Cosmologists have measured how fast distant galaxies are receding in different parts of the sky. To do this, they used two kinds of "cosmic rulers": galaxy clusters and a certain type of supernova explosion. Both methods showed the same thing: in one direction, the Universe is expanding slightly faster than in the opposite direction.
The difference is small — about two sigma, meaning it could be random, but it persists across all checks. The most intriguing part: the direction of this unevenness nearly matches the direction in which the entire sky appears to be pulled due to the motion of Earth and the Sun. This might not be a coincidence but rather a trace of some deep process in the early Universe.
If the directional difference in expansion rate is confirmed, it would crack the standard cosmological model. So far, all data fit the standard picture, but such "irregularities" could be the first warning sign.
The most precise way to measure the distance to a distant galaxy is to look at a Type Ia supernova explosion. Such explosions always have nearly the same brightness, which is why they are called "standard candles."