On the surface, Uranus looks calm. And yet, we've suspected for a long time that inside there must be something very weird going on. So, in 1986, when NASA was finally able to probe Uranus for the first time with its Voyager 2 mission, what they found was nothing short of incredible. While most people probably think that Uranus is filled with gas, we are now realizing that it's actually full of something massive - a strange combination of forces that appears to defy all logic. And it's taken NASA scientists more than 40 years just to get to the...