What observations lead us to conclude that the universe is expanding?

The Origin of the Earth Hubble’s observations showed that the greater the distance to a galaxy, the greater the redshift in its spectral lines. These measurements strongly indicated that galaxies appear to be moving away from us with speeds proportional to their distance.

Is the universe expanding and cooling?

Since the Big Bang the universe has been expanding and, as it expands, it’s cooling. The energy from the Big Bang spreads out as the universe expands, which gives us the cooling effect.

Does a flat universe imply an infinite universe?

Many textbooks erroneously state that a flat universe implies an infinite universe; however, the correct statement is that a flat universe that is also simply connected implies an infinite universe. For example, Euclidean space is flat, simply connected, and infinite, but the torus is flat, multiply connected, finite, and compact.

What is the shape of the universe?

The Universe is thought to (likely) have one of three intrinsic shapes —a closed round sphere, a negative saddle shape, or a flat sheet — and most physics leans toward the flat Universe. Image credit: NASA Run, Run, Run, Run Away…

Is the universe a sphere of stars?

Many early astronomers held that the universe was a sphere of stars, enclosing the solar system and centered on a fixed, unmoving Earth. But over the centuries astronomers found that our Sun was merely one of billions within a galaxy, and there were countless galaxies scattered across billions of light-years of space.

Is the universe with positive curvature infinite?

For example, a universe with positive curvature is necessarily finite. Although it is usually assumed in the literature that a flat or negatively curved universe is infinite, this need not be the case if the topology is not the trivial one: for example, a three-torus is flat but finite.