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collection of alien planets in front of the Milky Way galaxy, nearby exoplanets
collection of alien planets in front of the Milky Way galaxy, nearby exoplanets

Physicist: Copernican Principle Doesn’t Make Earth Insignificant

That, Marcelo Gleiser says, is a philosophical attitude, unrelated to the science

Theoretical physicist Marcelo Gleiser, author of The Island of Knowledge (2014) offers some thoughts on what the Copernican Principle means and doesn’t mean about Earth’s status as a planet — whether Earth is a special place or a pale blue dot.

He has no objection to the Copernican Principle (“a cornerstone of astronomy”) as such. The problem, he points out, is what happened next:

Copernicus famously proposed that Earth was not the center of the universe; the sun was. The Earth, he suggested, was just another planet orbiting the sun like Mars or Jupiter…

The principle, as understood today, is usually stated as, “Earth is an ordinary planet, and we, human observers, are ordinary too.” There is nothing special about either Earth or our species.

Marcelo Gleiser, “What does the Copernican principle say about life in the universe?” at Big Think (September 22, 2021)

We really don’t know enough to determine anything of the kind, he says:

We currently do not know enough about exoplanets to make a statement about how special Earth is. And we know far less about the possible existence of life in other worlds and about what kind of life that would be. So, to blindly extend the Copernican principle to guide our thoughts about Earth in comparison to other worlds when it comes to habitability is not just a false extrapolation but also imprudent. We simply do not know enough to make such pronouncements.

Marcelo Gleiser, “What does the Copernican principle say about life in the universe?” at Big Think (September 22, 2021)

He doesn’t think the Principle should be used as an argument against human exceptionalism either. That is just as well because, on this planet, humans simply are exceptional. Arguments against that tend to take us into some pretty irrational territory.

He offers considerable hope that the James Webb Telescope (late 2021) and the future Giant Magellan Telescope (2029) will tell us enough about exoplanets that we can begin to determine whether they could be inhabited by life forms as we currently understand them. But, of course, that doesn’t in itself tell us whether they are inhabited or, if so, by intelligent beings. Still, it is far more than we know now.

Re our claimed humble and insignificant position here on Earth, we might want to beware of false humility which is really inverted pride. If we have just decided that we are insignificant, absent evidence, we are claiming too much about ourselves. It is probably best not to think about it at all until we get more information.

Here is a variety of other takes on the Copernican Principle:

Is intelligence common or rare in the universe? A recent analysis says that life is common in the universe but intelligence—not so much. Let’s explore the reasoning. We really don’t know anything about life elsewhere in the universe so even university-trained scientists often try to WISH it into existence.

Maybe there are just very few aliens out there… The Rare Earth hypothesis offers science-based reasons that life in the universe is rare. Even if life is rare in the universe, Earth may be uniquely suited to space exploration, as the Privileged Planet hypothesis suggests.


Is intelligent life in the universe living in interior oceans of planets and moons? The Ocean Planets Hypothesis is that intelligent beings may flourish in the interior oceans of the moons of gas giant planets — or within exoplanets — but they are trapped there. If intelligent life forms are trapped in the interior oceans of rocky moons and planets, Earth is a special planet—much better suited to space exploration.

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Physicist: Copernican Principle Doesn’t Make Earth Insignificant