When we speak of loka-traya, we refer to the three primary planetary systems—Bhūḥ, Bhuvaḥ and Svaḥ—into which the universe is divided. Surrounding these planetary systems are the eight directions, namely east, west, north, south, northeast, southeast, northwest and southwest. Lokāloka Mountain has been established as the outer boundary of all the lokas to distribute the rays of the sun and other luminaries equally throughout the universe.
This vivid description of how the rays of the sun are distributed throughout the different planetary systems of the universe is very scientific. Śukadeva Gosvāmī described these universal affairs to Mahārāja Parīkṣit as he had heard about them from his predecessor. He explained these facts five thousand years ago, but the knowledge existed long, long before because Śukadeva Gosvāmī received it through disciplic succession. Because this knowledge is accepted through the disciplic succession, it is perfect. The history of modern scientific knowledge, on the contrary, does not go back more than a few hundred years. Therefore, even if modern scientists do not accept the other factual presentations of Śrīmad-Bhāgavatam, how can they deny the perfect astronomical calculations that existed long before they could imagine such things? There is so much information to gather from Śrīmad-Bhāgavatam. Modern scientists, however, have no information of other planetary systems and, indeed, are hardly conversant with the planet on which we are now living.