No, The Universe Cannot Be Expanding Differently In Different Directions
It’s one way to interpret recent X-ray data, but it conflicts with much, much better data we already have.
Earlier this month, a new study came out claiming something shocking: perhaps the Universe was expanding at different rates in different directions. They looked at more than 800 clusters of galaxies that emitted X-rays, measured their temperature, brightness, and redshift, and inferred how far away they were compared to how quickly they appeared to be moving away from us.
Surprisingly, they found that one direction was consistent with a faster-than-average expansion rate while a different, not-perfectly-offset direction was consistent with a slower-than-average expansion rate, with these two directions differing from the average by about 10% apiece. Unfortunately, this interpretation is already ruled out by a much better set of observations: from the Cosmic Microwave Background (CMB), also known as the leftover glow from the Big Bang. Here’s how we know the Universe isn’t expanding differently in different directions.
