What If

This is not some DVD floating in space. It's a megastructure that might one day become humanity's home. The Earth might not remain habitable forever. It could get engulfed by a massive solar flare, or become too hot due to climate change, or have all its life wiped out by one enormous asteroid. What if I told you we could outlive all these disasters? And that we could do that by building a space megastructure bigger than the Sun itself? Just how big would we have to make it? And what would life be like on a structure like that?

Its teeth are supposedly so sharp that if it were to bite you, you would only realize it after you saw the blood. But what if you were attacked by a school of these colorful, fast-moving carnivores? How much would you feel? How long would you last?

Death and the possibility of an afterlife have fascinated artists, philosophers, and scientists throughout history.  Fear, hope, dread ... these are all things we might feel when we ponder what happens to us after we die. But what does science actually know about the afterlife? If we knew that we went somewhere after we died, would we lead better lives? Or would we shrug off our earthly responsibilities, knowing that death wasn't the end?

What if you could shrink yourself down to the size of 1 mm (0.04 in), about the size of a frog's egg? Actually no, there too many creepy crawly predators, so let’s go smaller. What if you shrunk to 10 micrometers (0.0004 in), the size of an animal cell? That's pretty cool, but I think we can go even smaller. How about 100 nanometers (0.000004 in), the size of a virus? That’s better, but we're not in the mood to be swallowed by white blood cells. So let's keep going. What if you shrunk to 1 angström, the size of the atom?

We can build really big things in space. Okay, not that big - yet. But we've packed the Earth's lower orbit with about 5,000 satellites - some still functioning and some not. What if we could build a bigger, brighter satellite and put it into the Earth's lower orbit? Something that would reflect so much sunlight that we'd never have to turn our lights on again. I'm talking about an artificial moon. How big could we possibly make it? And why would it be a bad idea to proceed with this space construction project?

UY Scuti: It's the largest star that we've ever discovered. And if it were to replace our Sun, it would change a lot more than just the amount of sunscreen you'd have to put on. Like, how long would it take for our planet to orbit this massive star? What would that do to our seasons? And would we even survive a single orbit?