What Everyone Should Know about the Universe on the eve of Planck

note: the copyright of this does not belong to me

Image credit: European Space Agency (ESA).

“Scientific discovery and scientific knowledge have been achieved only by those who have gone in pursuit of it without any practical purpose whatsoever in view.” -Max Planck

Tomorrow morning, at 8 AM my time, the press conference that cosmologists have spent the past decade waiting for will finally happen, and the Planck satellite — the most powerful satellite ever to measure the leftover radiation from the Big Bang — will finally unveil its results about the origin and composition of the Universe.

Image credit: ESA / LFI and HFI Consortia.

They’ve figured out how to subtract the galactic foreground in all of the seven wavelength-bands where Planck operates to unprecedented sensitivity, and the science is ready to be released! Let’s use this opportunity to take a look back on what we know right now, where-and-what the uncertainties are, and what Planck can (or, at the very least, might) teach us about the Universe!

Image credit: Rhys Taylor, Cardiff University.

1.) The Big Bang is safe.

The Big Bang is the idea that the Universe was once in a hot, dense, ionized state and expanded to become our star-and-galaxy-rich cosmos that we live in today. There are three separate cornerstones that lead to this picture: the observed Hubble expansion of the galaxies, whose recession rates increase with increasing distance from us, the observed primordial abundances of the light elements, which are predicted by Big Bang Nucleosynthesis to give us a Universe with about 75-76% hydrogen and 24-25% helium (by mass), and the leftover, nearly uniform blackbody (CMB) radiation at just a few degrees above absolute zero, coming from all directions in space, which marks the leftover glow from the Big Bang itself.

Image credit: Whittle Rodman, University of Virginia.

In the context of General Relativity, our tried-and-true description of gravity in this Universe, only an expanding, cooling Universe in the context of the Big Bang leads to these three predictions simultaneously, and nothing the Planck satellite observes will change that.

Image credit: WMAP Science Team / NASA.

2.) The Universe is mostly dark energy, followed by dark matter, with normal (baryonic) matter making up just a small fraction.

There are three sets of large-scale observations that simultaneously lead to this picture, again in the context of General Relativity.

Image credit: J. Colberg and the VIRGO Consortium.

The observed patterns of large-scale galaxy clustering, combined with the data from ultra-distant distance indicators (like supernovae), and the already known patterns of fluctuations in the microwave background on both large (from WMAP) and small (from the South Pole Telescope and others) scales, all indicate a Universe that’s made up of about 71-74% dark energy, 20-24% not-too-hot dark matter, with the remaining 4.6% made up of normal, standard model particles. These standard model particles include everything we’ve ever observed directly, including protons, neutrons and electrons, photons and neutrinos, and all the exotic, unstable matter we’ve ever created.

Image credit: Kowalski et al., 2008.

So none of those things will change substantially, although the dark energy/dark matter numbers may shift around a small bit in that range. Although Planck will measure the large scales more accurately and in more wavelengths than WMAP before it, that science has already been done, and Planck will only refine it, not overthrow it. The way it will refine it is extraordinary; while WMAP was limited by the sensitivity of the instruments on it, that’s not the case for Planck, according to the ESA:

Planck will provide even more precise measurements with an accuracy set by fundamental astrophysical limits… In other words, it will be impossible to ever take better images of this radiation than those obtained from Planck.

But there are some things that Planck can shed some light on, which have the potential to be extremely exciting!

Image credit: LSST / AURA.

3.) The age, size and expansion rate of the Universe!

Yes, it’s true that we often quote that the age of the Universe is 13.7 billion years old, the diameter of the observable Universe is 93 billion light-years across, and the expansion rate — or the rate that all galaxies (on average) recede away from one another — is about 71 kilometers/second/Megaparsec. But these numbers are all related to one another, with the age-and-size numbers also dependent on the percentages of dark matter and dark energy.

Image credit: Moresco, Michele et al. JCAP 1207 (2012) 053.

But the expansion rate has a little bit of uncertainty attached to it. It probably couldn’t be as low as 60 or as high as 80, but no one would be shocked if it turned out to be 68 km/s/Mpc, or maybe as high as 74 km/s/Mpc. This could mean a Universe as old as maybe 14.2 billion years, or as young as 13.3 billion years, depending on how the dark matter and dark energy parameters adjusted. Half-a-billion years may not be a big deal to you, but when you consider that we’ve already got stars that push the 13-and-change billion year limit, it’s pretty important to astrophysicists that the Universe is at least as old as all the stars in it!

Image credit: Prof. Matt Strassler, 2011.

4.) There are three types of neutrino in the Universe.

We’re pretty sure of this one… aren’t we? I mean, we’ve got these huge particle colliders, we’ve been running them for decades, and we’ve seen how hordes of them decay. The decay of the Z-boson, for instance, tells us that there are 3.003 ± 0.006 neutrinos species whose mass is less than 4.5 × 10¹⁰ eV. Considering that the heaviest a neutrino is allowed to be is around 0.08 eV, it makes sense to conclude that there are three.

Image credit: Carlo Giunti, via Luca Merlo of http://neutel11.wordpress.com/.

But the cosmic microwave background should also measure the number of neutrino species in an independent way, and would also be sensitive to a bizarre, hypothetical type of neutrino that particle physics wouldn’t find conventionally: the sterile neutrino! WMAP, with lousy sensitivity, has claimed to have found about 3.6 ± 0.5 neutrino species, and so while not conclusive, it’s suggestive that there could be a new particle (or maybe even 2?) out there! Planck should improve on the WMAP constraints, and this could be interesting.

Image credit: “Cosmic Inflation” by Don Dixon.

5.) How did the Big Bang get started?

According to both the spectrum of density fluctuations imprinted in the CMB and the large-scale-structure of the Universe, and also the best theoretical solution to many open questions in cosmology, the answer to that is cosmological inflation, or a period where spacetime was expanding exponentially fast. At some point, inflation ended, setting up the Big Bang and creating all the matter and energy known to permeate our observable Universe.

Image credit: Ned Wright (+ possibly Will Kinney), via http://ned.ipac.caltech.edu/. (Notes by me.)

Of course, we don’t quite understand how all of this happened. As in, there are many models of inflation that could have successfully done this, and we have no way to discriminate between many of them. But the two main classes of models — models of new inflation and models ofchaotic inflation — have a major difference between them: chaotic models should produce large amounts of long-wavelength gravitational waves, while new inflation should produce almost none. In optimistic models of chaotic inflation, this would cause a polarization of some of the light from the CMB, something that Planck could — in principle — pick up. So Planck has the dual potential to either detect primordial gravitational waves and verify not only inflation but a particular model of it, or to disfavor the chaotic inflation scenario in favor of new inflation. (Full disclosure: new inflation has long been my preferred model.)

Image credit: Avi Loeb, 2006.

There are other, smaller refinements that could happen, such as a better pinning-down of the epoch of reionization or a more precise measurement of a few cosmological parameters, but these are the five big ones — confirmation of the first two and potential answers to the last three — that I’ll be waiting on. If you want to watch the NASA announcement live online, it’s at 8 AM pacific time on March 21st here, and you can check out the ESA’s page here or call in and listen to the teleconference. WMAP redefined the precision to which we understood the Universe when its first data release happened a decade ago, and now Planck has the potential to take us even further in our understanding of the greatest quest of all: the dream of understanding the entire Universe. I can’t wait to see what they found!

UK Super Train : Mega-structures 

Having set up their first railroad during the reign of Queen Victoria, it was about time that UK updated their railroad network to match the fast pace of 21st Centuries. UK Super Train, an episode of the National Geographic documentary series Megastructures tells the exciting tale of UK's high-speed train project that was then known as the Highspeed1. This super train traveled at a daunting 300 km/h and was a much more complicated task than building bridges and highways. Construction of railroads resulted in a more drastic change to the topography of land than road networks and required building bridges and tunnels; the latter being a risky venture, if the possibility of cave-ins and fluctuating air pressure is taken into account.

The project made use of existing Victorian landmarks such as the St Pancras Station that was turned from a liability into an asset. This National Geographic documentary film of Megastructures series follows the entire grueling tasks and procedures assigned to the engineers, from digging a trench through a chalk hill to a possible threat to the historical heritage of the country; the project had its fair share of setbacks. Stumbling across artifacts that were almost 4000 years old, the construction venture was exciting, but also raised a nationwide concern regarding the safeguarding of these precious items. Despite these challenges, the project managed to survive and was completed, while as well preserving the historical sites that were done with the undying efforts of Archaeologists, who outnumbered the construction workers at one point.

MegaStructures: UK Super Train: The National Geographic documentary film entails interviews and an engaging narration that gives in-depth insight into the nature of the project and the various challenges it battled. The construction began with the aim of turning loss-making infrastructure into assets and to cut down on the cost of building the high-speed rail network that already stood at an overwhelming 7 billion pounds. The venture was one of the largest and most expensive engineering projects carried out in UK and became a major tourist attraction. UK Super Train, the National Geographic documentary film of Megastructures series covers every aspect of the development of Highspeed1 that gave UK's railroad network a much-needed boost.

The Pack: When Lions Attack | Nature Animal Documentary

The Pack examines the hunting techniques used by lions in order to survive the Singita Game Reserve.

Cosmic Journeys : Birth of a Black Hole

It was one of the greatest mysteries in modern science: a series of brief but extremely bright flashes of ultra-high energy light coming from somewhere out in space. These gamma ray bursts were first spotted by spy satellites in the 1960s. It took three decades and a revolution in high-energy astronomy for scientists to figure out what they were.

Far out in space, in the center of a seething cosmic maelstrom. Extreme heat. High velocities. Atoms tear, and space literally buckles. Photons fly out across the universe, energized to the limits found in nature. Billions of years later, they enter the detectors of spacecraft stationed above our atmosphere. Our ability to record them is part of a new age of high-energy astronomy, and a new age of insights into nature at its most extreme. What can we learn by witnessing the violent birth of a black hole?The outer limits of a black hole, call the event horizon, is subject to what Albert Einstein called frame dragging, in which space and time are pulled along on a path that leads into the black hole. As gas, dust, stars or planets fall into the hole, they form into a disk that spirals in with the flow of space time, reaching the speed of light just as it hits the event horizon. The spinning motion of this so-called "accretion disk" can channel some of the inflowing matter out into a pair of high-energy beams, or jets. 

How a jet can form was shown in a supercomputer simulation of a short gamma ray burst. It was based on a 40-millisecond long burst recorded by Swift on May 9, 2005. It took five minutes for the afterglow to fade, but that was enough for astronomers to capture crucial details. It had come from a giant galaxy 2.6 billion light years away, filled with old stars.

Scientists suspected that this was a case of two dead stars falling into a catastrophic embrace. Orbiting each other, they moved ever closer, gradually gaining speed. At the end of the line, they began tearing each other apart, until they finally merged. NASA scientists simulated the final 35 thousandths of a second, when a black hole forms. 

Chaos reigns. But the new structure becomes steadily more organized, and a magnetic field takes on the character of a jet. Within less than a second after the black hole is born, it launches a jet of particles to a speed approaching light. 

A similar chain of events, in the death of a large star, is responsible for longer gamma ray bursts. Stars resist gravity by generating photons that push outward on their enormous mass. But the weight of a large star's core increases from the accumulation of heavy elements produced in nuclear fusion. In time, its outer layers cannot resist the inward pull... and the star collapses. The crash produces a shock wave that races through the star and obliterates it.

In the largest of these dying stars, known as collapsars or hypernovae, a black hole forms in the collapse. Matter flowing in forms a disk. Charged particles create magnetic fields that twist off this disk, sending a portion out in high-speed jets. 

Simulations show that the jet is powerful enough to plow its way through the star. In so doing, it may help trigger the explosion. The birth of a black hole does not simply light up the universe. It is a crucial event in the spread of heavy elements that seed the birth of new solar systems and planets. 

But the black hole birth cries that we can now register with a fleet of high-energy telescopes are part of wider response to gravity's convulsive power.

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The Big Bang - Lawrence Krauss and Michio Kaku

Professor Lawrence Krauss and Professor Michio Kaku explain the physics behind the events in the first second of The Big Bang, events which range from the first fractions of a second after creation: The Plank Era; The field symmetry breaking; Formation of elementary particles; Matter-antimatter annihilation (explained by Dr. Tara Shears); Formation of atoms and the last scattering of photons which make up the Cosmic Microwave Background to the billions of years of stellar evolution: the formation of stars and Galaxies which developed the visible universe as seen today.

Using High Energy Particle Accelerators and Observational and Theoretical Astrophysics, scientists are able to recreate the first few fractions of a second after the Big Bang, to the point of symmetry breaking, and in conjunction by using space and earth-based observatories observe the remnants of the Big Bang itself using powerful analysis of the CMB combined with the modelling of the large scale structure of the universe as done by The Sloan Digital Sky Survey..

The Initial Conditions of the Universe are still a mystery and debate has gone on recently to whether or not there were even any initial conditions at all, maybe the universe can form from no initial conditions in standard space-time and that the very fabric of space, curled up in perhaps infinite dimensions creates an infinite set of paths for scalar fields to branch off of and interfere to create the flow of energy from the initial big bang. 

Such a theory is predicted by M-Theory, which gives the Multiverse picture of curved Space-Time in 11 Dimensions which, through quantum mechanics, create many scalar fields that couple at different strengths in each universe creating a different set of physical laws in each universe.
Not all universes could be suitable for life, each universe seems to have the Planck Constant encoded into it, as it is the Uncertainty Principle and the Sum over Histories that lead to the Multiverse picture in the first place, however the coupling strengths of gravity and electromagnetism are completely arbitrary in this view. 

In some of these Universes, Electromagnetism could be very strongly coupled in certain schemes meaning that basic chemistry would not arise in some universes. In other Universes the Strong Nuclear force may be too weak to give sufficient binding energy to atomic nuclei, making fusion impossible. In other Universes, Gravity may be coupled far more strongly, creating a Universe of Galaxy Cluster-sized black holes. Other Universes still may be composed of nothing but vacuum energy. 

Hence we must be living in a Universe suitable for life as we are here observing it, that is the nature of The Anthropic Principle which is used to answer the question, "why is the universe the way it is?" However, the true meaning of the answer comes from Theoretical Physics and M-Theory: The Universe need not be suitable for life, our one just happens to be.

Muscles - Medical Science of Muscles 

National Geographic takes us on a journey inside the bodies of two extraordinary humans who suffer from startling muscular disorders.
The documentary investigates the science behind a rare disease that causes 31-year old Jason Dunn's brain to send faulty messages to his muscular system, every waking moment Jason's muscles flex out of his control, twisting his body into unusual positions.
For Ami Ankilewitz, who has Spinal Muscle Atrophy, he has a genetic disorder that has caused his muscles to wither away.

The Quantum Guide - Pulsars

Unknown to the general populace, young men and women from around the globe are being raised in a secret, underground facility. Using a library of alien knowledge that was uncovered early in the 21st century—code name: The Quantum Guide—these future astronauts prepare for the day when they will set out to colonize the galaxy. They must learn to decode the myriad of enigmas that exist in the great beyond if there is to be any hope of the human race becoming an interstellar power.

*what the bleep do we know * Quantum Physics, spirituality, neurology and evolutionary thought

What the BLEEP Do We Know — First released in theaters in 2004, WTBDWK!? went on to become one of the most successful documentaries of all time. Now distributed in over 30 countries, it has stunned audiences with its revolutionary cinematic blend of dramatic film, documentary, animation and comedy, while serving up a mind-jarring blend of What the BLEEP Do We Know — First released in theaters in 2004, WTBDWK!? went on to become one of the most successful documentaries of all time. Now distributed in over 30 countries, it has stunned audiences with its revolutionary cinematic blend of dramatic film, documentary, animation and comedy, while serving up a mind-jarring blend of Quantum Physics, spirituality, neurology and evolutionary thought.

Matter out of "Nothing": Hunting The Higgs Boson

Fascinating documentary regarding the illusive particle that gives energy its mass. The documentary was made before the Higgs was discovered which makes it even more interesting because the alternative to the Higgs are discussed as well as why the Higgs became a necessity with Cosmologists and Physicists over the last few decades.

 Venus: Death of a Planet

Watch this updated full res 1080p version of our classic show. Why did Earth thrive and our sister planet, Venus, died? From the fires of a sun's birth... twin planets emerged. Then their paths diverged. Nature draped one world in the greens and blues of life. While enveloping the other in acid clouds... high heat... and volcanic flows. Why did Venus take such a disastrous turn?

For as long as we have gazed upon the stars, they have offered few signs... that somewhere out there... are worlds as rich and diverse as our own. Recently, though, astronomers have found ways to see into the bright lights of nearby stars. 

They've been discovering planets at a rapid clip... using observatories like NASA's Kepler space telescope... A French observatory known as Corot ... .And an array of ground-based instruments. The count is approaching 500... and rising. These alien worlds run the gamut... from great gas giants many times the size of our Jupiter... to rocky, charred remnants that burned when their parent star exploded. 

Some have wild elliptical orbits... swinging far out into space... then diving into scorching stellar winds. Still others orbit so close to their parent stars that their surfaces are likely bathed in molten rock. Amid these hostile realms, a few bear tantalizing hints of water or ice... ingredients needed to nurture life as we know it. The race to find other Earths has raised anew the ancient question... whether, out in the folds of our galaxy, planets like our own are abundant... and life commonplace? Or whether Earth is a rare Garden of Eden in a barren universe?

With so little direct evidence of these other worlds to go on, we have only the stories of planets within our own solar system to gauge the chances of finding another Earth. Consider, for example, a world that has long had the look and feel of a life-bearing planet. Except for the moon, there's no brighter light in our night skies than the planet Venus... known as both the morning and the evening star.

The ancient Romans named it for their goddess of beauty and love. In time, the master painters transformed this classical symbol into an erotic figure. It was a scientist, Galileo Galilei, who demystified planet Venus... charting its phases as it moved around the sun, drawing it into the ranks of the other planets. 

With a similar size and weight, Venus became known as Earth's sister planet. But how Earth-like is it? The Russian scientist Mikkhail Lomonosov caught a tantalizing hint in 1761. As Venus passed in front of the Sun, he witnessed a hair thin luminescence on its edge. 

Venus, he found, has an atmosphere. Later observations revealed a thick layer of clouds. Astronomers imagined they were made of water vapor, like those on Earth. Did they obscure stormy, wet conditions below? And did anyone, or anything, live there? 

NASA sent Mariner 2 to Venus in 1962... in the first-ever close planetary encounter. Its instruments showed that Venus is nothing at all like Earth. Rather, it's extremely hot, with an atmosphere made up mostly of carbon dioxide.

The data showed that Venus rotates very slowly... only once every 243 Earth days... and it goes in the opposite direction. American and Soviet scientists found out just how strange Venus is when they sent a series of landers down to take direct readings.

Surface temperatures are almost 900 degrees Fahrenheit, hot enough to melt lead, with the air pressure 90 times higher than at sea level on Earth. The air is so thick that it's not a gas, but a "supercritical fluid." Liquid CO2. On our planet, the only naturally occurring source is in the high-temperature, high-pressure environments of undersea volcanoes. It comes in handy for extracting caffeine from coffee beans... or drycleaning our clothes.

You just wouldn't want to have to breathe it. The Soviet Venera landers sent back pictures showing that Venus is a vast garden of rock, with no water in sight. In fact, if you were to smooth out the surface of Venus, all the water in the atmosphere would be just 3 centimeters deep. Compare that to Earth... where the oceans would form a layer 3 kilometers deep.

If you could land on Venus, you'd be treated to tranquil vistas and sunset skies, painted in orange hues. The winds are light, only a few miles per hour... but the air is so thick that a breeze would knock you over. Look up and you'd see fast-moving clouds... streaking around the planet at 300 kilometers per hour. These clouds form a dense high-altitude layer, from 45 to 66 kilometers above the surface.

The clouds are so dense and reflective that Venus absorbs much less solar energy than Earth, even though it's 30% closer to the Sun.

Michio Kaku: The Intelligence Revolution

Professor Michio Kaku, famous Theoretical Physicist and one of the inventors of Light Cone String Field Theory (one of the Relativistic forms of M-Theory), hosts a documentary on the use of computer technology, cognitive science, mathematical groupings, faster computers, sophisticated algorithms and, most importantly, better education that will will lead to "The Intelligence Revolution". 

Ubiquitous computing is fast approaching us, with computer technology quickly becoming present in almost every facet of society and technology. Soon computers will be so ubiquitous that they will toil away in almost pure invisibility: in our glasses, in our clothing even in our own body.
The synthesis between computer fabrication, computer connectivity and of nanotechnology will mean that computers will be smaller, more connected and everywhere with minimal impact environmentally and spatially but creating a renaissance in information control by the individual.

Dr. Kaku was a high achiever in his youth, to say the very least. He constructed a small-scale, but fully functional, Cyclotron Particle Accelerator in his senior years at high school. His goal was no less than to fabricate antimatter. Such ambition did not go unnoticed and got the attention of a very famous physicist, Dr. Edward Teller. 
Dr. Teller noticed that young Michio was a very talented young man and promptly offered him a Harvard scholarship, starting his academic career. Michio's initial education of physics and inspiration which he had to build a reasonably complicated device was triggered by his own education of the subject early in life mixed in with a bold curiosity. 

Michio got his knowledge through books, children today are advanced data retrievers in comparison and can scour the internet for most of the content of human knowledge. Its no wonder children and young people are making such powerful innovations and ideas.
This synergy of Information Retrieval, Information Processing and Information Implementation is the engine of creativity and prosperity that, if we plan it correctly, could solve most of the problems facing us today: 
Global Warming, Environmental disasters, Disease, War, Hunger and Energy shortages are all problems which need quick access to information to solve and fast processing of plans to implement action. The Internet has given us one way to do this, but with more work on smart computing, cloud computing and the expanding field of Neural Networking and Grid Computing we may be able to solve problems as a Global Civilization would.

The fact that our world will be governed by computer intelligence in the necessities such as travel, health and even fabrication itself may spur a revolution on par with the development of agriculture: we may have all the time in the world to simply ponder existence and have an armada of computer brains to help us find the secrets of existence.

In this documentary Michio Kaku shows us how the information revolution may reach these amazing new heights and how we may use our intelligence to reinforce our wisdom for generations by educating ourselves to think critically on real world problems

5 Strange Theories About Stonehenge

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Sunset over Stonehenge. CREDIT: MPanchenko, Shutterstock  View full size image

Thousands of years ago, an ancient civilization raised a circle of huge, roughly rectangular stones in a field in what is now Wiltshire, England. Stonehenge, as it would come to be called, has been a mystery ever since.

Building began on the site around 3100 B.C. and continued in phases up until about 1600 B.C. The people who constructed the site left no written records and few clues as to why they bothered to schlep the stones to this spot.

Wild theories about Stonehenge have persisted since the Middle Ages, with 12th-century myths crediting the wizard Merlin with constructing the site. More recently, UFO believers have spun theories about ancient aliens and spacecraft landing pads. But Stonehenge has inspired a fair number of scientifically reasonable theories as well. Here are five major (and not necessarily mutually exclusive) reasons Stonehenge might exist. [Gallery: Stunning Photos of Stonehenge]

1. A place for burial

Stonehenge may have originally been a cemetery for the elite, according to a new study. Bone fragments were first exhumed from the Stonehenge site more than a century ago, but archaeologists at the time thought the remains were unimportant and reburied them. Now, British researchers have re-exhumed more than 50,000 cremated bone fragments from where they were discarded, representing 63 separate individuals, from Stonehenge. Their analysis, presented on a BBC 4 documentary on March 10, reveals that the people buried at the site were men and women in equal proportions, with some children as well.

The burials occurred in about 3000 B.C., according to study researcher Mike Parker Pearson of the University College London Institute of Archaeology, and the very first stones were brought from Wales at that time to mark the graves. The archaeologists also found a mace head and a bowl possibly used to burn incense, suggesting the people buried in the graves may have been religious or political elite, according to The Guardian newspaper. 

2. A place for healing

Another theory suggests that Stone Age people saw Stonehenge as a place with healing properties. In 2008, archaeologists Geoggrey Wainwright and Timothy Darvill reported that a large number of skeletons recovered from around Stonehenge showed signs of illness or injury. The archaeologists also reported discovering fragments of the Stonehenge bluestones — the first stones erected at the site — that had been chipped away by ancient people, perhaps to use as talismans for protective or healing purposes. 

3. A soundscape

Or perhaps Stonehenge's circular construction was created to mimic a sound illusion. That's the theory of Steven Waller, a researcher in archaeoacoustics. Waller says that if two pipers were to play their instruments in a field, a listener would notice a strange effect. In certain spots, the sound waves from the dual pipes would cancel each other out, creating quiet spots.

The stones of Stonehenge create a similar effect, except with stones, rather than competing sound waves, blocking sound, Waller reported in 2012 at the annual meeting of the American Association for the Advancement of Science. Legends associated with Stonehenge also reference pipers, Waller said, and prehistoric circles are traditionally known as "piper stones."

Waller's theory is speculative, but other researchers have confirmed that Stonehenge had amazing acoustics. A study released in May 2012 found that the circle would have caused sound reverberations similar to those in a modern-day cathedral or concert hall.

4. A celestial observatory

No matter why it was built, Stonehenge may have been constructed with the sun in mind. One avenue connecting the monument with the nearby River Aven aligns with the sun on the winter solstice; archaeological evidence reveals that pigs were slaughtered at Stonehenge in December and January, suggesting possible celebrations or rituals at the monument around the winter solstice. The site also faces the summer solstice sunrise, and both summer and winter solstices are still celebrated there today. [Gallery: Stunning Summer Solstice Photos]

5. A team-building exercise

Or perhaps Stonehenge was something like an ancient team-building exercise. According to the University College London's Pearson, the beginning of the site's construction coincides with a time of increased unity among the Neolithic people of Britain. Perhaps inspired by the natural flow of the landscape, which seems to connect summer solstice sunrise and winter solstice sunset, these ancient people may have banded together to build the monument, Pearson suggested in June 2012.

"Stonehenge itself was a massive undertaking, requiring the labor of thousands to move stones from as far away as west Wales, shaping them and erecting them," he said in a statement. "Just the work itself, requiring everything literally to pull together, would have been an act of unification."