What are the fundamentals of our Universe?
In the Universe it does not matter where you are or in which direction you look – you will always see the same picture of expanding space, with distances between galaxies becoming ever greater.
Wherever you are and in whichever direction you look, the Universe looks the same – at least on the largest scales. Also, in line with Albert Einstein’s general theory of relativity, empty space itself is expanding over time. The result is that the distances between galaxies are increasing – not because they are moving through space, but because space itself is expanding. Light travelling through expanding space is stretched towards longer wavelengths; this so-called redshift is a measure of the light’s travel time.
If you bake a cake, the dough expands in the oven. Raisins in the dough end up further away from each other than when you prepared the cake, although they don’t actually move through the dough. The same is true for galaxies in expanding space.