Is space within the universe, or is the universe within space?

I have an argument with a friend, he says that space is within the universe and I say that the universe within space.

I know that the universe is made out of space, but space is infinite and the universe is not, am I wrong?

He claims that because the universe is expanding, then it is infinite, how dumb is that?


Thanks all for your answers!

noetikos: But if space and the universe are not infinite, then what happens once you reach the end of them? Isn't there more space? or what?

14 Answers

  • Troasa
    Lv 7
    7 years ago
    Favorite Answer

    Space did not preexist before the Universe began. There was nothing before the Universe except for the Singularity. Nothing means nothing - not empty space - nothing. We must remember that our Universe did not blow up like a ball or balloon. Our Universe expanded metrically - all points expanded equally. There was never any 'outside' to our Universe and no 'outside' exists today.

    Keeping that in mind, our Universe did expand. The Singularity in its original state was smaller than the head of a pin. It was only through expansion that it cooled enough for matter to form.

    It was only after the Singularity began to expand that space was created but space is never empty.

    The Universe expanded at a phenomenal rate in its first few seconds. In just a fraction of a second, for example, our Universe was larger than the size of a galaxy. What existed in this Universe was space filled with a plasma and constituents of subatomic matter. While temperatures in this Universe were extremely hot, after about one second of expansion, this temperature cooled enough for baryons to form into protons and neutrons. After about 3 minutes, it was cool enough for protons and neutrons to combine to form hydrogen and helium nuclei.

    This was space for about 300,000 years until finally it had cooled enough for hydrogen and helium nuclei to attract electrons and form atoms.

    Gravity worked to clump matter together in groups and after about 200 million years the first stars were able to form in the space created by the Big Bang.

    So to answer your question... The Universe cannot exist without space, and space cannot exist without containing matter. The Universe then is a combination of space and matter. The two are inseparable. So neither argument would be correct or even make sense.

    In the very early stages of the expansion of the Singularity, space expanded faster than the speed of light. This is because mass was not under the effect of gravity (which was the last force to separate from the Fundamental Forces). So 'space' itself is larger than the part of our Universe which contains galaxies. However, although our Universe is extremely large, it is not infinite. Since our Universe is space (and matter), space is not infinite either. Both are one and the same.

    Space is still expanding as it always has been (not always at a constant rate) but the size (if we remember that our Universe is not a ball) is estimated to have a radius of 45.7 billion light years. Very very large - but not infinite.


    It's part of the Cosmological Principle: Space is isotropic and homogeneous. Therefore no matter where you are in our Universe you would always perceive yourself to be at the center of it. Travel anywhere in the Universe and you remain at the perceived center. In a metric expansion (as opposed to an explosion from a central point) there is no one center where things expanded out from. All points are the perceived center. Travel as far or as fast as you want, you always remain at the perceive center of the Universe.

    Unfortunately, there are no examples that exist which can demonstrate our Universe properly. You will find the surface of a balloon, the rising of bread dough, and the stretching of a rubber sheet but all would be objects which have an outer surface which the Universe does not have.

  • 7 years ago

    We don't know. But we can ask some questions.

    If space is infinite and time is eternal then it has no end. If so, why would a limited universe be at the center of it? Yes, because something infinite can only be observe from its center since it has no ends.

    Another alternative is that the universe is truly unlimited and if we could travel space and time we would discover anything that can exist, similar planets as ours, similar people as us and, in fact, exactly the same configuration of matter, space and time as we observe now. And we will not only discover one such place but an infinite number of them because infinity means, no end.

    If that is the case then how can we differentiate the "now and here" to "there and that?"

    In other words, the only infinity that makes sense is the cyclic one. A point, a circle, a sphere or a hypersphere.

    The idea isn't new. Ancient Indian wheel of life or the more recent Nietzsche's Eternal Recurrence. If time is eternal, what can happen, will happen. It is as simple as that.

    Of course, there is an argument against it. If you have two wheels spinning and one goes to a function of pi in relation to the other, they will never again align because pi is an irrational number that has an infinite number of decimals.

    However that supposes a infinite number of positions of the wheel. As Planck pointed out, if the universe was truly infinite, the energy of the sun being carried by waves would burn all at once since there are an unlimited number of frequencies. Hence the notion of quantum physics and a universe made of Planck units of time and Planck units of space. So infinitesimal small unit but yet a unit.

  • 7 years ago

    It's probably more accurate to say that space IS the universe. The size and layout of the universe is tricky to understand from a common-sense perspective. The distances involved are so vast, but we evolved and we live in a world where we don't usually have to deal directly with distances greater than a few kilometers at a time. Over longer distances, the curvature of space becomes more apparent.

    Again, it's counterintuitive, but don't think of it as floating in the middle of a big empty box. Instead, break it down to two dimensions and imagine living on the surface of a balloon. Space is infinite in the same way that the surface of the balloon is infinite - pick any direction and walk in a straight line, and you'll never hit a wall (though, like space, you'll wind up back at your starting point). Like the balloon, space can also expand. Instead of a box growing larger, the surface itself is expanding and the distances between fixed points is growing larger.

  • 7 years ago

    Basically what your friend says is correct.

    Current theory is that space is not infinite in size and the density of matter in it is the same in all of space - filled with stars and galaxies.

    The universe is expanding though, and both the space and the array of matter within it are expanding together. In other words, there is no current limit of galaxies, beyond which there is just empty space waiting for the matter to expand into it.

    The above being said, there is an independent theory (it doesn't contradict the above) that there might be multiple universes, each with its own independent space. What is between these multiple universes, you may ask. We don't know, but it isn't space; it probably has many spatial dimensions; at least more dimensions than our multi-dimensional universe's space has, which means that you can't just travel for trillions of light years in some direction that you can see and eventually arrive in another universe. Sometimes the environment of multiple universes (if it even exists at all) is called the "bulk".

    Source(s): (see the Physics section)
  • How do you think about the answers? You can sign in to vote the answer.
  • Anonymous
    7 years ago

    "Is space within the universe, or is the universe within space?"

    Space is a property of the system Universe. So space is within the Universe.

    "I have an argument with a friend, he says that space is within the universe and I say that the universe within space."

    Your friend is correct.

    "I know that the universe is made out of space,"

    It is more than that. Spacetime is produced by the system of mass and energy in the Universe, via the "laws of physics".

    "but space is infinite and the universe is not, am I wrong?"

    The number system used to describe / map the Universe is infinite. The Universe will not be infinite in size until another 125 billion years (or so) from now.

    "He claims that because the universe is expanding, then it is infinite, how dumb is that?"

    It *will be* infinite, in time.

    [EDIT: "But if space and the universe are not infinite, then what happens once you reach the end of them? Isn't there more space? or what?"

    The Universe is a *system*, and it has finite contents. What is more, its property space(time) changes from "Big Bang" (no space) to "Cold, Dark, Infinitely-diffuse Future". At the end, there will be infinite space, and still the system Universe will be present for all earlier times.


  • 7 years ago

    Space is within the Universe, as the Universe Expands Space and Time expands as well.

    Source(s): My Brain
  • Anonymous
    7 years ago

    Space-time IS the Universe. (At least, one definition of it.) The term "universe", it should be blazingly OBVIOUS, does not have a unique defintion or meaning. I count at least 4 different astronomical meanings of the term, but I won't bore you with them. Presenting a false dichotomy is a juvenile level debate tactic, incidentially. For all practical purposes, our universe is our Observable Universe. The term "observable universe" does have a specific technical definition. It is NOT infinite (in spatial dimension). Our current best model of Cosmology, the lambda-CDM model is based on General Relativity and the Cosmological Principle. The Cosmological Principle states that ANY observer looking out from anywhere in the Universe will see roughly the same Universe (in the same cosmological epoch). We continue to test this, but so far has held up well in the 300+ years since it was suggested. The implication of the CP is that an observer who is at the edge of our Observable Universe can look up and "see" us at one "edge" of his/her/its/their Observable Universe and look in the opposite direction and see just as far.

    That is the size of the total Universe is equal to the diameters of all of these Observable Universes added together: D+D+D...+D+D+... but since there is never and end to this chain of OU's (remember each observer is "no different" than any other) , the total is obviously ∞. (The estimated diameter of our OU is 93 billion light-years).


    I don't agree that it is meaningful to distinguish between "all of space-time" and the universe. They are the same, depending on context. We know that the Observable Universe HAS an edge, actually has many edges: it ends at the beginning: the Big Bang is an edge; it ends at the event horizon of any black hole that exists. but while it has (in this sense) "edges" it also will (according to what we know now) continue on forever into the future and continue on forever in any direction you care to point, that makes it infinite also. Our universe IS space-time. It is neither space nor time, but is a mixture of the two. You apparently are unable to think about it as a 4 dimensional thing. That's ok, but to accuse your friend of being stupid while he obviously is thinking about its fourth dimension...isn't too bright.

  • cosmo
    Lv 7
    7 years ago

    What we consider to be normal spacetime is finite and entirely within the Big Bang. The Big Bang now is likely to be a 4-d hypersphere with a characteristic radius of around 10^21 lightyears (much, much bigger than the distance to our event horizon which is "only" 13.7 billion lightyears away). That means that if you go in any direction at infinite speed, you'd wind up where you started after a journey of about 10^22 lightyears. (It has to be infinite speed because the Universe is expanding with time.)

    Now, this 4-d hypersphere may or may not be embedded in an "external manifold". That external manifold may or may not contain other "big bangs". We don't know.

  • 7 years ago

    ", but space is infinite and the universe is not, am I wrong?"

    Yes, that's wrong. The universe is all of space and time. If a space exists at some time, it is part of the universe.

  • 7 years ago

    Space exists within the universe. Neither is infinite.

Still have questions? Get your answers by asking now.