Another interesting data point I'd like to share here is that of multiple stories found mentioned in ancient Hindu texts called puranas (which means historic). These stories talk about humans traveling to far away planets (lokas) wherein the wheel of time moves much slower than on Earth and thus is an indication of ancient Hindu knowledge of the phenomenon of time dilation. For instance, consider this story of King Kakudmi and his daughter [0]:
> Kakudmi's daughter Revati was so beautiful and so accomplished that when she reached a marriageable age, Kakudmi, thinking no one upon earth was worthy of her, went to the Creator himself, Lord Brahma, to seek his advice about a suitable husband for his daughter. When they arrived, Brahma was listening to a musical performance by the Gandharvas, so they waited patiently until the performance was finished. Then, Kakudmi bowed humbly, made his request and presented his shortlist of candidates. Brahma laughed loudly and explained that time runs differently on different planes of existence, and that during the short time they had waited in Brahma-loka to see him, 27 chatur-yugas (a cycle of four yugas, totalling 108 yugas) had passed on earth. Brahma said to Kakudmi, "O King, all those whom you may have decided within the core of your heart to accept as your son-in-law has died in the course of time. Twenty-seven chatur-yugas have already passed. Those upon whom you may have already decided are now gone, and so are their sons, grandsons and other descendants. You cannot even hear about their names.[2] You must therefore bestow this virgin gem (i.e. Revati) upon some other husband, for you are now alone, and your friends, your ministers, servants, wives, kinsmen, armies, and treasures, have long since been swept away by the hand of time."[3]King Kakudmi was overcome with astonishment and alarm at hearing this news.[3] However, Brahma comforted him and added that Vishnu, the preserver, was currently incarnate on earth in the forms of Krishna and Balarama, and he recommended Balarama as a worthy husband for Revati.Kakudmi and Revati then returned to earth which they regarded as having left only just a short while ago. They were shocked by the changes that had taken place. Not only had the landscape and environment changed, but over the intervening 27 chatur-yugas, in the cycles of human spiritual and cultural evolution, mankind was at a lower level of development than in their own time (see Ages of Man). The Bhagavata Purana describes that they found the race of men had become "dwindled in stature, reduced in vigour, and enfeebled in intellect."The daughter and father found Balarama and proposed the marriage which was accepted. The marriage was then duly celebrated.
> Kakudmi's daughter Revati was so beautiful and so accomplished that when she reached a marriageable age, Kakudmi, thinking no one upon earth was worthy of her, went to the Creator himself, Lord Brahma, to seek his advice about a suitable husband for his daughter. When they arrived, Brahma was listening to a musical performance by the Gandharvas, so they waited patiently until the performance was finished. Then, Kakudmi bowed humbly, made his request and presented his shortlist of candidates. Brahma laughed loudly and explained that time runs differently on different planes of existence, and that during the short time they had waited in Brahma-loka to see him, 27 chatur-yugas (a cycle of four yugas, totalling 108 yugas) had passed on earth. Brahma said to Kakudmi, "O King, all those whom you may have decided within the core of your heart to accept as your son-in-law has died in the course of time. Twenty-seven chatur-yugas have already passed. Those upon whom you may have already decided are now gone, and so are their sons, grandsons and other descendants. You cannot even hear about their names.[2] You must therefore bestow this virgin gem (i.e. Revati) upon some other husband, for you are now alone, and your friends, your ministers, servants, wives, kinsmen, armies, and treasures, have long since been swept away by the hand of time."[3]King Kakudmi was overcome with astonishment and alarm at hearing this news.[3] However, Brahma comforted him and added that Vishnu, the preserver, was currently incarnate on earth in the forms of Krishna and Balarama, and he recommended Balarama as a worthy husband for Revati.Kakudmi and Revati then returned to earth which they regarded as having left only just a short while ago. They were shocked by the changes that had taken place. Not only had the landscape and environment changed, but over the intervening 27 chatur-yugas, in the cycles of human spiritual and cultural evolution, mankind was at a lower level of development than in their own time (see Ages of Man). The Bhagavata Purana describes that they found the race of men had become "dwindled in stature, reduced in vigour, and enfeebled in intellect."The daughter and father found Balarama and proposed the marriage which was accepted. The marriage was then duly celebrated.
0: https://en.wikipedia.org/wiki/Kakudmi