Hey You! What If... (2020)

Could you build a slide to the other side of the world? You would need to start in space, use the slippiest slide ever and make sure you have enough supplies before you go down it.

Wouldn't it be cool to be able to walk through walls? From turning into a gas to quantum trickery, we discover why it wouldn't be quite as useful as you'd like.

Bugs might be annoying, but we would soon regret it if we got rid of them - all our favourite foods would disappear, and there would be dung everywhere.

From cloning to 3D printing, what if we could actually make copies of ourselves?

Imagine if we had a thermostat that could turn the world temperature down - could we fix global warming? But be careful, a few degrees too far and could cause an ice age.

Venus has acid rain, crushing pressure and is hotter than an oven, so it might not sound like the ideal place to live. However, up in the clouds it's almost just like home.

Find out how to shout from one side of the world to the other.

We try out three potential ways to become invisible and discover some surprising side effects.

There is a way that Earth could have a second sun, so we try it out to see what happens.

We imagine a world where it's possible to move things with your mind like films, but find that the laws of physics mean that this superpower wouldn't quite work like you expect.

We look at whether some animals can get gigantic and find out that if you are being chased by a giant snail or a humungous butterfly, then fear not, you must be dreaming.

We try using a gravity-bending black hole and spinning the earth faster to see if we can make it possible to walk on the ceiling.

What would the planet be like if all other humans disappeared, leaving you as the last person on earth?

Is it possible to build a sand castle the size of a real castle? We imagine how it could be done, using a pneumatic drill and a huge, solid gold steamroller.

We find out what would happen if you shrank the earth. You could jump higher and move faster, but you would end up with altitude sickness even at sea level.

If you had a tree that could grow money, would that make you rich? Even if you wait 20 years for your tree to grow, you will probably end up no richer than you started.

Flying like a superhero may sound like enormous fun, but there are some serious downsides that Hollywood does not tell you about - weather, extreme cold and even fizzy blood.

Imagine removing all the colours one by one? It would change more than just how things look, and after taking out just three colours, we would not be able to see anything at all.

If everyone in the world ate nothing but cheeseburgers, we would run out of land, and even if we went meat-free, we would have to invent some crazy burgers to get the nutrients we need.

To throw a ball around the world, you need to start out in space, throw it ten times the speed of a bullet and make sure your ball does not explode when it hits the atmosphere.

We reveal how to create the ultimate in tall buildings by going to the moon and taking inspiration from wedding cakes.

To win a marathon, are you better off with the bouncing legs of a kangaroo, the long legs of a T. rex or sticking with the legs of a human?

We imagine becoming unbreakable by removing our bones, turning our skin to metal and finally by becoming completely elastic, but indestructibility isn't everything we hoped for.

Sometimes you want to go surfing, but it's too far to the beach, so we try surfing on land with the help of a volcano and some giant fans.

We try out a crazy idea from science fiction to build a giant sphere around the sun and give us more energy than we'll ever need.

We take inspiration from the natural world as we imagine a new kind of superhero that can walk up walls.