Our Universe Is Disappearing

Klein Bottle

A few days ago, astronomers announced that they have discovered the most distant object from Earth ever seen. Actually, they waffled a little and said that they think that it might be, possibly, a galaxy, or not, maybe. UDFj-39546284, the maybe-galaxy, is believed to be 13.2 billion light-years (LY) away -- which is to say that it took light that many years to reach Earth from wherever that galaxy was at that time. Who knows where it is now. To figure out this distance in kilometers, one takes the speed of light (300,000 km/sec; 671 million MPH) and multiples it times the number of seconds over the course of 13.2 billion years. You do the math; I'm busy writing this blog. The speed of light is generally expressed as "c". However, I'll refer to it here as SoL for reasons you might be able to figure out on your own.

I now should explain the details of the relationship between SoL and the time-space continuum, but the last time I delved into these topics [see Spooky Action at a Distance: Communication Faster Than the Speed of Light], I got the impression that no one understood anything, and that includes myself. Therefore, I'll try to keep my point simple: The Universe is more like an apple peel than a snowglobe. And it eventually will disappear from view even though it will continue to exist.

Now I'll try to keep the explanation simple, but this will not be simple to do. It is believed that the Universe began with the Big Bang, an event that is yet to be fully understood, about 13.7 billion years ago, give or take a few months. At that moment, in addition to all the atoms and molecules of mass and energy that came into being, Time and Space were also created. To allow for all the space junk that was being spewed out of nothingness, the actual fabric of Space had to expand. And it has continued to expand to this day. Ok, I know I'm already losing some of you, so I'll use metaphors instead:

Metaphor #1: You've glued some golfballs near each other on a basketball. Then you want to move the golf balls away from each other, so you pick them up and move them further apart, and then re-glue them on their new locations. Now all the golf balls are far from each other. This is not how the Universe is expanding. The galaxies are not moving apart from each other by occupying new areas of Space (the surface of the basketball) that were already there.

Metaphor #2: Let's say you have a huge explosion -- a big bang, if you will -- and all of the material that was at the epicenter of the blast is hurtled outwards, like a fireworks display. After awhile, the area is filled with material and sparks spreading outward from a central point, similar to snow inside an expanding snowglobe. This is not how the Universe is expanding. The galaxies are not randomly spreading around, filling up the three-dimensional space from the epicenter to the outer limits of the expansion.

Metaphor #3: Now you've glued a bunch of ping pong balls to the surface of a deflated balloon. You then begin to blow air into the balloon, greatly expanding it. As you you do this, the balls on the surface begin to move away from each other as the surface expands. Each ball is receding from every other ball; none is getting closer to any other. A-ha! This is how the Universe is expanding, but without the hot air, and not all the ping pong balls are white. Oh, and the Universe cannot be twisted by some celestial clown into the shape of a puppy. The galaxies are receding from each other, not because they are hurtling through heretofore empty space, but because Space itself, where the galaxies are "glued" in place, is expanding; and Space is just bringing the galaxies along with it.

But, wait, there's more: Retaining this same balloon metaphor, our known Universe encompasses only the balloon's membrane! There is no "center" of the Universe, a place where we can determine where the hot air came in, where the Big Bang occurred. There is no empty air inside the expanding balloon of galaxies. Instead of the membrane of a balloon, think of an apple peel that's in one piece. It's all curvy, right? And there is no air keeping it in place. In fact, it looks kinda flat, doesn't it? Well, that's our Universe (but without the anti-oxidants and fiber). Some have described the Universe as an expanding muffin, but let's move away from the food metaphors, because now I want a snack.

[4 Dec 2021 update: Sorry, but we are not done with food metaphors after all. I'm beginning to believe that the "expanding muffin" metaphor might be more illustrative than the "apple peel" one. However, I would prefer to talk about raisin-bread dough instead of muffins. Think of a galaxy, for instance, as a raisin in the dough. As the dough is heated, it expands as it becomes bread. All the raisins are moving away from all the other raisins! And the reason they are moving is because the dough substance itself (time-space in this tasty metaphor) in which they are embedded is expanding, bringing the raisins (galaxies) along with it.]

By observing the stars, we have determined that all of them are receding from us; none is coming closer. If we try to determine the path that the galaxies had taken over the millenia to get where they are now and reverse the process, they would all be coming toward us; it would seem that WE are the center of the Universe. However, the fact is that they all are receding from all the others (like the balls on the balloon). Therefore, if the Andromedans in the Andromeda Galaxy observed the same Universe and determined where all the galaxies apparently began, they would come up with the same answer we did -- they would deduce that they are the center of the Universe.

Lea design based on an Escher design based on a Möbius Strip

Wow. How can we explain this? I don't know; why are you asking me? I can tell you this: Space is curved. Einstein said so, so it must be true. Thinking again about the membrane of a balloon or the apple peel: Those are curved, right? And if the Universe is like the membrane of a balloon, why is it so hard for you to accept the fact that Space is curved? Also consider the Möbius Strip, a curvy thing that looks like it has two surfaces, but it only has one. Follow the ants in the image above to see what I mean; they never have to hop from one surface to another; it's all one single surface. An even better example is the Klein Bottle (see the image at the top of this blog). It looks very three dimensional, but it also has only one surface. "Regular" bottles have an "inside" surface and an "outside" surface. If you follow a point on the Klein Bottle and move it around, you will see again that there is only one surface, even though your instincts "feel" that there is an inside and an outside.

As with the representation of the three-dimensional Earth by a two-dimensional map, a straight line between two places on a 3D globe looks like a curved line on the 2D map (trust me on this one). That's why a straight flight between New York and Tokyo has to go by way of Canada. Let's face it, no one wants to go to Canada, but they must if they want a shorter flight. I'm kidding, Canada -- however, after I broke the news of your having invaded the Soviet Union [see When Canada Invaded the Soviet Union], readers of this blog might be upset with you.

So how fast is Space expanding? The correct answer is about 71 kms per second per megaparsec. However, I'll provide you with a different answer; otherwise, I would have to explain "megaparsec," and I know that no one wants that. So, my other answer is: It depends. Objects further away from us are receding faster than those that are closer. For instance, a star 30 million LYs away is fading away at about 700 kms/sec., which is a rate of only .23% of SoL. As you go further out away from the Earth, bits of the Universe are traveling ever faster:

• Objects 300 million LYs are receding at 7,000 kms/second (2.33% SoL)

• Objects 3 billion LYs away are receding at 70,000 kms/sec (23.3% SoL)

• Objects 12.857 LYs away are receding at 300,000 kms/sec (100% SoL)

• Objects 13.7 billion LYs away are receding at 319,667 kms/sec (1.65 x SoL)

Hey, wait a second! How can something travel faster than SoL? Nothing is doing that. Just as the objects are moving away from Earth, Earth is moving away from the objects. Even though both objects are moving at sub-light speed, their combined movement apart widens the gap at a speed faster than SoL. [Metaphor alert!] Let's say there are two trains that leave a station at the same time, in opposite directions. They are both traveling at 70 MPH. Although each train is receding from the station at only 70 MPH, the distance between the two trains is widening at 140 MPH.

Ok, now we get to the final fun fact. As objects become approximately 12.9 billion LYs away from Earth, the distance between the two points will be widening at a rate faster than SoL. Since the light from that distant object cannot attain that speed, we will never see that light. Eventually, that object will fade from sight, never to be seen again. If the Universe continues to expand, all objects will attain that distance from Earth, and the night sky will become completely black. Well, except for some of our neighbors in the Solar System, and a random firefly. Of course, since all this will happen billions of years in the future, there might not even be a Solar System then, and fireflies will have mutated into ethereal creatures that will be battling sentient cockroaches for mastery of the world. Humans? We'll be sitting with the Andromedans on their porch, reminiscing how UDFj-39546284 turned out not to be a galaxy after all, but was only a smudge on the Hubble Telescope's lens.