One of the most enduring questions for mankind is: are we alone in the universe? The science fiction author Isaac Asimov famously observed at the turn of the century that: “Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying.”
For most of our history, humans not only haven’t had a good answer to the question of the possibility of extraterrestrial life- we also haven’t had any good clues. That changed, however, in 2016.
What’s the Big Discovery?
Well, in 2016, astronomers studying Proxima Centauri, a small and nearby red-dwarf star, found a Goldilocks planet.
What’s a Goldilocks planet? Well, like the porridge in the story, it’s not too hot, not too cold….it’s just right, a planet in the habitable zone and orbit of its star.
The newly discovered planet, which the scientists called Proxima Centauri b, seems to be capable of supporting life, and is relatively nearby, about 4.2 light years away. Its mass is about 1.3 times larger than Earth, and it orbits its sun in only 11 days. (That’s a mighty short year!). It’s also different than earth because it is tidally locked: this means that the same side of the planet always faces its parent star.
Proxima Centauri b completes its orbit just far enough away from its star to receive enough energy to keep its surface above freezing. This is what makes it a Goldilocks planet.
Why is Temperature So Important?
We can’t know how life might evolve on other planets, but we do think that the more liquid water a planet has, the better the chance that it will produce and sustain life. Scientists base this conclusion on the fact that there is life in nearly every place that there is water on earth.
Proxima Centauri b seems to have enormous amounts of liquid water, which makes it a good candidate, though in a way different than earth.
An “Eyeball Earth”
Proxima Centauri b has a hot hemisphere (which faces the sun) and a cold hemisphere (which always faces away). This, scientists speculate, means an “eyeball earth” scenario, where the water on the surface is in constant motion, circulating all the way around the planet, from north to south and back again on the warm side.
Such a planet would look a bit like a human eyeball. The “night” (or dark) side would be permanent ice, while the “day” (and warm) side would have a giant ocean swirling around a central point (like the dark spot on an eye).
The icy side in this eyeball would be the white of the eye, the ocean the color of the retina, with a dark center.
The first of these eyeball earth-type planets was discovered almost 20 years ago, though much farther away. The presence of this kind of planet, scientists increasingly think, is relatively common.
So Where are the Aliens?
Since there are likely so many planets capable of hosting life, where are the aliens? Why haven’t we heard from anyone by now?
This is the heart of Fermi’s Paradox, a theory proposed by the physicist Enrico Fermi to explain the problem. Fermi’s paradox explains that there are billions of stars in the galaxy that are similar to the sun, and many of them are much older than the sun.
The fact, then, that so many of these stars are likely to have Goldilocks planets, would indicate that the chances of life are high, and the life on many of those planets should be older than we are, as a race.
Since so many other planets, it seems, should have intelligent life, why hasn’t at least one of them contacted us yet? “Where,” Fermi famously asked “IS everybody?”
So… Where Is Everybody?
We still don’t know. Maybe other civilizations are less common than we think possible. Maybe they don’t want to talk to us. There is a list of possibilities developed by scientists. These include:
- Extraterrestrial life is rarer than we think.
- Intelligent life is rarer than we think.
- Technology (such as that to communicate or travel between the stars) is rare.
- It is in the nature of intelligent life to destroy itself.
- Natural events mean periodic extinctions of intelligent life.
- Intelligent civilizations are too far away to contact us.
- We aren’t listening properly to hear other life forms.
- Other life is simply too different for us to understand.
- Earth is purposely isolated for some reason.
- Maybe, and terrifyingly, we really are alone.
Many hope that our continued efforts to reach out and find planets similar to earth will help us make contact with other races of beings who may be out there, or at least help us answer the questions we have about being alone in the universe.
Time and more research into eyeball planets like Proxima Centauri b may help us get some answers and learn more about the solar systems and worlds closest to our home.