FORGING THE FUTURE OF SPACE SCIENCE FIGURE 1.17 The Eagle Nebula, the “Pillars of Creation,” where stars have been formed in the last few million years. Dust obscures the birth sites, but JWST can see through the dust. SOURCE: Courtesy of NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University). the Kepler observatory in 20091 to find many more Sun but far from here—in the outer reaches beyond Neptune and in the asteroid belt between Mars and transiting exoplanets, including a predicted handful of Jupiter. Understanding how these pieces relate to our Earth-like planets around Sun-like stars. Needless to own existence is a great challenge for solar system say, the JWST will be devoted to following up these exploration, either by robot, in person, or by remote observations as well as possible. observation with telescopes. JWST will use all its in- Third, we know of locations where dust clouds struments to find and study the small bits, along with orbit distant stars in a way that suggests the presence the well-known planets. of planets. The shapes of the dust clouds sometimes Second, we know of dozens of transiting plan- tell us that a planet must exist and sometimes where it ets—objects that pass between ourselves and their ought to be and how big. The star Fomalhaut has a dust host stars, blocking starlight. The Hubble and Spitzer ring around it, offset a bit, and a good explanation is space telescopes have already been used to determine that there is a large planet at a particular spot, fairly far the orbit, temperature, and even the atmospheric com- position of a few exoplanets. NASA plans to launch 1The Kepler Spacecraft was launched on March 6, 2009.

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1 FROM THE BIG BANG TO THE NOBEL PRIZE AND ON TO THE JAMES WEBB SPACE TELESCOPE FIGURE 1.18 Drawing of dust ring around Fomalhaut, pulled off center by hypothetical planet that could be observed by JWST. SOURCE: Courtesy of NASA, ESA, and A. Feild (STScI). from the star. (See Figure 1.18.) Moreover, this system direct the starlight away from the image of the planet. appears to be young, so the planet might be hot enough But this is also difficult and requires formation flying to measure directly with the JWST. Three of the four technology with extremely good accuracy, which we do JWST instruments will have coronagraphs, devices that not have yet either. The third technology is a remote block the bright glare of a star to enable us to hunt for blocking device flying in formation tens of thousands faint planets nearby. of kilometers away from a general-purpose telescope in space. Such a device was proposed for the JWST but was not ready yet. Recent progress on blocking devices After JWST, The Search for Life Elsewhere (called occulters) has been rapid, and both Northrop The same committee report that recommended the Grumman and Lockheed are working with scientific JWST also recommended that telescopes should search teams to develop this method. The technology is still for planets around other stars. NASA and ESA have difficult, but it does not require perfect optics, and the studied three main types of such telescopes. First, an shifts the demands to spacecraft engineering. extremely well-made telescope with extremely good What would be signs of life on a planet around coronagraphs could see planets directly. For a long another stars? Earth seen at a great distance would be time, I thought that this would be the easiest method, recognizably alive, because of photosynthesis, which since the telescope is relatively small and could fit has filled our atmosphere with oxygen (Figure 1.19). into a single rocket payload, like the JWST. However, Oxygen is so reactive that it would quickly disappear perfection is difficult to achieve, and this technology if it were not continually regenerated by algae and is not quite ready yet. The second method would use land plants. So, if we could find signs of oxygen in the a group of infrared telescopes flying in formation in atmosphere of an exoplanet, along with other signs space, relaying light beams to a combining station.. like carbon dioxide and water, we could argue we had This is called an interferometer, which can be used to found another Earth. And on Earth, chlorophyll has a

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20 FORGING THE FUTURE OF SPACE SCIENCE already, either here or elsewhere, we have not noticed yet. But maybe it’s not impossible—have a look at Ray Kurzweil’s book The Singularity is Near. Big Questions, Open Now To conclude, let me say that there are many questions that are way too difficult to answer today, but that may become answerable in the near or distant future. These include: What happened before the Big Bang? What’s at the center of a black hole? How did we get here? FIGURE 1.19 Spectrum of Earth from a distance, showing features of water, ozone, and carbon dioxide. The combination Are we alone? What is our cosmic destiny? What are would not occur on Earth without photosynthetic life. SOURCE: space and time? The TPF Science Working Group, The Terrestrial Planet Finder Perhaps you who are in the audience or reading this (TPF): A NASA Origins Program to Search for Habitable Planets, later will be the ones to find these answers. JPL Publication 99-003, C.A. Beichman, N.J. Woolf, and C.A. Lindensmith, eds., May 1999. Courtesy of NASA Jet Propulsion Laboratory. ACKNOWLEDGMENTS Beginning with elementary school, my work has always distinctive color. We might also be able to tell if there been supported by the U.S. taxpayers. Thomas Jefferson are continents and oceans, even without making maps and Ben Franklin would be proud that their country has of other planets, because the color and brightness of produced scientific and technological knowledge that Earth changes as it spins. they could never have imagined. More specifically, my And what of life that is based on some different parents Martha and Bob, my wife Jane, my scientific chemical system? Biologists are taking this question mentors Paul Richards, Mike Hauser, Pat Thaddeus, seriously and there is even a professional journal about and Nancy Boggess, my project managers, especially it: Origins of Life and Eolution of Biospheres, a journal Roger Mattson, Dennis McCarthy, Bernie Seery, and of the International Astrobiology Society. So if there Phil Sabelhaus, and at NASA Headquarters, especially are other chemical systems that support life, at least we Ed Weiler, have all made enormous changes to my life. might think of them and recognize their signs. Without them, nothing would be the same. And with- Some argue that the function of carbon-based life out my co-author John Boslough, you would not have is to create artificial life, maybe based on silicon elec- our book The Very First Light to read about this series tronics that can travel through the universe. If it exists of fortunate events.

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