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National Aeronautics and Space Administration
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September 2005
The The discoveries of Alb ert Einstein spar ked the scien t@ revolution revolution the 20th century century and rank among humanity greatest achievements. Recent developments show that we ca n now com plete Einstein Einstein legacy and, in the jrst decade the 21st century, unravel the the m ysteries of the Un iverse that awa it us .
Second Printing: July 2005 Einstein images are used by permission of Roger Richman Agency representing Hebrew U niversity and the Albert Einstein estate. estate. Image of Einstein riding bicycle courtesy of the Archives, C aliforni Institute of Technology. Photo of Richard Feynman by Floyd Clark/Courtesy of Caltech Archives. Einstein letter to Georg es Lernaitre. Pe rmission to quote granted by the Albert Albert Einstein Archives, Archives, the Hebrew University of Jerusalem, as well well as by the Einstein Pap ers Project
Beyond Beyo nd Einstei How did the Universe begin? Does time have a beginning and an end? Does space have edges? The questions are clear and simple. They are as old as human curiosity. But the answers have always seemed seemed beyond the reach of science. Until now. In their attempts to understand how space, time, an d matter are connected, Einstein and his successors made three predicti predictions. ons. First, space is expanding from from a Big Bang; second, space and time can tie themselves into contorted contorted knots called “black holes” holes” where time actu ally comes to a halt; third, third, spac e itself contains some kind kind of energy that is pull ing the Univ erse apart. Each of these three predictions seemed so fantastic when it was mad e that everyone, including Einstein himself, regarded them as unlikely. Incredibly, all three have turned out to be true. Yet Einstein’s legacy is one of deep mystery, because his theories are silent on three questions raised by his f antastic predictions: (1 What powered the Big Bang? (2) What happens to sp ace, time, time, and m atter at the edge of a black hole? (3 hat is the mysterious dark energy pulling the Universe apart? The answ ers to these these quest questions ions-which -which lie at the crux of where our current theories fail us-w us-wil illl lead to a profo und, new unde rstand ing of the nature of time and space. To find answ ers, however, we must venture beyond Einstein. The answers require new theories, such as the inflationary Universe and new insig hts in high-energy particle theory. theory. Like Einstein’s theories, these these make fan tastic predictio ns that seem hard to believe: unseen dimensions and entire universes universes beyond our own. We must find facts to con front and guide these new theories. Powerful new technologie s now mak e this possible. And NASA an its partners are developing an armada of space-based observatories to chart the path to discovery. Here is where the Beyond Einstein story begins. By explor ing the three questions that are Einstein’s legacy, we begin the next revolution in understanding our Universe. We plot our way forward forward using clues from observations and from new ideas connecting connecting the worlds of the very small and the very large, from the atom out through the deepest reaches of the cosmos.
Aflerglow MAPping the Big Bang Aflerglow
The map the cosmic microwave background, the afieqlow NASA’s NASA’s Wilkimo Wilkimon n Microwa Microwave ve Anisotro Anisotropy py Probe
the
Powered th
Bang?
Gravitational Waves can Escape from Earliest Moments the Bang
(Big Bang plus l0J5 seconds?)
The answer to what powered the Big Bang is imprinted in its afterglow, called the cosmic microwave background, which which is still visible for us to study today. at uowered
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If the Universe is expanding, as countless observations observations have shown, it i s only logical a s s h e that the U niverse was more compact yester yesterday, day, even more compact the day before, today must and so on. At som e point in the distant past, all the matter and energy we see today have been confined to a m icroscopic region of unimaginably high density. This would be the moment of the Big B ang. We know a gr eat deal about the history history of the Universe, fiom its hot, formless beginnings to the glorio us hierarchal hierarchal structure of stars and galaxies in the modem era. Clues to the past ar around us. In the 1960s scientists scientists identified a pervasive microwave radiation eman ating from all points in the sky. This radiation, called the cosm ic microwave background, the afterglow of the Big Bang itself. Embedded in this this akrg low are slight temperature fluct fluctuat uatio ionsns-aa little warmer here, a little cooler there -that point back slight density differences in the infant Univers Universe-a e-a little mor e matte r here, a little less there. there. These fluctu ations are the seeds of all the structure we see today NASA NASA s Cosm ic Background Background Explorer (COB E) satellite discovered discovered the fluctuations and, most recently, NASA’ NASA’ss Wilkinson Microwave Anisotropy Probe (WMA P) has refined the the measurement. We see how gravity has pulled these wrinkles into stars and planets. planets. We can even determine the the ratio the ratio of matter to energy, the era of first starlight, and the age of the Univers 13.8 13.8 billion year s. Most of the X -ray sources seen in this 12-day exposure by by the C handra X-ray O bservatory are active galaxies and and quasar s powered by m assive black holes. Ground-based observations show that many of them are shrouded by d ust; many others remain unidentified, invisible except in rays. ._
..
..
Richard Feynman [Nobel Prize, 19651 showed that “empty” spac e was filled with virtual particles.
What we don’t know is the most basic fact of them all: What started started it all? Modem theoretical ideas that to answer this question predict predict that the wrinkles COBE discovered arose fiom two kinds of primordial particle particles: s: fiom the energy field that powered the B ig Bang; and gravitons, fundamental particles of space and time. Clues to the nature of these particles exist in the Big Bang afterg afterglow. low. Measurem ents from Beyond Einstein missions will coax information from this ancient light, which has held its secre ts for so long. This would enable us to piece togethe r the story of how time, space, and energy worked together to power the Big Bang.
What hamens hame ns to space. time. time. and matter at the edge
black hole?
The greatest extremes of grav ity in the Universe ar e the black holes formed at the centers of galax ies and by the collapse of stars. Gravity is so overpowering here that nothin g, not even light, can escape its grasp. By de finition black holes are invisible. invisible. Yet these invisible bodies disturb space considerably,offering us two ways to study them: by o bserving matter swirling into into them, and by listening to the waves of distortion they they make in spacetime. New data fiom X-ray satellites, such as NASA’s Chandra X-ray Observatory and ESA’s =-Newton, =-Newton, show signs of gas whizz ing about black holes at close to the speed of light and hint that that time is slowing as the gas plunges into the zone from which escape is impossible. Beyond Einstein missio ns will take a census of black holes in the U niverse and give detailed pictures of what happe ns to space and time at the edges of these roiling vortices. One key mission will create movies from the X-ray light emitted from multimillion-degree gas as it approaches a black hole’s border, called the event horizon. An other mission will listen for gravitational waves, wbich a re ripples in spacetime predicted by Einstein. These waves are created by black hole mergers; they they mov e acro ss the “sea” of space at light speed, unperturbed, and offer an unobstructed view of these pow erful collisions. Einstein Einstein himself never dream ed that it would be possible to d etect gravitational waves, which only distort the distance between objects as far apart as the Earth and Moon by less than the width of an an atom. Yet Yet the technology now exists to do so “I found it very ugly in deed that the field law of gravitation shou ld be
composed of two logic ally independent terms which are connec ted by addition. addition. Abo ut the justification of such feelings concerning logical simplicity simplicity it is difficult to argue. cannot help to feel it strongly and am unable to to believ e that such an ugly thing should be realized in nature.” to Georges Lem aitre -Albert Einstein, in a Sept. 26 1947, letter to
What is the t he mvsterious dark ene e ne rw Dull Dullin in the Universe Univer se apart? The landm ark discovery of the 1990s was that the expansion of the U niverse is accelerat ing. The greatest greatest mystery in astronomy today is the natur e of this force opposing gravity, wh ich we call “dark energy.” Because Einstein originally thought thought the U niverse was static, he conjectured that even the em ptiest possible space, devoid of matter and radiation, might still have an energy countering gravity gravity and keeping keeping the Universe from collapsing. He called it a “Cosm ological Constant.” Constant.” When Edw in Hubble discovered the expansion of the Universe, Einstei rejected his own id ea, calling it his greatest blunder. But the Universe isn’t just expanding; the expansion rate, which appears to have slowed several billion years ago, ago, is revving up. We live in a runaway Universe, in which the most distant galaxies visible today will soon fly off forever beyond the horizon. This acceleration could be due to the concept that that “em pty space” isn’t isn’t empty. Richard Feynman and oth ers who developed the quantum theory of matter realized that empty space is filled with “virtual” particles particles continually form ing and destroying themselves. These particles create negative pressure, like a vacuum energy, that pulls spac e outward. one, however, could predict this energy’s energy’s magnitude. Independent measurements reveal that dark energy comprises about 0% of the total mass-energy budget of the Universe. e still do not not know w hether or how th e highly accelerated expansion in the early Universe, called inflation, and the current accelerated expansion, due to d ark energy, energy, are related. Beyond Einstein mission will measure the expansion accurately accurately enough to learn whether this energy is a constant property of empty space, as Einstein conjectured, or w hether its strength varies over time, a property predicted by m odem theories of the forces of nature
The Beyond E instei Program Th BeyondEinstein program has three linked elem ents which adv ance science and technology towards two visions: to detect gravitational wave sign als from from the earliest possible mom ents of the Big Bang, and to im age the event horizon of a black hole. hole. The central element is a pair of Einstein Great O bservatories: Constellation-X Constellation-X and LISA. These powerful facilities will blaze new paths to the q uestions about black holes, the Big Bang, and dark energy. energy. They will also address other central goals of contemporary astrophysics. The second element is a serie s of competitively selected Einstein Probes, each each focused on one of the scie nce questions. The third element is a program of technology developm ent, theoretical studies and education to support the Probes and the vision missions: the Big Bang O bserver and the Black Hole Imager. The program offers competitive opportunities for mission leadership, technology developm ent, and groundbreaking scientific scientific research, with goals that excite the public.
While these m issions are focused on specific obser vational goals, the capabilities they provide are so dramatically innovative that they w ill also provide a broad science return that will impact all areas of astrophysics, as have H ubble Space Telescope and the Chan dra X-rav X-rav Observatorv before them.
Th e Laser Interferome ter Space Antenna (LISA) will detect detect gravitat gravitational ional waves waves These w aves, predicted predicted by E instein but but never detected directly, mov e at light speed an come in a rang e of frequencies, just like light waves. LISA’ LISA’S S three spa cecraft will act like buoys in space to monitor for a passing wave. The spacecraft will be separated from from each other by five million kilometer s and “tethered” by a laser. laser. Becau se gravitational waves hardly inte ract with matter, matter, they can penetrate the dusty environ ments surrounding black holes a nd provide us with an unobstructed view. view. LISA will probe spac e and time time at th e edges of black holes by listening to the so unds of vibrating spacetime: the booming roar of merging superm assiveblack holes, the chorus of death cries from star s falling toward toward black holes, and the zipping sound of a n ewly formed singularity. singularity. LISA may ev en hear hear whispers from the time of the Big Bang when o ur three-dimensional space forme d within the the unseen space of six or seve n dimension s, as som e new theories predict. LISA will plot the orbits of stars around black holes to test Einstein’s theory under extrem e conditions. conditions. LISA’S LISA’S precise m easurem ents of distances to merging black holes will provide a new yardstick with wh ich to measure the Universe and constrain the nature nature of dark energy. energy. LISA will also detect gravitational waves from thou sands of binary star systems, yielding new insights into the formation and evolution of binary stars. The Constellation-X mission will consist of four X-ray telescopes orbiting and observing in unison. This telescope teamwork will provide nearly 100 times the sensitivity of the pioneering X-ray ob servator ies now in or bit: NASA‘s NASA‘s Chandra X-ray Observatory, Europe’s XMM-Newton and Japan’s Suzaku. The great sensitivity of C onstellation-X will allow us to make “slow-m otion movies” of hot gas falling toward toward a black hole. This is d one not through through imagery but through a technique called spectroscopy, which is analogous to fin gerprinting the the gas to determ ine unique properties, such such as temperature, density, density, velocity and atomic number. We will be ab le to see how how time, from ou perspective, com es to a stan dstill as it approaches the black h ole event horizon. Einstein’s general relativity relativity makes specific predictions about the beh avior of m atter near a black hole; a nd any dev iation from theory revealed by C onstellation-X observations will expose flaws in Einstein’s Einstein’s math. Constellation-X will also dramatically increase our ability to ob tain high-resolution spectrosco py of faint sources. This will enable us to con strain the nature of dark matter and d ark energy by ob serving their effects on the formation of clu sters of galaxies, which are massive yet faint and distant structures. These measurem ents and those by LISA, the Dark Energy Probe and the In flation Probe will each constrain different possible properties of dark energy. Together they will lead to a better understanding understanding of d k energy. energy. Similarly, Similarly, Constellation-X and LISA together w ill help us understand the origin and nature nature of the giant black holes in the centers of galax ies, as they grow by consum ing gas gas and whole stars or by merging.
Einstein Probes Com plem enting the facility-class Einstein Great Ob servatories are three sharply focused mission s addressing addressing a specific science question. Answers to these three questions can take us beyond Einstein.
Many NASA m issions have laid the groundw ork for the Beyond Einstein program and w ill complement it. it. NASA’ NASA’ COBE discovered the first evidence for primordial density fluctuations in the C osmic M icrowave Background. NASA’ NASA’ balloon program (e.g., (e.g., the NA SA/N SF/Italian/UKBOOMER SF/Italian/UK BOOMER anG) has supported the discovery of the interaction of those fluctuations fluctuations with matter in the Universe. NASA’s WUAP satellite and the ESA’ ESA’ss plan ned Planc ksat ellite wi ll extend these discoveries and are vital precursors to the proposed proposed Inflation Probe. The Hubble Space Telescope has helped to find and measure the distant supernovae that have forced to accept the reality of d ark energy. X-ray missions, including NASA’s Chan dra X-ray Observatory and RXTE, ESA’s XMM-Nmton, and Japan’s ASCA, have discovered X rays from matter spiraling into black holes, illustrating the potential of Constellation-X. GP-B will test one of Einstein’s exotic predictions: that the rotation of the Earth drags space and time around the E arth into mild version of the tremendous vortical spin near a spinning black hole. Swifi studies gamma-ray bursts, bursts, believed to be a result of the stellar explosions and mergers which create black holes. Swift also tests tests technology for the Black Hole F inder Probe Japan/NASA’s Suzaku, Suzaku, launched in Ju ly 2005, will be the first to use NAS Aprovided micro-calorimeters that are prototypes for Constellation-X detectors. G U S T will provide more sensitivity and energy coverage than ever before for the stu dy of high-energy high-energy em issions from particles accelerated accelerated in gamm a-ray bursts and in the jet s from spinning black holes. ST-7and ESA’s SMART-2 will provide flight comparison of two disturbance reduction technologies competing for use on LISA. “How did th Universe begin?” The U niverse appears to have begun w ith a period of infl inflat atio ion, n, when it exp anded faster than the spee d of light. The rapid expansion enabled slight density differences in that incredibly dense kernel to ultimately grow into the stars, galaxies and vast voids we see today. today. Yet Yet wha t prope lled this inflation? Is it the same force that is accelerating the expansion of the Universe today? The Einstein Inflation Probe will investigate. Inflation theory predicts predicts that this expansion was driven by a quantum fluctuation, a split-secon split-secondd chan ge in energy that created negative pressure, or a vacuu m energy, which pulled the Universe apart. The Inflation Probe w ill look look for relics of quantum fluctuations hidden, like fossils, in the afterglow of the Big Bang. This afterglow is a pervasive blanket of microwav e radiation, called the cosm ic microwave background, still visible today across the the entire sky. The gravitational waves fiom the Big Bang should have created an imprint on the cosmic microwave bac backg kgro roun undd-aa unique pattern pattern of polarizatio n that speaks of these quantum fluctuations. fluctuations. One w ay to examine the theorize inflationary inflationary period is to study cosmic m icrowave background polarization, polarization, similar to how WMAP is measuring temperature fluctuations today “How do black holes form an grow?” Scientists have identified identified two m ain classes of black holes: holes: sm aller, stellar-sized stellar-sized black holes that form fro m the collapse of m assive stars; and supermassive black holes in the core of most galaxies. The latter can contain the mass of millions to to billions of suns and grow by swallowing S t a r s and gas that venture
too close. This consum ption releases great amounts of energy. Bu there is an accounting problem: N ot enough light is coming from supermassive black holes to explain their their growth. There are hints that much of the grow th occurs behind a shroud of dust. The “Black Hole Finder Probe” will conduct a census of hidden black holes, revealing where, when, and how they f orm. This probe will also identify new new so urces for the the powerful Constellation X-ray Observatory to study in detail. “Why the Universe acce leratin g?” This is a question that would not have been asked five years ago, before there was evidence that that the Universe was being pulled apart. understand this energy, energy, we must m easure the expansion of the U niverse with high precision. This will require the most precise cosmic yardsticks we can find. Several ideas for such joint dark energy mission with the Departm ent of Energy have be en proposed proposed-fo -fo exam ple, precision precision measurement of distant supe rnovae by wide-field spac e telescope. Indepen dent diagnostics of the dark energy will be crucial to verify the validity of results and to increase the precision of the measurements. The Inflation Inflation Probe and LISA will provide completely independent cosmic yardsticks with which to measu re the effects of dark energy, and C onstellation-X onstellation-Xwill will observe the first clusters of galaxies whose evolution depends critically on dark matter and d ark energy.
The Beyond Einstein Program
CONSTELLATION-X
mega-channel electron
BLACK HOLE FINDER PROBE
GREAT RVATO
PROGES
The Gam ma-Ray L arge Area Space Telescope Telescope (GLAST) is an international an multi-agenc multi-agencyy (NASA and DOE) project to study the m ost energetic objects and phenomena in the Universe, such such as antimatter and high-power high-power jets of matter shooting away from black holes. holes. GLA ST combines the fields of astronomy and high-energy particle physics
Now under construction, GLAST will build upon the suc cess the EGRET instrument on the the Compton Gamma Ray Observatory. Observatory. Nearly half of the 27 objects detected by EGRET in the 1990s remain unidentified. unidentified. GLAST, with more than 30 times the sensitivity sensitivity of EGRET, is primed fo r discovery. discovery. What could these objects be? be? Perhaps Perhaps long-hidden black holes or something new entirely? GLA ST may may provide the Beyond Einstein missions with with vital information abou t black holes, dark matter, matter, dark energy and gravity. gravity.
he Ultimate flswn The technology to go far beyond Einstein is within ou reach if we approach the grand goals systematically, mission building upon m ission, proving and refining refining the required technology. technology. Strategic investments in hardware,software, and astrophysical theory will lead the way forwar d t tw visions: explore the beginning of time, a "Big Bang Observer" will build upon LISA to directly measur gravitons from the early Universe still present today. In contrast to the Inflati Inflation on Probe's Probe's measurement of frozen imprints imprints of much lo nger waves on the m icrowave background, background, the B ig Bang Observer will ubserve gravitational gravitational waves theit original form, from still earlier in the Big Bang. The Big Bang Obse rver would give us a direct view of the creation of spacetime, a truly profound achievement. explore the the end o ftim e and the the edges of space, Constellation-X will measure the spectral signatures of gas swirling into black holes, and LISA w i l l record the tune to which s t a r s dance around it. Bu there is no substitute substitute for a direct image. A'B lack Hole Imager" based on X-ray interferometry, could could take this epochal picture, revealing directly the fate of matter near a black hole.
Technolorn While the enabling foundations are are well in hand, the Beyond Einstein program demands many refinements in in technology. Constellation-X will need lightweight optics and cryogenic X-ray X-ray calorimeters. LISA will need sensitive monitoring units coupled to micro-new ton thrusters to keep its test masses free of non-gravitational forces. It will also require very stable laser measurement systems. systems. The Einstein Einstein Probes require study of a broad range of technologies so that the m ost effective approach approach to their science goals can be cho sen. The vision missions, Black Hole Imager and Big B ang Observer, need still greater precision precision in spacecraft pointing pointing and control
Research and nalvsis he R&A program is the cradle for the necessary necessary technology and for the theoretical theoretical underpinnings of NASA space scienc e missions. It is the the first step in in a process that turns ideas into missions, as well as the final step in turning missions into scientific advances. universities, providing providing an NASA's R&A program draws heav ily on the resources of our universities, additional benefit: th training of students who become the architects and builders builders of future missions. missions. The Einstein Probes require new detectors for which ground-based and balloon tests will be essential. Laboratory m easurem ents of atom ic data are necessary to link observations to to scientific conclusions. Theory provides the intellectual context for any scientific effort. effort. Theoretical work is essential to the con ception and design design of missions and to the interpretation of the data they provide--especially for theBeyond Einstein missions, which are designed to test predictions that that ch allenge our beliefs.
Education and Public Outreach Beyond Einstei offers an unparalleled opportunity to involve the public in the excitement of cosmic exploration, and to inspire and cultivate the next generation of scientists and engineers. The public’s eagerness to share this adventure is reflected reflected in part by the many popular news reports, bestselling books, television television series, and even Hollyw ood movies that draw on Beyo nd Einstei themes. The television shows and educational materials for “Livefiom Black Hole” an “ L i v e f i m e E d g of Space” reached an estimated five million students. Public television’s television’s NOVA NOVA program on dark energy (Runaway Universe was seen by millions ofAm ericans. The origin of th Universe and black holes a re central to K- 12 science literacy standards and curricula. T he Beyond Einstein themes will soon provide the majority of materials on these subjects in our nation’s schools, and the missions will weave an ongoing story that is one of the most com pelling in all science.
Einstein Lesracy In 1905 an unknown patent clerk in Bern, Switzerland, named Albert Einstein ignited a scientific revolution. revolution. Practicing physics on the sly sly and with very little personal interaction with the scientific establishment at the tim e, Einstein wrote five seminal papers that year that encompassed the who le of the universe, universe, fiom the w orkings of the atom and out through space and time. time. One hundred years onw ard, still we marvel. An d we struggle to make sens e of Einstein’s outrag eous legacy-spacetime legacy-spacetime war ps, an accelerating universe, black holes, possible hidden di&ensions, and th notion that all of space is quantized, built from infinitesimal, discrete bundles of matter and energy. Einstein sought, but never ach ieved, an understanding of how n ature works at its deepest level. level. We now now seek to fulfill Einstein’s Einstein’s quest through through aprog ram of missions we are designing today to carry out over the next decade. There is tangible excitement among among scientists. e are on the verge of the next sc ientific breakthrough breakthrough that w ill define the 2 1st 1st century and beyond. This is the new scientific revolution, a race for the next great leap forward. Scientists around the w orld from a variety of once-disparate disciplines are uniting for the cause. Thus, we w ill follow matter to the very brink of black holes and detect particles of time left over from the beginning of the universe. universe. And w e will use breakthrough breakthrough technologies to see beyond the vision of Einst Einstein ein-t -too the utterm ost extrem ities of existen ce.
Y.
Sources
Further Information
NA SA Science Science Mission Mission Directorat littp://sciciicc.liq.nasa.po\~~ Beyo nd Einstei littp:i’:uiiivcrsc.nasa.go\~i Laser Interferometer Space Ante nna (LISA) Iittp:/,/lisa.nasa.gov/ Constellation-X p://coiist ell at on.ps .n
goy/
Suzaku l i t t p : l ~ s u z a k u . ~ s f c . n a s a . g o ~ ~ d o c c i a sactl-ocyof.htm1 troe Swift http;
ft gsfc. iiasa govi
Chan dra X-ray X-ray O bservatory bservatory http://cIiandra.liar~~ard.cdu/ Wilkinson Microwave Anisotro Anisotropy py P robe (W MA P) http://i-nap.&sfc.nasa.go\i/ Space Technology Technology http://iimp.jpl http://iimp.jpl .nasa.gov/st7/ High Energy Physics tt .ii t/ doc-hcp l i t t p : / / d ~ ~ - h ~ p . l i ~ p . n c t / HP E / IPr A p - ~ p ~ r t O02.pdf Labo ratory Astrophysic h t t p : i i ~ e b 9 9 . a r c . n a s ago\ /-astroclicni ’nasala\~iiwliitepapi.r.h t m l Rossi X -ray Timing Explore (RXTE) iiasa.gov docs,’xtc/xte s t h t m l 1ittp;//licasarc.~sfc Gamm a-ray Large Area Space Telescop Telescopee (GLAST) tt //gla st .gs fc iiasa .go\ Gravity-Probe tt //ci stcin stan ford.cd Planck http:i’/sci csa.int Iiome ’planck)
Beyond Beyo nd Einstein Einstein Timeli T imeline ne
2005
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LauncJz Date
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NASA: Explore. Discover. Understand hnp:l/www.nasa.gov/
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