Some progress has been made in filling in an 11 billion-year gap:
We know what the Universe looked like in its infancy, thanks to the thousands of scientists from around the world who have measured the relative amounts of elements created soon after the Big Bang, and who have studied the Cosmic Microwave Background. We also know its expansion history over the last few billion years from galaxy maps and distance measurements, including those from previous phases of the SDSS.
“Taken together, detailed analyses of the eBOSS map and the earlier SDSS experiments have now provided the most accurate expansion history measurements over the widest-ever range of cosmic time,” says Will Percival of the University of Waterloo, eBOSS’s Survey Scientist. “These studies allow us to connect all these measurements into a complete story of the expansion of the Universe.”
Media Release, “No need to Mind the Gap: Astrophysicists fill in 11 billion years of our universe’s expansion history” at Sloan Digital Sky Survey (SDSS)
It’s the part in the middle that’s the problem. And it highlights another problem:
“Only with maps like ours can you actually say for sure that there is a mismatch in the Hubble Constant,” says Eva-Maria Mueller of the University of Oxford, who led the analysis to interpret the results from the full SDSS sample. “These newest maps from eBOSS show it more clearly than ever before.”
There is no broadly accepted explanation for this discrepancy in measured expansion rates, but one exciting possibility is that a previously-unknown form of matter or energy from the early Universe might have left a trace on our history.
Media Release, “No need to Mind the Gap: Astrophysicists fill in 11 billion years of our universe’s expansion history” at Sloan Digital Sky Survey (SDSS)