When we don’t know something, our mind has its way of filling the empty spaces and transform the unknown into something we can relate to.
Transforming reality into something familiar
Our knowledge, our previous experience, our instinct, the way we look at things those are all instruments that we use to escape that feeling of insecurity that an unknown thing gives us.
It’s an intelligent mechanism up to the point where it isn’t and where we make assumptions about things that aren’t even close to what the unknown really is. We think we know because we hold no information that could contradict that fake belief.
Not to mention the myriad of situations that even when someone who knows better is trying to change our minds and we refuse. That’s the worst of us, and unfortunately, it rhymes with stupidity.
But that’s not what this article is about. It is about the try to set some clarity on what an Earth-like planet is and means. To bust the belief that there is some other planet out there that could compete with Earth. That Earth is all we have, and we should make an effort and protect it, instead of dreaming of a place that we’ll fly to after we’ve destroyed this one. There isn’t! And science supports this idea.
What makes a planet be considered Earth-like?
No more than what makes us say two people look alike: looks and behavior. Only the differences between the two planets are a matter of life and death. The perspective here must match the physics and math. And, the truth is, they never will.
First, a planet the size of Earth can be considered Earth-like.
If they aren’t like Earth, they are either mini-Earths or super-Earths. Size matters a lot. If a planet is too small, then the atmosphere can’t hold. If it’s too big, then the planet is covered into too much helium and hydrogen. But the Universe challenges even those universal truths. There are planets smaller than Earth that have stronger atmospheric pressure. So… when a planet is an Earth-like size, it doesn’t mean anything.
Second, a planet that exists in the habitable zone of its system can be considered Earth-like.
Science has grown to say that the concept of the habitable zone is childish. Since no two stars or planets are alike, no system of a planet and a star will be alike, hence the habitable zone is a matter of uniqueness. When they say that a planet resides in the habitable zone it doesn’t mean that in that place of that system there are conditions that would favor life.
Third, an Earth-like planet needs a Sun-like star.
Only 20% of the stars of the Universe are likely to share Sun’s fate. So, scientists are mostly looking for red-dwarf binaries since they are the most abundant and they seem to live longer than the Sun. The largest red dwarfs have only 10% of the Sun’s luminosity but they emit light through convection, which means little radiation. So, maybe they could be Sun-like. Studies are on the way, there is no sign yet that they can hold life, nor that they couldn’t.
Fourth, an Earth-like planet needs to self-regulate its biosphere.
Physics and chemistry must make a life-span tango on this Earth-like planet. Life needs stability and supportive changes. It needs specific chaos, with basic rules that don’t ever change and create sensibility, and the freedom of creating physical and chemical algorithms that leave open the possibility of evolution.
The fifth element of an Earth-like planet is the heavy one.
Without heavy elements, such as oxygen, carbon, or nitrogen, a planet can’t become rocky. We need a rock, not a gaseous planet. Only 1-2% of the total mass of everything in our Solar System is made of heavy elements. How much heavy elements that the planet needs to be Earth-like? That’s one of the trickiest questions, even for scientists. It could be that 1% is enough. Just as 500% would.
What does Earth-like planet mean?
The first thing you should know is that there are no two planets alike, nowhere in this Universe. Everything in it is unique. Planets and stars might share similarities, but no two of them are alike. There is no place in the Universe where the grass is greener. Actually, there might be no grass elsewhere but here, on Earth.
If there is another place in the Universe that could sustain life, most likely it can’t sustain our life. Another form of life? Even that is debatable. But let’s stick to the subject. The only way we could make it to live on another planet is by changing what we are. And when I say change, I mean DNA change.
Mars is considered somewhat Earth-like, and science is struggling to find ways to get us to live there. But so far, the only way found is this: to-live-on-Mars-humans-must-agree-to-genetic-changes-and-become-aliens. And that’s not a joke.
When scientists say Earth-like or Earth 2.0, they are talking possibility. Not probability. They are looking at the unknown and based on their knowledge, previous experience, instinct, and a certain way of looking at things they would transform the reality of a planet into something familiar, like Earth.