In the third programme of the series, Aleks gives the lowdown on how, for better and for worse, commerce has colonized the web - and reveals how web users are paying for what appear to be 'free' sites and services in hidden ways. Joined by some of the most influential business leaders of today's web, including Eric Schmidt (CEO of Google), Chad Hurley (CEO of YouTube), Bill Gates, Martha Lane Fox and Reed Hastings (CEO of Netflix), Aleks traces how business, with varying degrees of success, has attempted to make money on the web. She tells the inside story of the gold rush years of the dotcom bubble and reveals how retailers such as Amazon learned the lessons. She also charts how, out of the ashes, Google forged the business model that has come to dominate today's web, offering a plethora of highly attractive, overtly free web services, including search, maps and video, that are in fact funded through a sophisticated and highly lucrative advertising system which trades on what we users look for. Aleks explores how web advertising is evolving further to become more targeted and relevant to individual consumers. Recommendation engines, pioneered by retailers such as Amazon, are also breaking down the barriers between commerce and consumer by marketing future purchases to us based on our previous choices. On the surface, the web appears to have brought about a revolution in convenience. But, as companies start to build up databases on our online habits and preferences, Aleks questions what this may mean for our notions of privacy and personal space in the 21st century

Right now cosmic forces prowl the universe and threaten man's very existence. They're asteroids and comets; they've left their imprint on planet Earth, literally. Initially helping to build planets through violent collisions, during this fiery bombardment period they may have even seeded Earth with water and the building blocks for life. 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, including one that wiped out the dinosaur. New theories suggest that asteroid and comet dust harbour deadly viruses that may have triggered some of our worst pandemics. The possibility of future collisions remains a legitimate threat yet despite their dangers, asteroids and comets may hold vital natural resources, which could actually preserve

They've discovered water on other planets, and snatched the actual building blocks of life from a comet's tail. But can space probes find a new Earth...and even make contact with alien life? In the 21st century, space probes are photographing, drilling and even sniffing new worlds in the quest for life, and scanning thousands of distant suns trying to detect Earth-like planets. It's only a matter of time before space probes unlock the secrets to extra-terrestrial life and the universe itself.

Explore the latest science behind the headlines and the coolest scientific developments that impact our lives. Technology catapults to new heights in 2015, going faster and further than ever before. We have canvassed the world in search of the best and most fascinating science and tech stories of the year for 2015 YEAR IN SCI-TECH". This action-packed hour of fun and intrigue revisits the world’s first glimpse of Pluto and images of water on Mars while exploring what this all could mean for intelligent life in the universe – all while earthling’s inch closer to becoming actual space tourists. Throughout the hour, we revisit the year’s most amazing techological feats and scientific discoveries, including new and elusive animal species discovered deep under the ocean, as well as the hottest tech trends – from hover boards to driverless cars and trucks, and the newest advances in mind-blowing virtual reality.

We float along the river of time. But does that river have a source? Where did time come from? Some believe time and space are one thing, and the Big Bang started the cosmic clock. Others believe the universe existed for almost half a million "years" before light could move and time began. Still others say time is older than our universe. But what if time itself is an illusion? Incredible new experiments may hold the answer. One groundbreaking experiment gives us the power to punch holes in time…and another may create a machine that operates outside time’s boundaries!

Low Earth Orbit, 120 miles above sea level, is where the majority of space exploration has occurred. This 1,100 mile band around Earth is where--for a cool $20 million--any private citizen can take the vacation of his or her life on the International Space Station. Commercial prospects for LEO are huge; but dangers lurk for any individual willing to travel here--radiation, cosmic rays, and space debris numbering in the thousands threaten any spacecraft travelling in orbit. It's the new frontier, or the final frontier...and the possibilities are endless if you are willing to travel to the edge of space exploration.