4.6 The Shape of the Universe
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Einstein showed with General Relativity that the universe doesn’t necessarily need to be a “flat” geometry. But when you hear the word “flat,” you might think of a sort of pancake shape. Is that what Professor Guth means about the shape of our universe? What does it mean to be “flat,” geometrically? How can we know for sure if our universe is “flat”? How would we know if it were some other non-Euclidean geometry?
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December 21, 2020 at 10:10 pm
measuring an expansion of a flat shape would be linear vs measurement of a non-flat shape, especially once more than 3 dimensions are considered
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December 26, 2020 at 3:38 pm
We can probably measure the historical change of acceleration of the visible universe.
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June 2, 2021 at 4:48 pm
You can create a virtual triangle using light from distant stars and see if its angle adds up to 180 degrees in order to determine the universe’s geometry (at least on that scale).
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August 20, 2021 at 4:16 pm
We can know by measuring the composition of our universe.
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September 12, 2022 at 12:57 am
Hello Ladies and Gentlemen,
Most cosmological evidence points to the universe’s density as being just right — the equivalent of around six protons per 1.3 cubic yards — and that it expands in every direction without curving positively or negatively. In other words, the universe is flat, and has
flatness🥞It expands in every direction without curving positively or negatively. This is Euclidean- it has no curves. 🔶🔷🔶
Prof. Guth`s proof of flatness allows for flatness on a sphere or a torus.
Euclidean geometry exists over two dimensions.
The surface of a sphere is no loner flat. Hyperbolic and elliptical shapes are non-euclidean.
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Curves make a non-Euclidean object.Attachments:
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June 13, 2023 at 7:48 am
I like Rupert’s answer by measuring angle sums from three stars but this only validates that local area.
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March 20, 2025 at 3:25 pm
He means a triangle placed on the surface of the known Universe would have all angles add up to 180 degrees (Euclidean).
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