"For most of human history, the only light we knew came from the sky." "By day, the Sun." "By night, an uncountable number of stars" "From the beginning, our ancestors believe that Sun and stars were heavenly out of this world." "And there were right." "We have been watching the sky for thousands of years." "But until recently, we couldn't see well enough to understand our connection to the cosmos." "But now, our astronomical vision has sharpened" "We can see farther and clearer." "We can observe object that are invisible to human eyes" "Our increasingly improving vision has allowed us to make great discoveries." "revealing an astonishing and wonderful universe." "What follows are 13 of the greatest discoveries in astronomy." "The Planets Move" "Our first great discovery happened over centuries." "As the first human looked carefully into sky in places like this" "The empty cloudless deserts of the American southwest, the Middle East, Africa, and South America." "Of these ancient astronomers, the most important were the Mesopotamians" "They consider the objects in the sky gods." "And build giant tower so they can record the rising and setting of the Sun, the moon, and the stars." "For more than a thousand years, they use clay tablet to record what they saw." "To find out more, I paid a visit to professor of astronomy Owen Gingerich." "Here for example, is one of these clay tablets." "And have a read." "Oh." "Yes." "These guys, there people wrote small." "Yes." "Yes, I was perfectly amazed if somebody came into my office and picked it up and actually started reading it." "So what language is this" "I think this is in Babylonian" "Hundreds of these tablets were unburied." "Among these hundreds of tablets is a tablet called the Venus tablet of Ammisaduqa" "And this tablet contains the motion of the planet Venus." "That's the earliest record we have of a planet moving." "After the Mesopotamians made the fist records, it was the Greeks who took the next step." "Some of the Greek astronomers made a field trip out to Mesopotamia to find out what had been going on there." "And they seemed to brought (bring) back some systematical records." "So, it ultimately gave the basis for making a mathematical theory of the motion of the planets." "From their observations the Greeks developed the vision of the solarsystem that would stand for some 2000 years." "that the planets move revolving around the earth" "It will take our next great discovery to set the record straight." "The Earth Moves" "The year is 1543" "A seventy-year-old man is dying." "His name Nicolaus Copernicus." "A doctor and a lawyer by trade, but nearly for nearly 40 years he was also an amateur astronomer." "A pursue that had let him to challenge one of the most fundamental and sacred believes of his time." "As a young man, Copernicus had studied the heavens and found that the Greek's earth center system failed when it came to predicting planetary motion." "He began to wonder if the earth itself moved,but..." "Here is Copernicus's idea." " With the Sun at the center." " With the Sun at the center." "And now suddenly, all the planet are going always the same way around they are not stop" "Copernicus realized that the movements of the planet were better explained if the Sun were the center of the solar system." "And the earth circled it like an ordinary planet." "It was a revolutionary insight." "Despite any evidence that the earth was moving, he came up with this book, which gives his new theory." "This idea, this, this book changed the world." "Yes, because it made the earth a planet and it fixed the Sun in the center." "If you don't have that blueprint you don't march ahead to the physics, the physics of the cosmos." "As it happened, the final pages, which were just these here in the front of the book came to him on the very day he died." "I suspect, I mean, he was lying there partially paralyzed from a stroke he was probably just hanging in there until he could make it sure that it was done." "Planetary Orbits are Elliptical" "Everyone from the Greeks to Copernicus assumed the orbits of the planet had to be circular." "But in 1571, German mathematician Johannes Kepler shattered that assumption with our next great discovery." "Lacking calculus, Kepler improvised ways to compute circular orbit of mars." "The work was tedious." "Kepler wrote that he was almost driven to madness considering in calculating the matter." "His calculations began to reveal that the accepted notion of planet moving in circles simply did not work." "Then a new idea came to him" "Kepler realized somehow the Sun had to be driving the planet in some way he didn't fully understand" "And to get a self-consistent picture, he found that an ellipse was the path rather than a circle." "With this breakthrough, Kepler devised the first method for accurately predicting the movement of the planet and stars across the sky." "When his tables predicted the planet Mercury to pass across the front of the Sun" "And nobody else's tables were close.." "That was dramatical proof of the accuracy of his astronomy" "They linked the motions of the planets solidly to the Sun This was a very important point to helps stress the idea that the Copernicus's Sun-centered system really had physical significance." "Despite the success of Kepler's theory, many remain skeptical that the Sun could be the center of the Solar System." "But the final nail in that coffin was about to be driven home by a man who like Kepler prefer to use observational evidences to form his theories." "And that man was Galileo Galilei" "Jupiter has Moons" "Meet Galileo Galilei, a man determined to pursue truth no matter where it led." "In the case of our next great discovery, his determination led him to revolutionize our knowledge of the solar system." "The year is 1609 and Galileo was fascinated with the new invention called a telescope." "Essentially, that was a toy out of a carnival." "When Galileo heard about it, he went to work, making one" "He ferfected it and essentially converted the toy into a scientific instrument" "Galileo turned his telescope skyward and was the first to see the mountains on the moon." "And the star clusters of the Milky Way" "Then an extraordinary sight" "A group of 4 small bright stars arranged around the planet Jupiter." "We have the manuscript of his first week of observations." "And it was wonderful because you see him gradually coming to the conclusion" "That these little stars are carried along with Jupiter." "This was the moment of discovery." "Galileo realized that the stars were actually four moons orbiting Jupiter." "He had the insight that these moving dots were orbiting a planet." "And I sometime say he invented the satellite, And you say, wait a minute, they were there, how could he even invent them." "He invented the idea that they were going around the planet." "Here was proof that Copernicus was right about the structure of solar system." "If moons could orbit Jupiter, and the earth could orbit the Sun" "And Galileo's discovery demonstrated that knowledge in astronomy can only be advanced by actual observation." "A theory can only be viable when it supported by the facts." "Just like our next great discovery." "Halley's Comet" "For centuries, comets had been considered harbingers of evil." "By the end of the middle ages, comet's appearance invoked fear and terror." "But the renaissance scientist Edmond Halley, like Galileo was interested in facts, not superstition." "In 1695, he began searching for records of ancient and recent comet sightings" "He found 24 comets whose passages across the sky have been recorded with enough detail to allow him to roughly plot their orbits." "To his surprise, he found that three of the comets seem to follow the same approximate orbit." "Circling the Sun every 76 years." "On that basis, he figured, ok, this is a comet that is going to be back in another 76 years." " He figured out the three comets were actually the same comet." " The same comet." "Halley was so certain of the comet orbit that he made a bold prediction" "He said the comet would return in year 1758." " And guess what" " It was." "The comet came back." "Unfortunately, Halley was no longer live to see his discovery." "Since then, Halley 's Comet, as is known, has been greeted 3 more times by excited sky watchers across the globe" "No longer a harbinger of evil, Halley 's Comet became a milestone discovery in history of astronomy." "replacing a superstition belief with the rational scientific understanding of the physical universe." "Milky Way a Disk of Stars" "In the eighteenth century, William Herschel was a classically trained musician whose love of astronomy let him to give up music and turn his attention to the heavens" "This is setting stage for our next great discovery." "When he discovered the price of refracting telescope,which was beyond his meet." "He decided to make his own." "And he became the most fabulous and successful telescope builder of that period." "He used his telescope to methodically survey the sky, cataloging what he saw." "As he was searching the sky, he came across an object that looked a little bit different, turned out to be a new planet." "Oh, wow, and what planet was that" "That was the next planet beyond Saturn." "The planet Uranus." "Uranus was the first new planet to be identified in more than 3500 years." "But finding a new planet was nothing compared to Herschel's larger goal." "But finding a new planet was nothing compared to Herschel's larger goal." "And then divided the sky into equal sections, and began to systematically count the stars in each field." "It was a painstaking, monumental task." "Slowly, Herschel's star count began to reveal something extraordinary." "The Milky Way was much larger than anyone knew." "It was a gigantic disk of stars." "Some of its field were jam-packed." "One showed more than a quarter of a million stars alone." "Other fields, farther away, were practically empty." "Herschel's discovery was a revelation." "This is a reasonable model of the Milky Way as we know it now." " But Herschel was only work at an area about this big, is that right" " What Herschel was seeing, was a small range like this, maybe that big." "So was really a small part of the entire milky way." "But even that small part significantly changed the study of astronomy." "Herschel's discovery revealed that our solar system was just an island in a deep and expansive universe." "General Relativity" "Thanks to the musing of an obscure clerk worked in the Swiss patent office." "Our next great discovery revealed that the universe is a strange, mysterious place." "That clerk was Albert Einstein" "In the early 19 hundreds, he was puzzled, along with the rest scientific community by the orbit of the planet Mercury." "Despite the ability of Newton's laws of gravity to precisely predict the motion of the planets The laws failed when it came to correctly predicting Mercury's orbit." "The puzzle had to do with Mercury's perihelion that point of its orbit which is closest to the Sun." "Every century Mercury's perihelion advance slightly." "A change that Newton's equations could not account for." "In the bold and startling move, young Einstein proposed his own theory to explain the puzzle of Mercury's orbit and in the process developed a theory that refined the Newton's law of gravity." "Michio Kaku is the theoretical physicist at the City University of New York." "And Newton says that gravity travels instantaneously through around space." "And that's what Einstein thought there was a weakness in Newton's theory." "He wanted the theory that could explain gravity; he wanted the theory that could explain acceleration, zigzag and circular motion." "There has to be waves, gravity waves." "It takes time for gravity to work its magic." " To propagate" " To propagate" "So if the Sun disappears, it will take 8 minutes for us to know about that fact even gravity travels at this speed of light." "Einstein needed a new picture to explain that and that picture was curved space that space itself has curved." "And that's why objects move." "Einstein believed that his concept of curved space was responsible for shifting mercury's orbit." "Einstein called his idea the theory of general relativity." "Imagine a trampling net and place a bowling ball in the middle of the trampling net." "The bowling sinks into the trampling net" "And now shoot a marble, a marble around the trampling net." "The marble will orbit, orbit around the bowling ball." "Now, from a distance looking down, Newton would say that there is a force and instantaneous invisible force puling, pulling the marble down to the bowling ball" "But Einstein would say that's no force, there's no pull It's just a trampling net" "And why is the marble orbiting the around the bowling ball Because the trampling net is pushing the marble." "Therefore why I am sitting on this chair." "Not because gravity pulls you to the ground." "It's because space pushes me down toward the planet Earth." "The idea that space itself is worked by mass was too strange for many to accept" "An approaching solar eclipse gave scientists the perfect opportunity to put Einstein's new theory to the test." "Photographs were taken of the background stars before the eclipse and then afterward" "These pictures were then compared with the photos taken during the eclipse." "The photo show that the positions of the stars in the eclipse photo shifted slightly inward, bending is the lights from the stars passed the Sun's gravitational field." "Einstein's theory of general relativity was right." "His great discovery rocked the world." "General relativity strikes deep emotional core and anyone who's ever looked these equations." "These equations are one inch long and they answer these eternal question that dogged us ever since we first look into the sky and ask ourselves the question what it all means." "The Universe is expanding" "General relativity had showed that the space was weirder than anyone could imagine, anyone but Einstein that is." "To gain a clearer understanding of the strange universe, astronomers needed more observational data." "And that required larger more powerful telescopes." "Like the one that led to our next great discovery." "When the Herschels had finished his survey of heavens in the 1830s." "They cataloged thousands of these beautiful but hazy objects then called white nebulae." "At the time, no one knew whether they were part of our galaxy or distant island universe like the Milky Way." "In 1924, astronomer Edwin Hubble was studying the stars in several white nebulae using 100-inch reflected telescope at the Mount Wilson Observatory in California." "The telescope enabled Hubble to estimate that the galaxy were routinely many hundreds of thousands, even millions of light years away." "Here were objects as huge and populated with stars as our very own Milky Way galaxy, which is why we today call white nebulae galaxies." "The more Hubble studied these galaxies, the more he became intrigued." "At the time, scientists knew that the beam of light from the star appears as different color on a spectrum." "The color changed according to the motion of the star" "A shift toward blue on the spectrum meant the star was moving closer to the earth." "A red shift meant it was moving away" "The amount of the color shift also revealed the speed of that movement." "Hubble found when he measured the distance of the galaxy, its spectrum almost always was shifting to the red." "And something else, the farther the distance, the greater the red shift." "In other words, the universe was expanding" "It was an astonishing discovery with profound implications." "Measuring backwards from the expansion, scientists found that the universe appeared to have a cataclysmic beginning where one of the astronomers labeled the big bang." "Milky Way Emits Radio Waves" "Just three years after Hubble discovered the expanding universe, our next great discovery revealed a mysterious object hidden behind the dust at the center of the Milky Way" "And gave birth to a whole new branch of astronomy, using wave length invisible to the human eye." "In 1930, Karl Jansky was a 25-year-old physicist working for the bell laboratories in Holmdel, New Jersey." "Jansky's job was to identify the kinds of interference occurring at the 15 meter wave length then used for ship-to-shore and transatlantic communication" "After spending more than a year recording data, Jansky decided there were three forms of static at this frequency." "The first was clearly produced in the earth's ionosphere." "The second was caused by local thunderstorms." "And the third signal was mysterious, continuous." "It was coming from what appeared first to be, the Sun" "Each morning, this signal slowly rose with the Sun." "During the day, it rotated across the sky." "And then it set when the Sun did." "But as time passed, Jansky found that the mysterious radio signals slowly drifted away from the Sun as if it were coming from a point outside the solar system." "Eventually, Jansky pinpointed this location somewhere in the region of the constellation Sagittarius." "He believed he had discovered unknown interstellar object at the center of the galaxy." "And he was right." "Later astronomers confirmed that Jansky had discovered a super massive black hole." "Equal a mass to three million Suns." "Perhaps even more significant, he was the first human to look at the universe using radio astronomy" "A whole new way to study the sky" "It was a landmark discovery" "Jansky has proved that the sky does not merely sparkle with the gentle glow of the star light." "Hidden out there are many strange objects, many light years away that actually radiate more energy than whole galaxies." "Like quasars and pulsars, dead stars spinning madly with masses that are so dense that single teaspoon would weigh millions of tons." "Before astronomers could even begin understand the life and death of stars" "New telescope would have to be built that we can look at the sky in many different wave lenghs." "Before that could happened though, radio astronomy produced another great discovery, that, although predicted, was as unexpected by discoverer as Jansky's has been" "And once again, it happened in bell lab that Holmdel in new jersey." "Cosmic Microwave Background Radiation" "In 1964, bell labs had the spare 200-foot-microwave antenna sitting dormant." "Rather than destroyed it, the lab decided to let the astronomers use it for research." "Two physicists, 31-year-old Arno Penzias and 28-year-old Robert Wilson decided to use the antenna for measuring the temperature of the gas halo surrounding the Milky Way galaxy." "What happened next is one of the most exciting discoveries in modern astronomy" " Hello bill" " Doc." "Wilson." "And I came to bell labs to get the story first-hand from Robber Wilson himself." "Two of us, Arno Penzias and I, had just come to bell lab from graduate school." "And we were going to measure radiation from the Milky Way." "And that's was this antenna really fit in because we could reject the radiation from the earth." "And what was left is what's coming from the sky." "There are only getting about two degrees from the earth's atmosphere." "Maybe picked up one degree from the walls of this thing." "But, when we first turned it on, it was about twice that about seven degrees." "And this wasn't right." "Something from the earth must be on our instrumentation." "We have crossed around a hill here and overlooked New York City." "We had the ideal instrument for checking on that though." "We merely turned down horizon, scanned the horizon and, but pore nothing particular extra." "There was a pair of pigeon that lived here, and of course it was covered with like pigeon droppings." "So, we thought well, maybe the pigeon droppings are doing more than we think" "Arno and I got up in here and we cleaned all the pigeon droppings out." " You got to get rid of pigeons" " What had you do with pigeons" "Fist, we put them in the company mail and sent them as far as we could which was Whippany, New Jersey, to a pigeon fans there who said these are junk pigeons and let them go" " A couple of days they were back." " 40 miles away and they came back." "So then our technician brought out a shot gun" "And how did that work" "I wasn't here and I didn't see." "But basically it didn't solve our problem." "We still have an extra three or four degrees." "We were really being into perplexed." "Because we believed in physics, it's coming from somewhere." "We can calculate what the horn was doing except for this ex-noise." "At the time that Penzias and Wilson detected the radio static there are two competing theories about the origin of the universe." "There was the big bang theory which Hubble's expanding universe supported." "And there was the steady state theory, which propose that universe is timeless with no beginning or end, expanding forever" "When a friend heard what Penzias and Wilson had found he suggested they get in touch with some cosmologists at Princeton University who advocates the big bang theory." "They believed that the big bang would have left a faint thermal afterglow explode in the universe, traces of heat from the roaring of the bang itself, detectable across the entire sky." "And they were about to conduct research in hopes of measuring that afterglow." "We invited them over." "They came over and looked what we had done and immediately agreed that we had measured what they were setting out to do." "So what is your discovery mean" "It means that we live in a big bang universe" "And we are seeing the radiation from three hundred thousand years after the big bang" "Many cases when there is a paradigm shift of science, it takes a generation before people really accept it." "But in this case, I think the world is ready for it." "Human societies have always worried about where they came from." "There are religious stories in every civilization that has ever been found." "And I think we have the definitive answer that we came out of big bang." "Gamma Ray Bursts" "The coming of the space age ushered in a golden age of astronomy that is still going on today." "That golden age began strangely enough, not in space, but was the turning point in cold war relations." "That also contributed to our next great discovery." "In the nineteen sixties, despite a nuclear-test-ban-treaty The Soviet Union refused to allowed onside inspectors enter his nuclear facilities." "As a result, the US opted to monitor the soviets by developing an orbital satellite system capable of detecting gamma rays burst produced by nuclear explosions." "Because the satellites detector looked up as well as down." "Scientists decided to use them to see if supernovae produced gamma rays when they exploded." "Between 1969 and 1972, they detected evidence of 16 short gamma ray bursts, scattering across the sky." "There was just one problem" "None of the burst correlated with any of the known supernova events." "And the mystery deepened" "Over the next two decades, astronomers detected an average of one gamma ray burst a day." "But each burst happened so quickly that was over before astronomers could get a telescope aimed at it." "Finally, astronomers began to solve the puzzle with the help of the BEOOP SAX space telescope, which was designed specifically to detect the short burst of gamma and x-rays and precisely pinpoint their locations." "On December fourteenth 1997, BEOOP SAS located a gamma ray burst, leading to the first photographs ever taken a burst and wave lengths other than gamma" "To their astonishment, astronomers discovered that burst took place in a galaxy twelve billion light years away" "Making one of the universe most powerful explosions." "Since then, dozens of other gamma rays bursts have been similarly documented." "All just as powerful and far away." "As for what it all means the discovery of gamma rays burst have once again show us that hidden now there behind the veil of the earth's atmosphere are objects that are not only strange and hard-defined, black holes, pulsars, quasars." "But there are lethal too." "Gamma ray bursts are now considered the possible cause of past distinction events on earth" "The scientist sir Arthur Eddington once noted that" "Not only is the universe stranger than we imagine." "It is stranger than we can't imagine" "He could be talking about the gamma ray burst, the expanding universe or the theory of general relativity." "And it also happened to be a perfect description of our next discovery." "Planets Orbiting Other Stars" "Once it would been been impossible for astronomers to imagine discovering other solar systems with planets like our own." "But today, astronomers can imagine thanks to powerful space and ground-based telescopes like the one here in the Lick Observatory in the Mount Hamilton California where Geoff Marcy is hunting for new planets." "How do you go out finding a planet around a star" "Wow, it's very easy." "We watch the star to see if it wobbles in response to the planet, yanking around gravitationally" " Very easy" " Very easy" " you just need one of these." " that's right." "This is the 3-meter lick observatory telescope" "By definition, planets don't produce their own energy, they shine of course by the reflected light." "But planet are about a billionth as bright as their host star" "So you can't really see them even with the Hubble you need a trick and that is what we use with this telescope" " A trick" " The Doppler's effect are trick." "We measure the wobble of the star by the changing light waves that come from the star as the star wobbles" "The search for extra-solar planetary system gain momentary in the early nineteen nineties." "When a polish astronomer made a surprising discovery." "There was a wonderful discovery by Alexander Wolszczan of a system of three planets orbiting a pulsar and the way he found them was quiet exciting." "He watched the pulses coming from the pulsar." "And their arriveal of those pulses changes as the pulsars approaches and recedes us" "These are hideous stars." "Pulsars have ultraviolet x-rays gamma rays coming often." "They are the bizarre end products of a supernova explosion" "And despite that bizarre environment, here we have earth-size planets going around it" "If there are earth-size planet go around pulsars you can bet there are earth-size planets that around other stars." "There are earth-size planets around pulsars" "Earth-size and even moon-sized among the three" " He detected them." " Detected them by this wobble of the pulsars." " That's just the coolest thing in the world." " It's unbelievable." "Since wolszczan's discovery Marcy and other astronomers have found more than one hundred thirty extra-solar planets" "We thought we would have never found even one planet and we found the world's only triple planet system and the quadruple planet system with this telescope." " So, these are big planets though" " These are planets the size of out Jupiter, Saturn and smallest Neptune sized." " Oh, little Neptune" " So it's quite exciting that they are finding planets of Jupiter sized." "But even those a few times bigger than the earth" "Well, no Earth-like planets have yet been found." "The search continues" "How do you pick a star as a candidate" "We indeed try to choose stars that are more or less like our Sun some more massive some less massive, or sort of middle age or older so they've settled down" "What you want for an earth like planet to make it habitable is that temperature has to be just right." "Not so cold, the water's locked up in the ice." "Not so hot, that the water if that evaporated into steam" "But the planet just the right distance from its star so that the temperature is just right for liquid water over billions of years to let Darwinian evolution do its things" " Sound like the Goldilocks and her porridge." " That's right." "You don't want it to be too hot or too cold." "Suppose you have a telescope, a cosmos, a device, sensitive enough to find an earth-like planet" "Would you point at some of stars that you are already identified as having planetx" "Absolutely, the Jupiterx and Saturnx we are finding are the signpost the benchmarks of system that might harobr earth and dspecially if those Jupiterx far enough from the host star." "That leaves room for an earth in the habitable zone to be orbiting that star." "What made you go looking for planets on other stars" "Oh, I remember when I was a young kid, I thought to myself, I wonder if there are other earth out there and if so of any are habitable and then is there life on those planets, and particular intelligent life" "We humans I think in general would love to know are we alone in the universe" "Are there other creature out there that think and dream and indeed are searching for us" "In the end, I think we humans are trying to find out our roots out there chemically and biologically among the stars" "The Universe is Accelerating" "As the universe expanded following the big gang logic indicted that the gravitational attraction of all matter should pull at that expanding material and cause the expansion to slow" "But how much was the universe slowing down" "In the nineteen nineties, the Hubble's space telescope made it possible for teams of scientists to answer the question by studying the brightness of light from a special type of the exploding star called a type 1A supernova." "I paid a visit to the Lawrence Berkeley National Laboratory in San Francisco." "and met with astrophysicist Saul Perlmutter who has a supernova cosmology project" "So, what did you find out" "So, we started to make measurement to try to find how much the universe in its sustention is slowing down." "When we first saw the data,You say well, that's kind of funny, looks the universe isn't slowing down." "But you think, well we are already in the mid of doing all these checks, and collaborations and confirmations I am sure once we get over the numbers, you'll check out and figure out" " that the effect will go away and change the signs somewhere that will fix." " There are minus signs." "Sgns are like that." "You check each step and of the process." "Little by little you get the point we start you know this effect isn't going way." "This is the right answer." "It really looks like the universe is actually speeding up." "So, why is this so important" "This acceleration of universe doesn't fit at all." "We understand, pretty well the all forces of our universe and all the objects of our universe and this is the first time we come cross something that we wouldn't have predicted." "Now, we are having the fun to try to figure out what does this all mean, And if you come with me, I will show you what we are doing about." "Why is it accelerating" "Oh, that's the question, we are all dying to know the answer, and when we think about this if you have a energy of this odd sort that would pervade all space." "It can actually speed up the universe when gravity is trying to slow it down." "And we are calling it dark energy, just reflecting the fact we don't know what it is." " It's a mystery;" " it's completely mysterious, bizarre We've no idea what it is." "We wanted studies to figure out what could dark energy be like" "We want to do now is get data that could help pull apart the different answers" "So, where are you going to have data" "The big pictures of goal that were after is a project that you see you around you here which is a satellite project" "The design here we called SNAP which is short for supernova acceleration probe" "This would be a new space telescope with a very very big field of view." "So instead of looking througha little key hole of the universe, you'll be looking through a big picture of window of universe" "So let me show you what we are working on that we think might help us get out why the universe is accelerating, what this dark energy really is." "Here we have SNAP that we are hoping to be launched just in the future" "This one goes out to a location out past the moon." "From that point, you can measure expansion history with such detail that we could actually see the little changes when it goes to deceleration to acceleration" "Backwards universe was really dense and close together Gravity is more important, it slows the expansion down" "As it is kept expanding though even it went slower and slower and loss out and gravity became less important than the dark energy which took over and started to accelerate expansion," "And we are after exactly how that change over occur that would tell us about what different possible theories could be right to explain dark energy" "Always expanding." "Exactly always speeding up exactly." "It is an issue of it got slow down and come to a wobble and then take off." "What was that transition like" "Just like the ancient astronomers modern scientists have discovered something about the cosmos that we cannot yet explain" "It will up to observers and theorists to figure out what's going on in our expanding universe" "For this, only new ideas and better instruments" "No matter this mystery will solve soon or far in the future" "It could be certain of one thing." "We will keep watching the skies, to understand our place in the cosmos." "We will continue to explore, understand and discover"