We heard a delightful plenary last night from Michio Kaku, the co-founder of string theory and a great popularizer of science. He’s written a ton of books including one of the same name as this talk. He’s also got an upcoming series of episodes on the Science channel, starting August 10th, 3 Sundays in a row.

He began with a joke. A priest, a lawyer, and a physicist all face the guillotine. The priest is up for the chopping block first, and they ask him, “Do you have any last words?” Yes, says the priest, “Please, God, by your holy spirit, set me free.” They put him under the guillotine and, lo and behold, the blade stops just before it reaches is neck. “God has spoken!” says the magistrate, and they set the priest free. Next up is the lawyer, and he’s asked if he has any last words. “Yes,” he says, “the spirit of justice will set me free!” They let the blade fall, and it stops just short of his neck. “The spirit of justice has spoken!” cries the magistrate, and they set the lawyer free. Last up is the physicist. He’s asked for his last words. “I know little about God,” says the physicist, “and even less about justice. But I do know one thing. If you look up, you’ll see that the rope is stuck on the pulley. If you set it free, that blade should come down real good.” So, they did that, and indeed, the guillotine worked just fine for the physicist. The moral of the story? Physicists should learn when to keep their mouths shut.

That’s been true throughout history, says Kaku. Lots of physicists have looked foolish by, for instance, declaring certain things to be impossible. Lord Kelvin, for example, said that:

  • “Heavier than air” craft were impossible
  • X-rays were probably a hoax
  • The earth couldn’t possibly be older than a few million years old.

That last is interesting — he did the calculation based on a time-rate of cooling of the molten core of the earth and found it would be stone cold by now if it were older than a few million years. But, he didn’t know about the nuclear force at that point, and thus the nuclear decay which fuels the heat of the earth. The lesson learned here is that you have to understand all the laws of physics in order to make predictions about what is possible or not. New things are discovered all the time, and in the time of Lord Kelvin we didn’t know yet about quantum mechanics and relativity, to name a few, which are essential for understanding how the world works.

Another thing that was thought impossible was rocketry. The NY Times denounced Robert Godard (the father of modern rocketry) because rockets couldn’t possibly move in outer space. In outer space, they said, there is no air to push against. (Now, that’s true, but remember Newton’s 3rd Law — the rocket expels stuff out the back so the whole rocket has to move forward).

And of course, there are Arthur C. Clarke’s Three Laws:

  1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
  2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  3. Any sufficiently advanced technology is indistinguishable from magic.

On the other hand, there are some things that are really likely to be impossible, because they violate all the known laws of physics, like perpetual motion machines and precognition. See my previous post on crackpot science for some discussion of why folks like to think they’ve disproven those juicy laws like relativity.

But there are some things that we used to think are impossible we’re likely to see in the next few decades or, perhaps, the next few milennia. For example….


We used to say invisibility was impossible because light can’t wrap around an object and come together on the other side, like water can. If you’re downstream from a boulder, the presence of the boulder is “invisible” to you because the water wraps around the boulder. Another way of saying that is that light can’t bend with an index of refraction less than zero. But, now we know that’s not true, using stuff called “meta-materials”, which are artificially engineered, we can indeed bend light. This has been done with microwave frequency light (where the wavelength is about the thickness of your thumb) and with red and blue light. It’s done by putting impurities into the material that “kick” the “crest” of the wave a little bit, so that overall the whole direction of the wave gets changes in a way that we wouldn’t have predicted before these meta materials with negative index of refraction were created. This is just proof-of-concept right now. In order to make something completely invisible, we’d need 3 types of meta materials for each color of visible light. Plus, not only can people outside the invisibility “cloak” not see in, but those inside the cloak can’t see out, so you’d essentially need to cut two eyeholes to see out. Read more about how invisibility works.


So, it’s impossible to dissolve and reappear, right? Well, not if you’re a subatomic particle. They’ve now “teleported” particles a record of about 100 miles, between two Canary islands, and they’re asking for permission to teleport a particle to the moon. This uses the principle of quantum entanglement, which basically says that you can “entangle” two particles so that when one particle changes, the other one changes too. So it’s not the original particle that was sent between the two islands, but rather the information contained in that particle (it’s “quantum state”). Read more about it.

So, the question arises — if I were to be teleported, and it’s the information in the atoms that make up “me” (and not the atoms themselves) that are transported, then what does it mean to be “me”? Does the soul consist of the quantum state of your particles? If you have to be destroyed in order to be teleported, who would sign up? Well, we’re certainly not at the point of being able to teleport people, but perhaps in 10 years or so we can teleport an atom or even a molecule.

Death Stars

Is it possible to vaporize an entire planet? Could we have a portable source of power for a ray gun powerful enough to do that? A decade ago, people shook their heads, though certainly there’s no upper limit to the energy of an H-bomb, it just doesn’t seem feasible to direct all that energy at a planet in a thin beam. But there is one thing that occurs in nature that fires a huge amount of energy in a thin beam and could destroy a planet — gamma ray bursters. These are huge emissions of power from stars as they collapse to form black holes. It turns out there’s one candidate star which could feasibly maybe possibly turn into a gamma ray burst — WR104. It’s 8000 light years away. Who knows, maybe it detonated 5000 years ago and we just don’t know it yet? The chances are, of course, that it won’t.

Telepathy and mind reading

According to Kaku’s definition, this has already happened! A project called BrainGate has created a direct connection between the brain of a stroke victim and a laptop. With a little practice, the stroke victim can learn to control the computer, including surfing the web, sending email, and playing video games, just by thinking about it! This certainly seems to fit the definition of psychokinesis, though it’s aided by artificial means. And mind reading? We can scan people’s brains using MRI machines and, while we can’t tell just what they’re thinking, we can tell with 98% accuracy whether they’re lying. When you tell a lie, your brain lights up like a Christmas tree (at least on the MRI scan).


It’s been hard to ignore the progress made in terms of semi-intelligent and humanoid robots recently. The most advanced humanoid robot is Asimo in Japan. Its reactions are pre-programmed, but the amazing thing is that it can walk and move like a human — no small feat! There’s a reason why most robots roll around instead of walking. It took Honda 20 years to get it to move like a human. For those of us with a little less money (but still doing pretty well) there is of course the Roomba — the robot vacuum cleaner. We tend to anthropomorphize these robotic “creatures”. He found his wife clucking with some sympathy for their Roomba, saying they should ‘let the poor robot rest.’ There is also the (very cute) Ibo, the pet robotic dog.

Yet for all these advances, Asimo is still about as smart as a cockroach. A retarded cockroach. The rovers on Mars take a full day to recognize a rock, says Kaku. A cockroach does better than that.

See Kaku’s book on the Physics of the Impossible here.