The sookshma sareera (subtle soul) after death of a jeeva is posited to travel to various lokas like vaikuntha, kailaasa, brahma lOka, etc. depending on its karma phala.
According to saastra there is nothing beyond brahma lOka. It means one simply can't imagine what lies beyond the place where the Brahman, the primordial source of the universe and upaadaana (material) and nimitta (sentient) causes, exists.
Several researchers in the west tried to answer the question that our saastra is seemingly unable to answer. For example, the Nobel Laureate Prof.Schmidt and his team showed that universe is accelerating and expanding. (Accelerating Expansion of the Universe) The question is what is the universe expanding into? Suppose you are blowing air into a ballon. We know the balloon will expand into the surrounding air. Similarly one can imagine the universe is expanding like a balloon. What lies outside the universe?
Veda has an insight into this. As long as we can tell ourselves "I exist", the universe will keep expanding into the "I". It is because there has to be some difference between gnaata (observer) and gnEya (observed) for cognition to take place. The gnaata here is the sushuptaatma (which is the saakshi/witness of sushupti or deep sleep) and the gnEya is the body/manas/budhi/indriyas, etc. The sushuptaatma lives on even after the death of the jeeva. When we say "I exist", the "I" is the sushuptaatma.
One can imagine sending space ships at warp speed (greater than the speed of light) to catch up with the expanding universe. The objective can be to go to the edge of the universe. It will be futile because the fuel to drive the space ships will run out at some point. Also the black holes can destroy the space ship. The dark matter can engulf the ship. The pilot can meet with natural death. Let's imagine there are several couples with children that are driving the space ship. With many generations arriving into the ship, the travel will continue indefinitely and unendingly. And the saastra says the universe will undergo laya (involution or destruction) after some time leaving us unable to answer the question what/where the universe is expanding into.
To visualize, in the animated movie "Frozen", Elsa the princess could go whereever she wanted because a sheet of ice would magically appear at the place her stride takes her. She could traverse valleys and mountains with bridges made of ice created by her magic. Similarly wherever the space ship travels, the space will expand to let it pass. One can call it the "maaya sakti" of Ishwara who is the creator of the universe when the Brahman wills and who was created by Brahman with maaya. Since Brahman has no action, as per saastra, it is Ishwara's task to create the universe consisting of suns, planets, etc.
Virtually there is no end to the universe. Whereever we look, it is inflating. The sookshma sareera that can hypothetically travel faster than light will run out of its energy and lose its existence when the consciousness that asserts "I exist" ceases to exist.
