Our galaxy is one of hundreds of billions in the universe. View of universe through the Hubble telescope and go back almost all the way to the Big Bang.

In space travel there is a saying that the first 50 miles and the last 50 miles are the most dangerous. See how a single spark inside a spacecraft or a micrometeoroid less than an inch wide hitting a space station can turn a routine mission into a lethal nightmare. As the missions become longer, venturing to Mars and beyond, the potential disasters will only become bigger. What would happen if a spacecraft ventured too close to a black hole or was hit by a gamma ray burst?

According to the laws of physics we can never travel faster than the speed of light...or can we? Light speed allows us to see things instantly here on Earth, and shows us the entire history of the universe going back nearly 14 billion years. Learn all about light speed, the ultimate constant in the universe and discover ways scientists envision breaking the "light barrier" which may be the only way the star travel of our imaginations ever comes to reality.

As man moves to colonize the cosmos, the realities of sexual relationships and reproduction need to be addressed. Probe the physiological, psychological and cultural challenges of sex in space. From the sex act through birth, look at how the extreme environments of space exploration might effect copulation, conception and developing human tissues, as well as how issues around sex might impact the emotional lives of astronauts. Get to the bottom of the rumors to find out if space sex has already happened, and look at how the burgeoning space tourism business may soon lead to a boom in space sex.

They soar through the heavens, fly through the oceans and glide along land. But these are not creatures found on a wildlife safari. These are life forms from another planet. Armed with scientific fact and a little imagination, experts come together to take you on an unprecedented journey to the edges of our imagination. Scientists, astrobiologists and astronomers create five lines of extraterrestrial evolution, and explain how creatures on the surface of Earth offer a helping hand to understanding life in The Universe.

Asteroids and comets have left their imprint on planet Earth, literally. Since the turbulent formation of the solar system, these space rocks have continued to impact earth. Some have been so violent that they've led to mass extinctions. What's more, radical new theories suggest that asteroid and comet dust harbor deadly viruses that may have triggered some of our worst pandemics. The possibility of future cosmic collisions remains a legitimate threat. Yet, despite their dangers, asteroids and comets may hold vital natural resources, which could actually preserve mankind.

When mankind eventually leaves the cradle of Earth and ventures forth into the uncharted territories of the cosmos, where, and what form, will our new homes take? Will they be cities under glass, entrenched in distant alien soils? Will they be gleaming metropolises hanging in orbit above our heads, or in the lonely void of space? Will they be hollowed out asteroids, strip-mined for the valuables they horde? How will we grow food? What will the new era of spacesuits be like? The rovers that carry us around? Will robonauts, advanced robotic machines, perform the most dangerous tasks for us? How will we live... in space?

It sounds like a Hollywood blockbuster: a deadly asteroid is on a collision course with Earth. But in reality, it's only a matter of time before a giant space rock threatens to wipe out civilization. An asteroid took out the dinosaurs sixty-five million years ago. Are we next? This episode analyzes the threat and explores the many ways--from a nuclear bomb to ingenious new technology--that experts are proposing to stop Armageddon.

Could we be unique in the universe or is there another planet similar to earth somewhere in the cosmos? Is it possible that Alpha Centauri, our nearest star, is home to another earth-like planet? Earth sized planets have been hard to find, but indirect methods are coming on line to give scientists a good survey of how many such bodies may be in the universe. How rare would it be to find life on another earth-like planet?

An exploration of mysterious phenomenon, including alcohol clouds in space, pulsar planets, the possibility of a planet beyond Neptune, and dark matter.

There have been both helpful and harmful effects on life on Earth from cosmic effects. Cosmic Phenomena includes the beauty of the Aurora Borealis and rainbows to the dangers of UV radiation and cosmic rays, from the miracle of photosynthesis to the thrill of a meteor shower as we explore the effects caused by the sun and other extra-solar sources, which can get under our skin and scramble man's technology, make life possible and be a threat to our existence all at once.

The majority of space exploration has occurred in Low Earth Orbit, around 120 miles above sea level. For a cool $20 million, any person can take a ride on the International Space Station, around the 1,100 mile band around Earth. Commercial prospects for LEO are huge, there are big dangers lurking for anyone interested in traveling this way, such as radiation, , cosmic rays, and space debris numbering in the thousands threaten any spacecraft traveling in orbit. It's a new frontier and maybe the final frontier, and the possibilities are endless if you are willing to travel to the edge of space exploration.

Season 4 opens with an exploration of dying stars, the process where stars become supernovas, and, occasionally, become the biggest blast in the universe as a gamma ray burst (GRB). One death star, named WR104, lurks 8,000 light-years from Earth and some believe its GRB arrow is aimed directly at us. A death star galaxy named 3C321 is a frightening vision of what could one day befall the Milky Way galaxy: a companion galaxy's black hole being hammered with a constant blast of high-energy particles, wreaking havoc with its celestial bodies. Nearby, Death Stars Eta Carinae and Betelgeuse burn through their fuel supplies as they hurtle toward extinction...which just may be too close for comfort.

Without the moon, Earth would be a very different and desolate place today--four hours of sunlight with pitch-black nights, steady 100-mph winds spawning giant hurricanes that last for months, and virtually no complex life forms, much less humans. Safe to say, we probably owe our very existence to the moon. But what if it suddenly disappeared?

Every year, thousands of objects both natural and manmade plummet through our atmosphere and crash into the Earth. These menacing messengers from the sky provide scientists with amazing insights into the natural, and not so natural, phenomena of the cosmos. From space rocks crashing through homes to cosmic boulders triggering mass extinctions to rocket parts landing on front lawns, explore objects that fall from the heavens, such as asteroids, comets, meteor showers and space debris.

An examination of the most powerful explosions and blasts in the universe. Includes a look at the Mexico's Yucatán peninsula and the impact which caused the Chicxulub crater. Also a look at gamma rays and Big Bang Theory.

They are breathtaking, lethal and a constant source of surprise. The stunning rings of Saturn have mesmerized countless scientists over the centuries. With particles the size of a house shooting at 53,000 miles per hour around the planet, any spacecraft passing through would meet an instant and catastrophic end. Inside the rings is like a NASCAR race - with bumping, jostling and frequent collisions that can cause a massive spin-out. Lesser known are the other planets that have rings - Uranus, Jupiter, Neptune, possibly Pluto and Mars. Even Earth has a ring. Comprised of some 200 satellites in a geosynchronous orbit, it is the only known man-made ring in the universe. But the most remarkable thing about rings is that they contain the story of the birth of our solar system, and entire distant galaxies. Rings are more than a wonder of the universe - they reveal the secrets of our own origins.

Experts cook up ways you could destroy the Earth, including swallowing it with a black hole, blowing it up with anti-matter, hurling it into the Sun, and switching off gravity.

They are the one-stop-shopping places for learning all about the nature and variety of stars in the Universe. They're unique, because in clusters, all the stars were born at about the same time, from the same material and all are at the same approximate distance from Earth. This means we can be sure that any differences among them are due to their true natures and not distorted by different distances from Earth and other factors.

Outer space is already an essential part of America's ability to fight wars. Our military depends on satellites for many things, such as communications, reconnaissance and targeting information. But so far, no country has put weapons into space, although the U.S. and China have both shown they can shoot down satellites with ground-based missiles. If weapons do become a part of space, how will they work, how effective will they be, and what type of damage could they do? From ground-based lasers to telephone-pole sized rods hurtling from space at two miles per second to the far out weapons of the distant future, it's time to "lock and load" for Space Wars.

On alien planets, they rain from the sky as scalding iron. On distant moons, even at hundreds of degrees below zero, they slosh around in pristine lakes of methane. They can cover entire planets in miles-deep oceans of electrified hydrogen metal. Or erupt on alien worlds through miles-high geysers. They churn in the interiors of dead stars and even our own planet. They're so rare in the universe, they almost don't exist, but these are the magical liquids of our Liquid Universe.

They sort of sound like the same phenomenon, but Pulsars and Quasars are very different. Pulsars are tiny--only a few miles across--but they spin as fast as a kitchen blender and sweep the sky with beacons of radiation that make them appear to flash on and off. They have unbelievably strong magnetic fields, are more accurate than atomic clocks...and they can even tell aliens just where to find the Earth! Quasars are at the other end of the spectrum. Quasars are huge cores of galaxies with black holes that are called "monsters" and which spit lobes of radiating gas called "DRAGNs." Quasars are so far away, we see them as they were only in the distant past--meaning they existed only in the early universe, when they may have played a major role in the creation of the galaxies themselves.

Warp speed, transporters, wormholes and lasers--they are all staples of science fiction books, movies, and TV shows. But the fantastic world of tomorrow is quickly becoming the futuristic world of today. While you may not be "beaming" to your next appointment any time soon, researchers are preparing for the first tests of a present-day "transporter." And while scientists have long mocked Hollywood's visions of warp speed and faster-than-light travel as prohibited by Einstein's laws, a new generation of physicists continues to rewrite the fundamental rules of the universe. Is there a way around the cosmic speed limit? Maybe... as long as you're prepared to survive a journey through the ultra-high energies of one of the most violent places in the cosmos--the heart of a twisting, swirling vortex that leads either to strange, new worlds... or certain death.

Ours is a universe of energy, from powerful jets ejected from black holes to the raw nuclear fury of our Sun. But, the total amount of energy in the universe maintains perfect equilibrium--no more can be added or taken away. Because of this, there are enormous amounts of energy being transferred...electric, thermal, kinetic and magnetic energy are just a few that keep our universe balanced--and create awesome cosmic events and stellar displays.

What does the Universe sound like? From the sweep of a pulsar, to the deafening roar of our boiling sun this episode explores the undiscovered soundscapes of the solar system, the galaxy, and the entire cosmos. And, is it true that in space nobody can hear you scream?!? Our scientists reveal that there are places in the Universe that prove this sci-fi statement wrong.