Slashdot Mirror
Is the Universe a Hall of Mirrors?
PhysicsWeb is running an article by one of the researchers who has developed the theory that the universe may be finite, rather small, and soccer-ball shaped. The question is still open; it's one theory that fits cosmic microwave data from the Wilkinson Microwave Anisotropy Probe (WMAP). Apparently testing the theory by looking in the indicated way through the WMAP data would so far be computationally prohibitive. From the article: "The Poincaré dodecahedral space can be described as the interior of a 'sphere' made from 12 slightly curved pentagons. However, there is one big difference between this shape and a football [soccer ball] because when one goes out from a pentagonal face, one immediately comes back inside the ball from the opposite face after a 36 degree rotation. Such a multiply connected space can therefore generate multiple images of the same object, such as a planet or a photon. Other such well-proportioned, spherical spaces that fit the WMAP data are the tetrahedron and the octahedron."
No, nothing has to be "containing" it. Think of it like walking on the surface of the Earth. If you look in either direction you can see pretty far and you might imagine that the Earth goes on forever. If you start walking, you will walk all the way around the Earth and end up exactly where you started. The Earth simply curves back on itself. You could walk around the Earth forever and never reach a boundary where Earth ends, but the Earth itself is still finite.
As to what this soccer ball universe could floating in, well, the question itself is probably the largest issue. We don't know the answer, but the it could very well be that there is no "outside of the soccer ball". The universe could be all that there is. There could be no "beyond" the universe or "outside" of the universe. It is hard concept to visualize, but that is pretty much true of any concept that outside of the traditional Newtonian world.
Once you leave the safe world of Newtonian physics you need to develop a superhuman ability to try and NOT visualize the universe on the grand scale of the quantum scale. Human intuition and visualizations is was built for Newtons world. Once you leave that world, it breaks down and fails to be much help.
If anyone's looking to understand this, the book you need is "How the Universe Got Its Spots" by Janna Levine. It covers all the apparently valid but actually nonsensical questions that people have when they first hear about this (what's the universe inside then? what happens at a boundary? etc), and it explains it in such a way that you don't need a degree in topology to understand it.
If our universe resembles a video game, could it actually be a video game?
:D
That logic is fallacious, even if the observable universe is a "simulation", then this simulation runs inside a real universe, and we're at the start again figuring out what the universe is.
Plus I subscribe to another logic: if the universe is similar to a video game, then it's because as video games increase in complexity they start to approach the model of a little universe
If you have noisy data and you keep analyzing it enough, you'll eventually find some bizarre model that fits it better than a more plausible model.
It's probably best not to have a firm opinion on the shape of the universe until a lot more data is in.
The human mind is the product of millions of years of evolution designed to think in a Newtonian way. You are hardwired to think Newtonian. This hardware does very deep and is a fundamental piece of your core persona. Consider for a moment that if you toss a ball, a dog can jump up in the air and snatch it. This gives you an idea of how hardwired we are to think in Newtonian terms. This is an an ancient way of thinking that goes back well before we were primates, much less full blown humans.
Anyone can tell you what happens when you hit one object against another or toss one object against gravity at a certain angle. Even small children know roughly where a baseball is going to end up the second you release it from a throw despite the fact that the real calculation would take someone a few minutes to make. With quantum mechanics, you are never going to have that child like grasp of what happens when two atoms start interacting.
While we do make visual models to understand quantum mechanics, they really are only a crude ways to give our poor mammalian brain some straws to grasp at. We can visualize orbitals to some extent, but anything deeper then that kicks human intuition which has been developed to deal with a Newtonian world in the balls. You really can only truly 'understand' quantum mechanics and general relativity with math. And not just simple math, but ugly math that kids go to college for years to understand.
Without the hardwired machinery to give us answers like what we have for Newtonian physics, there is no ability to develop and "intuition" for quantum mechanics. Quantum mechanics is ugly math combined with concepts that have no Newtonian world analogy. Let the kids know that this stuff exists, but keep them in their happy Newtonian world where their hardwired physics engines can pick up the slack. Save quantum mechanics for after they know calculus.
Yes, they can, but that does not make them "hardwired" to do Newtonian physics; physics is the mathematical description of the real world, and so someone who lives in the real world and experiences it will have intuition into how physics works. If we lived and experienced in the quantum or the relativistic, we would have intuition into how that works as well. However, if you have never experienced something (even Newtonian physics), then you have no intuition about it because it is not something hardwired. Examples: on this very site a while back, there was a heated discussion about what would happen if there were a a tunnel bored completely through the Earth and you fell it in. What would happen? People disagreed. Also, Total Internal Reflection. I don't think that a dog, or a child, or anyone who hasn't taken a physics course or read about fiber optic cables would know about this. There is no intuition about it, but it is Newtonian physics. Physics is not hardwired into anybody's or anthing's brain. Our seemingly innate grasp is the ability to find patterns in the behavior of things, which is why the dog will know when to jump to catch a ball, or why the child knows where the ball will land (approximately). If we have no experience to find patterns in, we won't know our heads from our asses, metaphorically speaking.
As a consequence, you can grow intuition as you work with something. Which is why if you do enough quantum mechanical calculations, you will begin to have a sense of "what looks right," to have intuition about how quantum mechanics works. True, because we can only express quantum mechanics, our intuition in mathematical, but just like the physics student can translate the mathematical expressions of Newtonian physics into consequences in the real world (i.e. if the momentum of A is bigger than B, then they will both move mostly in the direction of A if they have an inelastic collision), the student of quantum mechanics can say "This Hamiltonian of an electron doesn't have any nodes. Then it must be in an s-orbital." Just because we are not as intimately familiar with quantum mechanics as we are with Newtonian physics because we live in the latter, not former, doesn't mean we can develop an intuition into how the former works.
It has been a nervous year, with people beginning to feel like Christian Scientists with appendicitis.