For a long time I've been fascinated by the fact that our universe is expanding because of the Big Bang that brought it into existence. I've visualized an edge to the universe, where a incomprehensibly vast tidal wave of raw existence cascades onward, into...
This is the question that always stymied me. What is the universe expanding into, if the universe is all that exists? Or at least, all that we know to exist. Even if we say the universe is expanding into nothing, doesn't "nothing" thereby become a something?
The marvelous mind-blowing nature of these cogitations is one reason why I've become so non-religious. I don't feel much of a need for supernatural speculating when the natural world is so mysterious and awe-inspiring.
In the July 2010 issue of Scientific American I read an article by Tamara Davis about the expansion of space that, fittingly, stretched my mind even further. It's title was a question: "Is the Universe Leaking Energy?"
Answer: no, even though the expansion of space causes photons to have a longer wavelength ("redshift"), which have less energy than shorter wavelength photons. The article ended with:
Thus, the universe does not violate the conservation of energy; rather, it lies outside that law's jurisdiction.
Meaning, if I grasped the author's point correctly, that laws of nature which apply to things within the universe don't necessarily apply to the universe as a whole. After all, the universe isn't a "thing," since there is nothing (no thing) outside of it.
This wasn't my favorite quotation in the article, though. That honor goes to:
The point is that our metaphor of the expanding rubber balloon, though useful to visualize the expansion, should be taken with a grain of salt: empty space does not have a physical reality.
I read those words, empty space does not have a physical reality, just before I went to bed. Falling asleep last night, I tried to visualize how the universe could be expanding if this were true -- if additional empty space wasn't physically real.
Today I fired up Google and did some research into the question of what, if anything, the universe is expanding into, since this bears on the notion of empty space not having a physical reality.
As is increasingly common these videocentric days, You Tube had a clear and concise presentation of both the question and the likely answers.
Basically, one possibility is that the universe is infinite. Adding more space-time to infinity doesn't change anything. Infinity plus any amount is still infinity.
Another possibility is that the universe is finite. It has an edge. But since the universe is expanding faster than the speed of light, we can never know what, if anything, if beyond the edge.
So the question of what the universe is expanding into is unanswerable. However, my admittedly brief foray into the science of the expanding universe led me to feel that the title of this post, "The universe is expanding into nothing," is defensible.
As noted above, our everyday intuitions and visualizations don't serve us very well when it comes to cosmic questions regarding the universe as a whole. As Wikipedia explains:
The metric expansion of space is the averaged increase of metric (i.e. measured) distance between distant objects in the universe with time.
It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. (In other words, the universe is not expanding "into" anything outside of itself).
A Cornell astronomer offers up a similar explanation:
If the universe is infinitely big, then the answer is simply that it isn't expanding into anything; instead, what is happening is that every region of the universe, every distance between every pair of galaxies, is being "stretched", but the overall size of the universe was infinitely big to begin with and continues to remain infinitely big as time goes on, so the universe's size doesn't change, and therefore it doesn't expand into anything.
If, on the other hand, the universe has a finite size, then it may be legitimate to claim that there is something "outside of the universe" that the universe is expanding into. However, because we are, by definition, stuck within the space that makes up our universe and have no way to observe anything outside of it, this ceases to be a question that can be answered scientifically. So the answer in that case is that we really don't know what, if anything, the universe is expanding into.
If this doesn't make much sense to you, join the club. I don't claim to grasp the cosmic implications of Einstein's Theory of Relativity and other tenets of modern science either.
What entrances me about the expanding universe isn't what I know about it, but what I don't. And that lack of knowledge extends even to the world's most competent physicists and cosmologists.
To everybody, in fact. We simply don't know what the universe is all about.
We don't know now; we won't know tomorrow; we will never know, so far as we know. The ultimate secrets of the universe are far beyond our comprehension, for reasons that, not surprisingly, can't be fully comprehended.
Many people are attracted to religiosity because they love mystery. Well, there's plenty of mysteriousness in science, in the natural world, in what lies at the farthest reaches of physical reality.
The expanding universe can expand our consciousness.
We just need to allow the majesty of the unknowable some room in our psyches, rather than wrongly believing that our all-too-human notions about ultimate reality have succeeded in placing bounds around the boundless.