Colleagues are paying tribute to him noting his brilliance and exceptional contribution to scientific knowledge. joining me now by phone is dr. jose bieda, a senior research associate at the university of adelaide in australia. just take us through stephen hawk's contribution, if you would, to sign. >> hello, max. well, stephen hawkings was one of the pioneers in studying the concept of black holes. black holes now we know are so important, this knowledge, because now we can understand better how galaxies behave, why they behave as we observe galaxies, and that's because in the center of every...