L ooking ahead, the first of the new tools we anticipate aiding the search for small and potentially habitable exoplanets is the Transiting Exoplanet Survey Satellite TESS , an M. TESS will use four identical cameras to stare at a large strip of the sky for almost a month at a time; over the course of two years, it will have observed 26 such strips, completing a survey of nearly all of the sky. Think of a transiting planet as akin to an eclipse, but blocking out only a part rather than all of a star.
Transiting planets are the easiest to discover at the present time because the planet does not have to be seen on its own, distinct from the star — an enormous technical challenge. Looking for transiting planets makes the problem more tractable: we monitor the brightness of a star over time, watching to see whether there is a tiny and repeating drop in brightness, as we would expect if a planet passed in front of the star as seen by the telescope.
We anticipate detecting tens of thousands of transit-like signals with TESS. My colleagues in the exoplanet-hunting community will then use ground-based telescopes to make follow-up measurements, primarily of planet mass, to determine if the signal is just a false positive or if it is a bona fide planet. TESS is designed to deliver fifty rocky planets with measured masses to the astronomy community.
Of those, we will choose perhaps a prize half-dozen or so, and propose to observe their atmospheres with another new tool that will soon be available: the James Webb Space Telescope JWST , currently scheduled to launch in from the spaceport in French Guiana. JWST will be larger, in a more favorable orbit, and much more powerful than the famous Hubble telescope that has already for two decades given us unforgettable images of and wonderful information about the universe, and so we hope to use JWST to find signs of habitability or even biosignatures on the exoplanets it helps us to peer at.
What are the chances that we will find signs of life in the atmosphere of a small, rocky exoplanet? But we will have to be very lucky to make any robust discovery amidst the handful of anticipated TESS-discovered habitable planets. Notwithstanding our high hopes that TESS and JWST will lead to important discoveries, searching for transiting exoplanets will always remain a less-than-ideal technique. For one thing, it requires an exoplanet to be fortuitously aligned between its star and our telescope.
A planet in an Earth-like orbit around a sun-like star has only about a one in two hundred chance of transiting its host star from our perspective. And the technique also relies on looking at the star and the planet together, making it more difficult to observe atmospheres of Earth-like planets around a sun-like star. To be able to search for and identify Earth-like exoplanets orbiting the nearest sun-like stars, we must image the planet directly. Which returns us to the difficulty of our analogy from earlier.
Is there any way to make it easier for us to see the firefly fluttering by the searchlight? This challenge actually involves two problems rolled into one. First, we would have to find a way to block out the bright light of the parent star. To give a sense of how difficult that is, our own sun is about 10 billion times brighter than the Earth at visible wavelengths. And then we would have to deal with the problem of diffraction — the bending of light rays as they encounter a surface.
A telescope observing a distant star will not see a perfect point of light. Instead the telescope would see a pattern of diffraction rings, which can be up to , times brighter than an Earth-like planet. Astronomers and engineers have proposed very clever ways to solve these two problems — and even to make the diffracted light part of the solution. One especially attractive idea involves launching a giant screen to block out the starlight, so that only the light from orbiting planets would enter the space telescope.
In order to deal with the diffraction problem, the screen would not be circular but would look something like a huge flat flower, a concept first suggested in the s by Princeton professor Lyman Spitzer in the same paper that proposed what would become the Hubble Space Telescope, and a shape brought to its modern essence by University of Colorado at Boulder professor Webster Cash. The starshade would make part of the image very dark — dark enough to image exoplanets. If you think of the diffraction pattern as something like the ripples around a pebble tossed into a pond, the starshade would counter those ripples so that the area around the pebble is smooth.
With its special shape, the starshade would not only block the bright light of a distant star but would also compensate for the diffraction i. L et us take a step back now to ask why we should search for and study exoplanets at all. Hundreds of researchers around the world are dedicating careers to this endeavor, and NASA and the European Space Agency, along with other international partners, are committing precious public funds. Why is it worth the resources and the effort? The main reason to study exoplanets is to satisfy our scientific curiosity. For instance, the search for exoplanets has already helped us better understand how planets and planetary systems form and develop.
In our solar system, Uranus and Neptune are about four times the size of Earth. We do not know how what appears to be the most common type of planet in our galaxy forms. We have already discussed above some of the other fundamental questions that the study of exoplanets might shed some light on, including whether there are planets just like Earth out there, with continents and oceans and thin atmospheres with clouds, and whether any of those other Earths will have signs of life.
Exoplanets: Worlds Beyond Our Solar System
These are questions of more than just scientific interest — they inspire hope that we might someday more fully understand our own origins and our place in the universe, and they fire the imagination about the possibilities that the future might hold for humankind. A second reason for studying exoplanets is, admittedly, one that applies also to other areas of science and technology: the possibility of spinoffs. There is a long list of everyday tools that only exist as applications or byproducts of pure research, including the laser with its ubiquitous applications from surgery to music to medicine , medical imaging, DNA testing for medical and forensic uses, and on and on.
Such technological breakthroughs can transform the world. They are, however, unpredictable. We cannot know for certain whether the search for exoplanets will result in major advances in, say, optics or data processing or automation or space operations, or perhaps other unanticipated fields. But by supporting basic research, we increase the likelihood that we will stumble upon some new technology or technique with surprising potential for wider application. The details of many of our advanced commercial and defense-related technologies are kept secret; they are either proprietary or raise national-security concerns.
But our work in space is on display for the world to see. Consider the James Webb Space Telescope discussed above.
Several innovative technologies have been developed and brought together to make this powerful new tool possible, including a folding, segmented primary mirror, adjusted to shape after launch; ultra-lightweight beryllium optics; detectors able to record extremely weak signals; microshutters that enable programmable object selection for the spectrograph; and a cryocooler capable of cooling the mid-infrared detectors to just a few degrees above absolute zero.
The search for exoplanets can also serve to inspire future leaders, including future innovators in science and technology. The exoplanet hunt, too, offers major opportunities for public engagement. The leaders of the tech revolution of the s and s grew up during the era of the Apollo moon landings; the leaders of the next generation will grow up as we search for other Earths.
For my part, I want to explore. That is what motivates me. I recall from my youth a two-month wilderness canoe trip on the seemingly endless subarctic tundra of Nunavut, Canada. Hundreds of miles from any remote outpost let alone from the nearest town, the trip oscillated between adrenaline-pumped rapids and tediously long lake crossings.
This was the original form of the DC multiverse. Concerned that their mother, Perpetua, had turned her creation into a self sustaining weapon the Monitor , Mobius , and World Forger called on her masters, the Source. Krona was a member of the ancient race of powerful, blue-skinned immortals from the planet Maltus. The Maltusians would later relocate to Oa and style themselves the Guardians of the Universe.
He was obsessed with observing the creation of the universe, despite an Oan legend that said attempting to uncover the secret would cause a great calamity. Krona created a machine that allowed him to witness the dawn of time. However, his machine interfered in the process, with terrible consequences—instead of a single universe, infinite universes were born in that moment.
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From the perspective of the Earth-One Universe, the first transuniversal journey occurred when The Flash Barry Allen accidentally changed his vibrational frequency to match that of Earth-Two , where he met Jay Garrick , the Golden Age Flash and his childhood comic book hero. That meeting resulted in years of interaction between the original super-hero team, the Justice Society of America , and their younger Earth-One counterparts, the Justice League of America.
As noted years later by the elder Superman , the JSA were too polite to mention that they were around first. However the general populace of Earth-Three reflected a society based on laws and good values, despite the majority of their super powered beings having evil natures. The JSA and JLA would get together once a year when the temporal matrices of the two universes were at their closest point, using a dimensional transporter. When Krona accidentally created the Multiverse, an Antimatter Universe was formed at the same time.
The Anti-Monitor caused a wave of antimatter to sweep across the Multiverse, in an effort to gain absolute power and remake existence to his liking.
He was opposed by his opposite, the Monitor. The Monitor's plans did not fully succeed in conquering the Anti-Monitor, ultimately costing the Monitor his life. In the end, only five universes remained. The heroes, at the Spectre 's urging, pooled their resources and traveled back to the Dawn of Time where they confronted the Anti-Monitor. The villains, meanwhile 1,,, years later , traveled to Oa to try to stop Krona from peering back in time and creating the Multiverse and, by extension, the Antimatter Universe the Anti-Monitor came from.
The Anti-Monitor revealed to the assembled heroes that he lured them to him to absorb their life forces. He explained:. Because of this battle at the dawn of time, the Multiverse was erased from existence. When Krona peered through the cosmic veil, he witnessed the birth of a single reality:. As explained later by Harbinger, the new reality contained only a single universe, with one Earth, and a single history.
Earth-One became the template for this new Earth, onto which elements of the remaining four were added. Below is a partial list of notable alternate worlds , and universes with known numerical designations. Beyond these, many other alternate worlds have been visited or explored by denizens of the DC Universe. Some of the supposedly destroyed Earths were revealed to live on in Hypertime , and even Earths that were destroyed like Earth-Three or Earth-S were found to have Hypertime equivalents.
In any case this set of infinite Earths was restored with the reconstruction of the Multiverse in the events of Convergence. After the Crisis on Infinite Earths, it quickly became clear that Harbinger's claim that only a single Earth and history existed was untrue. The Legion of Super-Heroes continued as if the Crisis never happened. This discrepancy was discovered by Cosmic Boy and it was explained that the past the Legion thought they knew was in reality a Pocket Universe created by the Time Trapper.
However, this still left some discrepancies, notably the existence of Mon-El, and the Legion's numerous visits to the 20th century. Armageddon raised more questions as since post-Crisis Barry Allen had still faced Professor Zoom from the 25th century and Abra Kadabra from the 64th century the timeline of the DC universe should have been "set" well past , but there were still alternate timelines to that year which per Harbinger's claim shouldn't have existed.
Hal Jordan was driven mad with grief, driven over the edge by the callous behavior of the Guardians of the Universe , he destroyed both the Guardians, and the Green Lantern Corps. After absorbing their powers, he took on a new identity.
Our galaxy is home to many, many more Earths than we ever thought
Calling himself Parallax, Hal would later use his newfound powers to tighten the loop of time that Krona had created in the Post-Crisis history  to collapse reality, and rewrite it from the Big Bang forwards. This temporal collapse caused various alternate timelines to temporarily merge with the main reality, again raising the question of whether the first Crisis had indeed wiped out all alternate realities, or whether some remained. At the end of Zero Hour, Waverider claimed that all alternate timelines had been retroactively erased.
However, Armageddon still occurred in this new timeline, which would require the continued existence of alternate realities. Furthermore, Matrix Pocket Universe still existed after Zero Hour, despite having originated in an artificial timeline. Eventually it would be revealed these alternate timelines were part of Hypertime, as the Superboy who had briefly appeared in the main timeline during Zero Hour still remembered meeting the mainline Superboy.
Some of these realities appeared in the Hypertime montage at the end of The Kingdom effectively weaving the Pre-Crisis and Hypertime multiverses together. They intended to fabricate a machine that would recreate the multiverse and allow them to fuse and combine Earths until the perfect reality was created.
A chain of events was set into motion, including the takeover of Batman's Brother Eye satellite , the unification of Earth's villains under the Secret Society of Super-Villains , the manipulation of the Spectre , and the movement of planets to spark war and unrest. The magic destroyed and recreated by the Spectre would serve as fuel for the machine, Brother Eye would give the machine programming and directive, the villains united under the Society would gather those people who still contained the genetic code of Pre-Crisis realities i.
Though their efforts failed, the consequences of their actions fundamentally altered New Earth, and gave birth to 51 additional identical universes, which were later altered by the malevolent Mister Mind to become entirely separate realities. Luthor's plan to use the Multiversal essences of natives of the original Universes to recreate Earth-Two also required:.
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After activating his device and the program "Earth: Spawn", a multitude of Earths and their respective universes appeared. That proved a difficult task, as the sky was filled with visions of multiple Earths, some mirroring Pre-Crisis Earths, others representing visions of past and future timelines, some known, some unknown. This unstable collection of realities collapsed back into a single New Earth after the Infinite Crisis. Below is a partial list of alternate worlds created by Alexander Luthor in his attempt to create the perfect Earth. After the events of Infinite Crisis, the remaining Earths created by Alexander Luthor collapsed back together, combining elements to form one New Earth.
However, the single universe was too small to contain the energy inside it and via Hypertime it began replicating—into 52 identical Universes: a new Multiverse. As Rip Hunter revealed to Booster Gold aboard his Time Sphere , in the few seconds after the creation of this new Multiverse, the Earths and their corresponding Universes "will occupy the same space, each on a different vibrational plane".
During their efforts to stop the vastly powerful Mr. Mind from destroying every universe, Hunter described Mind's efforts as "eating years and events from this universe's history—altering the Earth with every flap of his wings". This resulted in the Earths changing, becoming different from New Earth in varying degrees.
Hunter further states that "the notion that there's a Multiverse beyond the reality we know—that's too dangerous a secret to spread. Hunter also revealed that there is a coming Megaverse. How this related to Hypertime and the formation of the New 52 multiverse is unknown. The parallel dimensions were separated by an an inter-dimensional sub-reality barrier called The Bleed. Knowledge and control of the Anti-Life Equation, the Speed Force , and quantum mechanics are needed to travel between universes. The Multiversal Nexus is the reality in between known parallel matter based universes.
The Nexus was formerly occupied by the Monitors. From here, they observed and analyzed variances within the Multiverse; specifically citing instances wherein individuals migrated from one reality to another. According to the Guardians of the Universe :. The following is a list of the other Earths thus created, as seen for the first time. Earths of unknown designation known to have existed in this Multiverse include an Earth similar to that of Justice League: The Nail ,  a dimension home to a black President Superman that would be continued after Flashpoint in the form of Earth 23 ,  a recreated Earth-Prime,  and the home universe of Hot Pursuit , as well as possibly the world of All-Star Superman.
Following the company-wide reboot in see below , this multiverse was restructured with some worlds existing as before such as Earth-1 with others changed drastically. However, DC still published stories set on Earth and Earth after the reboot, and the events of Convergence fully restored these worlds. Manhattan altered the timeline, such that the state of the multiverse was changed significantly—for the greater good according to Pandora, and for unkown reasons by Manhattan.
Though Wally West believes it may in fact have been to weaken it for an upcoming attack. The result was 10 years being taken from the main timeline, as well as a merger of three disparate universes; the DC Universe , the Wildstorm Universe , and the Vertigo Universe , the latter of which was comprised of those characters who began their existence within the mainstream DCU, but continued on under the Vertigo imprint beginning in April Other Vertigo properties remain disconnected from this multiverse.
This new model of creation involves multiple incarnations of the Multiverse suspended within a "Multi-Multiverse",  with individual Multiverses existing as 'bubble' sets of grouped universes such as the local 52,  with mention of a destroyed "Multiverse-2" by the Empty Hand. The 'local' Multiverse is constructed on a central axis of the House of Heroes, former headquarters of the Monitors rotating through the Fifth Dimension, now headquarters of the team Justice Incarnate , and the Rock of Eternity , connected to the cornerstone Earths 0 and 33, aka Prime Earth and Earth Prime.
The Orrery is structured that the position of universes within it relative to certain realms in the Sphere of the Gods denote aspects of their nature: those closer to New Genesis are often kinder and nobler, those close to Apokolips often far darker, while the proximity to the realms of Dream or Nightmare denote Order and Chaos, respectively. Additionally, each Earth is parallel another Earth; in at least once instance with Earths 20 and 40, these parallel Earths have been seen to phase into a state of being capable of interaction.
The universes are capable of communicating with each other through comic books, chronicles of the adventures of the heroes of the universes being published on various different worlds, similarly to the relationship displayed between the pre-Crisis Earth-Two and Earth-One, and Earth-One with Earth-Prime. Earths 14, 24, 25, 27, 28, 46 and 49 are unknown worlds, created by an Inner Chamber of 7 Monitor Magi for an as yet unknown purpose. Earth 14 was later revealed as the home of The Justice Assassins.
The current Multiverse is home to an infinite number of universes, including those of previous incarnations of the Multiverse, with the core 52 worlds of the "local Multiverse" being:. On the border of the Orrery of Worlds containing the universes the border itself composed of the Speed Force Wall are several other realms, at least half of which are currently unknown. Those known include:. The metaphysical reality just outside the physical Orrery of Worlds. This reality is home to eight realms—six of which connect to Earths in the Orrery—that include:.
Beyond either the Orrery or the Sphere of the Gods. Former home of the Monitors, abandoned in the wake of the Final Crisis. The Source Wall on the border of the Monitor Sphere is the border between the Multiverse and the massive cosmic consciousness known as the Overvoid.
An inconceivably massive cosmic consciousness, the infinite, timeless white void within which the Multiverse floats, also known as the Over-Monitor. Upon discovering the existence of Creation within itself, the Overvoid extended a probe into the Multiverse, which upon reporting back the concept of events, irreparably altered the Overvoid's awareness. The probe having been split in two withdrew, and left behind as a result of the contact was a titanic entity in the shape of one of the inhabitants of the Orrery ; the Overvoid itself remains implacable, though the presence of the giant would infect its mind with perpetual questions, and thereby the concept of 'story'.
Brainiac observed and pulled cities from various Earths many of which belonged to the Pre-Crisis multiverse. Brainiac sends Superman , Supergirl , the Flash , and Parallax back with the promise that if they prevent the collapse of the original multiverse " everything will reset and return to what it was before I brought you all here" sic. They succeed but Brainiac comments that "each world has evolved but they all still exist. The only way any of this makes any degree of sense is if Brainiac reached into hypertime as we know there were hypertime versions of Earth-Three and Earth-S for the Earths he got his cities from.
The idea that Brainiac used hypertime is supported by the fact several of the cities were taken from hypertime realities. In the infinite Earths known to exist beyond the borders of the local 52 universes, including the 'defunct' infinite pre-Crisis Earths, the 52 post-Crisis Earths, and the far-flung realms of Hypertime, those additionally indicated as being included in the scope of the "Multi-Multiverse":. The Dark Multiverse is thought to be composed of dark energy and dark matter which is neither matter nor anti-matter. It is believed to be far vaster and older then the 52 multiverse which Prime Earth Barry Allen believed was all there was, somehow enclosing it in its mass  and made up of the fantasties and fears of its inhabitants.
Sign In Don't have an account? Start a Wiki. Contents [ show ]. Main article: Pre-Crisis. I vibrated so fast—I tore a gap in the vibratory shields separating our worlds! As you know—two objects can occupy the same space and time—if they vibrate at different speeds! My theory is, both Earths were created at the same time in two quite similar universes! They vibrate differently—which keeps them apart! Life, customs—even languages—evolved on your earth almost exactly as they did on my Earth! Destiny must have decreed there'd be a Flash—on each Earth!
The idea is that Earth-Two is about twenty years behind because of some time flux. Main article: Crisis on Infinite Earths. Main article: Post-Crisis. Only here, before creation can the future be changed! When Krona taps the cosmic forces, opening the door between matter and antimatter My hand which shall destroy the positive matter multiverse for now and forever!
My hand which shall make the antimatter universe supreme! The Multiverse will no longer exist! In the beginning there were many. A Multiversal infinitude For in that instant a Universe was born. A Universe with mighty worlds orbiting burning suns. A Universe reborn at the Dawn of Time. What had been many became one. Partial Pre-Crisis Earth list:. Main article: Zero Hour.
Main article: Hypertime. Main article: Infinite Crisis. I need thousands and thousands of worlds. Worlds I can sift through like sand, one grain at a time, combining and mixing until I find it.