We are often asked “If the universe is everything, how can there be more than that?” How can we be now talking in terms of multiple universes, or “the multiverse”? As usual, the problem lies with us. We often paint ourselves into a corner by using terminologies which imply absolute limits, and then find we have to go beyond them to accommodate the latest discoveries. For example, it was not that long ago when we assumed the Earth constituted all of creation. Everything in the sky was in the heavens, where the gods lived. Then we found that there are other worlds, and that our Sun is just one of billions of stars in a galaxy we call the Milky Way. Our telescopes were seeing faint, spiral, fuzzy things, which we interpreted as being new stars and planetary systems in the process of forming. Our universe had expanded to 100,000 light years across, the diameter of our galaxy. Better observations and better telescopes showed us that each of those faint, fuzzy spirals are galaxies in their own right, each with its own collections of billions of stars. Our “universe” had become a lot larger. More recently, thanks to instruments such as the Hubble Space telescope, we see billions of galaxies, extending out as far as we can see. In addition, mapping the cosmic microwave background, the “fading breath of the Big Bang”, shows the first traces of galaxies beginning to form.
Now that it looks as though the universe started just under 14 billion years ago and will expand indefinitely, very intriguing questions arise. One is “what happened before the event we call the Big Bang”? Another is “How come our universe seems to be designed to produce us?” Of course, it is hard to even approach this question because if the universe were not the way it is, we would not be here to pose the question. Non-existent life forms in empty universes would not be in a position to ask “Why are we not here?”
One argument could be that there are multiple universes, most of which are empty or chaotic, and lifeless. However, that might well be just a convenience to get around our limited understanding, with little or no factual solidity. It is true that at the moment we have no firm observational evidence of the existence of universes other than ours. However, theoretical models suggest they exist. One of them describes a “multiverse”, resembling a multi-dimensional “cosmic foam”, where universes appear as bubbles, forming, expanding and the dissipating. It is fascinating that in 1822, Shelley alludes to just this scenario in his poem “Hellas”.
The important requirement with theoretical models like this is for them to produce results that can be tested by observation. That we might be able to make those observations might sound incredible, but look how far we have come in the last two or three decades, and consider the capabilities of the new astronomical instruments coming on line or under development. We are now doing things that not long ago would have been deemed impossible. The next decade should be really fascinating.
Mercury lies very low in the west after sunset. Saturn rises around 8 p.m; Venus is very low in the dawn twilight. The Moon will be new on the 3rd.
Ken Tapping is an astronomer with the National Research Council’s Herzberg Institute of Astrophysics, and is based at the Dominion Radio Astrophysical Observatory, Penticton, BC.
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