This article http://news.bbc.co.uk/2/hi/science/nature/3085885.stm claims:
Astronomers in Australia say there are 10 times more stars in the visible Universe than all the grains of sand on the world's beaches and deserts.
The figure - presented to the International Astronomical Union conference in Sydney - is the kind that really can be called astronomical: 70 sextillion, or seven followed by 22 zeroes.
I have been unable to find a source for this comparison (e.g. an article or presentation by the authors) other than the BBC article itself.
The only estimation that I found online in relation to this claim is an exercise that was put up by Howard C. McAllister, a Professor of Physics University of Hawaii at Manoa here: http://www.hawaii.edu/suremath/jsand.html
Is there any way to verify or measure how reliable is this comparison?