Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Parallel Worlds: A Question From Olbers' Paradox

  1. Aug 5, 2005 #1
    I understand that background radiation that we observe actually dates from the time of the creation of the universe (The Big Bang).

    I also understand that nothing can travel faster than the speed of light.

    My question is how did we (the solar system) get here before the radiation did considering that we were both at the same point in space at the time of creation?

    Have we somehow travelled faster than light to get here before light itself? Or am I missing a fundamental point here? :confused:
     
  2. jcsd
  3. Aug 8, 2005 #2
    Sticking with the Big Bang theory the universe was opaque for the first couple of minutes. I suppose it matters which reference frame you use for the exact time but given it took some time for hydrogen and space itself to become transparent.

    So that’s the earliest the CBR could start on its way to us. With the cosmos already some real size, I don’t remember how large; google for a BB time line.
    Already in major motion we’ve been separating from the ‘stuff’ that made the CBR we now see all this time.

    Just as the ‘stuff’ that eventually turned into us sent out light back then as well. And it is just now that light is also reaching, as a CBR, a part of the Cosmos that was built from the stuff that sent the CBR that we see here.
     
  4. Aug 14, 2005 #3
    I'm not really sure what you're asking. Background radiation was here before the solar system started forming. The background radiation was formed in the hot, practically homogeneous gas that existed in the early universe. It's since cooled down to about 2.7K.

    How the solar system and everything else formed is described in Fabric of the Cosmos, where it's theorized to have come from random fluctuations and irregularities in the spacetime fabric that stretched to enormous proportions during the inflationary expansion (the higgs field coming off its high-energy plateau in nonuniform ways). This gave rise to enough irregularities in the background radiation that particles in various regions gravitated towards each other and grouped to form larger masses.
     
  5. Aug 14, 2005 #4

    My question is centered on the fact that nothing can travel faster than the speed of light. At the time of the big bang, we were created as was everything else, including the cosmic background radiation. So bearing in mind that nothing can travel faster than the speed of light, how did we get ahead of the light (from where we started at the big bang) before the cosmic background radiation did.

    From what you said though, I suppose that the irregularities and fluctions in space time could explain this so, if the laws of physics break down due to such irregularrities.

    BTW, is the fabric of the cosmos that you mention the book by Brian Greene?
     
  6. Aug 14, 2005 #5
    Did you understand the point that the CBR we see did not start from the Big Bang but from a time shortly After BB? A time when the cosmos became transparent so that light could move through space.
    Thus the CBR we see comes from a place NOT “from where we started at the big bang” but someplace already moving away from us..

    And the CBR light that ‘we’ created back then, is now reaching whatever solar systems have developed at the places that we see CBR coming from and reaching us now.

    Obviously for the light from those places to take so long to get here and to Red Shift so much would require that even then (ie. Shortly AFTER the BB) we’d have been traveling apart very fast. On your other point that, this large Red Shift would require separation speeds much faster than light. There is a lot of speculation on this point.

    A couple explanations:
    1) look up “Tired Light”; generally considered some where between being ‘just wrong’ to a ‘crack pot idea’.
    2) look up “Hubble Expansion”; A better explanation the basically says before the light gets to use additional space is being created some how between us so the light is traveling a greater distance than would have expected due to simple separation caused by speed.

    Hubble has its detractors, but it is generally accepted as best explanation.

    Are the detractors correct and Hubble wrong?, Or how is the extra Hubble Expansion space actually created? I’m not aware of anyone publishing a definitive answer either way yet.
     
  7. Aug 15, 2005 #6
    You guessed it.
    There was a PBS special about his book Elegant Universe a few years ago.
    He really screwed up one of his analogies (where was jumping off a building...I won't go into it). :rolleyes:
     
    Last edited: Aug 15, 2005
  8. Aug 15, 2005 #7
    I think what Crumbles is referring to is how is that we are seeing baby pictures of the universe. In other words, if the explosion occured, how can we look into deep space and see the beginnings when (assuming we are looking at photons) light travels outward much more quickly than matter.

    I take it from these replies (sorry, did not study them all closely but...), we (matter/solar system) were created much later after the acceleration slowed down and that's why we are so far away from the beginning point.
     
  9. Aug 16, 2005 #8
    When you say that the universe was transparent and light moved through space, do you mean that there was no matter, no dark matter, maybe even no dark energy (no spacetime fabric or whatever) for the light to travel through; that space was empty except for light?
    And wouldn't that be impossible? I mean, there can't be a completely empty something, can there? If space had truly been empty at some point, wouldn't space have all collapsed or crunched like it does in a true vacuum?

    Is space not defined and built by what's "in it"? Isn't space (the area that matter and energy occupy) somehow 'held up' by the outward push of dark energy (and perhaps to a lesser degree, dark matter and matter)?
    Or maybe it's something entirely different?....like, is it that there really is no dark energy but we have to give a name to the "force" that we think is causing the expansion? In other words, there is no force causing expansion but that expansion, as was hinted earlier, is just a continuation of the movement of the big bang explosion (albeit slowed)?
     
  10. Aug 17, 2005 #9
    ??????...I'm not sure if your joking or just haven't read about the big bang.
    First "Big Bang" is just a name - it does not mean 'explosion'

    Yes the universe IS transparent - look up at night we see stars with light moving through the universe to see them by ie. transparent.

    The BB point: Is that at some point in the past (but not all the way back to the start of the BB) the universe was was to dense for light to move. To much matter for light to move though or get around.
    Much like we cannot see the Sun while we look at the stars - there is a locally dense area of mass in the way. We call it Earth.
    Untill the stuff got out of the way, giving a little room for light to move somewhere without being absorbed by something, there could be no start to CBR.
    Therfore, the universe as it started according to BB could not have any CBR moving about until the universe itself became transparent to light.
    So, Crumbles concern about "getting ahead" of our own light is unfounded. We are seeing the light "CBR" from someone elses begining mass not our own. CRB cannot reach all the way back to the very start of BB.
     
  11. Aug 17, 2005 #10
    That was exactly my point. I have always heard claims that CBR observed nowdays dates from very shortly after the time of creation. But after some reading from here it seems that it actually dates from about a few hundred thousand years after the big bang. So it would then make sense that it is only now that we are seeing the light. :smile:
     
    Last edited: Aug 17, 2005
  12. Aug 17, 2005 #11
    Actually, no, I wasn't joking. Maybe I should give you some background so you'll understand where I'm coming from. Right now, though, I'll address what you said about Crumbles' concern over "getting ahead" of our own light being unfounded.
    In one sense, it is technically unfounded, yes. However, you have to consider possible scenarios before assuming why Crumbles came to that conclusion. For instance, it's been said more than once that scientists now have pictures of the Big Bang. Some of these statements may or may not have mentioned that these photos were actually pictures of what happened
    immediately after the big bang but the bottom line was that there was no further explanation given.
    Based upon such a short statement with no details given, one might easily conclude that the "pictures" or light (pictures brings to mind "light" being involved) should be propelled further from the point of origin than we (matter) are.
    The replies given to Crumbles have somewhat filled in more of the details about what the pictures of the big bang really are. But based upon the type of scenario I mentioned, it's completely understandable, in my
    opinion, how Crumbles first got the idea and it was actually a very perceptive observation.

    As for me, I do not know much about the big bang. What little I know, you will find conveniently embedded in the following paragraphs, where as I promised, I would give you my background.

    First off, I hope you don't assume that everyone who comes to Dr. Kaku's forum are highly educated or knowledgable on every detail of physics.
    Dr. Kaku speaks to the general public, not just to academicians. I fit the first category. I'm fairly good at spelling and somewhat articulate and maybe that
    might seem incompatible with the fact that I'm not very educated- didn't get past 7th grade science and never took biology, chemistry or geometry. And I'm quite certain that there are many other Michio Kaku fans in
    similar boats.
    What made my educational upbringing worse was that in those days ADD was unheard of and teachers assumed that a lack of concentration must be volitional (daydreaming) or that the student was simply stupid.
    Fortunately, my ability to concentrate has gotten better in recent years. For reasons such as this, I believe that people who are gifted intellectually are
    even more obligated than anyone else to treat everyone respectfully as if they are their intellectual equals.
    If someone is uninformed, why not inform them with a humble disposition? Educating others is a privilege. I suspect that Doc feels this way, also. His demeanor is never haughty, even when the silliest of questions (aliens, especially) is directed at him. This kind of humility is a common
    trait among many successful people.
    What I have heard of the Big Bang is that there was no empty space, basically nothingness before it occured. Some single, very dense, very hot (is it called a singularity?) came into being out of God-knows-where and it cooled and its denseness disintegrated as it expanded.
    The analogy of an explosion sounds as close as any other description that I can think of comparing it to. But of course there was no air, no empty space as is required for a regular explosion.
    Do I understand correctly that space, itself, was created as a result of the expansion? Here's how I picture the big bang. If you are old enough to have ever watched the Flintstones, perhaps you recall watching the little alien, Gazoo, pop into existence from apparent nothingness. Using this as a comparison to the big bang is, of course, flawed from the aspect that he's popping into an existing space as opposed to the big bang popping into nothingness. I don't believe in nothingness, to be honest, but the big bang from nothingness is so commonly referenced, Gazoo is the only way I can picture the big bang.
    The academic world has largely ignored the overwhelming prevalence of learning disorders. Those who have them have to work twice as hard as everyone else. So, there's no excuse for being impatient with or patronizing someone who simply wants to learn a certain subject but who might be having difficulty in some areas.
    I like Dr. Kaku's teaching approach. Whether he's educating the public or just speaking to his students or colleagues, he's able to describe things in such
    broad terms that make him easily understood.
    He may not always be as detailed as other teachers (Brian Greene as an example) but he is so very clear on what he does describe.
    Many of us may not have his gift of explaining physics so coherently, which can be exasperating, but it's important not to take that out on the person(s) we speak to.
    Shall we continue?
























    First "Big Bang" is just a name - it does not mean 'explosion'

    Yes the universe IS transparent - look up at night we see stars with light moving through the universe to see them by ie. transparent.

    The BB point: Is that at some point in the past (but not all the way back to the start of the BB) the universe was was to dense for light to move. To much matter for light to move though or get around.
    Much like we cannot see the Sun while we look at the stars - there is a locally dense area of mass in the way. We call it Earth.
    Untill the stuff got out of the way, giving a little room for light to move somewhere without being absorbed by something, there could be no start to CBR.
    Therfore, the universe as it started according to BB could not have any CBR moving about until the universe itself became transparent to light.
    So, Crumbles concern about "getting ahead" of our own light is unfounded. We are seeing the light "CBR" from someone elses begining mass not our own. CRB cannot reach all the way back to the very start of BB.[/QUOTE]
     
  13. Aug 17, 2005 #12
    Of couse not
    I'm sure few went though the entire long what ever that was.
    After all with a name like .....joker -- don't know what to expect.

    No I don't expect pro's but it is a good idea to do some basic Google look ups to find the easy stuff like a Big Bang Time Line etc.

    TIP on using the forum and getting used to using the quote feature.
    Use the "Preview Post" button to help edit your notes before posting to see how it wii realy look in advance.
    You'll get used to it quick enough
     
  14. Aug 17, 2005 #13
    Gosh and I wondered why so many people left this forum.
    Speaking of editing, you might want to invest in a spellchecker.
     
  15. Aug 19, 2005 #14
    Crumbles I think the simple answer that you are looking for is that space was created by the big bang as well as matter and there is no theoretical limit to how fast space itself can travel. The expansion of the universe is not limited to the speed of light.
     
  16. Aug 19, 2005 #15
    Excellent reply. Excellent spelling, might I add.
    Some people think to be a good scientist or engineer or mathematician, you have to be a bad speller.
    But Ed Witten is excellent at spelling, so it's a myth.
     
  17. Aug 20, 2005 #16

    Have you got any documentation on this?
     
  18. Aug 20, 2005 #17
    Crumbles I found this that addresses your exact question.
    http://www.wonderquest.com/ExpandingUniverse.htm
    These kind of fundamental puzzles are what makes physics interesting to me. Props to Dr. Kaku for inspiring us math-impared people to wonder about these things.
     
    Last edited: Aug 20, 2005
  19. Aug 20, 2005 #18
    Interesting webpage. As Dr. Kaku (also excellent at spelling, btw) has explained before, it states that a lot of things are additive, specifically the dark energy over large spaces.
    The no speed limit to expansion thing really throws me, though.
    I understand that dark energy is going to propel two things twice as far apart (if they are moving in opposite directions) but the speed limit thing, I don't quite understand.
     
  20. Aug 20, 2005 #19
    Yah it's difficult to wrap your head around space being created at all. I think if we look at the universe as a finite size like say, in a box. Can we say that the box can move? Move compared to what? By definition the universe contains everything. If the box could move it would move at infinite speed since it contains all of space and time.(not really true beause it is nonsensical but you get the idea) In this same way if we envision the very edge of the universe, the relative speed between space expanding outward and 'nothingness' is infinite.
     
    Last edited: Aug 20, 2005
  21. Aug 21, 2005 #20
    I don't get the speed limit thing either. I mean why would you say that the speed of space expanding outward is infinite relative to the nothingness?

    I mean if you take a piece of stretchy material and stretch it, the speed of the expansion of its edge relative to the outside world = the speed of expansion of any two points on the material itself.

    In other words, the speed of expansion of the universe = the change in distance between any two bodies in the universe divided by the time it took for the change. (assuming the universe is expanding uniformly of course).

    So I just don't see how this explains the no-limit to the speed of expansion.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Parallel Worlds: A Question From Olbers' Paradox
Loading...