Lecture delivered on ‘Crisis in the Cosmos’

Hyderabad: On the National Science Day, Dr B G Sidharth, director of BM Birla Science Centre Hyderabad on Wednesday delivered the CV Raman lecture on “Crisis in the Cosmos”.
Dr Sidharth and Das had pointed out that if there were no dark matter (or much less of it) then this 8 per cent surfeit of acceleration could be explained.

 It must also be mentioned that Sidharth has been arguing that an alternative candidate to dark matter would be a gravitational constant G that is very slowly decreasing with time. This was not an ad hoc conclusion but rather based on Sidharth’s cosmological model. This apart, we could now say that the slow decrease of G, based on the above observations started later, after the Big Bang nucleosynthesis.

Sidharth said that it is well known that the concept of dark matter was born around 1930 because Fred Zwicky and others noticed that the rotation curves of galaxies displayed a slight anomaly: Normally one would expect that as we went away from the center of the galaxies the rotation curves would die down as per Kepler’s laws. 

In contrast they appeared to flatten out, reaching out a constant velocity at about 300 kilometers per second. It was hypothesized that some additional unseen matter within the galaxies was responsible for this strange behavior. This additional or dark matter would speed up the slowing stars at the edges of galaxies.

Unfortunately for the past nearly nine decades we have not been able to get a fix on what exactly this hypothesized dark matter is. Could it be some exotic new type of particles like supersymmetric particles or sterile neutrinos or even the recently discovered pentaquarks and so on? Other speculations have attributed to dark matter such objects as low luminosity brown dwarf stars. 

Yet others have forwarded the idea that the center of galaxies are dominated by gravitational black hole which carries the extra gravitation. Unfortunately, the debate and speculation is still on.