Thread: Understanding the Cosmos...I Don't

Hi...I am utterly fascinated by astrophysics, cosmology, and astronomy. However, being an enviro-sci guy, I have some gaps. I have spent the last year or so digging around for easy to understand info, and have a lot of questions. Hopefully ya'll can help me figure some things out. I realize of course that this is the wrong field of study for "answers".

I have a desk full of questions on post it notes...I'll start with my first one.

We understand the universe to be roughly spherical, and we estimate it's age at roughly 13.7 billion years old. I had to (crudely) map it out to get a timeline in my head. So...does this mean that we cannot see the "other half" (that would be the right half of the image below, 'behind' the big bank point, traveling in the opposite direction) of the universe past the point of the big bang, as that light will never reach us? Also, and loosely related...but do we know what general direction we're heading? In other words...would it be correct to assume we are about 4.5 billion lightyears from the "edge" of the universe?



Thanks in advance, and please don't hesitate to have me clarify something...I fear that I know so little, I'm not even sure what to ask.

Oh...and it might help me if I understood how cosmic microwave background (CMB) cleared a few things up...I mean...what did the probes find, and how?

As far as I am aware, we do not know for certain whether the Universe is spherical or not. There are many theories about the shape of the Universe such as flat, spherical, hyperbolic, infinite etc.

See...here we go...questions galore, eh? :wink:

OK...I was reading up on Dr. Smoot, and his work, and listening to him lecture. I assumed that his interpretation of the universe being spherical, plus my general understanding of what would make sense as far as a debris field after an explosion was probably the most correct.

That's what makes this so fascinating to me...the more questions we try to answer, the more arise.

No, your concept of the universe is wrong. There is no edge, nor is there a center. You have to think in terms of space-time, not space. Don't ask me to explain it any further, but I know that much about it.

Right...I drew that "crude" sketch to apply it to a timeline...with time being the man-made measurement.

Originally Posted by Harold14370

No, your concept of the universe is wrong. There is no edge, nor is there a center.

Only if the Universe is infinite would there be no edge or centre.

But we are heading a direction...coming from somewhere, if you will. Am I incorrect for assuming we are heading away from "ground zero"...like putting a blasting cap in a watermelon; the pieces head away from the center.

Am I off?

Originally Posted by LunchBox

But we are heading a direction...coming from somewhere, if you will. Am I incorrect for assuming we are heading away from "ground zero"...like putting a blasting cap in a watermelon; the pieces head away from the center.

Am I off?

Indeed.

Originally Posted by CrimsonViper

Only if the Universe is infinite would there be no edge or centre.

In a 3-dimensional Cartesian world, that would be a true statement. But, you have fallen down the relativity rabbit hole.
The people who understand the math behind it, and I am not one of them, will tell you if you go far enough in one direction, you will end up in the same place, analogous to traveling around the earth, while believing you are in a 2-dimensional world.

Originally Posted by Harold14370

Originally Posted by LunchBox

But we are heading a direction...coming from somewhere, if you will. Am I incorrect for assuming we are heading away from "ground zero"...like putting a blasting cap in a watermelon; the pieces head away from the center.

Am I off?

Indeed.

Hang on..."Indeed" I am off? Or..."Indeed" we are traveling ina direction from somewhere...thanks again!

Indeed, you are off. There isn't any ground zero. All points in the universe are equally qualified to be ground zero.

The analogy that is usually given for explaining the curvature of space is to try to imagine someone from a universe of flat surfaces, who had never seen a sphere, being brought to Earth. No matter how far he roamed across the planet's surface, he would never find an edge. He might eventually return to the spot where he had started, and would be utterly confounded to explain how it had happened.

Just as there is no place where you can find an edge of the universe, so there is no place where you can stand at the centre and say: "This is where it all began". This is the centre most point of it all. We are all at the centre of it all. Actually we don't know for sure, we can't prove it mathematically.

The universe is a very strange place indeed.

Geo: According to measurements, the universe is most likely flat.

So in essence, everything moved away from itself, thus the midpoint between every cosmic body is the "center"?

Almost correct. The 'centre' is everywhere. The problems of understanding arise, I believe, because everyday words are being used with different meanings to describe something that is best expressed in mathematics. As Harold observed above most of us don't have the maths to do that, so we resort to verbal analogies - and the misunderstandings begin.

But if the universe started with a huge freakin bang, everything would be flowing outwards, which would start with all the objects moving away from one point. I am understanding this part, but as soon as everything started coming together from the point of creation, there must be a new spot, since there had to be a place for all this shtuff to go once it blew out.

Am I off as well?

“The universe is a sphere.” This refers to the observable universe that we can see from Earth. No matter what direction we point our telescopes, for as far as we can see there are galaxies. When we model what we can observe you get a sort of sphere. However, there is more to the universe than what we can see. Scientists differentiate between the observable universe and the whole universe, whereas most people don’t recognize the considerable difference. The whole universe may have no shape at all.
(An hypothesis states that colliding extradimensional membranes of energy caused the Big Bang and that multiple universes were similarly created. These universes float in a multiverse like spherical bubbles in a void. The hypothesis just needs a lot of that proof thing.)
“The universe is flat.” The observable universe has three possible futures. The inflationary force may increase to the point where everything tears apart in the Big Rip. The inflationary force may dissipate so that the mass of the universe will cause expansion to reverse and we get a Big Crunch. The inflationary force remains constant and the observable universe expands forever to a Big Freeze. If you plot these possibilities on a graph, then the Big Rip line would curve to the top of the graph and off the page, the Big Crunch line would curve to the bottom of the page and eventually back onto itself, but the Big Freeze line would continue as a straight diagonal line without a curve (hence it would be “flat”). We think that the future of the observable universe is flat…at the moment.
“Does the universe have an edge or end?” Again, the observable universe would of course. Since light has a speed limit, parts of the whole universe are beyond our observation. However, this is not a hard edge or end. Tomorrow we will be able to see light from more distant points than we have ever seen before. If you could magically go to the furthest visible point from the Earth, though, you would still see more of the whole universe out to a new event horizon. So, does the whole universe have an end? This is more a question for philosophy than for science. Due to the rate of expansion, the space between galaxies increases at a greater rate the farther you go from your start point. So, at some point the intervening space is increasing at more than the speed of light. These areas will forever be unknown to us and statements about their properties would remain pseudoscience.
So scientifically speaking, the universe can be a sphere that is flat and without an edge.

Originally Posted by Geo

there is no place where you can stand at the centre and say: "This is where it all began". This is the centre most point of it all. We are all at the centre of it all. Actually we don't know for sure, we can't prove it mathematically.

The universe is a very strange place indeed.

you realise that if that were true we would have no idea of a big bang

our whole thesis of TBB comes from looking at galaxies movement and tracing it in reverse. if there is no point of origin, either galaxies wouldn't move, or we wouldn't be able to trace them in a way that told us they all were in the same point at one time

Originally Posted by Booms

Originally Posted by Geo

there is no place where you can stand at the centre and say: "This is where it all began". This is the centre most point of it all. We are all at the centre of it all. Actually we don't know for sure, we can't prove it mathematically.

The universe is a very strange place indeed.

you realise that if that were true we would have no idea of a big bang

our whole thesis of TBB comes from looking at galaxies movement and tracing it in reverse. if there is no point of origin, either galaxies wouldn't move, or we wouldn't be able to trace them in a way that told us they all were in the same point at one time

If I understand the basics, though, mathematically speaking all points have an equal likelyhood of being the "center", thus there is no "center". Fascinating research, to say the least!