The last time Cosmos was on television was 34 years ago. In 1980, as the inimitable Carl Sagan was dazzling audiences across America, some 1 billion miles away two diminutive flying robots were approaching giant cold worlds never before seen by human eyes. Although other spacecrafts had been to closer planets before, the incredible journeys of the Voyager probes set an unprecedented standard and ushered in a new era of space exploration. Since then, data-gathering spacecraft have been dispatched to explore other planets and moons in greater detail than ever before, probe the sun's amazing structural layers, document asteroid and comet collisions and peer into the deepest reaches of space and time.
Since Sagan's days, what we've been able to learn about our ever complex universe has been nothing short of astounding. With Cosmos coming back to television this year, now's a fantastic opportunity to remind ourselves about the amazing achievements that science and human curiosity have made since it was last on.
Pluto was first observed in 1930, and apart from one of it's moons, Charon, no other objects beyond Neptune were found until 1992. The eventual discovery of Eris in 2005, a trans-Neputunian object bigger than Pluto, ended Pluto's distinction as a planet. Both objects are now classified as dwarf planets, and are known to orbit the sun not independently, but as part of a population of similarly sized objects known as the Kuiper Belt.
Although many scientists believed that water once existed on Mars, it wasn't until 2008 when NASA's Phoenix Lander was able to test soil on the Martian surface near the North Pole and finally confirm the presence of water ice on the planet. In 2011 Mars Reconnaissance Orbiter presented the most compelling evidence of flowing water yet, with images that revealed the growth of dark streaks in Martian gullies during the summer. Researchers suggest that these marks are consistent with salty water flowing downslope and evaporating.
We've discovered that water in our Solar System is actually fairly common. Water ice has been detected on the moon, at Mercury's poles and on the asteroid Ceres, and traces of water vapor have been detected in the atmosphere of all the other planets. Perhaps the most exciting discoveries so far are the giant geysers on the icy moons of Europa and Enceladus, which shoot out water vapor from potential subterranean liquid oceans.
The discovery of an exoplanet, or extrasolar planet, was first confirmed in 1992. Since then, thanks to advanced technology such as the Kepler spacecraft, close to 1800 exoplanets have been found, encouragingly demonstrating that alien worlds are common in the universe. But what's especially interesting is that most of these expolanets are closer in mass to the Earth than to Jupiter and many fall within the "habitable zone," meaning they're conducive to water and life. There may even be up to 30,000 habitable worlds within one thousand light years of Earth.
Nuclear fusion is the process that powers the sun, converting hydrogen to helium. For decades physicists have scratched their heads about why they could only detect one third of the expected amount of one of its by-products, neutrino particles. Initially scientists thought their model of the sun was wrong. In 2001 this mystery was finally solved when experiments revealed that in fact neutrinos can mutate into three different forms. Our general model of the sun was right, we were just unaware of all the particles it could produce.
Interestingly, our investigation of comets and asteroids have revealed that in some ways they're much more similar to each other than we previously thought. We've been lucky enough to witness the impacts of these objects with the Sun, the moon and other planets, as well as spontaneous disintegrations, providing spectacular images in addition to valuable information.
When Cosmos was last on air, black holes were thought to be rare, appearing in around 1 out of every 100 galaxies. But when the Hubble Space Telescope came along, it showed that in fact the interior of almost all galaxies rotate quickly — up to 1.1 million miles per hour. Scientists concluded this rotation was due to the presence of supermassive material and that black holes are a standard feature of most galaxies.
Observing the distances between stars and how fast they're moving can help scientists calculate the age of the universe. But before modern space telescopes, sufficiently accurate equipment was unavailable and the best estimates were between 10 to 20 million years. After 1990, the Hubble's clear optics allowed scientists to narrow down the calculation to between 13 to 14 billion years. Since then, the WMAP spacecraft has recorded high resolution cosmic background radiation maps, narrowing this figure down further to 13.8 billion years, with an uncertainty of under 0.3%.
Although scientists have long known that the universe is expanding, many commonly predicted that this expansion would eventually slow down due to gravity. But when scientists could finally measure the rate of expansion by comparing the speed of supernova at different distances, to their surprise they found that the expansion of the universe was accelerating. These observations seemed to contradict the prediction that the gravitational force generated by all the mass in the universe would eventually rein it in. Scientists think that there must be another force that works in the opposite direction — "dark energy." Estimated to account for 68% of the entire universe, dark energy is the next big cosmological mystery waiting to be unravelled.
Today, both Voyagers have since left the Solar System and are now the first human-made objects to explore interstellar space, some 19 billion miles away. Meanwhile back on Earth, Neil deGrasse Tyson is bringing Cosmos to a new audience.
Future space missions hope to put humans on Mars, probe for life in the subterranean oceans of Jupiter and Saturn's moons and build even more powerful particle colliders to better dissect the very fabric of the universe itself. Within this backdrop, today Tyson's remit is strikingly similiar to Sagan's 34 years ago: to inspire and renew a generation's passion and support for the beauty of science and space exploration.
Cosmos: A Spacetime Odessey can be seen on FOX on Sunday nights at 9 p.m., Eastern & Pacific, 8 p.m. Central, and National Geographic on Monday nights at 10 p.m.