The Oldest Structures Known

For those with an historic bent the CMB images in the adjacent panel are, well, historic! These deviations of the CMB temperature from the average are the oldest structures known in the Universe.

Since the CMB decoupled from matter only about 400,000 years after the big bang, the variations reflect fluctuations in the density that were present already in the Universe at that early date, almost 14 billion years ago. Remember that, when someone tries to impress you with how old some historical artifact on Earth is!