We can measure it, and if the planet itself were expanding, that surface area would increase over time. Surprisingly, our familiar planet also offers a useful way to think about something far harder to understand: what the universe might be like beyond the region we can observe. The simplest assumption is that beyond our cosmic horizon, there is simply more universe.
More AI-generated cat videos. It is similar to standing somewhere on Earth and assuming that beyond your visible horizon, there is still more Earth. But how large is the entire universe, including everything beyond what we can see?
The frustrating answer is that we may never know. The boundary of the observable universe is not merely the farthest distance our telescopes can currently reach. It represents a deeper limit on what information can ever reach us.
The universe contains a finite amount of information that can become accessible to us, even if we waited for an arbitrarily long time. Beyond that boundary, we are left to infer and speculate. One possibility is straightforward: the universe is infinite.
Space simply continues forever with no endpoint. But another possibility is that the universe is finite. That immediately raises an obvious question.
How can something be finite without having an edge? The surface of our planet has a finite area, yet someone traveling along that surface never encounters a boundary where the ground suddenly ends. Yes, Earth has an edge if you leave its surface in the third dimension and head into outer space, but that misses the point.
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