Last June of 2017 I posed a question:
Does time exist?
I mean “exist” – like the keyboard I am typing on or the screen I am looking at?
Does it physically exist like things I can touch or perceive? Or simply a mental construct.
Renaissance man that I am I have an interest in such things and absolutely no background or education in such things. So feel free to demolish any of my philosophical musings and errant conclusions.
You can read those posts if you’re so inclined here:
Today’s question is whether or not the universe has an “edge.”
I will not take it personally if you leave this page now. Toritto is waxing philosophical again! What were the lines of that old song? “If you go I’ll understand.”
Scientists now know the universe is expanding, at an ever-increasing rate. So if it’s ballooning, what is it growing into? In other words, what is beyond the known universe?
Defining this “beyond the universe” would imply that the universe has an edge. And that’s where things get tricky, because scientists aren’t certain if such a drop-off exists.
The answer depends on how one views the question.
One form of the question asks, “Could you go somewhere that you could look ‘beyond’ the universe,” the way one might peer beyond a cliff edge or look out a window to see the outside of a building? The answer to that query is “probably not.”
One reason involves the “cosmological principle,” said Robert McNees, an associate professor of physics at Loyola University Chicago. The cosmological principle states that the distribution of matter in any part of the universe looks roughly the same as in any other part, regardless what direction you look in; in scientists’ terms, the universe is isotropic.
The implication though, is that there is no “edge”; there is no place to go where the universe just ends and one could look in some direction and see what’s beyond it.
Tne analogy often used to describe this edgeless universe is the surface of a balloon. An ant on such a surface can walk in any direction and it would look like the surface was “unbounded” — that is, the ant might come back to where it started but there would be no end to the journey. So even though the surface of a balloon is a finite space, there’s no edge to it, no boundary (since you can go forever in any one direction). In addition, there’s no “center,” so there’s no preferred point on the balloon’s spherical surface.
The universe is a three-dimensional version of the balloon’s skin.
Using the balloon analogy again, if one were to add more air to the balloon, the ant would observe other things on the balloon’s surface getting farther away. And the greater the distance between the ant and some object, the faster that object would be receding. But no matter where the ant skittered, the speed at which those objects were receding would follow the same relations — if the ant came up with an equation describing how fast the farthest objects were receding, it would work the same way anywhere on the balloon’s surface. Nowhere on the surface of the balloon would the ant observe anything coming toward him.
But, Toritto, the balloon is expanding into a three dimensional space. Stephen Hawking said this doesn’t apply to the universe – the universe came from nothing at the big bang creating everything and therefore by definition, nothing can be outside of it. Hawking said the question is like asking what is north of the north pole.
Dr. Katie Mack, a theoretical astrophysicist in Melbourne has stated that rather than using the term “expanding” it is more proper to use the words “less dense'” The concnentration of matter in the universe gets less dense as the universe expands.
That is not because the galaxies themselves are moving away from each other – it is space itself which is expanding while the galaxies are relatively stable, as on the surface of the balloon. Any aliens in deep space would come to a similar observation – everything was moving away from them and they were at the center of it all.
“Because space is expanding, it’s possible for the galaxies to appear as if they are moving faster than light, without violating relativity — which says that nothing can go faster than light in a vacuum. The actual size of the observable universe is 46 billion light-years in any direction, even though the universe began only 13.8 billion years ago, Mack said. But that still sets a limit on the size of the universe humans can see, called the observable universe. Anything outside of that radius of 46 billion light-years is not visible to Earthlings, and it never will be. That’s because the distances between objects in the universe keep getting bigger at a rate that’s faster than the light beams can get to Earth.” It is space, not the material in it that is traveling faster than light.
You’re a sucker for punishment if you’re still reading this!
“And on top of that, the rate of expansion has not been uniform. For a brief fraction of a second after the Big Bang, there was a period of accelerated expansion called inflation, during which the universe grew at a much faster pace than it is growing now. Whole regions of space will never be observable from Earth for that reason. Mack noted that assuming inflation happened, the universe is actually 1023 times bigger than the 46 billion light-years humans can see. So if there is an edge to the universe, it’s so far away Earthlings can’t see it, and never will.”
Meanwhile, there’s the issue of whether the universe is infinite in space to begin with, which Mack said is still an open question. Or, the universe might wrap around itself in a higher dimension in the same way that the 2D surface of a sphere wraps around itself in three dimensions.
Mack said there are ongoing attempts to resolve the question of whether the universe is like a sphere, curving back on itself so that if you travel in one direction you eventually return to your starting point. Einstein posited that the universe is flat but today many in the field think that the universe is so large and the curvature so small that it is currently undetectable to us.
If astronomers found two places on opposite sides of the sky that were exactly the same, that would be a strong indication that the universe is curved in that way. There are no guarantees, though. While some cosmological theories such as string theory posit higher dimensions, most of those would be “rolled up” and small, whereas a curved universe’s “extra” space dimension would have to be large.
“All of this means that if there’s an end to the universe, humans might well never be able to see it, and there is the real possibility that the universe is shaped so that it can’t have a boundary to begin with.”
As a matter of full disclosure I should let you know I am highly qualified in the field of astrophysics, having earned my Bachelor’s Degree in Economics at night attending the City University of New York while working at my day job in a bank. I am also a card carrying member of the Flat Earth Society.
So you see I do know what I am talking about. We are now open for questions.
What ever happened to Lindsay Lohan?