# Absolute Center

We can point at the Sun and say, “That is the center of our planetary system.” We can point at (I think) Centaurus and say, “Yonder lies the hub of our galaxy.” If we accept the Big Bang and an expanding Universe, has anyone theorized about a physical direction to point and say, “That is THE Center.”?
–Alan Q

Well, in point of fact, Sagittarius is the direction you need to point to for the center of the Galaxy, and the center of the Local Group of galaxies is somewhere between that, and the Great Nebula in Andromeda (M31). The Great Attractor seems to be somewhere off beyond that, though, and we might well be orbiting it, or the center of gravity of it and a whole lot of other stuff we can’t see.

However, the center of the universe as a whole is a different sort of problem to solve. The orbital mechanics of galactic clusters is not something easily measured with respect to our current position and velocity with respect to their current position and velocity. We also cannot be sure what the current position of a distant object is, or even if the current value of current is consistent with our own. The geometry of universal space-time might well be a bit more complex than four dimensions. Does “center” mean the same thing in eleven dimensions that it does in three?

If you get an answer, let me know.

Tris

If the universe is a hypersphere, there is no center.

I’ve always thought there should be a better answer to this question (or should I say more satisfying to my mind). Unfortunately the answer is counter-intuitive.

EVERY place is the center of the Universe. You are, I am, Venus is and so on.

Space-time is four dimensional and unfortunately it is impossible (at least so far) for a human mind to grasp so lets take it down a step to three dimensions for an example.

Think of the Universe as a sphere like the Earth (assume the Earth is smooth and doesn’t have mountains and what not…like a big steel ball). Humans (in this example) are now two-dimensional creatures living on the surface of the sphere. The surface of the sphere is finite in size and infinite at the same time. We can travel forever around the sphere and never find an edge (this idea is from Stephen Hawking’s A Brief History of Time). Technically you should eventually get back to where you started if you travel long enough but since the sphere is growing faster than we can travel it’ll never happen.

The ‘center’ of our 3-D Universe is through the 3rd dimension towards the center of the ball. Unfortunately our poor 2-D minds can’t really grasp a 3rd dimension in this way so we’re out of luck. There is no ‘center’ on the surface of a sphere.

To get your mind around how the 2-D you looks at things let’s take us back to the 3-D realm we currently inhabit. You can easily grasp three dimensions (akin to your 2-D self understanding two dimensions). Taking the step to the fourth dimension isn’t so easy.

• 1-D is a line (x-axis)
• 2-D is a plane (y-axis at a 90 degree angle to x)
• 3-D is a [what would this be called?] (z-axis at 90 degrees to x and y)
• 4-D is a Tesseract? (another-axis 90 degrees to x, y and z)

Try making the above with toothpicks…the 4-D one is killer!

Hope that helps…I didn’t like it the first time I heard it either!

All of the stuff I said in my post is summed up by WallyM7 in one word: Hypersphere.

Question:
Just because we, as mere 3-D creatures, can’t poke our heads into the fourth dimension does that mean that there is no center to the Universe? If a 4-D person were around could they point the way to the center of the Universe? Does the concept of ‘center’ lose meaning past three dimensions?

This may be more detail than he wants to know, but I don’t think you could argue that something revolving around the sun is the center. We can measure the cosmic background radiation to judge our speed relative to the big bang. I’d say that any place not moving with respect to the background radiation could be the center of the universe.

According to Einstein absolute motion is impossible to detect. As weird as it sounds I think special relativity would let you say that it is as reasonable to suppose the sun orbit the earth as it is the earth orbits the sun. For practical reason most of us live with the earth orbits the sun idea.

Remember the 2-D/3-D spehere analogy above. Any point on the surface of that sphere can be considered the center (or you could say there is no center).

Now bump us up to our 3-D/4-D universe and it’s the same thing. Anypoint on the surface of the Hypersphere can be considered the center (or there is no center…I think both can be considered correct as silly as that sounds). The ‘real’ center that I think is being asked for in the OP is in the fourth dimension which we cannot get to.

I like to think that I am the center of the universe.

My girlfriend disagrees.

Of course you’re not the center of the Universe Lance! The correct answer (at least when facing your girlfriend) is that not only is SHE the center of the universe she IS your Universe!

At least, that’s the correct answer if you want to live long. I bet even Einstein and Stephen Hawking would agree with this one. Relativity and quantum mechanics are a snap to understand compared to women.

“Are you saying I’m fat?”

I don’t think that it’s impossible to detect as much as it is meaningless without a reference frame. However, the cosmic background radiation provides for us an “absolute” reference frame, or at least one that’s stationary with respect to the big bang. We can actually measure our group of galaxies’ motion towards the Great Attractor because the background is blue-shifted (slightly warmer) in that direction. The COBE satellite measured it. They had to compensate for it when looking for the small variations in the background that led to the formation of galaxies.

Back to the balloon analogy, any point on the balloon looks like it’s the center, but we can still tell if a point is moving on the surface of the balloon.