May 28, 2007
The Fantastic Four are silver-surfing back onto the silver screen this summer and Susan Storm, the Invisible Woman (played by Jessica Alba), is taking the spotlight. Even the director calls them "Jessica Alba and three other dudes". So we have decided to take a closer look at her - and the reason why you sometimes can't: Invisibility!
Invisibility — The Problem
Let's say you want to sneak into Dr Dooms Evil Lair (TM). Not easy, because light scatters off you, and into Dr Dooms eyes, sending signals to his brain that tell him you're there. As a result, he will then probably attempt to kill you. Not good.
Well you could turn off the lights but that would leave you as blind as him. And among all those high tech death devices, he probably has a flashlight anyway. If you try absorbing all the light so none scatters to his eyes, he'll see you as a walking talking iPod commercial - You'll become pitch black (which is how the human brain represents a lack of light).
Did You Know?
Visible light is only a tiny part of the electromagnetic spectrum - a huge range of electromagnetic waves. They differ only in the length of the waves, from thousandths of millionths of meters (the x-rays that beam right through you) to kilometers (radio waves). We see 'visible light' because it is the region our eyes are tuned to see. Invisibility — The Solution
If you want to stay unseen, you can't stop the light - you have to let it pass by as if you weren't there. Windows do this because the glass doesn't scatter or absorb much light in the visible region.
But you can't convince your flesh to do the same as it depends on the molecular structure of the material. You'd have to actually replace your flesh with glass (which I think a Fantastic Four villain did in one of the comics, but that's a different story).
Did You Know?
Regular window glass is transparent to visible light, but not to infra-red (So the Predator could see you through a jungle, but not hiding in a greenhouse). And you're transparent to x-rays, but not to visible light. 'Transparent' is all a matter of wavelength. Better to convince the light to go around then carry on as if you weren't there. In fact, scientists at the Imperial College of London have defined the properties a new material that can do just that: make light flow around an invisible 'bubble' in the center (like a river flowing around a rock).
"We can make things invisible if there was a magic new material that made things invisible". This sounds like cheating but thanks to the new field of metamaterials, it isn't.
We've traditionally depended on materials that already exist and whatever properties their molecular structure happens to give them to create new products.
With recent advances though, scientists are developing new materials called metamaterials - substances whose properties depend not on the atoms put together by nature, but on tiny structures put together by man - structures which can be designed to behave in new ways.
For example, a coating that makes items almost invisible to microwaves has already been demonstrated which could make planes that are not just stealthy, but absolutely invisible to radar. Since the only difference between microwaves and visible light (and your cellphone signal) is the length of the electromagnetic wave, those responsible believe that extending the device to the 'invisibility' is only a matter of time.
Did You Know?
Invisibility won't help you if Dr Doom has evil armies of bats or whales (however you manage that) - these animals use sound waves to find prey by echolocation. Sound waves are pressure variations in the air, not electromagnetic waves like light, and will reflect from these light-bending metamaterials just fine. Invisibility — The Problem...again
So getting an invisibility device sounds like fun by now, right? The problem is when you redirect all the light around you to become invisible, none comes to your eyes - making you blind. You've turned the lights off but only for yourself.
Even if others can't see you, they're going to see the things you knock over and hear you walking into walls. All that work to become invisible, and you'll look as dumb as the filmmaker who decided "Let's give Jessica Alba a power that means you can't see her".
Marvel Comics: Fantastic Four
MSNBC on the Imperial College project, simple style
Science Magazine on the Imperial College Project
Wikipedia on Metamaterials
Duke University: Negative Index Metamaterials
Luke McKinney blasts things for a science studying a PhD in laser physics in the University of Toronto. He enjoys keeping fit, meeting people and trying new things. He also writes for Cracked.com.