How can the universe be flat if it is 3D?

One way to think of this is that on a sphere a triangle’s sides don’t add up to 180 degrees, but they do on the surface of a pool table. Measurements to the farthest reaches of the observable universe reveal that the angles of a triangle do add up to 180 degrees, so we believe that the universe is “flat”.

Is the universe only 3 dimensional?

The universe is three-dimensional. The universe is four-dimensional—three for space, one for time. For all we know, space is 3-D, and spacetime is 4-D; but if string theory is true, then space turns out to be 9-D, and spacetime 10-D.

Is the universe 5 dimensional?

The world as we know it has three dimensions of space—length, width and depth—and one dimension of time. But there’s the mind-bending possibility that many more dimensions exist out there. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 dimensions.

What would the 4th dimension be?

Many physicists, including Einstein as part of his ‘Special Theory of Relativity’, proposed that the fourth dimension is time. He said time should be a dimension like the other spatial dimensions because space and time are inseparable. Time’s dimension is a line going from the past to present to future.

Is the universe flat or curved?

It’s easy to make examples in 2D space (ie. a flat piece of paper vs. a curved piece of paper, or the surface of a balloon). It’s not so easy to illustrate flat 3D space – since we are 3D! So it’s totally understandable that the concept is confusing This is refering to the theory that the whole universe is flat.

Will the universe extend forever like a piece of paper?

But if the actual density of the universe is equal to the critical density, as scientists think it is, then it will extend forever like a flat piece of paper. (Image credit: NASA/WMAP Science team.)

How can we measure the flatness of a structure?

So there you have it: You can measure the “flatness” of a structure just by watching how parallel lines behave. In our 3D universe, we could watch beams of light: If, say, two lasers started out perfectly parallel, then their long-term behavior would tell us important things.

What are the properties of the universe?

In cosmology, the universe is considered as a whole object. And as an entire object, it has certain properties. For example, starting from some very large linear scales (60 megaparsecs [~ 180 million light-years ], and 150 Mpc), matter in the Universe is distributed uniformly and isotropically.