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A Question About the Universe and Infinity

I have a rather brain-bending question for you.

If the concept of infinity exists,(which it does), then shouldn't matter be infinite just like numbers?

The universe is made up of matter, and at a certain point (we believe) it just stops. No more universe. But then, how does that make any sense? How can there be nothing? From alot of intense thinking on my part, as well as some digging, I have found that the concept of infinity works in two ways: 

1. You can have an exponential growth of numbers, going on and on infinitely.
2. You can take a finite number such as 1, and divide it infinitely.


Both of the above create infinities, so technically, a finite amount of matter (such as the universe) could be infinite, or that is, infinitely split in half. 

But what about the first infinity?

Numbers are infinite, but is matter bound by the same rules?

Does this expose a flaw in the way we think about the universe? 


The same issues occur in our concept of time, if it is measured with numbers, shouldn't not only the future, but also the past be infinitely long? I have also heard (and believe) that time is an illusion created by humans to create order in things, and the only reason it looks like it is moving forward is because of entropy. In which case, I must ask, doesn't this make time travel possible?
(I realize this gets into the whole 4th-12th dimension thing, but I wont go there.)

If you could maybe give your thoughts on this barrage of questions that would be great.

Thanks

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kelseymh3 years ago
Let me address your last question first. You write, "Does this expose a flaw in the way we think about the universe?" I think that it exposes some lack of understanding of current knowledge in how you are thinking about the Universe. That's not a flaw, rather it should be a goad for you to increase your knowledge, then go back and work through your ideas again.

Now, back to the top. Just because you have a concept, doesn't mean that concept has to exist in reality. I present for for your consideration the following concepts, shared by many people, none of which exist in reality: Santa Claus, phlogiston, the communist utopia, and magical sky beings.

You write, "The universe is made up of matter, and at a certain point (we believe) it just stops. No more universe." Nope. Our consensus cosmological model doesn't say that at all!

The universe, as we understand it, is only made up of about 5% matter. There's another 26% of so-called "dark matter" (something which has mass and gravitational interactions, but not electromagnetism), and the remaining 69% is a form of energy with negative pressure (sometimes called "dark energy" or "quintessence" or "the cosmological constant).

There is a limit to how far out in the Universe we can observe, corresponding to a light-travel time of 13.3 billion years. That is not an "edge" as you might think of it: we have good evidence that the "whole Universe" is much larger than our observable bubble, but we have no data one way or the other whether it is infinite, finite and bounded, or finite and unbounded (like a balloon or doughnut). You probably want to read the Wikipedia article on "Cosmology" to fill in the details.

You write, "Numbers are infinite, but is matter bound by the same rules?" No, matter is bound by different rules. Matter is made up of molecules, which are made of atoms, which are discrete entities. Atoms are made up of electrons and nucleons (protons and neutrons). The former are pointlike and indivisible, while the latter are made up of triplets of quarks. Quarks, like electrons, are pointlike and indivisible. So there is a limit to how far you can "divide" matter before you get to something indivisible, and that limit is different depending on how much energy (real energy, in joules) you can invest in doing the dividing. That isn't true of abstract concepts like numbers.

Time doesn't have to be infinite, either in the past or the future. You may look up "gravitational singularity" in Wikipedia, or "FLRW" for a (too technical) discussion of the form of spacetime which describes our current cosmology, and which has a past t=0.

So I take it you are *not* a mathematical realist? :P :)

Also, a communist utopia DOES exist!

In the form of yo' mama, because she's so classless.

No, I'm not. I am awed at just how well mathematics, even (especially) mathematics invented as an abstract formalism, describes nature; but nature was there first.

vroom...vroom... (author)  kelseymh3 years ago
Wow. Thanks, that seemed to answer most everything I was wondering about.

And I guess when I say matter, I really mean everything that exists- including dark matter.

So simply put, you are saying that we can't observe past a certain point. So we can never really know weather the universe is infinite or finite.
Correct?

Now from a purely theoretical standpoint, you could keep dividing matter- Given the right resources. So I guess I am looking at it from a more "what if" sort of direction, and your are seeing it as a logistical problem. 

So to end my soliloquy,
We can never really know can we? 
You write, "We can't observe past a certain point." That is true today. The reason is trivial: we cannot see anything which is so far away that light from it hasn't had time (13.67 billion years) to get to us (look up "cosmological horizon"). The Universe is expanding, but it is expanding more slowly than light-speed. So as time passes, that "farthest distance" gets larger and larger, and we will be able to see things further away.

Physical models of cosmology make testable predictions, including predictions of observerable effects due to different sizes of the whole Universe. For example, suppose the Universe were really a closed hypersphere or hypertorus (finite in size, but without an edge). In that case, we would see patches of the cosmic microwave background in different parts of the sky which are identical! How many such patches, and how far apart they are, would tell us the true size of the "whole Universe". Currently, no such correlations are observed, and so we know the "whole Universe" is larger than our observational resolution (I think it turns out to be something like 500 billion light years). That's just one example; other cosmological models make other, but still testable, predictions.

You are wrong about the divisibility of matter. Once you get to pointlike entities without substructure -- electrons, neutrinos, and quarks -- by definition they cannot be divided further (that's what "pointlike" and "without substructure" mean).
pewtu3 years ago

There is a basic problem with trying to look at the problem.

Even the most powerful computational device ever to operate on this planet, the human brain, is unable to deal and comprehend 2 numbers. Remember numbers and mathematics were created by this brain. The number or concept of infinity and zero are not comprehended by the very same brain that conceved the idea.

Goodhart3 years ago

One of the problems of comparing infinite physical entities with numerical values is that, in math, not all infinities are equal.

That may shock some, but in a one to one comparison, some infinities have "more" numbers in them than others. For instance: the two infinities of even numbers, and odd numbers, one can match them up one even for each odd...but if you take all the integers, and attempt to match them up one for one, with all the fractions...one finds an inequality despite both sets being infinite...the infinite list of fractions will be much larger than the infinite list of integers.

Time travel is easy we are doing it now, we are traveling into the future through liner time.

And we observe the past when we look at Gliese 581 we see it as it was about twenty years ago. So in a sense we travel to the past through the lens of the telescope.

caitlinsdad3 years ago
In Space, no one can hear you scream. There is a vacuum in the great infinite void. Not that that matters.

Someone came up with the theory, E=mc^2..

You can ring Mr. Kiteman on the topic of Creationism.

Do the birds in the size worry about their next meal? Read that question before from a famous maker.
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