Like most people, I’ve always thought it would be cool to have superpowers. For the socially awkward, the autistic, or both, the ability to turn invisible would be a massive boon, and I can think of plenty of situations where shrinking to the size of an ant or growing to the size of a redwood tree would come in handy. Super speed, super strength, X-ray vision – who wouldn’t want those capabilities?

But unlike most people, I’ve put a little too much thought into the subject – enough to realise the little facts that make most superpowers totally impossible. Want to ruin your enjoyment of comic books and Marvel movies? Read on.

Invisibility – Susan Storm, Little Miss Incredible

Unless it’s a special suit, or the ability to bend light around you, most versions of invisibility in fiction involve the subject allowing light to pass through them. This makes perfect sense – our vision, after all, is based on light photons bouncing off objects and into our eyes, so if light doesn’t bounce off an object, you can’t see it (though you might be able to detect refraction, a la the Predator).

Unfortunately, the way our vision works has a terrible implication for the would-be invisible person. We see by detecting light photons hitting our retina at the back of our eye, so if we were invisible, and light passed through us, we’d be completely blind. So much for sneaking into the girls’ locker room!

Another downside is digestion. While we were invisible, the food we eat would not be. Nor would our urine. Or our poop. We’d be a walking diagram of our digestive system. Yuck.

And since our clothes wouldn’t be invisible either, we’d have to go everywhere naked. That might be okay for midsummer, but in the winter? When it’s raining? On gravel? Have you seen how dirty the soles of your feet get from just a few minutes walking around your garden?

So. Blind, naked, cold and gross. Not so desirable anymore, is it?

Super small and supersize – Ant-Man, the Wasp

The principles of growing really, really big or shrinking really, really small are exactly the same – you stretch or compress the empty space within and/or between our atoms. And there’s a lot of empty space to play with – if you imagine an atom is the size of the Earth, the nucleus is about the size of a football stadium. That means you could go incredibly small or incredibly big.

Trouble is, whether an ant or a skyscraper, you’ll still have the same mass, because nothing is being added and nothing is taken away. And as every good schoolboy knows, pressure equals force over area. It’s the reason a 90lb model in stiletto heels damages gym floors, but the 400lb wrestler in sneakers doesn’t.

So, if it takes around 100psi for a nail gun to drive a piece of metal into wood, imagine what would happen to a 200lb man shrunk to the size of an ant – you’d embed yourself into the floor. If you jumped in a swimming pool, even accounting for buoyancy, you’d plummet to the bottom, smash through the tiles and dig into the ground underneath. And then drown.

What about the other extreme? If you’ve ever walked in a strong wind, and felt the way it blows you about, imagine being fifty or a hundred times taller, with an exponentially larger surface area, but weighing the same. Your body would be your own sail, which might make it impossible to walk in anything other than a dead calm.

Your voice and hearing would change too. Given that vocalizations are related to the length of your larynx and your perception of sound to the size of your eadrum, if you shrank to the size of an ant, your voice would be higher than a choir boy with tight underwear, and everything you heard would be really deep and booming; whereas if you became Trump Tower, your voice would be a rumble of thunder and everything you heard would be a high-pitched mosquito whine.

When you really stop to think about it, anything other than the size you are now is a non-starter.

Super Speed – the Flash, Quicksilver

Who hasn’t wanted to whizz to the shops, grab all your groceries, and rush back home in the time it takes the kettle to boil? To dodge the rain, read a book cover-to-cover the minute before the book report is due, and catch that fly that’s been bugging you for days? Super speed could be the answer to all your problems.

Except that it creates more than it solves. When the plane accelerates down the runway and presses you back in your seat? That’s G-force. Too high a G-force, and your body starts to break. Star Trek has magical ‘inertial dampers’ to prevent the crew of the Enterprise being a red spot on the back wall every time they manoeuvre, but a person with super speed doesn’t have that. Going from a standing start to a thousand miles a second would squish your brain against the back of your skull – if, that is, your skull hadn’t already snapped off your neck.

Another problem is heat. Travelling at super speed causes super friction with the air. Worse would be the heat generated by the compression wave you create in front of you, like a spacecraft entering the atmosphere. Super speed? You’d burn to a crisp.

Also, just because you’re super fast doesn’t mean you’re super strong or super fit. Who the hell wants to run all the way to the shop and carry their own shopping home? In any case, get used to that trip, because you’ll have to eat non-stop to make up all the calories you burn.

But worst of all is the speed of perception. You couldn’t have super speed without the ability to perceive things at such speeds, and our awareness of time is directly related to our perceptions. Imagine how bored you’d get if every second felt like an hour, every hour like a day, every day a month. Imagine how hard it would be to watch a movie, listen to a song, have a conversation. After a couple of years, you’d be in a straitjacket.

Super Strength – Mr Incredible, the Hulk

Super strength is an awesome idea. Pick up a car. Swing a tank around by its gun. Unscrew every jar in the fridge. Seems like it’d be a real asset to have.

But, as Newton showed us with his Third Law of Motion, for every action there is an equal and opposite reaction. Punch someone hard enough to put them through a wall, you’ll probably throw yourself through the wall behind you – that is, if you don’t punch a hole clean through their chest, because if you apply that much force to a human body, I don’t fancy your chances of keeping red goo off your hands. So supposing you’re fighting a supervillain who can take such punishment and you punch them up into the sky? You’re likely to drive yourself down into the ground.

To balance these forces, you’d also need to be super heavy, or you’d be throwing yourself all over the place. So forget ever climbing the stairs again, or sitting in a comfortable chair, or lying in a bed that isn’t triple reinforced.

Then you have the same problem as being super small – exerting a massive force over a small area. If you tried to pick up a car or a tank – supposing it doesn’t bend, break and crush – several tons of pressure would be concentrated in an area the size of your hands; they’d puncture right through. And even if you could carry it, with your normal-sized feet it’d push you down into the ground again. To be useful, super strength would also require super size, which is a different kettle of fish altogether.

But the worst part of having super strength is that you’d break everything – everything designed for humans, at least. Even with my very modest human strength, dozens of times I’ve exerted more force than the capabilities of the material to withstand. Imagine being ten or even a hundred times stronger than the strongest human – you’d break practically everything you touched.

X-Ray Vision – Superman

This one’s pretty easy to dispel. X-rays are ionizing radiation, meaning they can penetrate cell walls and damage DNA. Every time you open your eyes, you’re giving people cancer, including yourself. Not the most heroic of superpowers, is it?

Flight – Superman

Which leaves flight. If you forget about gravity, thrust, drag and lift, flight is the most plausible superpower. If you forget about gravity, thrust, drag and lift.

I’d be great at parties, wouldn’t I?