Description

How many other universes are there? How are they created? How big would a multiverse be? In this episode, learn not only how to visualize the size of our universe, but also the staggering number of multiverses you generate without even thinking about it.

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caedmonv55
caedmonv55
4 posts

This is lovely but there are some mistakes going on here - the universe is not infinite in size. The observable (and existing unobservable) universe expanded from the big bang, and has expanded for 14-15 billion years since then. All expanding matter has expanded at less than half of the speed of light; the most distant objects we have observed are going around half of that speed, and it seems likely that speed is about as high as they get. Even if objects were moving at the speed of light, that would put a total distance between any two "ends" of the universe at about 28-30 billion light years. While it is true that two objects at opposite ends' observable universe would intersect very little, it is not as if there are 14 billion light year spans going on and on linearly to an infinite degree as stated here. There is a 28-billion light year span, and objects within it having varying visible percentages of this span. Due to our galaxy and cluster's relatively slow speed through the cosmos, it is likely that we are relatively near the center of the universe and have a view of the vast majority of the visible universe (say, somewhere between 70 and 90%). In fact, according to the theory of Relativity and our current understandings, "space" is created only when an object (or ray of light, etc) passes into it; space is literally the space between objects in the universe. So objects at the edges of the universe, such as the 13.2 billion year old galaxy mentioned likely is due to its incredible speed, can "see" very little beyond them in the direction they are going; there's simply nothing there yet, nothing to send back rays of light (and supposedly that space does not even exist yet). While they can see back from their "half" of the universe toward the "center" and thus see about half of the universe, they cannot see the opposite half due to the 28-billion light year span and only 14 billion years in which for the light to travel (whereas our more centric position gives us a view of the vast majority). For there to be 14 or 28 billion light year spans of objects (galaxies, planets) going on indefinitely in any or all directions, there would literally have to be a multitude of big bangs; so far as are not aware of there being even more than one. Though I do hope there is more than one, as it would very much complicate the question of the universe's beginning and the impetus that caused it, and maybe help lead us to answers as to why it happened.

caedmonv55
caedmonv55
4 posts

Just chiming in again here and I hope these are helpful to the layman - since the universe is not infinite ("merely" 28 billion light years across), there are not an infinite number of worlds, stars and so forth. The number is often compared to (and within a few orders of magnitude of) the number of grains of sand on all the beaches in the world. An incredible number to be sure, but finite enough to make it quite unlikely that there's another "you" in this universe, in this dimension -- though I would certainly not discount the science fiction trope that four-limbed body plans do happen frequently. Though there might be a svelte lizard man somewhere looking up at the stars tonight who also likes music that sounds a lot like Portishead, he's probably not you.