This has lead cosmologists to prefer the Cold Dark Matter theory, initially proposed by Peebles in 1982 . In this simple version, the cold dark matter theory, has no free parameter but the normalization. The matter power spectrum can be constrained by several observational ways, one is to use the observational distribution of X-ray clusters in flat or open models . This has been the final kick to the CDM theory in its so called standard version . The reason being that the fluctuations detected by COBE are not so far from what was expected anyway, as the theory was able to predict the shape of the power spectrum over nearly four orders of magnitude in length within a factor of two.
Various solutions exist to slightly modified the spectrum.
The first reaction of many cosmologist has been to laugh to such a proposition, a result that the authors considered as very positive. However, it has been considered a very depressive remark, especially from our colleagues involved in observations. However, we also believe that controversy on the definitive value of the Hubble constant may not be close soon, and that the history of the field allows us to consider this possibility at least to examine its implications. The age of the universe could be as large as 20 Gyr, and would easily accommodate the longest stellar ages which are quoted from time to time. In addition, a low value of the Hubble constant help to accommodate the high baryon fraction seen in clusters.