#ExpandingUniverse Could a cosmological blueshift exist in any scenario, or does the expansion of the Universe prevent it? #physics #iTeachPhysics

#ExpandingUniverse The Hubble’s law states that the recession velocity is proportional to distance. This holds for any observer, regardless of their location. "Cada pasa en una masa de pan que se está expandiendo observa que todas las demás pasas se alejan de ella".

#ExpandingUniverse Homogeneity and isotropy mean that from any galaxy, all others appear to move away. There is no privileged point.

#ExpandingUniverse There is no center of the expansion of the universe. The expansion described by modern cosmology (based on the Friedmann-Lemaître metric, among others) is homogeneous and isotropic

#ExpandingUniverse If all galaxies appear to move away from us, does that mean we are at the center of the universe, or that expansion occurs in a similar way from any point in space?

#ExpandingUniverse Imagine points drawn on an inflating balloon. Do they move apart because they are moving, or because the surface is expanding? Does this analogy help us understand cosmological redshift? #Physics #iTeachPhysics

#ExpandingUniverse The idea that we don't occupy a privileged place in the universe is supported by these symmetries. From another distant galaxy, the overall appearance of the cosmos would be statistically similar to what we observe from Earth. #physics #iTeachPhysics #Cosmology