Where Did Earth's Water Come From?

 Our  planet  is  wet.  Seventy-one  percent of Earth's surface is covered  in water. Most of that water is in the  oceans, but another 3.5 percent is in  rivers and lakes, locked up in the ice caps, or floating in the atmosphere in the form of water vapor. More fresh and salty water hides beneath the surface,  and  scientists  have  even discovered  that  Earth's  mantle  is replete with the wet stuff. The watery nature of our home planet makes it unique. So where did all this water come from?

      

 At least some of that water was here at the moment of creation. Scientists estimate that 30 to 50 percent of the water on Earth today originates from ice from the dust cloud that eventually coalesced into the Sun and its planets. Thanks to Earth's mass, volcanism, and distance from the Sun,  our  climate  now has  the  right temperature and atmospheric pressure for that ancient ice to exist in a state of liquid water (whereas on other planets, it either froze or outgassed back into space).  

   

   But where did the rest come from? For years, the most obvious source was comets -miles-wide snowballs that roam the solar system and could have bombarded the planet in the first billion years. Recent spectrographic observations of comets that buzzed Earth, and the latest findings from the European Space Agency's space probe, Rosetta, point in another direction. The spectrographic signature of the water of these objects indicates higher levels of heavy water-water with deuterium rather than ordinary hydrogen-than is found on Earth. Other findings from Rosetta indicate the presence of a bluish hue on pan of one comet   known   as   67/Churyumov- Gerasimenko, which would suggest the  presence of frozen water beneath the surface of dust and rock. So, if not comets, what and where did our water come from?   

     

  The process of elimination leads us to asteroids or, more specifically, a class of meteorites   called   chondrites,   which originated from space rocks in the inner solar system. These potential candidates harbored water on their surface without releasing it, thanks to the younger and cooler Sun, depositing the moisture.

How Will the Universe End?

     

    In 1929, Edwin Hubble discovered that the universe is not in fact static, but expanding. In the years following his discovery, cosmologists took up the implications of the discovery, asking how long the universe had been expanding, what forces caused the expansion, and whether it will ever cease. 

      

   Cosmologists are pretty confident about the first question: just shy of 14 billion years. A great deal of evidence supports the predominant answer to the second question: The universe rapidly emerged from  a  singularity  in  an  event  that cosmologists call the Big Bang. The third question is a bit more mysterious, and the answer relies on an obscure, confounding phenomenon known as dark energy. The density of dark energy in the universe determines  its  ultimate  fate.  In  one scenario, the universe does not possess enough dark energy to forever counteract its own gravity and thus ends in a "Big Crunch."  Under  this  scenario,  the universe's gravity will overcome its expansion and the cosmos will collapse in on itself, resulting in a singularity that may precipitate another Big Bang. However, the evidence cosmologists have gathered over the last few decades leads us away from this scenario.

      

    For the Big Crunch to occur, we'd see signs that gravity was winning out over dark  energy,  slowing  its  expansion. However, measurements of distant galaxies indicate that cosmic expansion is not slowing   down-it's   speeding   up! Apparently, the density of dark energy in the vacuum of space is simply too high to permit a Big Crunch. That leaves two possible fates for the cosmos: 1) a Big Freeze, in which the acceleration  eventually  halts  but  the universe  keeps  expanding,  creating  a system  where  heat  becomes  evenly distributed, allowing no room for usable energy to exist and thus, "heat death," or 2) a Big Rip, in which the expansion of the universe continues to accelerate forever. In  the former scenario, the universe will  progressively become darker and colder  until the end of time. In the latter, all  matter down to  the  most  fundamental  particles will be torn asunder.    

  

   All the recent data from the Planck  space observatory and the Sloan Digital  Sky Survey suggest there is just enough  dark energy to continue the universe's  expansion, but not enough to keep it  accelerating  forever.  This  conclusion  points toward the Big Freeze, or "heat   death" of the universe. The most up-to-date science leads us to the conclusion that our  universe-and Robert Frost's-is more  likely to end in ice than in fire. That, however, assumes that what we believe about dark energy is true. Considering that dark energy itself is a phenomenon cloaked deeply in mystery, such assumptions may yet prove untenable.

Alcohol - How Over Consumption Affects Your Body?

  

  Alcohol addiction commonly known as alcoholism is a fairly common problem that has shown to affect people from every walk of life. Scientists have tried to pinpoint the absolute cause behind alcoholism, but to no success. Certain factors like sex, genetic, and socioeconomic factors have shown to have some effect on alcoholism. The cause of alcoholism is never singular. Alcohol addiction is indeed a disease, where a person may not have full control over his actions and is seen to change the neurochemistry of the brain.

    

  The symptoms of alcohol addiction can be seen in many ways and the severity of the situation varies from person to person. Other factors such as the frequency of consumption may also be specific. While some people are heavy drinkers and drink throughout the day; others may drink occasionally and remain sober for a few days.

     

  A person who is dependent on alcohol will prioritise drinking over other essential activities and will eventually cause disruption in his social life, work or other areas of his life. It can also create a negative effect in the victim’s life along with their families and their near and dear ones.

  

  What are the signs of alcohol addiction and alcohol abuse?

 

   The signs and symptoms of alcoholism or addiction are rather conspicuous. Since drinking alcohol is common in social events in most cultures around the world, it becomes difficult to recognise when someone is addicted to alcohol, unlike drugs like cocaine and heroin.

 The physical signs of alcohol abuse include:

    

   Loss of control over the quantity of alcohol consumed.Lack of adequate sleep, followed by overcompensation for sleep.Expression of anger and other negative behaviours my increase in inappropriate places and situations.Lack of proper attention towards the priorities in life.

 How does alcohol affect the body?

    

   Chronic abuse of alcohol can have negative effects on almost every part of your body and plays havoc in your system. Alcohol is liable to cause irreversible damage to several organs of the body which is vital for sustenance:

Nervous system, Stomach or

Intestines, Liver,Heart, Brain

Alcoholism in itself can lead to several diseases like:

 High blood pressureCancerIncreased incidences of osteoporosis, especially in womenSexual issues

What Is Dark Energy?

    

        In 1929, Hubble  American astronomer Edwin  studied  exploding determined  a  number  of  stars, or supernova, and  that the  universe was  expanding. The notion galaxies were moving ours was a radical idea.  that distant  awav trom  It seemed obvious to astronomers  that gravity-the mutual attraction between all matter-would   affect  the   expansion process. But how? Would the pull of gravity completely halt the expansion of  the universe? Could the universe stop  expanding and then reverse itself back  toward  us?  Or  would  the  universe  eventually escape the gravitational effect  and continue to expand? The universe may  be  expanding,  reasoned  the  scientific community, but its expansion was surely slowed by the forceful effects of gravity.

        Fast forward nearly 70 years to a time when two teams of astrophysicists-one led by Saul Perlmutter at the Lawrence Berkeley National Laboratory and the other by Brian Schmidt at Australian National   University-began   studying supernovas  to  calculate  the  assumed deceleration  of  expansion.  To  their astonishment,   they   discovered   that supernovas as far as 7 billion light-years away were not brighter than expected but rather dimmer, meaning they were more distant than the teams had calculated them to be. The universe isn't slowing down, they concluded. It's speeding up.

        

   The discovery turned the scientific world on its head: If gravity isn't the most dominant force in the universe, what is? In 1998, American theoretical cosmologist Michael S. Turner dubbed the mysterious new something "dark energy." Yet even with a name, we know little about dark energy.

      

  Theorists have come up with several explanations for dark energy. The leading theory claims that dark energy is a property of space. Albert Einstein claimed it is possible for more space to come into existence and that "empty space" can have its own energy. "As more space comes into existence," reports NASA, "more of this energy-of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster."   

   

     NASA reports that scientists have been able to theorize how much dark energy there is out there because we know how it affects the expansion of the universe. Roughly 69 percent of the universe is dark energy. Dark matter accounts for about 27 percent,  leaving  the  rest-all  normal matter, everywhere-adding up to less than 5 percent of the universe.   

      

   Another explanation posits that dark energy is a new type of energy field or energy fluid that fills space but affects the expansion of the universe differendy than matter and normal energy. Scientists have labeled this energy "quintessence," but we still don't know what it interacts with or why it even exists.

Are There Habitable Planets Beyond Our Solar System?

     Ever since people first tilted their gaze up toward the heavens, they have wondered about the possibility of other worlds like ours orbiting distant suns. Until very recently, such questions were left to the realm of speculation.  Today,  thanks  to telescopes like the Iepler space  observatory    and    increasingly advanced surveys from ground-based technology, we know that the galaxy is swarming with planets. But are any of them habitable? Do any of them resemble our own? 

      The question of habitability is a tricky one, and the odds of any individual planet possessing Earth-like properties are rather low. That said, the numbers are in our favor.  Kepler  recently  confirmed  the discovery of its l,OOOth exoplanet. Some astronomers now estimate that there is one exoplanet for every star, on average. That means there are billions and billions of planets in our universe! Many of these planets,  though,  are nothing close to habitable.  The  first  exoplanets  that astronomers  found  orbited  impossibly close to their suns, tidally locked, exposing one side to scorching heat and radiation and the other side to permanent night. In contrast. Earth orbits the Sun in the so- called Goldilocks Zone: not so close that all liquid water boils away, but not so far that it is perpetually frozen in ice.   

     What's water got to  do with the existence of other planets? The capacity to harbor liquid water is the key characteristic that astronomers look for in the search for habitable alien worlds, due to water's paramount importance to life on our own planet. But liquid water and a planet's average orbital distance are but two of several key factors. For instance, the class of star that serves as the sun is important: Habitability requires a sun that emits the right type of radiation and is likely to live long enough to allow life to evolve. A stable orbit is also important, ensuring that the  planet's  climate  doesn't  fluctuate wildly. The mass of the planet-massive enough so that it's capable of generating and holding onto an atmosphere, but not so massive   that   the   atmosphere   is oppressively dense-is also critical.   

     While  astronomers  have  not  yet confirmed  the  presence  of  habitable exoplanets, all signs currently point to the affirmative. Scientists reviewing data from the Kepler observatory recently discovered eight planets, roughly the size of Earth, in their respective sun's Goldilocks Zone. Other candidates exist, from as nearby as 40 light-years to thousands of light-years distant, some orbiting superclose to colder suns, and some much larger than Earth; so- called super-Earths range in size from two to 10 Earth masses. We seem on the verge of discovering a planet that might not only be capable of supporting life, but could hypothetically support life. 

      Whether these habitable planets already support Iife-forms and whether those life-  forms are intelligent-well, that's a whole other mvstery.

What Is the shape of the Universe?

     Most casual observers would assume that the cosmos is a space that expands into infinity, but the answer is not as simple as gazing into a starry   sky   and   hazarding   a measurement. Einstein's theory of general relativity, when paired with estimates of the relative amounts of matter and energy in the cosmos, allows for only one possible solution -the universe is infinite. 

     

    General relativity requires that the universe remain the same throughout (homogeneity) and appear the same in all directions (isotropy). Therefore, the shape of the universe is the result of the push and pull of gravity and dark energy. This may sound familiar. The same characteristics determine the universe's three possible fates: the Big Crunch, the Big Rip, and the Big Chill.   

       

   Just as a universe with an energy density less than its gravitational pull will eventually collapse in on itself (the Big Crunch scenario), the same gravity will overcome dark energy to mold the universe into a sphere. A spherical universe implies that there is a finite amount of space (just as there is a finite amount of surface on a sphere), that two lines appearing parallel will eventually converge (just as lines of longitude  on  Earth  converge  as  they approach the poles from the equator), and that by traveling far enough we can return to our original position.   

    

    Conversely, a universe with an energy density greater than its gravitational pull will exhibit the opposite geometry, better resembling a saddle than a sphere. In such a universe, the overwhelming force of dark energy pulls the universe into an inverted curve where initially parallel lines will gradually diverge. Much like the previous scenario, this universe is still finite.   

      

   However, just as cosmologists are fairly confident that the cosmos will not end its life in a Big Rip or Big Crunch, they are equally confident that the geometry of the universe is neither spherical nor saddle- shaped.  When both gravity and  dark energy reach a balance in their effect on the cosmos, the math implies that the universe will simply stretch out forever as an infinite flat plane. In this universe, two initially  parallel  lines  remain  parallel forever, and we will never be able to return to our starting point by traveling any distance in the same direction.   

       

   It is worth noting that confidence in this measurement depends on the correctness of Einstein's assumptions about homogeneity and isotropy as well as the accuracy of the current understanding of dark matter. These assumptions underlie the standard models of cosmology, but should they prove  even marginally inaccurate,  we could be living in a much different universe indeed.

What Causes Jupiter's Red Storm?

    

    At one time, the storm was at least 20,000 miles (32,000 km) in diameter and big enough to envelop three Earths. It is similar to a hurricane on Earth, rotating counterclockwise with a maximum wind speed of 268 miles per hour (430 kmh), almost twice as fast as the worst hurricanes on Earth. Historic observations date as far back as the 1600s. Since then, the spot has changed, fluctuating between a deep red and a pale salmon color.  Laboratory experiments suggest that complex organic molecules,  red  phosphorus,  and  other sulfur compounds cause the vibrant color. But since the 1930s, the storm has shrunk to half its largest diameter. Even though it may be dwindling in size, the longevity and enormity of our solar system's biggest storm is full of mystery. 
    
      The reason for the persistence of the Great  Red  Spot  is  unknown,  but presumably comes from the fact that it never moves over land, unlike hurricanes on Earth. Jupiter is composed of hydrogen and a small amount of helium and has no "land" in its form. Jupiter's internal heat source is a driving force, and the spot tends to absorb nearby weaker storms. However, based on computer models, the spot should have disappeared after several decades. Waves and turbulence in and around the storm sap it of energy. The powerful jet streams that surround the spot should slow its spinning. And even though the storm absorbs smaller ones, researchers say that doesn't happen enough to explain the storm's longevity. Some scientists think vertical flows in the storm are just as important as the more-studied horizontal flows. When the storm loses energy, vertical flows move hot and cold gases in and out of the storm, restoring energy.  

    

      Understanding Jupiter's red storm could reveal more clues about the vortices in Earth's oceans and also the nurseries of stars and planets. Philip Marcus, a fluid dynamicist and planetary scientist at the University  of  California  at  Berkeley, explains the importance of understanding the Great Red Spot: "Vortices with physics very similar to the GRS are believed to contribute to star and planet formation processes, which would require them to last for several million years"-even as the Great  Red  Stmt  shrinks,  it  retains enormous significance for Earth and the very beginnings of the solar system.

Are There Habitable Planets Beyond Our Solar System?

  

    Ever since people first tilted their gaze up toward the heavens, they have wondered about the possibility of other worlds like ours orbiting distant suns. Until very recently, such questions were left to the realm of speculation.   Today,   thanks   to telescopes like the kepler space observatory    and    increasingly advanced surveys from ground-based technology, we know that the galaxy is swarming with planets. But are any of them habitable? Do any of them resemble our own?

      The question of habitability is a tricky one, and the odds of any individual planet possessing Earth-like properties are rather low. That said, the numbers are in our favor.  Kepler  recently  confirmed  the discovery of its l,OOOth exoplanet. Some astronomers now estimate that there is one exoplanet for every star, on average. That means there are billions and billions of planets in our universe! Many of these planets, though,  are nothing close to habitable.  The  first  exoplanets  that astronomers  found  orbited  impossibly close to their suns, tidally locked, exposing one side to scorching heat and radiation and the other side to permanent night. In contrast. Earth orbits the Sun in the so called Goldilocks Zone: not so close that all liquid water boils away, but not so far that it is perpetually frozen in ice. 

       What's water got to do with the existence of other planets? The capacity to harbor liquid water is the key characteristic that astronomers look for in the search for habitable  alien  worlds,  due to water's paramount importance to life on our own planet. But liquid water and a planet's average orbital distance are but two of several key factors. For instance, the class of star that serves as the sun is important: Habitability requires a sun that emits the right type of radiation and is likely to live long enough to allow life to evolve. A stable orbit is also important, ensuring that the  planet's  climate  doesn't  fluctuate wildly. The mass of the planet-massive enough so that it's capable of generating and holding onto an atmosphere, but not so massive   that   the   atmosphere   is oppressively dense-is also critical.   
   
      While  astronomers  have  not  yet confirmed  the  presence  of  habitable exoplanets, all signs currently point to the affirmative. Scientists reviewing data from the Kepler observatory recently discovered eight planets, roughly the size of Earth, in their respective sun's Goldilocks Zone. Other candidates exist, from as nearby as 40 light-years to thousands of light-years distant, some orbiting superclose to colder suns, and some much larger than Earth; so- called super-Earths range in size from two to 10 Earth masses. We seem on the verge of discovering a planet that might not only be capable of supporting life, but could hypothetically support life.  

     Whether these habitable planets already support life-forms and whether those life- forms are intelligent-well, that's a whole other mystery.

How Long Would It Take to Walk a Light-Year?


       If you had started just before the first dinosaurs appeared, you'd probably be finishing your hike just about now. 

    

     Here's how it breaks down. One light-year -the distance light travels in one year, used as the yardstick for interstellar distances-is about 5.9 trillion miles (9.5 trillion km). If you hoofed it at 20 minutes a mile, it would take 225 million years to complete your journey (not including stops for meals or the restroom). Even if you hitched a ride on NASA's Mach 9.8 X-43A hypersonic scramjet, it would take more than 90,000 years to cover the distance.    You'd need to bring a big backpack, too: Walking such a distance requires substantial supplies. The average adult bums about 80 calories per mile walked, so you'd need about six trillion granola bars to fuel your trip. You'd also produce a heap of worn-out shoes. The typical pair of sneakers will last you 500 miles (800 km), so you'd burn through some 11.8 billion pairs. And all that effort wouldn't get you anywhere, astronomically speaking: The closest star to the Sun, Proxima Centauri, is 4.22 light-years away.

Does Alien Life Exist?

       It's  easy  to  proclaim  that  the existence of aliens is a crazy idea, until you consider these words from astrophysicist Stephen Hawking: "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is working out what aliens might actuallv be like."

        Other scientists agree.  But while the existence of alien life is mathematically probable, humans have not been able to prove that extraterrestrial life does exist. The quest to find that life has taken several forms.  The  Search  for  Extraterrestrial Intelligence (SETI)  Institute,  based in California, uses giant radio telescopes to try to detect radio signals sent by far-off, technically advanced life forms. NASA's Kepler Space Telescope has found planets within the Milky Way that could have the right conditions for life to develop. By one estimate, as many as 20 percent of the stars in the galaxy have such a suitable planet. A 2015 report highlighted one planet in particular, about 150 light-years away from Earth,  that  seemed  like  a  possible candidate to support the development of alien life. It orbits a star called Epic 201367065, which is about half the size and mass of Earth's Sun. 

         While some people wonder about the complexity of possible alien Iife-forms, some scientists think it makes more sense to   imagine   "aliens"   as   simple microorganisms. Life on Earth started out as single cells, and life on other planets might still be at that stage of evolution. And as Hawking notes, Earth was lucky to avoid a cataclysmic collision with an asteroid or comet in the past 70 million years. Other planets could have had their early life-forms wiped out in such a cosmic crash.    NASA research done in the 1990s found what scientists thought were signs of ancient bacteria on a meteorite from Mars that  reached   Earth   in   1984.   Other scientists, though, dismissed the claim, and no one has proved the  existence of microbes on Mars, now or in the past.   

        The possibility that the Red Planet once had water, however, was raised in 2014 after  NASA  scientists  studied  another meteorite from the planet that reached Earth. That same year, the NASA rovers, Curiosity and Opportunity, were able to capture high-resolution images of what are believed to be ancient riverbeds on the surface of Mars. The presence of water raises the possibility of biological activity as well. So does the discovery of large amounts of methane, which Curiosity also detected. The methane, however, could be the product of geochemical processes, rather than biological.  

        For now, scientists can feel confident in the odds that alien life does or did at some  point form.  exist, but without any idea of its As for the possibility of intelligent alien life ever visiting us on planet Earth, Hawking had this insight: The arrival of aliens could turn out to be much like Christopher Columbus's arrival in the Americas-and be followed by a steady stream of conquistadors and explorers from another universe. And we all know how that turned out for the people already living there.

Why Do Pulsars Pulse?

    

 

   Seven  thousand  years  ago,  a supermassive star in the constellation we now call Taurus collapsed in on itself and  into a supernova so bright that-when its light reached Earth in 1054 C.E.-it could be seen in broad daylight. What was left behind was the brilliant Crab Nebula, a  well  as  the  Crab  Pulsar  that illuminates  it.  This  neutron  star pulses out radiation across the entire electromagnetic spectrum at a rate of 30 times per second. But why does it Dulse at all?  Only half a century ago, nobody knew that pulsars, short for "pulsating stars," existed. In 1967, when astronomers Jocelyn Bell Burnell   and  Antony  Hewish  first discovered a pulsating source of emissions all coming from the same point in the sky, among the first hypotheses was that these pulses were radio waves emitted by an alien civilization. Burnell and Hewish even went so far as to name the object LGM-1, short for "Little Green Men." Subsequent discoveries of new pulsars, including the Crab Pulsar, ruled out the alien emissions hypothesis.  
 
        

     Today, scientists know that pulsars are generated by rotating neutron stars. The stars rotate quickly due to the conservation of angular momentum: When a large rotating body collapses, the remaining matter spins at a much higher rate, akin to the   effect  spinning  figure  skaters experience when they hold their arms close against their body. Some of these neutron stars have strong magnetic fields-in the case of pulsars, about 1 trillion times as strong as Earth's-and emit a beam of radiation that coincides with their magnetic poles. This radiation can be the result of the  quickly  spinning  star's  slowing momentum, the accretion of matter as it falls into the star, or the twisting of the star's magnetic field. This magnetic axis is not always the same as the axis of rotation. When they do not coincide, the beam of radiation wobbles about the rotational axis. The result of this wobbling is a beam of radiation that, when viewed from Earth, seems to be pulsating. 

       

     Since  Burnell  and  Hewish  first discovered pulsars, astronomers have identified nearly 2,000 more, emitting visible light, X-rays, and, in some cases, only gamma rays. And while we have a general idea of why pulsars pulse, astrophysicists believe that there is still much more to discover.

Why Don't Moons Have moons?

  
    Astronomers  can  say with  near certainty that there are no moons with moons in our  system. But that doesn't   mean   it's   physically impossible. After all, NASA has successfully put spacecraft into orbit around our moon.

      Although astronomers have spotted some asteroids with moons, a parent planet's strong gravitational tug would make it hard for a moon to keep control of its own natural satellite, says Seth Shostak, a senior astronomer at the nonprofit Search for Extraterrestrial    Intelligence    (SETI) Institute. "You would need to have a wide space between the moon and planet," he says. Orbiting far from its parent planet, a relatively massive moon might be able to hold onto a moon of its own.    Condiuons like these might exist in far- off solar systems, but while hundreds of exoplanets (planets outside of our solar system) have been detected, there's almost no chance we'll be able to spot exomoons, much less moons of exomoons, for decades to come. Most planet-hunting methods- such as spotting one as it passes a large star -lend themselves  to  detecting huge, Jupiter-Iike planets, or sometimes Earth- sized, rocky planets, but not their moons.   

    

     Even if astronomers spot a moon with a moon, it probably won't last long. "Tidal forces from the parent planet will tend, over time, to destabilize the orbit of the moon's moon, eventually pulling it out of orbit," says Webster Cash, a professor at the University of Colorado's Center for Astrophysics and Space Astronomy. "A moon's moon will tend to be a short-lived rfienomenon."

What Are Fermi Bubbles?

     
        In 2010, data gathered by the Fermi Gamma-Ray   Space   Telescope revealed a new discovery. Scientists were surprised to find two enormous, bubble-like clouds that extend 50,000 light-years across the center of our galaxy, the Milky Way.
   

    The  two  gamma-ray-emitting  bubbles stretch across more than half of the visible sky and may be millions of years old. (Gamma rays are electromagnetic radiation at  the highest-energy,  or  shortest- wavelength, end of the electromagnetic spectrum.) The origin of these previously unseen structures, however, remains a truly baffling mystery.  

       

   A research paper appearing in the Astrophysical Journal in 2014 described some features of the aptly dubbed "Fermi bubbles."  First,  the  outlines  of  the structures are very sharp and well defined, and the bubbles glow evenly across their  enormous surfaces. The most distant areas of the bubbles feature extremely high- energy gamma rays,  yet there is no apparent cause for them that far from the  galactic center. Lastly, the parts of the  Fermi bubbles nearest the nucleus of the  Milky Way contain both gamma rays and  microwaves, but as the bubbles extend  farther out, only the gamma rays are  detectable.
      
       Theorists   have   offered   several explanations for the unusual structures. The two most predominant theories both suggest the bubbles were formed by a large, rapid energy release.  
    
        One possibility claims that enormous streams or jets of accelerated particles originating  and  blasting  out  of  the supermassive black hole at the center of the Milky Way created the Fermi bubbles. Astronomers  have  observed  such  a phenomenon in other galaxies, and while it is unknown if the Milky Way black hole has an active jet today, it may have had one millions of years ago.

       Another commonly held theory argues that the Fermi bubbles were created during star formations over a period of millions or even billions of years. The gas ejections created from bursts of star formations, similar to the ones that produced huge star clusters in the Milky Way, theoretically rode massive galactic winds out to far-off distances and are held there by powerful magnetic forces.
 
       Scientists are eager to unravel the mystery of the Fermi bubbles' origin. "Whatever the energy source behind these huge bubbles may be," says David N. Spergel, a theoretical astrophysicist at Princeton University, "it is connected to the many deep questions in astrophysics."
   
    

What Is the Moon Illusion?

      The Moon seems larger when it is near the horizon than when it is high in the sky, a phenomenon called the Moon illusion. Although recognized for centuries-the horizon Moon was important to early civilizations that functioned according to the Moon's cycle-this ancient phenomenon has only recently been explained.

   

     Early astronomers believed the Moon at the horizon was physically closer to Earth than when it was high in the sky, and the closeness meant a larger Moon. However, Newton's description of the Moon's orbit showed the contrary to be true. The Moon is actually closest to the observer at its zenith, or when it is high in the sky, but the difference is so small that it is negligible anyhow. Others theorized that the Moon illusion was caused by refraction when light rays passed through more of Earth's atmosphere. Today, scientists guess that the illusion occurs not externally, but through a trick of our brains.    Opucal illusions play a big role in the appearance of the Moon. When the Moon is placed as a backdrop against objects of known heights-such as trees, cars, or buildings-it appears larger than when it is isolated in the sky. In one experiment, researchers asked participants to view the horizon Moon through a cardboard tube, which caused background objects to disappear. They found the Moon seemed to shrink to a size similar to the zenith Moon. 

     

    The Ebbinghaus illusion describes this perceived effect. Two circles of identical size are placed near each other. One circle is surrounded by smaller circles, and the other circle is surrounded by larger circles. Although we know the original circles are identical, we perceive the circle surrounded by smaller circles as larger than the neighboring circle surrounded by larger circles. We also view the Moon as we do other objects, like clouds and birds, that recede into the skyline. We expect them to look smaller as they get farther away. In what is known as the Ponzo illusion, our brain tricks us into thinking the Moon is our minds only, farther away from Earth. But the Moon is still mostly the same distance away in its orbit. Nothing has changed in its size or its distance from our planet. To practice this, draw two identical parallel lines horizontally across a photo of a receding railroad track. The line closest will appear smaller than the line farther away, because as the tracks recede into the horizon, they become smaller, and your brain expects the line to do the same.  

     

    Still not convinced? Try taking a picture of the large Moon at the horizon. The camera doesn't suffer from the same visual cues that make the Moon appear as massive as in real life. This illusion is not unique to the Moon-the Sun and stars show the same properties. And while interesting to consider, the Moon illusion offers little insight into astronomy and the atmosphere. Instead, it proves an example of ODtical illusion. getting smaller as it rises in the sky.

Does Spontaneous Human Combustion Ever Happen- and How?

     
      In 1980, Henry Thomas, a 73-year- old man living in Wales, was found burned to death in the easy chair of his living room-the trunk of his body nearly completely incinerated, but oddly, his feet unburned and the remains of his legs still clothed in socks   and   pants,   practically untouched by the fire. Thomas's death was ruled "death by burning," although no cause of the apparent fire was noted. 

    

     In December 2010, the body of 76-year- old  Michael  Faherty  was  discovered burned beyond recognition in the living room of his home in Galway, Ireland. The damage caused by the fire was limited to Faherty's burned body, the ceiling above, and the floor beneath him. The coroner concluded Faheny's death "fit into the category   of   spontaneous   human  combustion."  

       

   Can human bodies spontaneously burst  into flame without being ignited by an  external source of heat? Most scientists  would argue that humans cannot catch fire  without an apparent cause. In fact, in the  more than 200 cases of spontaneous human  combustion (SHC) that have been reported  worldwide, the true causes of death are far  less fanciful than SHC.
 
       In a study of 30 cases of alleged SHC.  investigators Joe Nickell and John Fischer  showed that candles. lamps, fireplaces,  cigarenes, and other sources of heat were  the likely reasons for ignition. Clothing,  chair stuffing, and floor coverings usually provided additional fuel sources to sustain  the fire.   
       
       One of the most commonly accepted explanations  for alleged  SHC  is  a phenomenon called the "wick effect." This theory suggests thar an ignition source, such as a lit cigarette, will burn through the victim's clothing and into the skin. This releases body fat, which is absorbed into the clothing and burns like a candlewick. The fire will burn until the body's fat and the clothing are both consumed. Scientists believe such a "self-contained" fire is the reason victims' bodies are incinerated, yet their surroundings barely suffer damage.   
    
    "SHC is a non-explanation for bizarre burning deaths, no better than positing the attack of a fiery demon," says forensic analyst Nickell, "because there is not only no scientifically authenticated case of SHC but no credible mechanism by which it could happen."

What's at the Bottom of a Black Hole ?

      Black holes are already among most  mysterious  objects  in  the the  universe, even before we begin to  contemplate "bottom" of  what might be at the  one.  The concept of a tiny star whose gravitational field is so strong that neither light nor matter  can escape was so foreign to those  who first theorized their existence  that even Albert Einstein himself,  whose math confirmed   their possibility, dismissed the likelihood of their existence. As to the question of what's at the bottom, the answer- depending on the physicist-may be just about anything, or nothing, or even another universe. 
  
         At the outer edge of a black hole is the  event horizon, the boundary where velocity  required to escape its gravity exceeds the  speed of light. Past this point, all energy and matter that enter the black hole will proceed infinitely toward the singularity, a point of infinite density that, according to Einstein's theory of general relativity, represents a bottomless pit of space-time. Jf the hole is truly infinite and nothing can escape past the event horizon, then the  bottom of a black hole could theoretically  hold an infinite amount of matter and energy.   
     
       However, while that interpretation may square with general relativity, the laws of thermodynamics maintain that a system cannot infinitely increase its mass while maintaining a similar temperature and level of disorder. Other theories that account for black hole thermodynamics suggest that anything falling toward the event horizon never  really  reaches  the  singularity, eventually evaporating back into space. According  to  astrophysicist  Stephen Hawking, this is because black holes aren't truly black: They emit a minute amount of radiation, far less than the background radiation  of  space,  but  enough  to eventually return the mass of the black hole back to the rest of the universe.  

       

    Other more exotic theories posit that at the bottom of a black hole lies an entire universe.  How  can  this  be?  The combination  of the insanely high temperatures,  densities,  and  rotational velocity at the center of a black hole is so powerful that it could produce a massive expansion in space-time that might give rise to a new universe-a process not unlike that of the Big Bang that gave rise to our own universe. The logical extension of this theory implies that even our universe may lie at the bottom of a black hole.   
    
      The mystery has only deepened of late as prominent astrophysicists (including Hawking) change their minds on whether black holes even exist. According to Hawking and others, the laws of quantum mechanics may prevent a neutron star from collapsing beyond a small enough radius to fit within its event horizon. This would mean that no black hole is ever small enough for its escape velocity to exceed the speed of light, and thus there is no black hole.

Will We Ever Be Able to Harness Nuclear Fusion?

    

    The year is 2050. The carbon crisis is a thing of the past. A new source of power  delivers  cheap,  plentiful electricity to large, contained cities populated by millions of people.  Fusion power has birthed a utopia on  Earth  by  neutralizing  the  most  imminent threat to human survival, the finite supply of fossil fuel, while eliminating a persistent source of conflict. All is well-until a robotic alien from outer space destroys your fusion plant along with the rest of your city. 
    
      The scenario just described is familiar to anyone who grew up playing the popular  1990s simulation game SimCity 2000. As far as fusion power is concerned, the predictions of Maxis (the company that designed SimCity) from two decades ago seem prescient: Steve Cowley, a plasma physicist and the CEO of the United Kingdom's Atomic Energy Authority, expects the first viable demonstration reactors to be available sometime in the 2040s. That said, critics and proponents alike lament that nuclear fusion is "always 30 years away." What's changed? Recent breakthroughs indicate that the future of fusion is brighter than it has been in some time.
 
      Physicists since the 1950s have been  seeking to harness the power of the Sun.  As it turns out, birthing a miniature star in a lab and keeping it under control is a  difficult undertaking. The fusion reaction requires more energy than the reacuon itself produces. It wasn't until October  2013 that any project broke even, when the National  Ignition  Facility  (NIF)  in California produced more energy than it consumed.   

     The success at the NIF, aIthough exciting, is just another step on a long journey. To be commercially viable and to overcome basic  inefficiencies in the conversion of raw energy into electricity, the reaction must continually produce 10 umes the amount of power that goes into it. Candidates for exceeding this threshold include the International Thermonuclear Experimental Reaction (known as ITER, pronounced "eater"), a project with the backing of seven countries that should come online by the end of the decade. Recently, aerospace and technology giant Lockheed Martin's covert Skunkworks facility has announced a breakthrough in fusion technology that may yield results within the decade. 
    
      Secrecy still surrounds the research, but scientists  hope  that  covert  research facilities like Skunkworks will make "the impossible" possible.

What Does Space Smell like?

     The final frontier smells a lot like a NASCAR race- a bouquet of hot metal, diesel fumes, and barbecue. The source? Dying stars.
      The by-products of all this combustion are smelly  compounds  called  polycyclic aromatic hydrocarbons. These molecules "seem to be all over the universe," says Louis  Allamandola,  the  founder  and director  of  the  Astrophysics  and Astrochemistry Laboratory at NASA Ames Research Center. "And they float around forever," appearing in comets, meteors, and space dust. These hydrocarbons have even been short-listed as the basis of the earliest  forms  of  life  on  Earth.  Not surp risingly,   polycyclic  , aromatic hydrocarbons can be found in coal, oil, and even food.  
        
        Though a pure, unadulter- ated whiff of outer space is impossible for humans (space is a vacuum, after all; we would die if we tried), we can get an indirect sense of the scent: When astronauts work outside the International Space Station, spaceborne compounds adhere to their suits and hitch a ride back into the station. Astronauts have reported smelling "burned" or "fried" steak after a space walk, and they aren't just dreaming of a home-cooked meal. 

     

    The smell of space is so memorable and distinct that, three years ago, NASA asked Steven Pearce of the fragrance maker Omega Ingredients to re-create the odor for use in its training simulations. "Recently we did the smell of the Moon," Pearce says. "Astronauts compared it to spent gunpowder."

          

    Allamandola explains that our solar system is particularly pungent because it is rich in carbon and low in oxygen, and "just like a car, if you starve it of oxygen, you start to see black soot and get a foul smell." Oxygen-rich stars, however, have aromas reminiscent of a charcoal grill.  
       
       Once you leave our galaxy, the smells could get really, really interesting. In dark pockets of the universe, molecular clouds full of tiny dust particles may host a veritable smorgasbord of odors, from wafts of sweet sugar to the rotten-egg stench of sulfur.

Why Can't the Voynich manuscript Be Deciphered?

        Polish antique book collector Wilfrid Vovnich was convinced he hit the jackpot when he purch sed a highly  unusual manuscript in Italy in 1912. It was written in a strange script and profusely illustrated with images of plants, the cosmos and zodiac, and naked women cavorting in bathing scenes.    Voynich    himself acknowledged the difficult task that lay ahead: "The text must be unraveled and the history of the manuscript must be traced."   

     

   The Voynich manuscript is a codex written  on vellum sheets, measuring 9 inches (23.5 cm) by 4 inches (11.2 cm). The codex is composed of roughly 240 pages, with a blank cover that does not indicate a title or author. The text consists of "words" written in an unknown "alphabet" and arranged  in  short  paragraphs.  Many researchers say the work seems to be a scientific treatise from the Middle Ages, possibly created in Italy. The time frame, jackpot when he purch sed a highly  unusual manuscript in Italy in 1912. It was written in a strange script and profusely illustrated with images of plants, the cosmos and zodiac, and naked women cavorting in bathing scenes.    Voynich    himself acknowledged the difficult task that lay ahead: "The text must be unraveled and the history of the manuscript must be traced."  at least,  seems correct:  In 2009,  the   Voynich manuscript was carbon-dated to    1404-1438.   
          

   There's only one problem: The contents   of the book are a complete mystery-and   not a single word of it can be understood.      The enigma of the manuscript certainly   isn't due to a lack of research and careful  study. The text had already been analyzed  for  many  decades  before  Voynich  purchased it. Once in possession of the  codex, Voynich embarked on a brisk  campaign to have its text deciphered,  supplying photocopies to several experts.  Since then, dozens of cryptographers and linguists have tried and failed to crack the code and decipher its base language. Astronomers,    historians,    chemists, mathematicians, and scores of laypeople have also proposed solutions, but none has shed any light on what the text says. Botanists, however, have identified many of the plant species as New World or European.   Indeed, the Voynich manuscript may actually contain no meaningful conrent, possibly because  it was  a  deliberate deception on the part of its author or because its meaning became muddled in the writing process. In 2007. Austrian mathematician Andreas Schinner claimed the manuscript may have been created by "an autistic monk, who subconsciously followed a strange mathematical algorithm in his head." 
    
      To this day, scholarship, speculation, and debate over the meaning of the Voynich manuscript continue unabated. Among recent theories are that the manuscript was written by a young Leonardo da Vinci or by Cornelius Drebbel, a 17th-century chemist and optics developer, in collaboration with English philosopher Francis Bacon, which would put the carbon dating calculations into question. Another theory suggests the document originated with the Aztecs in Central America.    And of course, there is the possibility that the manuscript is a hoax.

the Antikythera Mechanism the World's First Analog Computer?

      In 1901, divers exploring the remains of an ancient shipwreck off the Greek island of Antikythera, northwest of Crete, recovered a bizarre-looking mechanical object that baffled the international scientific community.
   
      The mysterious device, found in 82 fragments  heavily  encrusted  with corrosion, is composed of 30 bronze gear wheels covered with Greek inscriptions. Decades of scientific examination revealed that the  ancient device, called the Antikythera mechanism, is an analog computer-the world's first-designed to calculate the position of heavenly bodies, predict eclipses, and even pinpoint the dates of the Olympic Games.    In 2014, James Evans, professor of physics at the University of Puget Sound, and Christian Carman, history of science professor at the University of Quilmes, Argentina, published an article in the Archive for History o Exact Science claiming that the mechanism was timed to begin in 205 B.C.E., establishing the device to be as many as 100 years older than  most  researchers  thought.  The incredibly   complex   machine   was engineered and built by ancient Greeks, although "it's probably safer not to try to  hang it on any one particular famous  person,"  according  to  Evans.   The  researchers believe the mechanism was  designed   on   Babylonian   arithmetic  principles adopted by the Greeks.  
     
       The  front  dial  of  the  mechanism  features  two  concentric  scales  that  represent the movement of the twelve  zodiac constellations in the sky. The outer  ring is marked with the months of the 365-  day Egyptian calendar in Greek letters,  while the inner ring is marked with the Greek symbols of the zodiac. The rear face of the mechanism includes numerous dials believed to predict lunar and solar eclipses. The mechanism was operated by turning a small crank that was linked to the largest gear on the front dial.   
     
       In 2012, in an exhaustive study of the Antikythera mechanism, researchers Tony Freeth and Alexander Jones concluded that the device is "the sole witness to a lost history  of  brilliant  engineering,  a conception of pure genius, one of the great although "it's probably safer not to try to  hang it on any one particular famous  person,"  according  to  Evans.   The  researchers believe the mechanism was  designed   on   Babylonian   arithmetic  principles adopted by the Greeks.     The  front  dial  of  the  mechanism  features  two  concentric  scales  that  represent the movement of the twelve  zodiac constellations in the sky. The outer  ring is marked with the months of the 365-  day Egyptian calendar in Greek letters,  while the inner ring is marked with the Greek symbols of the zodiac. The rear face of the mechanism includes numerous dials believed to predict lunar and solar eclipses. The mechanism was operated by turning a small crank that was linked to the largest gear on the front dial.     wonders of the ancient world-but it didn't really work very well!" The researchers attributed  the  mechanism's  lack  of exactness to its imprecise  mechanical engineering   and   the    inaccurate mathematical and celestial theories of the time.   
       
      To date, no other ancient machine like the Antikythera mechanism has been found. The story behind this ancient marvel of engineering has been long lost to time.

What Caused the Decline of the Mayan Civilization?

     The  collapse  of  the  Mayan civilization at the end of the so-called classic period, between 200 and 900, is  a  persistent  archaeological mystery.  The  classical  Maya  were  the  most advanced   of   the   pre-Columbian civilizations, anchored by a collection of city-states in the lowlands of morden-day Guatemala.  Belize,  and  the  Yucatan Peninsula. But around 700, these city- states began an inexorable decline that ended in their total abandonment. While the independent Maya survived until the Spanish conquest in the late 17th century. the postclassical Maya were a less urban and populous civilization.   Archaeologists have posited a number of theories explaining the decline of the classical Maya, from foreign invasion to disease epidemic to a collapse in trade with neighboring cultures, but one of the oldest and most persistent theories centers on drought. The Yucatan Peninsula and Peten Basin were already pamcularly susceptible to variability in rainfall-the soil is thin and sandy, and a regular seasonal drought complicates  agricultural  productivity.
 
       Though the Maya had solved this problem    through advances in fertiIization and    irrigation, studies of soil and stalagmites in    the region indicate a decline in rainfall of   between 25 and 40 percent in the late    classical period. For a culture living off an   already  fickle  water  supply,  this   megadrought may have been too much for   even  advanced  Mayan  hydrological   engineering to overcome.
   
        Drought by itself, however, doesn't  explain the fall in its entirety. It doesn't  explain why the Maya didn't return to the  classical cities after the climate righted  itself in the second millennium or why the  northern  cities  that  ascended  in  the  aftermath never reached the heights of the  lowland city-states. Nor is it clear why the  drought occurred in the first place. It may have been cyclical, but some researchers believe that the Maya instigated the drought by clear-cutting rain forest, cutting short the water cycle that topped off the reservoirs that slaked their thirst during the dry periods.
  
      Almost as mysterious as the decline of  the Maya is the fact that the classic Mayan civilization took root where it did. Dense, urban settlements dependent on agriculture have not historically thrived in jungle climates rooted in limestone soil. That the Maya flourished there at allis testament to the ingenuity of their civilization.

Can We Travel Through time ?

    

     The mystery of time travel as it is portrayed in science fiction is not as simple as building a time machine. In fact, these fictional ideas require overturning Albert Einstein's special theory of relativity and somehow traveling close to the speed of light. 
     Physicists  continue  to  ponder possibilities  of  faster-than-light  I (FLT) and what it means for : exploration and our universe. The    the travel  space  first  example of faster-than-light speeds in popular culture occurred in the television series Star Trek, when "warp drive" sent spaceships traveling billions of light-years away in a matter of seconds. If this were possible, those space travelers might return to their original location and find that time had progressed at its usual speed, meaning  50 years may have passed during the short  time the ship was absent, simulating time  travel.    
        While most people view time as a  constant, Einstein proved that time is  relative to how fast an object moves  according to its surroundings. Einstein  pointed out that time is not a consistent flowing entity, but linked with space, and so the faster one travels through space, the more the perception of time changes, a phenomenon called time dilation. If an astronaut can somehow travel close to the speed of light, he will experience time differently than his friends left behind on Eanh traveling at the usual speed. Time will pass much slower for the astronaut, and when he returns to Earth, his friends will have aged faster. However, the laws of physics state that the speed of light is constant, represented by c in Einstein's famous equation E  mc. The speed of light in a vacuum is 186,000 miles per second (299,337 kmIh), and while some physicists have identified processes like quantum entanglement that travel faster than light, they do not carry mass or information. For a particle with mass, reaching the speed of light would require infinite acceleration and therefore infinite energy-an unrealistic accomplishment. 
   

     In  2011,  physicists at the CERN institute in Switzerland thought they wereclose to a FLT discovery. A new subatomic particle called the neutrino, which carried a very small mass, appeared to travel faster than the speed of light. Their experiment launched particles from Switzerland to Italy, and the neutrinos arrived in Italy in record time, intriguing the world with thoughts of time travel and visits to distant galaxies. Unfortunately for CERN, the experiment was flawed. One cable was not properly connected, resulting in incorrect measurements.   
       

     According to Einstein's theory, objects with mass cannot exceed the speed of light because they would require an infinite amount of energy-be they spaceships or neutrinos. Even in all theoretical scenarios in which we travel faster than light, we can never travel backward in time, only forward. However, many scienusts believe that traveling into the future is still a possibility that just needs more study. Wormholes, a theoretical passage through space-time that connects distant points in the universe, are attractive starting points for these theoris , But however enticing the possibilities, it seems that succes still light years away.

Do Atoms Last Forever?

   

  

    Despite what you may have heard, diamonds  are  not  forever.  Given enough time, your sparkling rock will degrade into common graphite. The carbon atoms  that constitute  that diamond, however, are forever, or close enough. Stable isotopes of carbon are thought to enjoy lifetimes that extend far longer than the estimated age of the universe.
    

   But not every atom of carbon lives forever. Radioisotopes  are  forms  of  chemical elements with unstable nuclei and emit radiation during their decaying process to a stable state. Carbon-14, a radioisotope, is unstable, with a half-life of less than 6,000 years; after 5,730 years, there is a 50 percent chance that a carbon-14 atom will lose an electron and become nitrogen-14 (which  is  itself  stable  and the most common  form  of  nitrogen on Earth). Carbon-14 is the key element in carbon dating: Since radioactive carbon is only absorbed through respiration by living creatures, the date of their death can be determined by measuring the remaining carbon-14 in the specimen.    In addition to carbon-14, there are scores  of  other  naturally  occurring radioisotopes and more than a thousand manmade. Each of these radioisotopes tends to decay into another isotope: some in a matter of days, others in hundreds of millions of years. In this sense, these atoms do in fact die. In another way, however,they are  simply reborn as different isotopes.   
    

    There is one mechanism by which even stable atoms might "die." Some exotic models of physics hypothesize that protons (which along with electrons and neutrons constitute atoms) can decay into lighter subatomic particles. Even if protons do decay,    they    are    nevertheless incomprehensibly durable.  Experiments put the lower bound of a proton's half-life at 1033 to 1034 years, or 23 orders of magnitude longer than the current age of the universe. In conclusion, atoms ore forever  on  just  about  any  relevant timescale.

Is Cold Fusion Possible?

    

       Italian inventor Andrea Rossi really wants us to believe in cold fusion. He claims that his Energy Catalyzer, or E-Cat,  a liter-sized device he designed, can output three times as much energy as it draws via low- energy nuclear reactions, or LENRs. As  hydrogen  passes  over  an electrified  nickel-based  catalyst, hydrogen nuclei supposedly fuse to the nickel, transmuting the metalinto copper and releasing heat in the process. If we could harness that heat, the process could furnish cheap electricity  while  simultaneously banishing   the   production   of greenhouse   gases-all   without creating any harmful waste. 

      

    There's only one problem: Cold fusion is almost certainly a myth. Backers aside, Rossi  has  yet  to  perform  a  truly independent test of his E-Cat; in most tests by  third  parties,  Rossi  handled  the materials or was involved in some way. Critics argue that Rossi's device doesn't produce nearly as much energy as he cIaims and that his suggestion of building factories for large-scale production of electricity is baseless. They also note that his backers refuse to publicly reveal themselves and that the physics behind the project are at best unclear.   

      

    Worst  of  all,  every  purportedly successful attempt at cold fusion up until now has been the result of experimental error  or  downright  fraud.  Martin Fleischmann and Stanley Pons. chemistry professors at the University of Utah, claimed to have discovered cold fusion in 1989. No one has been able to replicate their results since and their ideas were discredited. Rusi Taleyarkhan, a Purdue University professor who claimed to have produced a "bubble fusion" reaction, was found guilty of "research misconduct." Besides, most physicists say that the findings just don't make sense: The energy required to bond hydrogen is simply too high for a catalyst to achieve at earthly temperatures.   

    

     Except in one case: Muon catalyzed fusion is the only instance in which a catalyst is known to enable nuclear fusion. Muons are subatomic particles that occur on Eanh principally as a result of cosmic rays slamming into the atmosphere. When muons replace the hydrogen atom's electrons, they can draw those hydrogen atoms close enough to fuse together. Unfortunately, muons require substantial energy to produce, and they don't last long enough for the chain reaction to produce more energy than goes into the reaction. Until physicists overcome these barriers, cold fusion will remain elusive.

What Is the Hottest Temperature Possible?

         It's easy to understand the theoretical minimum temperature: absolute zero. The absolute maximum, on the other hand, is squirrely. "We just don't know whether we can take energy all the way up to infinity," says Stephon    Alexander, a physicist at Dartmouth University. "But it's theoretically Dlausible."  The most straightforward candidate for an upper limit is the Planck temperature, or 142 nonillion (1.42 x 1032) kelvins (K)- the highest temperature allowable under the Standard Model of particle physics. But temperature comes about only when particles interact and achieve thermal equilibrium, Alexander explains. "To have a notion of temperature, you need to have a notion of interaction."   

    

     Many cosmologists believe the hottest actual temperature in the history of the universe was several orders of magnitude cooler than the Planck temperature. In the first  moments  after  the  Big  Bang, expansion occurred so rapidly that no particles could interact; the universe was essentially temperatureless. In the tiny slivers  of  a  second  that  followed, Alexander says, ripples of space-time may have begun to vibrate with matter and forced that matter into thermal equilibrium. This would have caused a quick reheating of the universe to something like 1027 K. It has been continually expanding and cooling ever since.