The allegory of the cave

What is real and what is imagined? What are the limits of our understanding of what we perceive? And yes, this has everything to do with the search for extraterrestrial life.

This famous allegory appeared in Plato’s Republic. Supposedly Socrates came up with this, but since Plato often put his ideas in Socrates’ mouth, it may just as likely have been Plato’s idea.

And now I will describe in a figure the enlightenment or unenlightenment of our nature:

Imagine human beings living in an underground den which is open towards the light; they have been there from childhood, having their necks and legs chained, and can only see into the den.

At a distance there is a fire, and between the fire and the prisoners a raised way, and a low wall is built along the way, like the screen over which marionette players show their puppets.

Behind the wall appear moving figures, who hold in their hands various works of art, and among them images of men and animals, wood and stone, and some of the passers-by are talking and others silent.

They are ourselves, I replied; and they see only the shadows of the images which the fire throws on the wall of the den; to these they give names, and if we add an echo which returns from the wall, the voices of the passengers will seem to proceed from the shadows.

This applies to the search for extraterrestrial life in this way: We are observing extraterrestrial phenomena, filtered, at the very least, through millions of miles of space, often looking only at data delivered by very complex technology. Many times this data is only a stack of numbers. In order to begin interpreting this data, or shadows on the cave wall, so to speak, scientists have to make a number of assumptions; otherwise, the numbers remain only numbers. In order to interpret this to the public, the need to leave out the numbers and the assumptions that they make, and present only the particular conclusions that they make.

So many times, when we observe stellar phenomena, we are essentially assigning names to the dancing shadows on the wall, often with nothing more than a working theory as to what actually cast the shadows. And scientists are constantly re-working their theories about the sources of these shadows.

So when you read about astronomers explaining stellar phenomena with constructs such as “pulsars”, “magnetars” and “blitzars”, please understand that these are the theories of humans who have never left the Earth. Take it with a grain of salt.


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