"The sun is the superpower of our solar system, a thermonuclear blast furnace, erupting with massive explosions." "It can be the same amount of mass of mont Everest coming out from the Sun and flying out into the space." "At 93 million miles away it would seem that we are safe from the sun's wrath." "But are we?" "It matters, especially in modern times, what the sun is doing." "From the center of the sun, as it rotates around, as the kill zone." "With some experts predicting the most violent outbreak of solar activity in modern history." "it's never been more important to understand the secrets of the sun." "The Universe episode 1x01" " Secrets of The Sun" "Traduzione e Synch:" "Supersimo, Cochrane, Hipopo, Kickaha, Zio Campori" "Revisione:" "Supersimo" "There are bilions of stars in the universe but one alone dominates our cosmic neighborhood:" "the Sun" "It's an infernal sphere, of mostly hydrogen and helium, superheated into a plasma, that burns at millions of degrees." "Its surface reages with violent explosions, as expelled outstorm of deadly radiation, milions of miles into space." "Our Sun is a type of star, known as a yellow dwarf." "Yellow because of the color of its surface." "And dwarf because it's small for a star." "But small it's relative." "Within its boundaries, you can fit one milion earths." "In our solar system, there's simply no bigger star than the Sun." "At a milion miles across, it's a massive celestial blockbuster." "The Sun is really pretty huge." "It dominates our solar system." "Not only is the bigger star of the Solar system, it's the only star of the solar system." "It's sorrounded by a bunch a smaller stuff, that we called planets, comets and moons." "But the Sun is our star." "Our star is an enormous source of heat and energy." "It has a surface temperature of 10.000° Farenheit." "An generates 380 billion billion megawatts of power." "This dwarf anything on a human scale." "Hoover Dam in Nevada only generates 280 megawatts." "In one second the sun churns out more energy than has been used in all of human civilization." "All that power in the blink of an eye." "Incredibly, it's been burning this way for billions of years." "Early astronomers didn't quite understand how the Sun could generate so much energy for that long period of time." "though is the first mistery was really how the sun generate this energy." "In the early nineteenth century, scientists assumed that the Sun work just like any fire on Earth, that there was a source of fuel, pheraps coal, that was slowly burning away." "But that was a serious problem with this theory:" "I've got a fire in front of me here, if I wanna as keep burning, I had to keep adding woods to it." "This fire last maybe an hour, must to add some more woods." "Now, if I had a pile of the woods the size of the all Sun, and somehow enough oxygen to burn it, it would only take about 5000 or 6000 years to burn out." "That's a long time, but it's not long enough to substain life on Earth." "By the early twentieth century, carbon dating of earth rocks and fossils have prooved it, that the Sun was in existence at a temperature warm enough to substain life not for thousand of years, but for 3 billions." "If you want to build a fire that would last that long, you'd need 72 trillions cords of firewood." "That's 12 thousand cords for each man, woman and child on the planet." "Clearly, there had to be some other process, unknow on Earth, that would powering the Sun." "In the 1920's scientists found the answer to the puzzle, in a process that would later be harnest to fuel the hydrogen bomb." "Nuclear fusion." "Fusion occurs when atoms are smashed together in a high rate of speed and literally fused." "To get this to happen, conditions have to be just right." "For any interaction that happen there's two proton, each has a positive electric charge and so they would repell each other." "So you got to get in close enough together, and to do that, it's got to be hot, which means" "The part is moving fast, and dense enough that they, they hit each other and they can get close enough together and actually fused." "The core of the Sun is the perfect coaler for nuclear fusion." "It's the hottest place in the solar system, as it sweltering 27 milion° F." "And it's also incerdibly dense." "It's so dense, it's ten times the density of lead, and you would think that high density should be a solid, but it's not because it's so hot that remains a plasma." "If you heat a gas to high enough temperatures electrons fall off the atoms and float around in the soup." "And so it has behavior that's different from what a gas would do, that we have a different word for it, called plasma." "To truly understand what goes on in the core of the Sun, you have to find someway to imagine the almost "unimaginable"." "In addition to study the Sun, I also play pool and the Sun is a place where there are billion of particles, colliding interacting with each other." "And it is really not unlike a cosmic pool table, on an imaginable scale." "It doesn't matter how hard you hit a ball." "You would never hit hard enough to actually fuse that ball together with another ball." "But there's so much pressure and such high density in the core of the Sun, that two objects impacting each other, will actually fused." "In the Sun, these objects are hydrogen atoms, flowned together by immense pressure, to form helium atoms." "In this fusion process, the resulting atom is slightly less massive than the ones they created it." "The missing mass is given off as energy." "Each second, inside the Sun, 600 million tons of hydrogen are fused into 595 million tons of helium." "That five million tons of mass lost in the process is converted into energy equal to one billion one megaton hydrogen bombs." "That's every second." "When you look out into the cosmos the process that gives you the highest return of energy for free, is what goes on in the center of a star like the Sun." "So, we now know that the Sun is powered by nuclear fusion." "It's the only fuel we know, that can substain the burning in the Sun long enough to substain life on Earth, billions of years." "Sunlight:" "it's so central to life that we don't often give it a second taught." "But how light gets from there, to here turns out to be an incredible story." "The energy created in the fusion process is carried out of the core by particles of light and heat called photons." "They are what bring the warming race of the Sun to Earth." "To reach our planet, these glowing travelers from our nearest star must first take a long whining road to all the layers of the Sun, like Dante's journey to the levels of Hell." "First, a foton entries the 185.000 miles take radiating zone, the region is so densily pathed that fotons constantly bums into other particles, like hydrogen and helium atoms." "It struggles outward in a chaotic zigzag pattern that scientists called the random walk." "A foton can't escape without interacting over and over and over again, getting absorbed by atoms and readmitted and it can be absorbed and readmitted milions of times." "As the density decreases as you get further up in the Sun, it become easier and collusions and interactions are less." "When it finally reaches to a thin 130.000 miles from the surface, the foton enter the convective zone, and the pace suddenly quickins." "It's carried outwards by a kind of boiling riding along in huge columns of gas at hundreds of miles in hour." "Taking only ten days to emerge on the solar surface." "The incredible journey is almost over as the photon lifts off through the wispy gasses of the solar atmosphere" "From there it takes only 8 minutes for it to zip across 93 million miles of space." "To our planet." "Incredibly by the time sunlight actually reaches Earth" "It's already been in existence for hundreds of thousands if not millions of years." "For the Sun even a million years is a small blip in time." "The simple perfect disc of the sunset, the lies the long, violent history of our star." "It is a ball of fire spawned billions of years ago in a massive explosion known as a supernova." "After this titanic explosion where a star much larger than the sun exploded" "There would have been a huge cloud of gas many times larger than the solar system." "and small nuts of material would have gradually collapsed in this very large cloud." "About five billion years ago" "Some ten billion years after the big bang, that scientists believe kickstarted our universe" "This cloud started to collapse under the pull of gravity." "Our solar system probably arose from one such nuts of self gravitating gas that pulled itself together and gradually span itself up it is pulled in, like a skater pointing his arms in bringing spin" "Until the star and the various planets collapsed around it." "Ultimately, when the star was dense enough it would have turned on fusion, started glowing and giving off sunlight." "Why do scientists believe the Sun was born from the ashes of a supernova?" "The evidence lies beneath our feet." "Complex heavy elements like the uranium we mine from the Earth to fuel our nuclear powerplants could not have been forged in the Sun, there was simply not enough heat in a star of that size to create elements any heavier than iron." "Heavy elements, like uranium, can only be created in a catastrophic cosmic explosion" "Earth and the other planets in the solar system formed out of the same nut of gas that produced the Sun" "In this process the Sun holded 99% of the mass" "This means that's the biggest object in our celestial neighborhood" "With the strongest gravitational power that's why everything else revolves around it." "Of all the planets Earth earned a privileged place in relation to the Sun." "If we were closer in our oceans would boil away and the ground would be hot enough to melt lead." "If we were further out our planet would be a frozen wasteland." "So that's like Goldylocks and the three bears not too hot, not too cold, it's just right." "Here we are at about 93 million miles away from the Sun and we're happy to be here, we're lucky to be here." "In some sense we're here because it's the right circumstance for us to be here." "Earth may be just the right place in the solar system." "But we're also close enough to the Sun to be a target of its fury." "This face on Mars is not an alien monument" "Explore Mars in "The universe" next week." "Thousands of nemetic explosions rock our Sun every year." "You might expect this explosive force to come from nuclear reactions in the core but in reality what drives all outburstive solar violence is magnetism." "Since Earth rotates as a solid, our magnetism is simple, we have two poles:" "North and South" "This is what a compass so useful for finding your way around the planet." "But imagine if instead of two poles you had 1 to 10 million." "This is what happens on the Sun." "The Sun's magnetic field is a tangled web because even tough it's held together by gravity the plasma doesn't rotate evenly." "Plasma at the equator rotates once every 25 Earth days while plasma at the poles takes roughly 35 days to circle once." "The Sun has what we call differential rotation" "You have all this plasma... that is really turning and turning and that causes magnetic field lines to become twisted and inner twiddled and mixed up." "Although magnetic fields lines are invisible we know they exist on the Sun by looking at features called "coronal loops" and "prominences"." "Rising up into the solar atmosphere." "Just as metal shavings line up in the presence of a simple magnet" "These loops of plasma perfectly outline the magnetic structure that supports them from below." "These plasma arches are so tall and wide that you could slide a planet as big as Jupiter right through them." "Sometimes magnetic fields can twist plasma in the Sun's atmosphere into majestic helical shapes called flux ropes" "A magnetic flux rope is sort of like a slinky." "The magnetic field line is wrapped around many times in a helical structure" "And when you have highly twisted magnetic field lines it carries a lot of stored free magnetic energy and sometimes it will even kink in on itself which kinks even more stored magnetic free energy." "These plasma prominencies can last for weeks or months, but eventually the stored up energy has to be released." "And the mass is flown off in the space." "Where the Sun's magnetic field is at its most twisted and complex" "Heat bubbling up from below is kept and the material is cooled by as much as 1000 degrees." "what results are relatively dark blemishes on the solar surface called "sun-spots"." "Sunspots are only dark in relation to the bright material around them." "If you could somehow suspend one alone up in space it would shine 10 times brighter than the full Moon." "These apparently tiny blemishes are actually plasma creatures the size of the entire Earth." "Galileo was one the first modern scientists to observe sun spots" "Using a telescope he projected the image of the Sun on the paper and traced it." "He realized that the blemishes were moving across the face of the star which was the first indication that Sun rotated." "Not only does the sun rotates but some spots themselves can spin and when they do, their magnetic field lines become extremely twisted." "Twisted magnetic field lines mean more energy and more energy means the potential for huge eruptions." "Think of a rubber band as magnetic field line" "If you twist it, and you twist enough it's goin to have all the energy and when you let it go it's going to release it" "If you just take an untwisted rubber band and release it it's not going to fly." "When a Sun spot unleashes its magnetic energy what results are the most colossal explosions on the solar system:" "solar flares." "A single flare releases as much as a billion megaton of energy." "The combined power of a million vulcanic eruptions on Earth." "They appear as these very... white regions and they're so bright because the temperature is so high." "on the order of ten million degrees and they can last for hours." "But the energy is massive." "The whole explosion... is equivalent to millions of nuclear bombs leaving the surface of the Sun all at once." "Solar flares don't just explode out in the space." "They also funnel high energy particles down to a layer of the sun called the cromosphere, where they quickly transfer their energy like a cue ball striking the rack in the game of billiards." "So you have a cue ball, actually like one of these very high energy particles coming from the flare agent." "A cue ball smacks very quickly into the 8-ball rack, and once it impacts the head ball, it's going to transfer that energy to the balls behind it and then they will all flyout because the energy is transferred to all of them." "If a large flare shoots enough high energy particles at once, strange things start to happen." "This is actual footage of a sunquake." "In 1998 there was a solar flare up in the corona that was so powerful that the material flying down toward the surface of the sun actually slack the surface and cause ripples to spread out from there." "While thay may look like ripples on a part, these are actually waves two miles high travelling at a maximum velocity of" "250 thousand miles per hour." "The 1998 sunquake would have measured in 11.3 on the Richter scale." "More than one million times stronger than the 1989 earthquake that shocked San Francisco." "In order to shake the surface of the sun that much, the solar flare had to release a colossal amount of energy." "It turns out that's almost the same amount of energy as if you cover the entire land mass of the earth with dinamite, about a yard thick." "And set it all off at once." "These explosions are not small." "Earthquakes aren't the only natural disasters with equivalents on the sun." "A flare can also kick-off a solar tsunami." "As waves of plasma in the sun's atmosphere rock it up at 700 thousand miles per hour, spreading around the entire face of the star in a matter of hours." "While sunquakes and solar tsunami pose no danger to earth, the violent action of a flare frequently triggers dangerous eruptions called coronal mass ejections, or CMEs." "In a CME energy from a flare flees a blob of highly charged radioactive plasma out of the solar atmosphere." "Coronal mass ejections range and speeds, but take in a curl as quick as" "800-900 miles per second, which is extremely fast and it expell a massive amount of material." "It can be the same amount of mass as, say, mount Everest, coming out from the sun and flying out into the space." "Where does this blob of superheated radioactive plasma go when it leaves the sun?" "Sometimes it sails out harmlessly in the space." "Other times it may head closer to home." "Coronal mass ejections from the sun are perhaps the most dangerous threat you've never heard of." "Also known as solar storms, they hurl a large masses of supercharged particles across 93 million miles of space." "Most takes several days to travel from the sun to the earth, but some rocket across the solar system at up to 6 million miles an hour, reaching our planet in less than 16 hours." "These storms can induce currents in the outer atmosphere knocking out satellites and cross-country power grids and carry the potential to rid just as much heavy gunner our infrastructure as a hurricane or a tornado." "But who on earth is keeping an eye on this potentially hazardous cosmic blasts?" "This is the headquarters of the National Oceanic and Atmospheric Administration, home to the US governments national weather service." "Their daily forecasts, whatches and warnings are essential information for everyday life on our planet." "But there is a lesser known group of forecasters working here in a special division called "The Space Environment Center"." "Out primary job is to monitor the sun and put up the alerts, watches and warnings for solar activity." "Good morning and welcome bright in briefing." "We have one unknown on the ration seen flare from east slam as a possible CME." "We have not had protons but we have had electrons." "One thing you notice is that this region pretty stall the activity in the sun." "Bristol thinks it might be packing up your head the next couple of weeks." "These space forecasters are on high alert for solar storms that might disrupt life on earth." "Solar storm clouds are made up of charged particles, so they are initially diverted around the planet by a magnetic field, just like waves breaking around the bow of a boat." "It turns out to be very important because if it impacts to the outer atmosphere directly, it would knock little bits of the atmosphere off in the space." "One reason why Mars doesn't have an atmosphere is that it doesn't have a strong internal magnetic field." "And so gradually over million or maybe billions of years the atmosphere was gradually knocked off in the space by the influence of the solar wind and by the CMEs that skim past the planet." "But our magnetic field is not the perfect force field of scifi movies." "Some particles can penetrate it charging up the upper atmosphere." "Solar storm would even bend and break the magnetic field lines on the far side of the earth, allowing charged particles to zip back down the field lines toward the north and south poles." "Extremely powerful storms distort the magnetic field even futher, inducing electric currents that span a continent." "When this happens technology like long-distance powerlines can become overloaded." "Because damaged the trasformers at either end of the line." "In fact, in 1989 most of the canadian provinces go back blacked-out because a transformer was blown out by a solar vent." "If we have that storm and hits our communication system and hits our our companies and all these things that we depend on" "there is all kind of chaos that can lay out there." "If power operators have time to react, thay can reduce the current being sent over their wires and avert disaster." "Satellite operators can also prepare for the onslaught with proper warning." "When there's a big space storm coming, we'll actually put some of the satellite to sleep, so that the storm doesn't cause an electrical short or otherwise somehow knock out the satellite." "So the more warning time they have, the better." "We wouldn't go sailing unless we knew what the weather is going to be." "Similarly when we have a large system like a power system or a telephone grid that can be effected by the weather and space, we need to know what the weather is going to be so that we can try to mitigate it." "Solar storms can also disrupt high frequency radiocommunications used by aircraft." "In the 1980's" "Airforce One was transporting president Reagan on a trip to China when a solar storm struck." "All communications were lost for several hours, effectively severing the head of the United States government." "The urgency is just like a worse weather." "One we have a tornado warning we know the order is to get that out to the public to let the people know that this is happening." "The same thing is with space weather." "Uses of this information need to know what do they need to know and now." "A just few hours back we experience a coronal mass ejection." "We wanna see what this blast is going out in, and then we can measure then and see how long it may take from that to reach the Earth from the sun." "We're seeing a very huge explosion of material that's coming out and if you look at this small image here, here's the sun is covered up, and look at the mass that's been thrown out in the space." "So it's huge, very huge." "Because magnetic field lines emanate from the North and South Poles energy from solar storms has easy access to those regions." "For that reason, experts worry that airplane passengers flying over the Poles during a powerful storm, might be exposed to armful levels of radiation, perhaps are those equal to a hundred chest x-rays." "It's not something that we want to mess around with, because we never know when that radiation might all of a sudden become a lot more intense while there's an airplane in the sky." "The threat from solar radiation is just one more reason scientists keep a close watch on our sun." "It matters, especially in modern times, what the sun is doing." "Earth is not an island." "We are partecipant in the activities of the solar system." "Sunspots are the triggers for more severe solar storms, so forecasters track them carefully, as they rotate across the surface of the sun." "Location, location, location." "We see CMEs all the time from the sun." "A lot of them are as the center is rotated around from the backside of the sun." "That would not be face towards the Earth, so that would be less of a concern." "As the sun rotates around and that active region gets more into the center of the disk, looking at us, then that's when we'll be concern with." "From the center of the sun, as it rotates around, as the kill zone." "As the sunspot rotates around and begin to face directly the Earth, that's when we really have to worry about a storm." "If a big storm leaves off then, it can aim directly at Earth, and the full force of the storm slams into the planet." "It's like a shotgun aiming at the target." "The more dead on the shot, the more likely serious damage would be inflicted." "With great danger also comes astonishing beauty." "Solar storms generate majestic planetary lightshows." "The shimmering courtains of color, called the Aurora." "Auroras work like neon signs, on an enormous scale." "In a neon sign, electricity introduces charged particles into a gus filled tube." "The particles in the gas are excited and start to glow." "If the tube has only neon inside, it will glow red." "By adding other gases, like argon, a whole range of colors can be produced." "The neon sign is driven by the electric field inside the tube, whereas the Auroras is actually driven by the magnetic field and energy from the sun." "As the energetic particles in a solar storm stream along Earth's magnetic field towards the Poles, the excite elements in our atmosphere, causing them to glow." "Oxygen molecules emit a green or red color." "And nytrogen emits pinks, blues and violets." "While these ghostly lights are usually confined to the Poles, extremely strong solar storms can drive them closer to the Equator." "In 1859 a geomagnetic storm ignited by a huge solar flair created Auroras as far south as Rome." "The 1859 storm was an unusually powerful event that some have called "the perfect solar storm"." "The 1859 storm told us a little something about what the sun can do." "The storm was so intense and the alignment was so perfect, that it simply overwhelmed Earth's natural difenses." "A huge solar flair erupts on the surface of the sun." "Less than a day later and 93 million miles away, the wires the carries communications across the Earth, begin to spark." "Business grinds to a whole world wide as wild fires are ignited by the small lights." "At the same time, colorful Auroras light up the skies of cities around the globe." "Earth has just been visited by the perfect solar storm." "The sun kicked up this just incredible solar flair and a massive amount of energy headed towards Earth." "Not only was this storm one of the 2 most powerul on record." "It was also one of the fastest." "Ejecting from a sunspot and directly at Earth, it would race from the sun to our planet in less than 18 hours." "Now, it takes a really fast rocketship, years to get to the sun." "This storm, this cloud of electrified particles, managed to get here in less than a day." "That's incredibly fast." "Fortunately, the perfect solar storm took place in 1859, when the only technology vulnerable on Earth, was the telegraph." "Since the era in wich we've become dependant on high technology, we wait to see another perfect solar storm." "The question remains." "Could it happen again?" "What if we had another one like that?" "Can we have another perfect storm?" "I'd say yes we can, there's no doubt about that." "The... effects that would be on us today, compared to 1859 could be... devastating." "The effects on Earth and on our communication systems..." "We don't exactly know." "That's the scary part." "It's likely that our modern technologies would be battered like beachfront houses during a hurricane." "Imagine if we lost all the satellite that we lay cellphone calls, television signals and bank transactions." "And what if at the same time, the failure of powergades cascaded the all regions into darkness for hours, or weeks." "If these essential services couldn't be restored quickly, caos wouldn't be far behind." "It would definitely be a rip effect upon society and every man and woman and child that lives on this Earth." "Solar storms can be as hard to predict as hurricanes." "Well, forecasters lack the technology to fortell the next pefect storm." "They do know that one would be more likely to hit at the peek of the sun's eleven years sunspots cycle." "What happens is the sun reverses the direction of its magnetic field every eleven years." "So in 22 years it reverses and comes back were it was." "As we're near to reversal every eleven years, the number of sunspots encreases and there's a spike in solar activity." "We call that period solar maximum and those periods are inner spreeads by 5 years apart from periods we call solar minimum." "So you have this eleven year back and forth between the sun beeing sometimes very feroscious, and it goes crazy, it's like the 4th of July with fireworks all the time." "And then it starts to r down and for few years it gets quiter until it gets into a low point where there is a firecrack every now and then but not a lot going on." "Just like hurricane's seasons, solar maximums vary in intensity." "Sun produce many more powerful storms than others." "Although we're currently at solar minimum, scientists are watching carefully to see when may have the next solar max might unleash." "The last solar maximum was in about 2001 and so the next one ought to be in 2012, but there's different predictions." "The whole field of solar physics is basically waiting to baite is breath to see what actually happens." "There are some loudly divergent opinions on what's gonna happen." "One group is suggesting that this next solar cycle could be the strongest in modern times." "If those predictions are correct, Earth could be in for a wild ride." "We might have to worry about a repeat of the 1859 event." "If that would happen today it would wreak untold damage." "We're gonna learn a whole lot about what can happen to modern technology when the sun bows its top." "Much of the violence in the sun erupts here, in the hellish outer atmosphere known as the corona." "This region has long held one of the great solar mysteries." "Because even though it's half a million miles from the heat generating core, it burns at millions of degrees." "This seems to violate the very laws of physics." "That's very strange." "I have a thermometer here." "If I hold the thermometer close to the fire, it reads a very high reading." "Where the probe is right now it's over 200 degrees." "And if I pull the probe out a little farther from the fire, ok, it drops down to about 90 degrees." "Now, the farther I get from the center, the cooler it gets." "In the atmosphere of the corona of the sun the temperature soars hot as the core." "That's as if, I would say, well, way half behind me there, the heat from the fire is as hot as the fire itself, even though it's very far from the fire." "What force could possibly cause the superheating of the corona?" "The answer will rock you." "The hellish solar corona rages at millions of degrees." "For centuries scientists have been baffled how anything so far from the sun's core could still burn so hot." "Recently, as improved satellites offered a closer view of the solar surface, clues began to emerge." "Below the corona the sun's surface is literally boiling." "The reason is that the entire surface of the sun is covered with convection cells, hot material from the inside of the sun, that rises up through, reaches the surface, cools off by glowing, giving off sunlight and then sinks back down." "Each bubble of material that comes up is about the size of Texas." "It spreads out across the surface, cools off and sinks down in 5 minutes." "So, that's a tremendously violent process that's happening in, literally, almost a milion places over the entire surface of the sun, all the time around the clock, 24/7." "This boiling is not only violent." "It's also extremely loud." "The sun is a tremendously loud place." "You can imagine... covering the entire surface of the sun with speakers being driven as hard as the loudest rock concert you've ever been to." "That would be comparable to how loud it really is on the surface of the sun." "The sun's churning surface creates enough sound energy to superheat the corona to millions of degrees." "Scientists believe that the combination of these sound waves and energy from the sun's magnetic field is responsible for the extreme temperatures found in the corona." "The only time you can actually see the corona from Earth is at the climax of one of the most dazzling displace in the solar system, a total solar eclipse." "Before scientists understood them, these unsparing events instilled only fear." "The ancient Chineses believed that a dragon was devouring the sun." "So what's really happening in a solar eclipse?" "In simplest terms it's when the moon blocks our view of the sun." "Imagine that you're sitting in a movies watching very happily something going on on the screen and then somebody in the row in front of you comes across and blocks your view." "In a movie, in theory you might not want that person to come across in front of you, but at... in a eclipse we're very lucky to have the moon come across the sun, we're lucky to have it come right across the middle." "We're also lucky that the moon, although is 400 times smaller than the sun, is also 400 times closer to us." "This cosmic coincidence means that the two objects just happen to be the same apparent size in our sky, which allows for one to completely block out the other." "This magnificent cosmic event only happens when the path of the moon intersects the line between the earth and the sun." "The moon's orbit is tilted slightly about 5 degrees." "If it wasn't we would have an eclipse every month." "And then we'd be bored, but we're not bored because most months the moon goes above or below the place where the line goes from the earth to the sun." "So instead of one every month we get a total eclipse somewhere on earth about once every year and a half." "As the moon slides in front of the sun, it casts a shadow onto the earth." "The outer part, where the shadow is fainter, is called the penumbra." "If you're standing within the swath traced by the penumbra, as it moves along the earth's surface, then you'll see only a partial eclipse." "But travel to a spot within the path of the dark inner shadow, called the umbra, and you'll experience the majesty of a total eclipse." "There's another option if you can't travel to the path of totality, wait in one place long enough and a total eclipse will pass right over your head about once every 300 years." "The Sun, that shining star of our solar system is capable of both astonishing beauty and ferocious violence." "It seems impossible to believe, but it won't be around forever." "Eventually even the sun must die." "The sun has a fixed amount of fuel in its core, it is undergoing fusion, at a rate that you can calculate." "So here's the rate it's using its fuel, here's how much fuel you have, so it's a simple calculation to show when the sun will die, and that's in about a five billion years." "Well, unfortunately the sun will not go out with a bang." "It's too small to erupt in a supernova." "However stars do a peculiar thing, the one of the few things around that get hotter as they cool off." "As it exausts its hydrogen fuel our nearest star will cool and gradually collapse under the force of gravity." "Energy from this collapse will start heating up the core again to hundreds of millions of degrees, hot enough to start burning helium." "Onto the extraheat of the helium burning the star will expand into a monstrous orb called a red giant." "It'll get so big it will engulf the entire orbits of Mercury, Venus and Earth." "You don't want to be around for that." "You'd wanna be **climbed** upping your way to safety, long before this happens." "The earth is likely to change it's orbit slightly as the star expands, so that we won't be engulfed." "Still, talking about global warming, you wouldn't want to be here." "The outer layers of our sun will eventually become so unstable that they will fly off into space, leaving behind a small core about the size of the earth." "So now will be shrunk most of the sun, which is a million miles across to the size of the earth which is well like 6000 miles across." "Our once great star reduced to a slowly cooling cinder." "Life as we know it on earth will cease to exist." "And that was the death of the sun." "All of this is bad news for the human race, but look on the bright side." "We've got five billion years to repair for this disaster." "For now, humanity basks in the glow of a sun in the prime of its life." "Science has uncovered many of the secrets of our nearest star, but we remain awed by its beauty, and ever more wary of its wrath."