Mar 18, 2026 09:35 PM
https://bigthink.com/starts-with-a-bang/universe-flat/
KEY POINTS: The shape of the Universe didn’t have to be flat; it could have been positively curved like a higher-dimensional sphere or negatively curved like a higher-dimensional horse’s saddle. The reason space can be curved is that its shape is not absolute, but rather determined by a mix of factors like its mass and energy distribution, as well as its expansion rate. Nevertheless, when we measure it, we find that our Universe really is flat. Here’s what we can learn from that, and why, from a cosmic perspective, it matters so much.
EXCERPTS: Right now, we’ve only measured the curvature to a level of 1-part-in-400, and find that it’s indistinguishable from flat. But if we could get down to these ultra-sensitive precisions, we would have the opportunity to confirm or refute the predictions of the leading theory of our cosmic origins as never before. We cannot know what its true shape is, but we can both measure and predict its curvature.
[...] Although the Universe appears indistinguishable from flat today, it may yet turn out to have a tiny but meaningful amount of non-zero curvature. A generation or two from now, depending on our scientific progress, we might finally know by exactly how much our Universe isn’t perfectly flat, after all, and that might tell us more about our cosmic origins, and what flavor of inflation actually occurred, than anything else ever has... (MORE - missing details)
KEY POINTS: The shape of the Universe didn’t have to be flat; it could have been positively curved like a higher-dimensional sphere or negatively curved like a higher-dimensional horse’s saddle. The reason space can be curved is that its shape is not absolute, but rather determined by a mix of factors like its mass and energy distribution, as well as its expansion rate. Nevertheless, when we measure it, we find that our Universe really is flat. Here’s what we can learn from that, and why, from a cosmic perspective, it matters so much.
EXCERPTS: Right now, we’ve only measured the curvature to a level of 1-part-in-400, and find that it’s indistinguishable from flat. But if we could get down to these ultra-sensitive precisions, we would have the opportunity to confirm or refute the predictions of the leading theory of our cosmic origins as never before. We cannot know what its true shape is, but we can both measure and predict its curvature.
[...] Although the Universe appears indistinguishable from flat today, it may yet turn out to have a tiny but meaningful amount of non-zero curvature. A generation or two from now, depending on our scientific progress, we might finally know by exactly how much our Universe isn’t perfectly flat, after all, and that might tell us more about our cosmic origins, and what flavor of inflation actually occurred, than anything else ever has... (MORE - missing details)