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In the shadow of the world’s worst nuclear disaster, thousands of feral dogs roam the eerie quiet of the <keyword id="24385385" type="General" weightage="20" keywordseo="Chernobyl-Exclusion-Zone" source="keywords">Chernobyl Exclusion Zone</keyword> (CEZ), a 1,000-square-mile area abandoned by humans since 1986. These dogs, descendants of pets left behind during the hurried evacuation, are now the focus of a fascinating new study. Scientists are diving deep into their DNA to explore how decades of exposure to radiation might have shaped their genomes — and possibly even sped up evolution.<br /><br />The research analysed the DNA of 302 feral dogs living at the nuclear power plant and compared them to their counterparts just 10 miles away in Chernobyl City. The findings revealed significant genetic differences between the two groups. While this doesn’t definitively prove that radiation is the culprit, it offers tantalising clues about the long-term effects of living in a radioactive environment.<br /><br />So, why study these dogs? According to Elaine Ostrander, a dog genomics expert involved in the research, the goal is to unravel how these animals have genetically adapted to survive and reproduce in such a harsh environment. Ostrander wonders if they possess mutations that allow them to live and breed successfully in this region.<br /><br />However this isn’t the first time scientists have wondered whether radiation could drive evolution. Back in 2016, researchers observed that Eastern tree frogs within the CEZ were more commonly black instead of their usual green. They theorised that the darker pigmentation, linked to a mutation in melanin, helped neutralise radiation. Could the same be true for Chernobyl’s dogs?<br /><br />While the study offers a starting point, proving a direct link between radiation and genetic changes is no easy task. Other factors, like inbreeding or environmental stress, might also explain the differences. As one environmental scientist noted, isolating radiation’s impact from everything else is “incredibly difficult.”<br /><br />Still, the implications of this research stretch far beyond the CEZ. Understanding how organisms adapt to extreme environments could shed light on the impacts of radiation, help refine evolutionary theories, and even inspire new approaches to tackling challenges like climate change.<br /><br />For now, Chernobyl’s wild dogs remain a living puzzle, their resilience offering a unique window into the interplay of genetics, environment, and survival in one of the planet’s most hostile landscapes.<br /><br />The findings of this research have been published in <em>Science Advances</em>.<br />

Could radiation really be making Chernobyl’s wild dogs evolve? A new study suggests so!

<p><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"><p class="source"><span><a href="http://keplerscience.arc.nasa.gov/K2/Science.shtml">NASA</a></span></p></div><p></p></div></div>Sometimes, when a massive star reaches the end of its life, its core collapses in on itself, causing an epic explosion that can light up the entire sky.</p><p>If this explosion happens close enough to our planet, it can bombard us with high-energy radiation.</p><p>A new paper published in The Astrophysical Journal Letters <a href="https://arxiv.org/abs/1605.04926">explores the effects of two exploding stars</a>, or supernovae, that occurred somewhere between 1.7 to 3.2 million and 6.5 to 8.7 million years ago.</p><p><span>The scientists used computer models to follow the radiation down through the earth's atmosphere to find out its effects, as well as how much of it actually reached the ground. </span></p><p>What they found was surprising.</p><h2><strong>Bathing in cosmic radiation</strong></h2><p>According to their models, at first, the explosions would have caused blue light in the night sky "<a href="http://www.eurekalert.org/pub_releases/2016-07/uok-asb070616.php">brilliant enough to disrupt animals' sleep patterns for a few weeks</a>," said a University of Kansas press release.</p><p>Then, the explosion would have exposed our atmosphere and biology to a "long-lasting gush of cosmic radiation." For hundreds to thousands of years, this radiation would have increased by a factor of a few hundred.</p><p>This boost in radiation would have had "substantial effects on the terrestrial atmosphere and biota," the authors wrote in the study, causing as much as a 20-fold increase in irradiation by cosmic particles at Earth's surface. This would just about triple the radiation dose that creatures at ground level would be exposed to.</p><p>Melott said this radiation would have packed doses equivalent to one CT scan per year for every creature living on land and in shallow parts of the ocean. This increase in radiation would have been high enough to boost the mutation rate and frequency of cancer, as well as possibly speed up evolution.</p><h2><strong>An era of lightning</strong></h2><p>As the radiation poured down on Earth, it would have ionized the atmosphere, tearing apart atoms and molecules, so that electrons were running around by themselves, kind of like gas inside fluorescent tube.</p><p>This would conduct electricity easier, so scientists think that there's a good chance that the rate of lightning may have increased a lot during the hundreds to thousands of years that cosmic radiation was hitting Earth.</p><p>This could have caused more wildfires and could have potentially changed the climate of the planet. In fact, the more recent explosion coincides with a minor mass extinction around 2.59 million years ago.</p><p>"There was climate change around this time,"<span>Adrian Melott, professor of physics at the University of Kansas and co-author the new paper, said in a press release</span>. "Africa dried out, and a lot of the forest turned into savanna. Around this time and afterwards, we started having glaciations - ice ages - over and over again, and it's not clear why that started to happen. It's controversial, but maybe cosmic rays had something to do with it."</p><h2><strong>What comes next</strong></h2><p>The next step is for scientists to look at the geological record around the time of the more recent explosion, and see if there were more things like wildfires and mutations.</p><p>At the time of the study, the scientists believed the explosions both happened about 300 light years away, but new results that have come out since the paper was published that suggest that one of the explosions might have happened at about half that distance. So, the scientists also plan to redo their models with that shorter distance. They expect that the effects will be even bigger. </p><p>Even though these explosions might have transformed life on Earth at that time, you shouldn't be too worried about <span>supernovae today</span>. </p><p>"This is not something for people to worry about for the immediate future," Melott said. "Events like this only come along over long time periods of millions and millions of years."</p>    <div class="margin-top">        <h3>NOW WATCH: <a href="http://www.businessinsider.com/supernova-explosion-when-two-stars-collide-2016-4">This is what a supernova looks like</a></h3>        <div>            <div>        <div class="ooyala-video-player" data-video-autoplay="false" data-video-id="RoMGZzMjE64--5sXcacg0iibE2058Kax" data-player-variable="ooyalapopvideo" id="ooyalaplayer_popvideo" style="width:1280px;height:720px"></div>        </div>        </div>            </div>

2 nearby exploding stars might have had some surprising effects on our planet

<ul class="summary-list"><li>Scientists have long thought Earth's inner core is like a huge solid metal ball. </li><li>But an experiment revealed it may be a lot softer — more like butter, a lead scientist said. </li></ul><p>A new study challenges the <a target="_blank" href="https://www.businessinsider.com/earths-mysterious-core-is-a-lot-weirder-than-you-think-2023-9">long-held assumption</a> that Earth's inner core is hard, like a solid metal sphere.</p><p>Instead, our <a target="_blank" href="https://www.businessinsider.com/earth-core-encased-by-ancient-ocean-mountains-taller-everest-2023-9">planet's heart</a> is likely much gooier than previously thought, "kind of like how butter is soft in your kitchen," said Sichuan University's Youjun Zhang, a lead author on the study, in a <a target="_blank" rel="noopener noreferrer" class="c-link" href="https://news.utexas.edu/2023/10/03/iron-atoms-discovered-on-the-move-in-earths-solid-inner-core/">press release from the University of Texas</a></p><p>The findings could help explain some of our planet's long-standing mysteries, like why Earth's magnetic field constantly defies expectations.</p><h2>We've never seen the Earth's core</h2><p>There's no way for us to sample the very insides of the Earth directly. We can't drill that far down and even if we could, human instruments would struggle to cope with the temperatures and intense pressure further into the planet.</p><p>That's why scientists usually rely on information they can glean from <a target="_blank" href="https://www.businessinsider.com/pieces-planet-theia-buried-in-earth-mantle-2021-4">shockwaves</a> that spread from earthquakes.</p><p>By looking at how these waves ping off of structures inside our planet, they can infer what's happening in there.</p><p>Coupling this seismic data with computer models, scientists had previously predicted the pressure at the very center of the Earth was so intense that the iron atoms found there were forced into solid form, in spite of the scorching temperatures.</p><p>Per these models, the atoms were stuck together in a hexagonal pattern — meaning there was effectively a <a target="_blank" href="https://www.businessinsider.com/earth-inner-core-may-have-stopped-spinning-reversed-direction-study-2023-1">huge solid metal ball</a> at the heart of our planet (the inner core), swiveling in a pool of molten metal (the outer core).</p><p>It turns out, however, that's not the whole picture.</p><div type="image" title="A scientist holds up a structure made of red balls and metal rods, representing atoms in a hexagonal pattern the inner core. The scientist, wearing a cap adorned with a bull's head and smiling at the camera, is standing in front of wall art. " height="1536" width="2048" msid="104215105" hostid="261" sizebytes="211512"></div><h2>The Earth's inner mush revealed</h2><p>A <a target="_blank" href="https://www.sciencedirect.com/science/article/pii/S0031920121001606?via=ihub#!">2021 study</a> had already started to question the big-iron-ball assumption. Seismic waves, they found, weren't really going through the Earth in a way consistent with a fully solid core.</p><p>"The more that we look at it, the more we realize it's not one boring blob of iron," said Jessica Irving, a seismologist at the University of Bristol in England, <a target="_blank" href="https://www.livescience.com/earth-inner-core-mushy">to Live Science in 2021.</a></p><p>The new study, published Monday in the peer-reviewed journal <a target="_blank" href="https://www.pnas.org/doi/10.1073/pnas.2309952120">Proceedings of the National Academy of Sciences</a>, sought to solve this puzzle.</p><p>It recreated the intense pressure and temperature conditions found in the inner core inside a lab, and combined that data with a much more advanced computer model.</p><p>They found that the atoms were indeed stuck in a hexagonal pattern.</p><p>But, surprisingly, individual iron atoms were still able to shift around inside that pattern — like guests moving around a dinner table, per the press release.</p><div type="image" title="An animation shows individual atoms shifting around inside a lattice made of hexagonal shapes. " height="361" width="600" msid="104215107" hostid="261" sizebytes="33288"></div><p>"The big discovery that we've found is that solid iron becomes surprisingly soft deep inside the Earth because its atoms can move much more than we ever imagined," said Zhang.</p><h2>Knowing what is going on inside the Earth can help protect us</h2><p>There's more to this finding than the satisfaction of understanding our planet better. Knowing what is going on inside the Earth is crucial to figuring out its mysterious magnetic field, which protects us from space radiation and pins down our atmosphere.</p><p>Thinking of the magnetic field, you may be picturing orderly concentric rings, like the layers of an onion.</p><p>But it turns out our magnetic field is a lot more complex than that. It <a target="_blank" href="https://www.businessinsider.com/earth-north-south-poles-flip-magnetic-field-2018-4">shifts</a>, sometimes <a target="_blank" href="https://climate.nasa.gov/explore/ask-nasa-climate/3104/flip-flop-why-variations-in-earths-magnetic-field-arent-causing-todays-climate-change/#:~:text=Paleomagnetic%20records%20tell%20us%20Earth's,the%20past%20160%20million%20years.">flips</a>, and is peppered with <a target="_blank" href="https://www.businessinsider.com/earth-magnetic-field-weakening-satellite-problems-2020-5">mysterious dents</a> that we can't quite understand.</p><p>Because the magnetism of our planet stems from how the molten metal in the Earth's core swishes around, knowing exactly how the inner core behaves is crucial to cracking the mysteries of our magnetic field.</p><p>"Now, we know about the fundamental mechanism that will help us with understanding the dynamic processes and evolution of the Earth's inner core," said Jung-Fu Lin, a professor at the UT Jackson School of Geosciences and one of the study's lead authors, in the press release.</p>

Earth's inner core is more like a ball of butter than a solid metal sphere, a new study suggests

Astronomers now routinely discover planets orbiting stars outside of the solar system they're called exoplanets. But in summer 2022, teams working on <keyword id="6360409" type="General" weightage="50" keywordseo="nasa" source="Orion">NASA</keyword>'s Transiting Exoplanet Survey Satellite found a few particularly interesting planets orbiting in the habitable zones of their parent stars.<br /><br />One planet is 30% larger than <keyword id="6359982" type="General" weightage="100" keywordseo="earth" source="Orion">Earth</keyword> and orbits its star in less than three days. The other is 70% larger than the Earth and might host a deep ocean. These two exoplanets are super-Earths more massive than the Earth but smaller than ice giants like Uranus and <keyword id="175328" type="General" weightage="50" keywordseo="neptune" source="Orion">Neptune</keyword>.<br /><br />I'm a professor of astronomy who studies galactic cores, distant galaxies, astrobiology and exoplanets. I closely follow the search for planets that might host life.<br /><br />Earth is still the only place in the universe scientists know to be home to life. It would seem logical to focus the search for life on Earth clones planets with properties close to Earth's. But research has shown that the best chance astronomers have of finding life on another planet is likely to be on a super-Earth similar to the ones found recently.<br /><br />Common and easy to find<br /><br />Most super-Earths orbit cool dwarf stars, which are lower in mass and live much longer than the <keyword id="24879" type="General" weightage="50" keywordseo="sun" source="Orion">Sun</keyword>. There are hundreds of cool dwarf stars for every star like the Sun, and scientists have found super-Earths orbiting 40% of cool dwarfs they have looked at.<br /><br />Using that number, astronomers estimate that there are tens of billions of super-Earths in habitable zones where liquid water can exist in the Milky Way alone. Since all life on Earth uses water, water is thought to be critical for habitability.<br /><br />Based on current projections, about a third of all exoplanets are super-Earths, making them the most common type of exoplanet in the Milky Way. The nearest is only six light-years away from Earth. You might even say that our solar system is unusual since it does not have a planet with a mass between that of Earth and Neptune.<br /><br />Another reason super-Earths are ideal targets in the search for life is that they're much easier to detect and study than Earth-sized planets. There are two methods astronomers use to detect exoplanets. One looks for the gravitational effect of a planet on its parent star and the other looks for brief dimming of a star's light as the planet passes in front of it. Both of these detection methods are easier with a bigger planet.<br /><br />Super-Earths are super habitable<br /><br />Over 300 years ago, German philosopher Gottfried Wilhelm Leibniz argued that Earth was the best of all possible worlds. Leibniz's argument was meant to address the question of why evil exists, but modern astrobiologists have explored a similar question by asking what makes a planet hospitable to life. It turns out that Earth is not the best of all possible worlds.<br /><br />Due to Earth's tectonic activity and changes in the brightness of the Sun, the climate has veered over time from ocean-boiling hot to planetwide, deep-freeze cold. Earth has been uninhabitable for humans and other larger creatures for most of its 4.5-billion-year history. Simulations suggest the long-term habitability of Earth was not inevitable, but was a matter of chance. Humans are literally lucky to be alive.<br /><br />Researchers have come up with a list of the attributes that make a planet very conducive to life.<br /><br />Larger planets are more likely to be geologically active, a feature that scientists think would promote biological evolution. So the most habitable planet would have roughly twice the mass of the Earth and be between 20% and 30% larger by volume.<br /><br />It would also have oceans that are shallow enough for light to stimulate life all the way to the seafloor and an average temperature of 77 degrees Fahrenheit (25 degrees Celsius).<br /><br />It would have an atmosphere thicker than the Earth's that would act as an insulating blanket. Finally, such a planet would orbit a star older than the Sun to give life longer to develop, and it would have a strong magnetic field that protects against cosmic radiation. Scientists think that these attributes combined will make a planet super habitable.<br /><br />By definition, super-Earths have many of the attributes of a super habitable planet. To date, astronomers have discovered two dozen super-Earth exoplanets that are, if not the best of all possible worlds, theoretically more habitable than Earth.<br /><br />Recently, there's been an exciting addition to the inventory of habitable planets. Astronomers have started discovering exoplanets that have been ejected from their star systems, and there could be billions of them roaming the Milky Way.<br /><br />If a super-Earth is ejected from its star system and has a dense atmosphere and watery surface, it could sustain life for tens of billions of years, far longer than life on Earth could persist before the Sun dies.<br /><br />Detecting life on super-Earths<br /><br />To detect life on distant exoplanets, astronomers will look for biosignatures, byproducts of biology that are detectable in a planet's atmosphere.<br /><br />NASA's <keyword id="145694" type="General" weightage="50" keywordseo="james-webb-space-telescope" source="Orion">James Webb Space Telescope</keyword> was designed before astronomers had discovered exoplanets, so the telescope is not optimised for exoplanet research. But it is able to do some of this science and is scheduled to target two potentially habitable super-Earths in its first year of operations.<br /><br />Another set of super-Earths with massive oceans discovered in the past few years, as well as the planets discovered this summer, are also compelling targets for <keyword id="1102401" type="General" weightage="50" keywordseo="james-webb" source="Orion">James Webb</keyword>.<br /><br />But the best chances for finding signs of life in exoplanet atmospheres will come with the next generation of giant, ground-based telescopes: the 39-meter Extremely Large Telescope, the Thirty Meter Telescope and the 24.5-meter Giant Magellan Telescope. These telescopes are all under construction and set to start collecting data by the end of the decade.<br /><br />Astronomers know that the ingredients for life are out there, but habitable does not mean inhabited. Until researchers find evidence of life elsewhere, it's possible that life on Earth was a unique accident.<br /><br />While there are many reasons why a habitable world would not have signs of life, if, over the coming years, astronomers look at these super habitable super-Earths and find nothing, humanity may be forced to conclude that the universe is a lonely place.<br /><br /><strong>SEE ALSO :<br /><br /><a target="_blank" class="c-link c-message_attachment__title_link" href="https://www.businessinsider.in/business/startups/news/if-india-can-import-dark-chocolate-why-cant-we-sell-imli-candy-abroad-says-this-startup-founder/articleshow/94309775.cms">If India can import dark chocolate why can’t we sell imli candy abroad says this startup founder</a><br /><br /></strong><a target="_blank" class="c-link c-message_attachment__title_link" href="https://www.businessinsider.in/stock-market/news/how-indian-equity-gold-and-debt-investments-have-performed-over-the-past-two-decades/articleshow/94304653.cms"><strong>Story in charts: How Indian equity, gold and debt investments have performed over the past two decades</strong></a><br />

All about Super-Earths, their dwarf stars and how they're more habitable than our earth

<br /><ul><li>A new study shows that Venus might have been a habitable planet 700 million years ago.</li><li>Earth’s twin would have had a temperate climate and shallow oceans.</li><li>This means exoplanets in the ‘Venus belt’ could also be habitable.</li></ul>Venus is often called Earth’s twin since it’s around the same size and distance from the Sun. But that’s where the similarities end. Its air is toxic, and its is 90 times thicker than Earth. <br /><br />That might not always have been the case. Around as 700 million years back, it’s possible that Venus had stable atmosphere and shallow oceans.<br /><br />A <a href="https://www.europlanet-society.org/could-venus-have-been-habitable/">new study</a> based on data collected by the National Aeronautics and Space Administration’s (NASA) Pioneer 12 mission suggests that Venus was a temperate and habitable planet for two to three billion years before its current state.<br /><br />This opens up the possibility that exoplanets — planets outside our Solar System — located in the ‘Venus Zone’ could also host water and have temperate climates to support life.<br /><br />Using the data from the mission Michael Way and Anthony Del Genio, the authors of the study, created a series of five simulations that varied in water coverage of the planet.<br /><br /><strong>Temperate vacation planet<br /></strong><br />In all the five situations, Venus was able to maintain temperatures between 50 degrees Celsius to around 20 degrees Celsius. This is a stark difference from the current sizzling temperatures that average around 462 degrees Celsius — a temperature than can melt lead. <br /><br />According to the study, Venus would have undergone cooling and its atmosphere would have mostly been made up of carbon dioxide around 4.2 billion years go — just like Earth when it first started out. <br /><br /><br />If Venus followed the same pattern at Earth, its evolution over the next 3 billion years would mean the carbon dioxide would slowly disappear from the atmosphere. It would either get absorbed by the rocks or locked into the surface.<br /><br />So, 700 million years ago, Venus’ atmosphere would — more or less — be similar to that of Earth. It would consist mostly of nitrogen with trace amounts of carbon dioxide and methane.<br /><br />The simulations and their success also bring into question the assumption of Venus being too close to the Sun to support liquid water.<br /><br />"Venus currently has almost twice the solar radiation that we have at Earth. However, in all the scenarios we have modelled, we have found that Venus could still support surface temperatures amenable for liquid water," stated Way.<br /><br />And, it could have stayed that way. <br /><br /><strong>How Venus got so hot<br /></strong><br />Somewhere between 700 to 750 million years go, the planet’s surface released all of its carbon dioxide — and no one can definitely say why.<br /><br />"It is possible that the near-global resurfacing event is responsible for its transformation from an Earth-like climate to the hellish hot-house we see today," remarked Way.<br /><br />One popular theory is that there was a large volcanic eruption where massive amounts of magma bubbled up. Rocks that got in its way melted, releasing the carbon dioxide into the atmosphere.<br /><br />Meanwhile, the magma solidified before reaching the surface creating a barrier between the carbon dioxide and the rocks to reabsorb the gas.<br /><br />The carbon dioxide had nowhere to go, causing a runaway greenhouse effect and Venus’ resultant high temperatures.<br /><br /><strong>Could humans survive on Venus?<br /></strong><br />In order to figure out whether or not Venus was truly habitable 700 million years ago, scientists still need to find out how fast the planet cooled down 4.2 billion years ago. The rapid cooling needs to have been fast enough to condense vapour to water, otherwise the oceans would never exist.<br /><br />They also need to determine whether or not the global resurfacing event, volcano or otherwise, was a one-time occurrence or something that played out over the years.<br /><br />"We need more missions to study Venus and get a more detailed understanding of its history and evolution," said Way. <br /><br />

Venus might have been habitable 700 million years ago with temperate climates and shallow oceans

<p></p><div class="KonaFilter image-container display-table lead-image-small"><div><div class="image on-image"></div><p></p></div></div><ul class="summary-list"><li><strong>A <a href="https://www.businessinsider.com/category/black-holes" target="_blank" rel="noopener">black hole</a> 4 million times heavier than the sun lurks at the center of the <a href="https://www.businessinsider.com/category/milky-way" target="_blank" rel="noopener">Milky Way</a> galaxy.</strong></li><li><strong>Telescopes just took the best-ever observations of hot gas circling the edge of the black hole.</strong></li><li><strong>The gas burst out three powerful flares as it zipped around and fell toward the black hole at about 30% the <a href="https://www.businessinsider.com/category/speed-of-light" target="_blank" rel="noopener">speed of light</a>.</strong></li><li><strong>Astronomers called the observations "mind-boggling" and the closest-ever look at the edge of a monster black hole.</strong></li></ul><p>Astronomers just observed the supermassive black hole at the center of the <a href="https://www.businessinsider.com/what-milky-way-galaxy-looks-like-2016-9">Milky Way galaxy</a> sucking blobs of hot gas toward their doom at a blistering 30% the speed of light.</p><p>That's an incredible 201 million mph, which was enough to trigger three powerful bursts of radiation from the clouds. Researchers detected the flares from Earth using the Very Large Telescope (VLT) array in Chile.</p><p>Scientists behind the observations of Sagittarius A* (pronounced "A-star"), as the monster black hole is known, say the data is a "<a href="https://www.eso.org/public/news/eso1835/" target="_blank" rel="noopener">mind-boggling</a>" closest-ever look near the edge of a black hole. It's not the traditional point-of-no-return, called the <a href="https://www.businessinsider.com/photograph-event-horizon-black-hole-milky-way-heart-2017-3">event horizon</a> - from which light cannot escape - but a physical one where, if anything made of matter teeters too close, it will begin an inescapable death spiral.</p><p>The group published <a href="https://www.eso.org/public/archives/releases/sciencepapers/eso1835/eso1835a.pdf" target="_blank" rel="noopener">a study</a> of its work on Wednesday in the journal Astronomy &amp; Astrophysics.</p><p>"Astronomers have observed material as close as you can get to a black hole without being consumed by it," <a href="https://twitter.com/josieapeters" target="_blank" rel="noopener">Josephine Peters</a>, an astrophysicist at the University of Oxford who wasn't involved in the study, told Business Insider.</p><p>"Even though [Sagittarius A*] is our closest supermassive black hole, it is still incredibly mysterious," she added. "This marks the beginning of understanding more about our nearby astronomical monster."</p><h2>Staring the 'monster' of the Milky Way in the eye</h2><p></p><div class="KonaFilter image-container display-table float_right"><div><div class="image on-image"></div><p></p></div></div>Sagittarius A* is thought to be a black hole about 4.14 million times the mass of our sun, or 1.3 trillion times as massive as Earth.<p>Definitively proving either of those two facts is tricky, though, since the presumed black hole is some 25,000 light-years from Earth. It's also practically invisible because the gravity of <a href="https://www.businessinsider.com/third-gravitational-waves-event-heard-2017-6">black holes</a> is so strong that not even light can escape beyond their event horizons, where Albert Einstein's calculations of the universe fall apart and <a href="https://www.businessinsider.com/stephen-hawking-how-the-physicist-inspired-my-career-2018-3">Stephen Hawking's begin</a>.</p><p>However, knowing as much about Sagittarius A* as possible is crucial for a number of good reasons.</p><p>On big scales, it's a window into the history and evolution of the <a href="https://www.businessinsider.com/milky-way-galaxy-crystal-ball-image-2018-6">Milky Way galaxy</a>, which rotates its spiral arms of hundreds of billions of stars about the giant black hole at its center. That galactic story is also intimately tied to the emergence of the solar system and life itself. (And the same is true of the hundreds of billions of other galaxies in the <a href="https://www.businessinsider.com/entire-universe-picture-logarithmic-map-2017-6">visible universe</a> - some of which <a href="https://www.businessinsider.com/alien-signals-search-for-extraterrestrial-intelligence-study-2018-10">may harbor aliens</a>).</p><p>There's also its weirder utility: The closest supermassive black hole we know of is a laboratory for the physical laws of the universe. It is so massive and spins so rapidly, it dramatically warps and twists spacetime, and accelerates objects to <a href="https://www.businessinsider.com/theory-of-relativity-2017-12">relativistic or near-light-speed</a>.</p><p>Nature gets very, very weird when this happens, but it happens nowhere near Earth. So being able to watch it, even from tens of thousands of light-years away, is like having a front-row seat to the cutting-edge of human knowledge.</p><p>This is why astronomers aimed an instrument called GRAVITY at Sagittarius A*.</p><p></p><div class="KonaFilter image-container display-table"><div><div class="image on-image"></div><p></p></div></div><p>In uncomplicated terms, GRAVITY combines the light harvested by four 30-foot-diameter telescopes in the VLT array, which is operated by the European Southern Observatory.</p><p>GRAVITY does so as a super-precise, super-cooled instrument that allows researchers to extract more information from the incoming light. This turns the array into one very powerful "<a href="https://www.businessinsider.com/eta-carinae-winds-highest-resolution-image-2016-10">virtual</a>" telescope equivalent to 425 feet in diameter.</p><p>This extra resolving power helped astronomers peer at a plane of gas and dust that's falling toward Sagittarius A*, a feature called an <a href="https://www.businessinsider.com/black-holes-hide-behind-star-exhaust-2016-9">accretion disk</a>. The disk is about 100 million miles wide, or a little wider than Earth is distant from the sun.</p><p>GRAVITY helped the team look for flares of infrared light, which astronomers had seen for more than decade. But this time - with incredible resolving power - they tried to stare at the innermost edge of the disk.</p><p>During observations on the nights of May 27, July 22, and July 28, GRAVITY saw three flares. The data suggested the flares came from a blob of hot gas circling clockwise around the black hole.</p><p>"As a cloud of gas gets closer to the black hole, they speed up and heat up," Peters said. "It glows brighter the faster and hotter it gets. Eventually the gas cloud gets close enough that the pull of the black hole stretches it into a thin arc."</p><p>This happened just outside the event horizon, in an area astronomers refer to as a physical point-of-no-return, called the "innermost stable circular orbit" or ISCO - a region not yet observed before.</p><p>Move a blob of matter closer than the ISCO, the thinking goes, and it can't escape. The gravity of a black hole will accelerate the blob of matter, giving it more energy, which will - as Einstein's work explains - give it a stronger gravitational force. This then pulls it faster toward the black hole, creating a feedback-loop of relativistic physics that ends in oblivion.</p><h2>What the edge of our supermassive black hole might look like</h2><p>This thin arc is shown in the ESO's picture at the top of this story, though the image is not a photograph.</p><p>Rather, it's a visual simulation that uses data collected by GRAVITY and other telescopes. Orange shows what researchers think is a blob of superheated gas, or plasma, while blue shows radiation that bleeds off the matter and occasionally bursts into bright flares.</p><p>The picture also illustrates the bending and distortion of light caused by the black hole <a href="https://www.businessinsider.com/warp-drive-study-department-defense-real-fake-2018-5">warping spacetime</a> with its concentrated mass, an effect called gravitational lensing.</p><p>ESO also created an animation of the gas cloud and flares, below.</p><p>The signal seen on Earth is in infrared light, which is just out of the range of human visibility, but it's not the only form of flare radiation.</p><p>"If you were close enough to observe these flares, you'd be in a lot of trouble," <a href="https://www.linkedin.com/in/tanadjoseph/" target="_blank" rel="noopener">Tana Joseph</a>, an astrophysicist and fellow at the University of Manchester who wasn't involved in the study, told Business Insider in an email. "We would see extremely bright flashes of optical light, and there would be lots of high energy radiation, like gamma rays and X-rays, that would be very damaging to our bodies."</p><p>Peters says flares have been seen coming from Sagittarius A* before. However, she added the new observations - which show the very edge of the black hole - are like going from the resolution of an old television to a high-definition flat-screen TV.</p><h2>A flashing spacetime lens?</h2><p></p><div class="KonaFilter image-container display-table"><div><div class="image on-image"></div><p></p></div></div><p>What causes these flares is an active mystery.</p><p>One idea is that extreme forces around the black hole, primarily intense magnetic fields, will occasionally toss off and accelerate some of the hot plasma into jets, which then bleed off energy as flares.</p><p>"We see plasma flares associated with magnetic fields in many places, including our own Sun, but we don't yet fully understand the exact causes of such flares," <a href="http://www.astro.gsu.edu/~bentz/" target="_blank" rel="noopener">Misty Bentz</a>, an astrophysicist at Georgia State University at who also wasn't part of the study, told Business Insider in an email.</p><p>But something far weirder may be at play: large distortions in spacetime caused by the spinning of a black hole at some fraction of the speed of light. Such distortions might be focusing the energy that's bleeding off of orbiting blobs of hot plasma into a beam, and the beam occasionally flashes across the telescopes of Earth - creating a flare.</p><p>"The black hole is like this lighthouse lens that's causing this thing to flash at us as it goes around," Avery Broderick, an astrophysicist at the Perimeter Institute of Theoretical Physics and the University of Waterloo, <a href="https://www.quantamagazine.org/astronomers-creep-up-to-the-edge-of-the-milky-ways-black-hole-20181030/" target="_blank" rel="noopener">told Quanta</a>. (Broderick first proposed this idea in 2005.)</p><p>The ESO's press release claims the flares "provide long-awaited confirmation that the object in the center of our galaxy is, as has long been assumed, a supermassive black hole."</p><p>This claim is likely over-blown, however, since it's virtually impossible to directly confirm the existence of a black hole, short of visiting one or <a href="https://www.businessinsider.com/gravitational-waves-ligo-2016-2">"listening" to them crash together</a>.</p><p>"One might argue that you can never prove the existence of an invisible object like a black hole," Bentz said. "But this new study with GRAVITY confirms that a compact object with a mass of 4 million suns is still the only way to explain all the observations."</p><p>Bentz is eager to know what the flares foretell. She also said the very circular orbit of the blob of plasma was unusual. This may suggest the rotational axis of Sagittarius A*, like a tilting spinning top, was <a href="https://www.businessinsider.com/2-million-mile-per-hour-winds-at-galaxy-center-2015-1">aligned with the Milky Way</a> a few million years ago, but has inexplicably pointed toward Earth.</p><p>If true, Bentz said, "that would be quite a puzzle."</p><div><div style="position:relative; padding-bottom:100.00%"></div></div>    <div class="margin-top">        <h3>NOW WATCH: <a href="https://www.businessinsider.com/how-universe-will-die-2017-4">How our universe will end: 'The black holes will eat up everything'</a></h3>        <div>                    </div>    </div>

A 'mind-boggling' telescope observation has revealed the point of no return for our galaxy's monster black hole

<p class="source"><span>American Museum of Natural History</span></p>Plenty of threats could wipe humans out - including climate change, nuclear war, and disease. But after we (and all other animals on the planet ) go extinct, one tiny, miraculous organism will live on: the tardigrade.<p>Sometimes called water bears or moss piglets, tardigrades are usually about .5 millimeters long, and can survive in a stunning range of environmental conditions.</p><p>As the researchers behind a recent study involving these minuscule creatures point out, tardigrades can live for a few minutes at temperatures as low as -450 degrees Fahrenheit, or as high as 302 degrees. They can hang on for decades at temperatures of -4 degrees. (Humans, by comparison, wouldn't make it more than 10 hours in cold like that.)</p><p>For the new study, <a href="https://www.nature.com/articles/s41598-017-05796-x">published Friday in the journal Scientific Reports</a>, three University of Oxford scientists investigated the astrophysical events that could be catastrophic enough to annihilate all life on Earth.</p><p>Since tardigrades are the most resilient species on our planet, the researchers used them as their barometer.</p><h2>Annihilating life</h2><p>The simplest way to kill every living thing on Earth, the scientists decided, would be for our entire oceans to boil. For that to happen, the planet would need  to get an energy input of 5.6 x 1026 joules by their calculations - roughly equivalent to a million years' worth of total human energy production at our current rates.</p><p>Three types of disasters could hypothetically cause this to happen: a supernova, a gamma-ray burst, and a large asteroid impact.</p><p>For an asteroid to deposit enough energy onto our planet to boil the oceans, they calculated, it would have to be enormous (a weight of 1.7 x 1018 kilograms). We only know of 17 candidates in our solar system close to that mass-  one of which is Pluto - and none have orbits that coincide with Earth's. So that scenario is highly unlikely.</p><p>Gamma-ray bursts are mysterious explosions that focus incredible quantities of energy into narrow jets. To kill tardigrades on Earth, such a burst would have to originate from within 42 light years away, the scientists found, and would need to direct the beam directly at us - a situation that's also extremely improbable.</p><p>Supernovae are massive explosions of stars that produce more than enough heat to boil Earth's oceans. But for a significant portion of that heat to travel to Earth, the supernova would have to be fairly close in cosmic terms.</p><p class="source"><span>NASA</span></p><p>The nearest star to Earth (besides our sun) is called Proxima Centauri, and is too far away - a supernova there would only raise the temperature of our oceans .1 degree Celsius. Plus, Proxima Centauri is the wrong type of star for a supernova anyway.</p><p>Because all three of these events are so unlikely, the researchers conclude, tardigrades will probably hang around on earth until our sun explodes - about a billion years from now.</p><h2>The powers of tardigrades</h2><p>Tardigrades are considered extremophiles, a term for organisms that have been discovered in environments that scientists once thought could not sustain life. They have been revived after being <a href="http://www.businessinsider.com/tardigrades-survive-being-frozen-for-30-years-2016-2">frozen in Antarctic moss for 30 years</a>. They've been shown to survive in space.</p><p>Two of the authors of the new study elaborated on the microscopic creatures' remarkable resilience in a <a href="https://theconversation.com/we-worked-out-what-it-would-take-to-wipe-out-all-life-on-a-planet-and-its-good-news-for-alien-hunters-81006" target="_blank" rel="noopener noreferrer">recent piece for The Conversation</a>.</p><p>"Increase atmospheric pressure to more than 1,000 times that at the Earth's surface, or drop it to the vacuum of space and they continue," the researchers wrote. "They can survive for up to 30 years without food or water. They can even withstand thousands of grays (standard doses) of radiation. (Ten grays would be a lethal dose for most humans.)"</p><p class="source"><span><a href="http://www.wired.com/images_blogs/wiredscience/2012/04/tardigrade-water-bear-esa-schill.jpg">Ralph O. Schill/European Space Agency</a></span></p><p class="caption">The microscopic tardigrade is one of the most resilient organisms on the planet.</p>There are more than 1,000 different species of tardigrades, living in all kinds of environments around the planet. The primary reason they're so durable is that they can enter a state of cryptobiosis, which is remarkably close to death. In this state, the organisms' metabolic activity gets reduced to undetectable levels. Their bodies contract, losing all but 3 percent of their water. In essence, they're completely dehydrated.<p>Scientists are still researching cryptobiosis, which <a href="https://www.ncbi.nlm.nih.gov/pubmed/16380155" target="_blank" rel="noopener noreferrer">some have called</a> a "third state between life and death," as well as other aspects of tardigrades' biology.</p><p>When researchers sequenced the creatures' genome in 2015, they found that nearly <a href="http://www.businessinsider.com/afp-water-bears-are-huge-dna-thieves-study-2015-11">a sixth of tardigrades' DNA came from foreign organisms</a> (compared to just 1% for most animals). They believe this happens because tardigrades' DNA actually breaks into small pieces when they're under intense stress, such as extreme dryness. When the cells start to rehydrate, their membranes and the nucleus housing the DNA temporarily become leaky, allowing other large molecules to pass through.</p><p>They repair their own DNA and absorb foreign DNA when rehydrating - a process that gives them a patchworks of genes from other species.</p><p>In 2016, scientists from the University of Tokyo also <a href="http://www.businessinsider.com/water-bear-indestructible-radiation-shield-2016-9">discovered a new protein in tardigrades</a> that shields them from harmful radiation. </p><p>Such abilities have challenged how scientists understand the process of evolution, and has yielded clues about ways we could increase human survival.</p><h2>Applications in the search for alien life</h2><p>The larger point of the new study was not to highlight how remarkable tardigrades are. Instead, the Oxford researchers wanted to find out what the chances are that life will survive on an Earth-like planet after it arises.</p><p>If the emergence of life on other Earth-like planets gives rise to organisms as durable as tardigrades, the authors suggest, then the chances are good that life is still around on those planets.</p><p>This is reason for hope in the hunt for alien life, since it means that if life took hold on any planets similar to ours, there are probably still survivors that we might one day be able to find.</p><p class="source"><span>NASA/JPL-Caltech</span></p><p class="caption">An illustration of what it might look like on the surface of TRAPPIST-1f, a rocky Earth-like planet 39 light-years away.</p><p>There are, however, a number of caveats to this good news. The researchers behind the study didn't factor in the effects that come from a feedback process like severe climate change, so there are hypothetical scenarios in which an initial catastrophe might be somewhat weak, but its effects could get compounded over time.</p><p>They also assume that life on other Earth-like planets is similar to what we've got here.</p><p>Nevertheless, the researchers point out that while the human race may be relatively fragile, life as a whole is "incredibly hardy."</p><p>"We do not fully understand the mechanisms by which life started, but once it exists on an Earth-like planet, the complete removal of all life (other than through evolution of the host star) is a very unlikely event," the conclude in the study.</p>            <h3>NOW WATCH: <a href="http://www.businessinsider.com/closest-places-discover-alien-life-nasa-2017-6">The closest, most compelling places where we could discover the first alien life</a></h3>                                    Please enable Javascript to watch this video

Researchers say tiny 'water bears' will survive until the sun explodes - and it's good news in the search for alien life

<p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><p class="source"><span>20th Century Fox</span></p><p class="caption">In the 1979 movie "Alien," the xenomorph tries to attack Sigourney Weaver's character.</p></div><p></p></div></div></p><ul class="summary-list"><li>The horror flick <a href="https://www.businessinsider.com/alien-original-ending-2017-4">"Alien"</a> hit the screen 40 years ago, in the summer of 1979. The film is one of Hollywood's best known <a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=9&amp;cad=rja&amp;uact=8&amp;ved=2ahUKEwiXwLOSt4_kAhUwZN8KHQirCSUQFjAIegQIAxAB&amp;url=https%3A%2F%2Fwww.businessinsider.com%2Fsci-fi-movie-predictions-2019-5&amp;usg=AOvVaw0_c70dOI1IDc3B0kG4ugv3">sci-fi blockbusters</a>.</li><li>In the decades since "Alien" came out, depictions of aliens in movies have changed dramatically.</li><li>Instead of showing extraterrestrial life as humanoid, directors have instead <a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=1&amp;cad=rja&amp;uact=8&amp;ved=2ahUKEwiXwLOSt4_kAhUwZN8KHQirCSUQFjAAegQIAhAB&amp;url=https%3A%2F%2Fwww.businessinsider.com%2Falien-movies-ranked-2017-5&amp;usg=AOvVaw3oVhGwvggUxN2iehAQxvmS">depicted aliens</a> as bacteria, as in the movie "Life," or as amorphous lifeforms like in the movie <a href="https://www.businessinsider.com/alien-language-in-arrival-linguist-2016-11">"Arrival."</a></li><li>According to one scientist, these depictions are more scientifically realistic and align more with <a href="https://www.businessinsider.com/microbes-under-alaskan-ice-could-mirror-alien-life-2019-7">what researchers think</a> potential aliens may look like. </li><li><a href="https://www.businessinsider.com/?hprecirc-bullet">Visit Business Insider's homepage for more stories</a>.</li></ul><p>The 1979 blockbuster "Alien" opens with tension-filled scene: A spider-like creature attacks astronaut Thomas Kane on an unknown planet.</p><p>The crew of Kane's ship bring him back on board with the mysterious critter still attached to his spacesuit. Under the fluorescent lights, the creature seems to die, detaching from Kane's face. When the astronaut eventually wakes up, he seems unharmed by the encounter.</p><p>But a miniature alien later bursts out of his chest in a shower of blood, as his shocked crewmates scream.</p><p>The xenomorph, as it's called, grows to be larger than any human, with glossy black skin, razor sharp teeth, claws, and a tail.</p><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><p class="source"><span><a href="https://www.youtube.com/watch?v=BHSf7MXTlKM">20th Century Fox via YouTube</a></span></p><p class="caption">An alien attaches itself to astronaut Thomas Kane's face in the 1979 movie "Alien."</p></div><p></p></div></div></p><p>In the four decades since "Alien" came out - the film's 40th anniversary was in May -that creature's image has influenced movie-goers' mental pictures of alien life.</p><p>But as NASA has embraced the objective of searching for extraterrestrial life in our galaxy, the scientific understanding of what extraterrestrials might look like has converged around a type of lifeform far different than director Ridley Scott's brainchild.</p><p>Today, astrobiologists suspect that extraterrestrial lifeforms are likely to be microscopic in nature, akin to the bacteria scientists find in <a href="https://www.businessinsider.com/microbes-under-alaskan-ice-could-mirror-alien-life-2019-7">extreme environments on Earth</a>.</p><p><em><strong>Read More:</strong> <a href="https://www.businessinsider.com/microbes-under-alaskan-ice-could-mirror-alien-life-2019-7">Deep below Alaskan ice, tiny life forms went untouched for 50,000 years. Scientists are probing them to improve the hunt for aliens.</a></em></p><p>Hollywood filmmakers have started to embrace this idea and depict aliens as less humanoid, according to physicist and author Sidney Perkowitz. In other words, the days of little green men and giant scaly monsters in alien movies are gone.</p><p>"In the old science-fiction flicks of the 1950s and 60s, if you did an alien, monster, or robot, it was a guy dressed up and stomping around a sound stage," Perkowitz, who cofounded the National Academy of Sciences'<a href="http://www.nasonline.org/programs/science-and-entertainment-exchange/"> Science and Entertainment Exchange group</a>, which connects directors with <keyword id="41551" type="ENTERTAINMENT" weightage="100" keywordseo="science">science</keyword> advisers, told Business Insider. "In the last few decades, CGI has changed that, allowing for the potential of really life-like, imaginative creatures."</p><h2>No more little green men</h2><p>The chance that alien life looks humanoid is infinitesimal.</p><p>"We don't have any reason to believe that they would look anything like us," Andrew Siemion, director of the Berkeley SETI (Search for Extraterrestrial Intelligence) Institute, <a href="https://www.vox.com/videos/2018/3/15/17126340/science-fiction-aliens-vfx-seti">told Vox</a>. "The form of a human being is the result of several billion years of evolution."</p><p>Perkowitz said that Scott and other directors' decisions to make extraterrestrials appear human-like could simply boil down to cost.</p><p>"Humanoid aliens are cheap to portray," he said. </p><p>He added that the problem with "Alien" wasn't just that the movie portrayed the alien as humanoid - it was that the extraterrestrial was depicted as unintelligent and beast-like. The xenomorph doesn't try to communicate with the astronaut crew; instead, it eats them one by one until Sigourney Weaver's character blasts it into space.</p><p>"It's hard to imagine a different lifeform would have such a negative reaction to another lifeform - nothing lives for pure evil." Perkowitz said, adding, <span>"if we always decide that 'the other' is hostile or contemptible how does that encourage our efforts to relate to them?"</span></p><p>But the examples of non-hostile aliens in Hollywood are few and far between (Steven Spielberg's E.T. not withstanding). That's because, according to Perkowitz, society uses film to explore what it's afraid of. </p><h2>Sci-fi films are reflections of what society is worried about</h2><p>Hollywood blockbusters' references to science don't arise in a vacuum - they mirror current trends in scientific discovery and their effects on our culture. In the 1950s and 1960s, for example, movies like Doctor Strangelove featured nuclear scientists because people had memories of the atomic bomb and a fear of nuclear war, Perkowitz said.</p><p>"Even if the sci-fi film doesn't know it's doing it, a closer watch shows that the movies reflect society's current anxieties," he said.</p><p>Alien movies are no different. These days, Perkowitz said, humanity isn't afraid of carnivorous xenomorphs. Instead, we worry about "something viral - a biological entity that spreads quickly and causes harm."</p><p>In an era in which mosquitoes carrying viruses like Zika and dengue fever are spreading farther due to climate change, "nuclear radiation isn't the concern anymore," Perkowitz said. So some alien movies now depict a contagion that comes from outer space.</p><p>In the 2017 movie "Life," for example, Jake Gyllenhaal's character and his crewmates aboard the International Space Station discover a<span> life form that supposedly caused extinction on Mars and threatens life on Earth. </span></p><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><p class="source"><span>Sony Pictures Entertainment, Inc.</span></p><p class="caption">Jake Gyllenhaal in a scene from the 2017 science-fiction movie "Life."</p></div><p></p></div></div></p><p>Film studios primarily choose to present aliens as malevolent microbes in this way to get people to the box office, Perkowitz said - "on the whole, Hollywood isn't concerned with the social responsibility of getting the science right."</p><p>But in this case, he added, the depiction could help establish more appropriate expectations for any potential discovery of life that NASA might make. The agency plans to look for extraterrestrial life on Jupiter's moon Europa with its planned <a href="https://www.jpl.nasa.gov/missions/europa-clipper/">Clipper mission</a> in 2025. Scientists expect any potential life there "<span>may look like microbes, or maybe something more complex," <a href="https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/">a NASA report said</a>. </span></p><h2>The best portrayal of aliens in film?</h2><p>Perkowitz pointed to the creatures called heptapods in the 2016 movie "Arrival" as an exemplary depiction of non-humanoid aliens that attempt intelligent contact. That's because they don't remotely resemble humans, are not hostile, and try to communicate rather than attack.</p><p>In the movie, Amy Adams plays a linguistics professor who works to communicate with the heptapods, which sport long muscular torsos and seven legs. Eventually, she discovers that the aliens speak using logograms - inkblot-like <span>symbols that can stand for a word, an entire sentence, or even a feeling. </span></p><p><span>The humans and aliens, through extensive trial and error, establish a mutual language without destroying each other.</span></p><p><div class="KonaFilter image-container display-table"><div><div class="image on-image"><p class="source"><span>Paramount Pictures</span></p><p class="caption">Amy Adams' character tries to communicate with alien lifeforms in the 2016 movie "Arrival."</p></div><p></p></div></div></p><p>"That movie is a great example of, perhaps, how would we really go about meeting aliens if we do ever meet intelligent life out there," Perkowitz said.</p>    <div class="margin-top">        <h3>NOW WATCH: <a href="https://www.businessinsider.com/how-humans-could-talk-to-aliens-2018-8">How humans can communicate with aliens</a></h3>        <div>                    </div>    </div>

The iconic film 'Alien' came out 40 years ago. A scientist explains why Hollywood depictions of extraterrestrials have changed since then.

<p>Human-induced warming is sending Earth into frightening and uncharted climate territory - but humans are not the first force to cause colossal changes to our climate.</p>
<p>Other celestial bodies, including planets, tug at Earth causing it to move in ways that affect our ice caps in history-shaping ways, as discussed by narrator and astrophysicist Neil deGrasse Tyson on Sunday's <a href="http://www.hulu.com/watch/630892">Cosmos: A Spacetime Odyssey</a>.</p>
<p><div class="KonaFilter image-container display-table float_left"><div><div class="image"><p class="source"><span>GIF From Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</span></p><p class="caption">Earth's axis is constantly changing.</p></div><p></p></div></div></p>
<p>For example, the pull of the planets influences Earth's tilt. They cause Earth's axis to wobble in a circular motion similar to the spin of a top. You can can see these movements in the Cosmos GIF to the left.</p>
<p>If you could stick a pen out of Earth's north pole, it would draw a circle about every 26,000 years. In 14,000 AD for example, our north star was not Polaris, as it is now, but Vega. In 12,000 years , Vega will be our north star again.</p>
<p>The pull of the planets also cause the Earth's tilt to change between 22.1 and 24.5 degrees over 41,000 years. When our tilt is more extreme, seasons can be more severe, with <a href="http://www.ncdc.noaa.gov/paleo/milankovitch.html">warmer summers and cooler winters</a>. When the tilt is less, we get cooler summers and milder winters. Currently our tilt is about 23.4 degrees - near the middle.</p>
<p><div class="KonaFilter image-container display-table full"><div><div class="image"><p class="source"><span>NASA and Mysid</span></p><p class="caption">In addition to Earth's rotation about its own axis, Earth wobbles like a top (left) and changes it's tilt (right) in response to the gravitational pull of other celestial bodies.</p></div><p></p></div></div>In the GIF below, you can see another effect of planetary pull. Earth's orbit is not round, but slightly egg-shaped or eccentric.</p>
<p>"The shape of the Earth's orbit changes from being elliptical (high eccentricity) to being nearly circular (low eccentricity) in a cycle that takes between 90,000 and 100,000 years," according to <a href="http://earthobservatory.nasa.gov/Features/Milankovitch/milankovitch_2.php">NASA's Earth Observatory</a>.</p>
<p><div class="KonaFilter image-container full"><div class="image"><p class="source"><span>GIF From Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</span></p><p class="caption">The Earth's eccentric and unsymmetrical orbit.</p></div><p></p></div>Currently, Earth is at its closest to the sun at the beginning of January when it is about 91.5 million miles away and at its furthest in July when it is about 94 million miles away. This corresponds to about a 6% difference in how much solar radiation the Earth receives.</p>
<h3>Earth, planetary pull, and ice ages</h3>
<p>During a highly elliptical orbit, the Earth would receive 20 to 30% higher sunlight intensity between its closest and furthest passes by Earth, "resulting in a substantially different climate from what we experience today," according to NASA.</p>
<p>The pull of every celestial body combines to create Earth's eccentricity, wobble, and tilt. These movements determine how our planet is positioned to receive sunlight and how much sunlight it can receive. Which of these is the dominant determiner of ice ages, however, is still not completely understood.</p>
<p>"There is still some discussion about how exactly this starts and ends ice ages, but many studies suggest that the amount of summer sunshine on northern continents is crucial: if it drops below a critical value, snow from the past winter does not melt away in summer and an ice sheet starts to grow as more and more snow accumulates," said the <a href="https://www.google.com/search?q=ice+ages+IPCC+2014&amp;oq=ice+ages+IPCC+2014&amp;aqs=chrome..69i57.4223j0j7&amp;sourceid=chrome&amp;es_sm=91&amp;ie=UTF-8">Intergovernmental Panel On Climate Change in their 2007 report</a>.</p>
<p>One glacial period, or lack thereof, was particularly significant to human history: Fifteen to twenty-five thousand years ago, the northern ice cap shrunk, revealing a land bridge that our ancestors would use to cross from Eurasia into North America.</p>
<h3>How ice forms civilizations</h3>
<p>When Earth's northern region is ill-positioned to bathe in the sun's rays, the top third of the world becomes entombed in ice. You can see the northern polar ice cap expand all the way down over California and consume the better part of North America: <div class="KonaFilter image-container full"><div class="image"><p class="source"><span>GIF From Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</span></p></div><p></p></div> When the ice grows, it siphons water from the sea, lowering sea levels 400 feet, said deGrasse Tyson. This exposes more land in coastal regions.</p>
<p>When Earth is at a prime angle for sunbathing, this ice thaws and sea levels rise. When Earth thawed about 15,000 to 25,000 years ago, receding ice exposed a land bridge connecting Eurasia and North America. This bridge would later be humanities route into North America. <div class="KonaFilter image-container full"><div class="image"><p class="source"><span>GIF From Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</span></p></div><p></p></div>Roughly 10,000 years ago, "the manic swings of the climate and sea levels," subsided, said Tyson, "a new and gentler climate age began."</p>
<p>We entered an interglacial period that we still live in, "one of those balmy intermissions in an ice age," he said. Rivers transported fertile sediments into deltas, where some humans made their homes.</p>
<p><div class="KonaFilter image-container"><div class="image"><p class="source"><span>GIF From Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</span></p></div><p></p></div> Once solely wanderers, humans had time and resources in this interglacial period to settle and build the civilizations at the dawn of our history.</p>
<p>"The way the planets tug at each other, the way the skin of the earth moves, the way those motions affect climate, and the evolution of life and intelligence, they all combined to give us the means to turn the mud of those river deltas into the first civilizations," said Tyson.</p>
<p>Now go enjoy the beautiful interglacial period. You've only got about another 50,000 years. That is, if we don't throw it all out of wack with our greenhouse gas emissions.</p>
<p><em>GIFs from <a href="http://www.cosmosontv.com/">Cosmos: A Spacetime Odyssey, The Lost Worlds Of Planet Earth</a>. Watch the full episode <a href="http://www.hulu.com/watch/630892">here.</a></em></p>

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