Build a simple roller coaster, and out of basic materials - paper, sellotape, blu tak. All you need to do is drop a marble down the start of the rollercoaster when the timer reaches 0s and make ...

But what if we built a roller coaster even taller? What if there was a coaster that went as high as the tallest building on Earth, the Burj Khalifa? Well, it's a good thing we don't, because ...