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Is Space an Idea?

  1. Oct 1, 2012 #1
    My younger brother is being an absolute idiot. We are currently having a debate about the existence of space among other aspects of physical nature and no matter what I say he retorts with,"Space is an idea. We take up space and that space is gone." RUBBISH.

    I tell him that ideas don't physically exist and that they are merely things used by the human mind to express thoughts and whatnot. His idiocy doesn't appear to support such a claim.

    I ask,"We exist right?" He says,"Yes."
    I ask,"Space exists right?" He says,"Yes."
    Then I say,"If space is an idea and ideas exist only within human minds, wouldn't that mean that we don't exist?" His reply was,"NO! We take up space so that space no longer exists but we still exist."
    In anger at his stupidity, I state that there is space between atoms that make us. He just shakes his little used head and says that I just don't understand.

    That imbecile doesn't seem to want to wrap his head around the subject whist stating that he understands more about the nature of space and time more that I do. Infuriated, I decided to find someone educated about the subject of conversation and came to this forum in search of that one that can prove this fool wrong. The answer is so obvious but I can't find a way to correctly explain to him why he's wrong. Thank you for reading my little rant and for providing an answer if you can and sorry for the amount of the berating of my younger brother, but he really is an idiot.
  2. jcsd
  3. Oct 1, 2012 #2
    Well I can't be 100% on your side or your brothers.

    Space is a really strange thing has been debated by physicists for many centuries. Some think it is pure nothingness, others think it's an "aether" in which particles are able to travel through, and even others thought it was a "sea of electrons" coined "the Dirac Sea."

    Is space dark matter? Does it contain an innate force that can explain astronomy's problems in gravitation. Is it a bunch of superstrings?

    Ok you get the point. It's really up in the air. With that said, is space just an idea? Well no, I wouldn't completely agree with that. I mean particles everywhere occupy this space, move through this space, exert forces on each others through this space. So space is a very real concept in terms of physical laws. Space obeys the laws of physics. So you can't say "well space is this idea to me, but it's a different idea to you." No, there are set in stone laws that it must obey.

    The other part of me thinks this is more of a philosophical question than a physics question though. Many philosophers could successfully argue that space is "just an idea." Have you ever heard of the famous "brain in a jar" argument? We could all be brains in a jar being manipulated by mad scientists. No fact could ever dispute this, as much as you'd like to think or say, you can't have an objective truth about such a thing. So, philosophically, I believe there is no objective truth, so many people could successfully claim that to humans space is simply "an idea" to help us understand the laws of physics, but perhaps space doesn't exist and is just an idea that helps us explain the laws of nature.

    So from a scientific point of view, I agree with you. Philosophically, in slight disagreement.
  4. Oct 1, 2012 #3
    Well yes, I agree philosophically with what you stated. However, my brother is supposedly taking this on a scientific stance, he just told me such, thus we just can't seem to come to a definitive conclusion scientifically.
  5. Oct 1, 2012 #4
    Well I think space is very real then, scientifically speaking. It's just as real as time, and as far as I'm concerned, time is a proven entity in physics, just as space is. So if you want an argument, talk about how space is necessary for the vast majority of physical laws and equations. Also maybe ask if he thinks time is just an idea, because I don't see space as any less real than time.
  6. Oct 1, 2012 #5
    I told him exactly as you said but his head just can't seem to get around the idea that space exists, not as an idea, but as a physical plane for matter for act in. He did say, however, that time does "exist" with the past, present, and future happening "at the same time" in which I agree, but now he also thinks that time is just an idea. After hours of debate I feel ready to simply give up on him and his illogical theories.
  7. Oct 1, 2012 #6
    look buddy, we perceive both space and time.

    stretch out your arms, look at your watch.
  8. Oct 1, 2012 #7
    I think you need to define your terms precisely before debating the nature of them. Do you both agree on the meaning of the word "space"? Because otherwise you're debating semantics.
  9. Oct 1, 2012 #8


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    And the meaning of "an idea".

    That looks like a pure wording issue to me. See if those different words lead to different predictions about observations. If not, it is pointless to discuss it. If yes, it can be tested.
  10. Oct 1, 2012 #9
    It's important to understand that physics is not about what something truly is. It's about how things behave. In fact asking for the true nature of something may be as meaningless as asking for the true speed of an object. It's relative.
    That is because instruments can only measure behavior. There is no way to measure the true nature of something.
    The behavior of the world is expressed in two ways. Equations and models. Every concept in physics that is not an equation is a model. Matter, energy, space, time, gravity, force, velocity, electrons, protons, etc. Simply everything.
    A model is a way to think about something or a mental image that in combination with the right equations allows you to make predictions about the physical world. But models are always limited. They don't work correctly under every circumstance. e.g. you can model electrons as particles and get correct predictions for many experiments but for some experiments the predictions will be completely wrong because an electron doesn't behave exactly like a particle. Thats even true for a macroscopic object e.g. a stone. It behaves only approximately according to Newtons laws.
    Now the concept of space is a model of course. But that model works very well and usually makes correct predictions. So you could simply define the word "real" to mean any model that makes correct predictions. In fact that's pretty much the only definiton of "real" that makes any sense in physics. So then space would be perfectly real.
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