SO far, despite over half a decade of searching, humans are yet to prove positively that life, other than that on Earth, actually exists.
Some believe this is evidence that life on Earth is unique while others say it is far too early to draw any conclusions. A simple analogy is to take a glass of water from the ocean and and ask, if there are no fish in the glass do we assume that the ocean contains no fish?
In February this year, Nasa astronomers made a discovery of seven Earth-sized planets around a star, Trappist-1, just 13 light years away (a relatively short distance, but one that would take several hundred thousand years to reach using current technology).
Our first question is; is there life on these or other planets? Next, we need to ask if it multicellular life (or some other form of complex life we don’t yet understand) and not just bacterial or even viral? Then, finally, is it technologically intelligent like us (whales may be even more intelligent than humans, but they do not build rockets and go into space).
Scientists have established a way to categorise hypothetical creatures on other worlds according to the amount of energy their inhabitants could potentially harness according to the Kardashev scale. The scale takes energy use as the key indicator of a civilization’s advancement, and places each civilisation in one of three categories:
Type 1 civilisations are able to utilise all of the energy that reaches its planet from its parent star. Humans are still only, perhaps 70% of the way to being a Type 1 civilisation. Type 2 civilisations are capable of using all the energy put out by its star and planetary system and a Type 3 civilisation can harness all the energy of its home galaxy.
Although the most commonly used scale, the Kardashev scale, doesn’t take into account how a civilization’s use of energy affects its planet.
In the 100 or so years we have been burning fossil “fuels” it appears that the amount of carbon released into the atmosphere has had a significant effect on the makeup of our atmosphere. For example, if oil deposits form from the compression of carbon (in the form of forest litter – leaves, bark and other forms of carbon-based material) then, in the last 100 or so years we have released millions of years-worth of stored carbon into the sky. Currently, most of the energy on Earth comes from fossil fuels.
Adam Frank, a professor of physics and astronomy at the University of Rochester, devised a new classification scheme for the evolution of civilizations based on the idea that it’s not just how much energy you use, but how you use it that matters.
With this new scale, the researchers determined that in order to survive long-term, a civilization must learn to “think like a planet” – or risk the civilization’s demise.
The Kardashev scale is concerned with extracting energy and reasons that you can’t use energy without causing different kinds of waste.
The discovery of seven new exoplanets orbiting the relatively close star Trappist-1 has forced us to think about life on other planets and, more importantly, how they may be detected. It also lays the foundations to explore a path to long-term sustainability.
Earth’s biosphere – the global layer where life exists – is unique because the presence of life has altered the planet’s surrounding atmosphere. Rapid urbanisation, including deforestation, air pollution, and increasing energy demand.
Humans will need to find new ways of generating work from the energy they harvest in order to sustain civilization, researchers say.
The new classification system for planetary evolution is composed of five levels:
Class I: Planets without an atmosphere. The ability of the planet to change and evolve is severely limited. (Mercury or Earth’s moon)
Class II: Planets with atmospheres but no life forms. The flow of gases and fluids leads to change and evolution in the form of climate and weathering. (Venus and Mars)
Class III: Planets with a “thin” biosphere that might sustain some biological activity, but this does not affect the planet as a whole. There are no current examples of Class III planets. However, Earth 2.5 billion years ago, before life created the oxygen atmosphere, would have been a Class III world. If early Mars hosted life when it had liquid water on its surface then it too might have been a Class III world. Once life appears, new forms of change, evolution, and innovation become possible.
Class IV: Planets with a thick biosphere strongly affecting the flow of energy and work through the rest of the planetary systems. Planets co-evolve with their biospheres as life dominates many of the processes happening between the surface and the upper atmosphere. (Earth today)
Class V: Planets in which an energy-intensive technological species establishes a sustainable form of cooperation with the biosphere that increases the productivity of both. On these planets, the civilisation enhances the ability of the biosphere to innovate and evolve.
According to researchers, Earth might reach Class V in the future if humanity successfully advances to harvest energy in forms like solar that do not harm the biosphere.
And what might a Class V planet look like?
Frank lists several ways humans on Earth might form a technological cooperative between biosphere and civilisation, including “greening” large desert land masses such as the Sahara by finding ways to plant trees that will absorb carbon and release oxygen; or creating genetically modified trees with photovoltaic leaves that covert the sun’s energy into electricity.
“Civilization arose as part of a biosphere,” Frank says. “A Type 2 civilization on the Kardashev scale that is super space-baring could live without a biosphere. But a young civilization, like ours, has to see itself as a part of the biosphere. We’re not separate from it, we’re just the latest experiment Earth is running in the evolution of life. If we’re not careful, it will just move on without us.”