Marko Jukic August 16, 2023

will never forget the sunset when I first saw the solar system with my naked eyes. I was standing on the deck of a boat plodding slowly through the Nile River, closer to Sudan than to the Mediterranean Sea. I had not yet seen the Egyptian night sky, so I was excited to be so far south, with so much unlit desert on either side.

As a result, I was early. The Sun was still illuminating the western horizon. I didn’t plan it that way, but it was too bright to see the stars, yet dark enough to see the Moon and the gleaming dots of Mars, Venus, Jupiter, and Saturn. As it dawned on me that I was seeing five distant planets at once, it dawned on me also that they were all in a perfectly straight line across the sky, perpendicular to the Earthly horizon that tells us we are standing up straight and balanced. All of a sudden, I wasn’t standing on a boat. I was falling face-forward and down the side of the Earth, an incomprehensibly large sphere suspended in an invisible flat disk of planets surrounding a star.

Our animal eyes can observe planets, stars, and even the heart of our galaxy as much as they can observe mountaintops or ocean waves. It is a reminder that our natural habitat on Earth requires at least three separate planetary bodies. The Sun’s light and heat make the Earth habitable. So does the Moon, through gravitational stabilization of the Earth’s tilt and rotation, which keeps the days 24 hours long and the seasons regular and mild. Perhaps the Earth is not our natural habitat, but only a part of it.

This poses an existential problem because it means we cannot think of ourselves as only a terrestrial species. We rightly believe that we must take care of our natural environment. But drawing the border of our natural environment at the Earth’s atmosphere is only a convention. This boundary helps us feel like we are masters of our fate, since our economic and technological capacity to affect the Earth is currently far greater than our capacity to affect the rest of the solar system, let alone the cosmos. If we are not only a terrestrial species, then what are we?

Since the nineteenth century, we have known that the Earth is not the world, but an infinitesimal part of it. The combined knowledge and power of humanity, therefore, extends only to an infinitesimal part of the world, with the rest a seemingly infinite mystery. Perhaps the most common response to this is to throw up one’s hands and say that this has shown humanity is irrelevant in the grand scheme of things. But this is not a way to incorporate the scale of the cosmos into our understanding of humanity, but a denial of the importance of humanity altogether.

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