Evaluate: The universe must be finite, because if it were infinite...

Jump to Last Post 1-9 of 9 discussions (33 posts)
  1. Eric Newland profile image61
    Eric Newlandposted 6 years ago

    ...there would be no gravity.

    My reasoning comes from the Shell Theorem:

    http://en.wikipedia.org/wiki/Shell_theorem

    Simply put, a spherical shell exerts no net gravitational force on objects inside it. Likewise, there will be no net gravitational force on a point at the very center of a solid sphere.

    Now consider an infinite universe, with infinite size and containing an infinite amount of matter. It's safe to say that at any point in this universe there will be an infinite amount of mass in all possible directions, exerting an infinite gravitational force. Gravity decreases exponentially with difference, but that doesn't matter: infinite mass = infinite gravity.

    However, because this force is exerted in all directions at once it must cancel itself out. Effectively, an infinite universe behaves like a solid sphere of infinite radius, and any point might as well be the center.

    Local variations in density of matter, therefore, would be negligible. Nearby bodies (if bodies of matter even existed, with no gravity to pull matter together into planets and stars) with finite mass could not counteract the effect of infinite mass even by their proximity.

    Thus, an infinite universe would mean no gravity. Right?

    1. lobobrandon profile image88
      lobobrandonposted 6 years agoin reply to this

      Hmm Good point, will have to do a bit of thinking about this. I'll be back to reply smile Tomorrow when I'm at University during some boring classes I've got something to think about. Thanks Eric.

      1. lobobrandon profile image88
        lobobrandonposted 6 years agoin reply to this

        What if from the very beginning, the universe didn't expand symmetrically about a point?

        Before the big bang all matter was dense at a tiny point right - not sure abt the size. If at all the expansion was not symmetric it would never form a sphere until some parts slow down and others accelerate so as to form a unison (what's the probability?). But, if this happens would the universe come to a stand still or would it result in the great crush?

        1. lobobrandon profile image88
          lobobrandonposted 6 years agoin reply to this

          Addition: It won't result in a complete standstill as everything is already in motion so gravity won't disappear altogether. In comparison to the size of the universe I guess you can consider stellar systems to be electrons revolving around the nucleus (the center of their respective galaxies and neighbouring galaxies as other atoms in the vicinity). Gravitational forces in such a case is negligible, but nuclear forces are rampant - I'm considering the masses even though they may seem uniform throughout the universe would be disproportionate in the galaxy and hence gravity would exist; but, on the scale of the entire universe it would be negligible. But, it does exist!

    2. kirstenblog profile image76
      kirstenblogposted 6 years agoin reply to this

      So inside a singularity there would be no gravity? I assume a singularity is going to have a spherical shape as its the most efficient shape in nature and it would have to be under those pressures.
      I don't actually think we understand what gravity is well enough to deduce this. Is gravity an effect of the accumulation of mass or is it to do with the relationship between mass and motion?

      I am not saying you are right or wrong, just that we don't know enough for something like this to be anything more then a bit of fun food for thought smile


      How would this theory explain gravity inside a sun? I ask because it is a sphere and as far as I knew it does have gravity inside it, but maybe I am not understanding the theory there?

      1. lobobrandon profile image88
        lobobrandonposted 6 years agoin reply to this

        Good point and just as you say it's just a thought to ponder on. The sun isn't exactly a sphere and nothing can be perfectly a sphere I guess. It would be spherical instead.

        1. kirstenblog profile image76
          kirstenblogposted 6 years agoin reply to this

          Sure is fun to think about this stuff tho isn't it? big_smile

          1. lobobrandon profile image88
            lobobrandonposted 6 years agoin reply to this

            Yup smile

      2. Eric Newland profile image61
        Eric Newlandposted 6 years agoin reply to this

        Likely. A singularity could probably be considered a sphere of zero radius, and besides, any net force would have to project matter outward from the singularity, and you know that's not happening.


        As you travel "downward" into a spherical body gravity decreases, as the "shell" formed by the matter "above" you no longer exerts a net force on you. Of course, you still have gravitationally affected matter pushing down on you, which is why pressure would increase. At the very core there is no net gravity, but the "weight of the world," in a fairly literal sense, would be pressing in on you from all directions, so unless you could construct an ultra-strong room with air at a livable pressure you couldn't exactly enjoy the experience of floating.

    3. kirstenblog profile image76
      kirstenblogposted 6 years agoin reply to this

      I am still trying to work out in my mind what the conditions at the very center of a sphere might be like. When I think of our planets core, I just am not sure that there is a weightless center. Our core of liquid metals and other elements is super hot due to the pressures from everything above and more importantly spins. The engine of the planet as it were. I am trying to zoom in (in my minds eye) on that spinning mass to a point where, it doesn't spin anymore? How big could that space be? A single atom of space? If it were anything bigger surely one atom is going to have ever so slightly different pressures from the mass around it as its an atom off-center as it were. Next, I am going to be asking how long a piece of string is!!! lol

      I of course also have to consider that in my thinking, using a planet to help me visualize this zero point in spherical mass for gravity, I am working with inaccurate tools. The planet of course is not a perfect sphere, it's spheroid but oblongs because of outside forces like the sun and moon, hence our tides etc.
      In relation to your question this could parallel to the theory of multiple big bangs (creating outside forces to distort the sphere of our universe). There is a body of thinking that considers that the universe might be doughnut shaped, to explain how it might be impossible to get 'outside' the universe because it would allow you to travel in a straight line yet bend without ever reaching the 'end' or boundary that defines our universe as infinite.
      Something in a sphere universe should in theory be able to escape the outer boundary of the sphere without being deflected back around.

    4. Jesus was a hippy profile image61
      Jesus was a hippyposted 6 years agoin reply to this

      Is it possible that everything in this universe has an equal counterpart (antimatter). Maybe gravity is reversed with anti matter. If the total amount of matter is equal to antimatter, then the gravity caused by the two would equal zero.

      Maybe there is no gravity?

  2. agvulpes profile image88
    agvulpesposted 6 years ago

    From what I can remember you are right up to a point!  Outside of the Earths gravitational pull there is no 'gravity'
    The gravity on Earth is created by it's own rotational forces (or something to that effect) Correct me if I am wrong I am always willing to learn something new? smile

    1. Eric Newland profile image61
      Eric Newlandposted 6 years agoin reply to this

      Gravity is exerted by all bodies on all other bodies as a function of mass and distance. Well, distance squared, technically.

      1. lobobrandon profile image88
        lobobrandonposted 6 years agoin reply to this

        If you test a bomb to explosion, does it explode spherically? I'm not sure just asking. The BB would be the same

      2. kirstenblog profile image76
        kirstenblogposted 6 years agoin reply to this

        So when you are in a elevator and it suddenly goes up, you get that momentary feeling of being heavier, is that not gravity? Likewise, when the elevator suddenly drops from under you and you get that second of almost weightlessness is that not the reduction of gravity by another force? What I am getting at is that mass and distance are just two factors but motion does seem to be an equal factor to consider when understanding gravity.

        1. Eric Newland profile image61
          Eric Newlandposted 6 years agoin reply to this

          Gravity is constant. When other forces (such as an elevator) change your motion you merely perceive it as a change in gravity. But earth is still accelerating you toward its center at 9.8m/s^2 regardless of anything else affecting your motion.

  3. kirstenblog profile image76
    kirstenblogposted 6 years ago

    Another question, when you say 'the universe' are you only talking about the matter that came from the big bang but not the 'space/emptiness' it banged into?

    I am not aware of the big bang still spewing matter into the universe so the matter originating from it would indeed be finite smile

    1. lobobrandon profile image88
      lobobrandonposted 6 years agoin reply to this

      lol I still can't imagine the big bang. Wonder what the density was smile

      1. kirstenblog profile image76
        kirstenblogposted 6 years agoin reply to this

        I sometimes wonder, could it be the collective density of all the black holes that will be when entropy sees the last star burn out and either become a black hole or be consumed by one. When there is nothing but black holes left would they all pull at each other, collide and become massive super black holes and could enough of them join to create a force capable of creating a new big bang? I think maybe smile

        1. lobobrandon profile image88
          lobobrandonposted 6 years agoin reply to this

          Never thought of it that way smile Good point. I guess there should be black holes being consumed by others and as I type this I'm sure there's one happening somewhere out there.

    2. Eric Newland profile image61
      Eric Newlandposted 6 years agoin reply to this

      Yes, I'd say that Big Bang Theory necessarily supposes finite mass, in which case the exponential decay of gravity with distance means most bodies don't affect us in a noticeable way

      But yes, if the universe is finite and roughly spherical then it must exert gravitational force effectively originating at its center of mass, wherever that is. It stands to reason that the closer you get to that center the less that universal gravitational force would be.

      1. lobobrandon profile image88
        lobobrandonposted 6 years agoin reply to this

        At the center there wouldn't be any gravity then and I guess time would remain still?

  4. kirstenblog profile image76
    kirstenblogposted 6 years ago

    As much fun as I am having with this thought line I have a computer that is trying to do a back up and I will mess it up if I don't let it get on with it sad

    bbl to read all you cleaver folks conversations and reply late big_smile

    1. lobobrandon profile image88
      lobobrandonposted 6 years agoin reply to this

      Will wait for you to reply as well smile I have to go for my dinner and complete my assignments too. Doing them atm

  5. Druid Dude profile image61
    Druid Dudeposted 6 years ago

    We are in a black hole, within a black hole, within a black hole, within a black hole, and one day, we will enter another black hole. Do you know how many holes it takes to fill the Albert Hall?

    1. IWantFroyo profile image61
      IWantFroyoposted 6 years agoin reply to this

      The volume of a black hole (not counting the event horizon) is theoretically 0. Therefore, that's dividing by zero, or infinity.

  6. Druid Dude profile image61
    Druid Dudeposted 6 years ago

    This universe is inside a black hole, inside a black hole, inside a black hole, and one day will slip inside a black hole. Do you know how many holes it takes to fill the Albert Hall?

  7. knolyourself profile image62
    knolyourselfposted 6 years ago

    Mr. Memory would know, Hitchcock: 39 Steps

    1. Druid Dude profile image61
      Druid Dudeposted 6 years agoin reply to this

      A line from a Beatles song?

    2. Druid Dude profile image61
      Druid Dudeposted 6 years agoin reply to this

      sory about repeating myself. I'm having another weird day. Hohum!

  8. knolyourself profile image62
    knolyourselfposted 6 years ago

    Hitchcock film, his first good one, 1938. The spies steal the plans and they hide them in Mr.
    Memories mind.

    1. Druid Dude profile image61
      Druid Dudeposted 6 years agoin reply to this

      This is where Hawking was before he published his latest theory. He stil refuses to acept that science has found God and re-labeled 'him'(it).

  9. scottcgruber profile image78
    scottcgruberposted 6 years ago

    This would only make sense in a Newtonian conception of gravity, in which gravity is instantaneous. However, gravity obeys the same speed limit as light. The gravity affecting us is not the gravity of the entire universe - just the portion in a 13.7 billion light year radius around us. The gravity of objects farther away has not reached us yet. The same would apply to every other point in the universe, so there cannot be infinite gravity. It has to be finite, allowing the inverse square law to apply.

 
working

This website uses cookies

As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

Show Details
Necessary
HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
LoginThis is necessary to sign in to the HubPages Service.
Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
AkismetThis is used to detect comment spam. (Privacy Policy)
HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
Features
Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
MavenThis supports the Maven widget and search functionality. (Privacy Policy)
Marketing
Google AdSenseThis is an ad network. (Privacy Policy)
Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
Index ExchangeThis is an ad network. (Privacy Policy)
SovrnThis is an ad network. (Privacy Policy)
Facebook AdsThis is an ad network. (Privacy Policy)
Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
AppNexusThis is an ad network. (Privacy Policy)
OpenxThis is an ad network. (Privacy Policy)
Rubicon ProjectThis is an ad network. (Privacy Policy)
TripleLiftThis is an ad network. (Privacy Policy)
Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
Statistics
Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)