diksa tatra divaukasam
samajo brahmarsinam ca
rajarsinam ca sattama
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Once upon a time King Prthu initiated the performance of a very great sacrifice in which great saintly sages, brahmanas, demigods from higher planetary systems and great saintly kings known as rajarsis all assembled together.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In this verse the most significant point is that although King Prthu’s residential quarters were in India, between the rivers Ganges and Yamuna, the demigods also participated in the great sacrifice he performed. This indicates that formerly the demigods used to come to this planet. Similarly, great personalities like Arjuna, Yudhisthira and many others used to visit higher planetary systems. Thus there was interplanetary communication via suitable airplanes and space vehicles.