With all the speculation on aliens out there, there is one place we often forget to look when theorizing what some far-out intelligent species could possibly be like—Earth.
Astronomer Nikolai Kardashev was one of those speculating about aliens that had more brains than a microbe. Back in the '60s, he devised a scale that uses energy use to rank the development of civilizations on an astronomical scale. We are edging Type 1, which is a civilization able to manipulate all of its planet’s energy for its own ends (which sounds more nefarious than it actually is). Type 2 civilizations have found a way to control the energy of their host star, and Type 3s can do that with their whole galaxy. That is somehow both fascinating and terrifying.
Physicist Robert Frank has revisited the Kardashev scale to develop a version 2.0 that relates more to our experience on Earth. We are at the dawn of an era when humans have the power to alter the environment of our planet drastically, what scientists call the Anthropocene period of evolution.
"In our perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization of the planet, a transitional stage from one class of planetary systems to another," said Frank and colleagues in a study recently published in the journal Anthropocene. "From an astrobiological perspective, Earth's entry into the Anthropocene represents what might be a predictable planetary transition."
Besides sounding like the coolest science fiction movie ever, Frank’s idea of a hybrid planet defines five classes of planetary evolution:
Class 1: The planet has no atmosphere. No atmosphere, no life as we know it. No life, obviously no intelligence.
Class 2: Think Mars. There is the ghost of an atmosphere with greenhouse gases, but still no signs of life.
Class 3: Houston, we have a biosphere—but there still isn’t enough activity to actually affect any change in the planet’s evolution.
Class 4: Photosynthesis is happening, which also means life is happening, and that life is strong enough to affect energy flow throughout the planet.
Class 5: Intelligent beings are now swarming the biosphere and manipulating planetary energy, which has a profound impact.
Since we don’t exactly know of any other planets teeming with intelligent life, we only have our own to go by when applying Frank’s thesis. Thinking of ourselves in these terms makes us sound like aliens (which we are, in a way), but that is only a plus as we continue to discover more and more exoplanets on the heels of TRAPPIST-1. Hypothetical planets with intelligent life could be classified and compared to Earth using this system.
Even if we find nothing for the next billion years, the scale could be a guide for us as we develop alternative types of energy that will maintain a sustainable planet, but just imagine if there really is a Class 5 out there.