One of the hallmarks of good science is reproducibility. We know that theories are correct in large part because the results they predict are not only observed once, but observed repeatedly under similar circumstances by different people.

This is why this recent article from the BBC is so interesting. It isn’t the first time that we have been able to observe dark matter; rather, the importance lies in that we have found a second example of dark matter that matches the first. This helps to prove that our first observations were not mistaken, or anomalous. This latest observation confirms our current theories and predictions about how dark matter should behave.

This phenomenon has been seen before, in a structure called the Bullet Cluster - which also formed after the collision of two large galaxy clusters. The Bullet Cluster lies closer to Earth, at a distance of 3.4 billion light-years.

“It puts to rest all the worries that the Bullet Cluster was an anomalous case. We have gone out and found another one,” co-author Richard Massey, from the Royal Observatory Edinburgh, told BBC News.

So while it may not be as earth-shattering as our first observation of this type, it is nonetheless an important part of the scientific process. By observing these properties, we are able to proceed with increased confidence in our theories about dark matter.

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• BBC.co.uk: Cosmic crash unmasks dark matter