Gospel & Universe 🔭 The Sum of All Space

The Outer Reaches 2

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Hubble Volumes

In cosmology, a Hubble volume or Hubble sphere is a spherical region of the observable universe surrounding an observer beyond which objects recede from that observer at a rate greater than the speed of light due to the expansion of the Universe. The Hubble volume is approximately equal to 1031 cubic light years. […] the term is also frequently (but mistakenly) used as a synonym for the observable universe; the latter is larger than the Hubble volume. [from Wikipedia]

Locating another universe would probably require a Hubble-sized leap in technology. I use the phrase Hubble-sized leap as one might use quantum-leap, yet I also want to recall that Hubble was the first to verify other galaxies in 1923. Perhaps some day universe clusters will be revealed to us, just as the stars in Andromeda were revealed to Hubble. 

While I imagine that other universes exist in the same space-time continuum as ours, I suspect that these universes are so far away that they don’t necessarily share all the things we take for granted in this corner of our galaxy. Our understanding of our own universe is just beginning. It’s barely a hundred years old. I’m not sure we can even make assumptions about the constants of the far-off galaxies that we can presently detect, let alone make assumptions about galaxy clusters or universes we haven’t even detected. The following is a cropped NASA image of MACS0647-JD, which “is a candidate for the farthest known galaxy from Earth and is at redshift of about z=10.7 or 13.3 billion light-years (4 billion parsecs) away. It formed 420 million years after the Big Bang. It is less than 600 light-years wide.”

A Hubble volume gives us a type of measure of the size of other universes we might find some day, although just as stars, solar systems, and galaxies come in different sizes, so other universes may differ in size. The notion of a Hubble volume is also helpful in that it reminds us that what we see is dependent on where we see it from. And, of course, the way we interpret what we see.

My position regarding other universes is even more precarious than that of the 9th century astronomer al-Sufi, who called Andromeda a small cloud, and who would need to have lived another millennium to fully understand that what he saw was in fact a far-off galaxy. We may have already seen some tiny dot or cloud of light — some blip, pulse, particle, or wave — that in a hundred or a thousand years we’ll know comes from a universe sextillions of gigaparsecs from Earth. The following Wikimedia image is of “the Andromeda constellation, from the 10th C. Persian astronomer al-Sûfi's Treatise of the fixed stars”:

Of course, it’s possible that we may never see anything like al-Sufi’s little cloud. Perhaps even in a million years, and from the perspectives of a billion alien life forms, such a thing will never be seen. The wonderful thing about practical space, however, is that this doesn’t mean another universe doesn’t exist. Unless we can verify that it curves in upon itself and that there’s nothing beyond the bent universe that we can see.

While the notion of universe clusters has no data to back it up, it nevertheless derives from two simple expectations. First, in every case, be it physical or intellectual, we find that there’s always something outside or beyond the case in point. In thought as in space. Whatever we see or imagine, we can see or imagine something beyond that. Second, why would we assume that the astronomical precedence of mind-blowing discovery stops precisely at the limit of our present detection? To discount the possibility of universe clusters may be to think in the same way we thought prior to Edwin Hubble and the 1920s, back when this galaxy seemed so vast that it simply had to be everything there was: The Milky Way, Via Lactea, Galaxías Kýklos, astronomical Goddess of Absolute Space. Hubble showed us that our galaxy wasn’t all there was to space, not in a million years. Today we see that our 100-400 billion stars need to be multiplied by hundreds of billions of galaxies to get a sense of the way our universe is populated by stars. This may be the tip of the iceberg: our universe may be an infinitesimal fraction of total space. Why would our universe be any different — any more absolute a framework — than the Milky Way?

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Next: 🔭 The Unknown Arcs of a Sphere

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