Can one even discuss something so personal as “heaven” using the same tools that are used to trace galaxies? “Up”, in colloquial is a direction rather than a co-ordinate. But the massive bulk of religious literature impels the eye upwards, and the geometricalness of nature above, beyond, higher, has long been tempted to a literal challenge, whether eventually a man would come to a point where the material world gave way to another.
Modern cosmology has boundaries of a sort, although not the walls. They are limits that have been set by space, by the space and time of space. The most important discovery is that Edwin Hubble discovered that the movement of the galaxies works in the reverse way: the further the galaxy is located, the faster it appears to accelerate. This relationship was known as the Law of Hubble to imply that there are distances so far that the light that is currently emitted, at the other end of this distance, will never reach us. That is not the case, the distance between this light escalates too fast that the signal may not be able to cover the distance.
That peripheral language horizon, periphery, beyond, is apt to be crammed into a single phrase: “the cosmic horizon.” In the popular versions it might be heard as though it were a special place to which a rocket might come so long as its engines were only powerful enough. Cosmological horizons may however be better thought of as observer-based limits: what may at some point in time be ever visible in the frame of the expansion of the universe. The current boundary of the observable universe, known as the radius of particle horizon (46.5 billion light-years), is the boundary of a single common framing, but another, called the event horizon, is where the light emitted today never makes it to the observer in the future. Those distinctions matter, because they separate “not yet seen” from “never seeable,” and they keep a metaphor from hardening into a location.
Religious traditions have been used as well with layered language which could sound architectural. The sky, the place of stars, and a spiritual zone above the material world may have been the original meaning of “heaven”, and is occasionally referred to as a three different “realms” rather than the stratification levels. That is vocabulary that is frequently antagonistic to the vocabulary of cosmology itself, which also has its levels: when we say something is “near” or “far” we are baffled by lookback time: when we look at a distant galaxy we are also looking at them as they would have been long ago.
A lot has been drawn on this overlap by one of the former lecturers at Harvard, Dr. Michael Guillenen, who has proposed that heaven may be located, in an extra-horizontal place beyond a horizon beyond which physical travellers would never be able to travel. The distance of 273 billion trillion miles in his calculation is fictitious, and he uses it to mark the edge, reached by recession that is travelling at the speed of light, and thus will forever be beyond the reach of any normal journey of exploration. The fantasy of the idea is self-explanatory: the “beyond” which is not accessible is compared to the human intuition of a place that cannot be accessed through the regular channel.
And cosmology cannot be projected into a map of the afterlife. The horizons in standard models do not behave as gates whereof the clock is no longer to run; they describe the behaviour of the signals in the expanding spacetime, and the influence of distance on observation. Put differently, a horizon can be an ultimate limit on contact without being a physical border that something “sits behind.”
The mode of thinking of the universe, which the horizon can and habitually can give and which is selectively concealed, is what the horizon can and reliably can give. There may be a greater Cosmos that can ever be seen, but this is not a secret but an elaboration of geometry and an extension into geometry and an extension. That is enough to give “beyond” an airing fresh to some readers; to some it is a reminder that limits can be described in terms of physics without them being places.
