The four types of planetary civilizations, explained by Michio Kaku

• We physicists have often wondered: Are there signs of intelligent life in the galaxy? And if so, how advanced might they be? So we categorize these alien civilizations on the basis of energy, energy consumption. Type one would be planetary: They control the weather. They control anything planetary because they have the energy of a planet.

Then there's type two: A type-two civilization has exhausted the power of their planet, and they use the sun. They basically take the energy from their sun to power their machines, sort of like the Federation of Planets in "Star Trek."

Then there's type three: Galactic. They roam the galactic space lane; they play with black holes, sort of like the Empire of "Empire Strikes Back." That would be a type-three civilization.

And then the question is, "What are we?" We are type zero: We get our energy from dead plants, oil, and coal. We don't even rate on this scale. We have not attained planetary energy at all.

But what would it take to move between universes, to enter a black hole, to break the light barrier? You would have to reach the energy of type three. This is called the Planck energy. The Planck energy is the energy of a black hole; it is the energy of the Big Bang. It is the greatest energy in the Universe.

So how long before we can attain the Planck energy and move between universes? Well, a modest calculation shows that you would have to be about 100,000 years more advanced than us. Sorry about that.

The next question is, "How would we know of a type-three or type-two civilization if we were to bump into one?" Let's say that, scanning the heavens, we see evidence of a type two or type three civilization. How would we know?

Well, we've looked. We've looked for type two because type-two civilizations give off an energy, a characteristic blackbody radiation, that we can measure. So far, we find none. Now, that doesn't mean that there aren't these civilizations out there. It just means that our devices are so primitive that we have not yet been able to conclusively show that they exist.

But if they can go faster than the speed of light, then it's possible they may have the energy of a wormhole. And at that point, they would be type three. They would have the Planck energy to create universes or to move between universes.

Also, when we talk about intelligence in outer space, we have to be open to the idea that their intelligence may be quite different from our intelligence. And therefore the question is, "How do we tell where real intelligence is, given the fact there could be more than one type of intelligence?"

Well, let me give you an example. I was in a swimming pool with dolphins. Sensors picked up the squeals and chirps from the dolphins, and then they ran it through a computer. They found bingo! Yes, they are intelligent. Yes, there's a pattern, a regularity to their chirps.

And so it is possible to rank intelligence using computers that look for an algorithm. We'll do that in outer space now. In outer space, there's lots of garbage. There's lots of gibberish out there. And we think that most of the gibberish is just exploding stars, random events of no particular importance.

But maybe, using a quantum computer, we may be able to go through the mountains of data coming from outer space and find the signals of intelligence.

Historically, when physicists were asked about flying saucers and UAPs and extraterrestrial civilizations, you just can't say that, "Gee, I saw something going across the sky last night." Maybe you did. Maybe you didn't. You have to have data.

About 90% of these sightings can be explained using natural phenomena, or weather anomalies, or weather balloons. But 10% of them seem to defy the known laws of engineering. So we have to look at them very carefully.

Very little data has been collected until recently. And we physicists need data so that we can make objective statements about what these things are. The burden of proof is on the military now to prove that these things aren't extraterrestrial - and that's a sea change.

We now realize that these objects can travel up to Mach 20, 20 times the speed of sound. And they can even fly underwater, believe it or not: underwater, in the air, into outer space. And they zigzag.

When you calculate the centrifugal force inside the rocket ship, you realize that any living thing would be crushed, crushed by the zigzagging of these objects, whatever they are. So in other words, we're talking about a new law of engineering beyond anything that we can muster here on the planet Earth.

So is it an optical illusion, or is it extraterrestrial? We don't know until we analyze the data. Now we have the data. And now we have physicists looking frame by frame, and perhaps coming up with a conclusion as to where these objects come from.