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Questions and Doubts about the Big-bang

  1. May 5, 2005 #1
    Taken from http://http://ssscott.tripod.com/BigBang.html

    Einstein's Theory of Special Relativity says that an object travelling at the speed of light will go into the future, and an object travelling at speeds more than the speed of light will go back into the past. Is this correct?

    Why? Don't ask me, but I guess that must be correct since it is accepted by the scientific community, so I'll have to take it for granted.

    Now, according to the theory of the Big-bang, the particles that were blasted by the explosion should have travelled back in time. And if they have maintained the speed (which was greater than c - the speed of light - ~300 000 km/s) long enough, they should have travelled way back, before the Big-bang.

    Now, you could say that the only thing that was "undergoing a rate of expansion many times the speed of light" was the dimension of space.
    But let me give you this good example: Say we have a big rubber band with people on it. Stretch the rubber band and the people will recede from each other.
    Thus, if the dimension of space was expanding, particles contained by this dimension must have expanded also.

    If those particles travelled somewhere, sometime before the Big-bang, where and when did they end up? Since the dimensions of time and space started to exist at t=0, the Big-bang.
    When I say "particles" I refer to the Universe as has ever been, in a form or another.

    We, even now, don't know the speed at which galaxies are receding from each other, or from their place of origin. We only know their speed of recession relative to our solar system (or Earth): which is ~ +72 km/h per 3.26 light years of recession.
    Our solar system is moving too. So the speeds of recessing galaxies are surely greater.
    My question is: what if the galaxies' speeds, relative to an inert point in space, are still greater than c?
    This would mean that we are still travelling back in time...

    2. The Big-bang Theory says that prior to the great explosion, there was only one minuscule "primordial atom" or "nucleus". It also says that at the time of the explosion the dimensions of time and space were created.
    The problem is: were did the primordial atom reside in?
    Or was it that the only space available was the one occupied by the primordial atom?

    3. I know that scientists haven't decided yet if the Universe is infinite or not.

    I have an argument, but it is supported by the Big-bang theory, so it's pretty weak:

    An infinite amount of matter cannot have a shape. To figure out it's shape, one must reach it's borders, but it is impossible since the amount is infinite.
    The standard model Big-bang suggests that prior to the explosion, the Universe was compressed into a minuscule atom. We have our shape, thus the Universe is finite.

    4. How did Friedmann and Lamaitre find out that the dimension of space is expanding?
    I mean, we cannot measure it's expansion, because along with the expansion of space, we have the expansion of its contents. So this means proportions are kept.
    Even reaching the margins of space, one cannot observe that it is expanding, because proportions are kept, and there is no exterior point to the Universe, to which we can compare distances.

    Please share your opinions and arguments/counter-arguments about this.

    P.S. I don't have thorough knowledge of the Theory of Relativity and I'm not sure that this is the right forum to post this thread in.
     
  2. jcsd
  3. May 5, 2005 #2
    "Einstein's Theory of Special Relativity says that an object travelling at the speed of light will go into the future, and an object travelling at speeds more than the speed of light will go back into the past. Is this correct?"
    - SR says nothing with mass CAN reach the speed of light. I read Einstein's book Relativity and it said nothing that you said. I think Star Trek IV - The Voyage Home was the thing that proposed the theory you mention.

    "Now, according to the theory of the Big-bang, the particles that were blasted by the explosion should have travelled back in time. And if they have maintained the speed (which was greater than c - the speed of light - ~300 000 km/s) long enough, they should have travelled way back, before the Big-bang."
    - The thing with expansion is it is the space between particles that expands, not particles being 'blasted' away. I don't know of a speed limit for space expansion. I know there is a question of why the universe looks similar on both sides when no light could have made it from one side to the other during this inflationary period, but I don't know if there's an answer. You have to remember that anything travelling at any speed does not feel the effects of relativity upon itself, it is only when viewed by something else in a different frame of reference. A photon receding at the speed you talk about would not be seen. Talking of which, mass as far as I am aware came later, so we're talking pure energy here, which has no trouble travelling at light speed right now.

    "Now, you could say that the only thing that was "undergoing a rate of expansion many times the speed of light" was the dimension of space.
    But let me give you this good example: Say we have a big rubber band with people on it. Stretch the rubber band and the people will recede from each other.
    Thus, if the dimension of space was expanding, particles contained by this dimension must have expanded also."
    - Well if the laws of physics were anything like now, there would have been a Doppler effect, yes. Photons would have lost energy, or cooled down.

    "If those particles travelled somewhere, sometime before the Big-bang, where and when did they end up? Since the dimensions of time and space started to exist at t=0, the Big-bang."
    - Look at it this way. Say there were only two photons created by the big bang and the space between them was expanding faster than the speed of light. Now, according to you, in one of those photon's frame of reference, the other would have travelled back in time. In the other's frame of reference, the first would have travelled back in time. So now are they both going backwards? Okay, so backwards, one of them to the other would now be going forwards. And the other one to the first. Welcome to the brain-bending of relativity. Neither are going backwards in time... like politics, it's all about appearance, and since they can't see each other anyway, they can't observe each other to be going back in time.

    "We, even now, don't know the speed at which galaxies are receding from each other, or from their place of origin."
    - There's no such thing as a 'place of origin'. Every point in space now comes from the big bang. There's no other place in space where a galaxy really came from. There's also no such thing as an absolute speed... any relative speed is as good as another.

    "My question is: what if the galaxies' speeds, relative to an inert point in space, are still greater than c?
    - This would mean that we are still travelling back in time..."
    We wouldn't see them, that's all.

    "2. The Big-bang Theory says that prior to the great explosion, there was only one minuscule "primordial atom" or "nucleus"."
    - No, the old exploding pie notion is a myth. There was no such thing.

    "An infinite amount of matter cannot have a shape. To figure out it's shape, one must reach it's borders, but it is impossible since the amount is infinite."
    - An infinite amount of matter would also never get off the ground, so to speak.

    "The standard model Big-bang suggests that prior to the explosion, the Universe was compressed into a minuscule atom. We have our shape, thus the Universe is finite."
    - If you're interested, Einstein's theory was that the universe was infinite but bounded... like the area of the earth. You can just go on forever and get back to where you started.

    "I mean, we cannot measure it's expansion, because along with the expansion of space, we have the expansion of its contents. So this means proportions are kept."
    - The thing is, it is believed to be expanding equally everywhere. Take two neighbouring galaxy clusters, figure out their gravitational attraction, add that to their rate of recession and you have the expansion of space. Okay, it's probably a lot more complicate than that, but it's the basic idea. You've also got background radiation to go by... right now it's microwavey, but originally it would have been gamma-ish. The expansion would have caused that Doppler effect.
     
  4. May 5, 2005 #3
    To simplify your time-travel theory, think of a planet with one ship one one side of it and another on the other side. The two ships leave the planet at 90% SoL. Now, in ship 1's frame of reference, according to you, ship 2 will be travelling at 1.8 SoL and should travel back in time. But to ship 2, ship 1 will be travelling back in time. And to a guy back on the planet, neither are travelling back in time. Speed leading to time travel makes no sense.
     
  5. May 5, 2005 #4
    Then it must have been a myth of mine; I've never completely understood Relativity since I haven't read it in my native language.
    Are tachyons without mass too? I've heard that they go beyond the speed of light.
    What happens if something has a speed greater than the one it needs to reach a certain point instantaneously? Or is that possible?

    Weren't photons carried along with the expanding space as the rest of particles were?

    Relative to each other, shouldn't they remain in the same time?

    If it is only about appearance, then why are those examples of one twin aging and another not?
    Also, why is observation so important?

    Have you taken into consideration the fact that time is in reverse?
    I have a hunch that this would explain the previously unexplainable recession (when scientists expected things to slow down).

    What is the current theory then?

    What do you mean?

    Yes, I'm aware of that. But did Einstein say anything about its creation? I know that he agreed with the Big-bang.
    Also, I'd don't think the Universe is infinite anymore if we regard it this way - a human being might tell that he is running in circles.

    I'm not quite sure - do microwaves have lower frequencies than gamma rays?
    Also, can only the expansion of space cause this lowering of frequency? (I don't agree with this).

    I understand your example. But why would ship 2 travel back in time with respect to ship 1's frame of reference?
     
  6. May 5, 2005 #5
    Yes, tachyons are the other way round. The speed of light is a limit that can't be reached. The reasoning behind tachyons is that there is no reason why the speed must always be one side of that limit. Therefore tachyons have a minimum speed of the speed of light. These are not strong scientific theories, though, and they are not in favour in the scientific community. As such, I have little knowledge of them.

    Well... lets start with instantaneity. Quantum entanglement and time travel is a subject I've literally just got off and I'm asking for some more information. I think quantum entangelement is about quantum states (I'm shaky here so somebody else might need to butt in). If you have two adjacent particles occupying all the allowed quantum states, then separate them, a change to a quantum variable (such as spin) in one necessitates instantaneous change to the other. A possible medium might be a particle travelling back in time from one of the pair, then forward in time (or vice versa) to reach the other at the time it originally left the first. If the medium was a photon, it would look like two photons being absorbed at the same time and having opposite effects (probably a bad choice... I have no idea how you change spin )o: ). If this were true, then there would be no reason why the photons had to be absorbed at the same time. The photon could arrive at its destination before it set off. That's about the only thing I can think of where you might say something travelled faster than an instant, and I don't think it's really the thing you had in mind.

    Well... yes. And still are. Hence the Doppler effect. In the time it takes a photon to reach us from a galaxy receding from us, the distance will have increased, but the photon will have arrived in the same amount of time as if it hadn't with only its energy diminishing. Same thing during expansion.

    If one photon is travelling FTL with respect to the other, does that not in your outline lead to that photon travelling backwards in time?

    These are not examples of travelling backwards in time - these are cases of time travelling differently for different observers. While general relativity back offer the ability to travel backwards in time (or, more accurately, arrive earlier than you left), all special relativity can afford you is that time will run slower for you than your friends, if you travel fast enough.
    Why is observation important? Imagine a universe with a single solitary particle in it. Is it moving? How could you tell? If there were to and they were getting closer, is one moving towards the other or are they both moving towards each other? Are they moving at the same speeds or different ones. Absolute values of speed, size, energy, mass, time don't exist. All you can say about something is what it looks like in a given frame of reference.

    I don't see why it would be. If something were receding from us at SoL, then any it light coming from it would be red-shifted down to nothing. No such galaxy would be visible to us at all. Why do you think FTL travel would make something travel backwards in time? Time dilation occurs in Special Relativity. Time travel, to my knowledge, does not.

    The big bang theory. Or more accurately, the hot inflation model. Space and time appeared from a point containing all the energy in the universe. There was no dense super-atom waiting to explode. There was no space for it to occupy or time for it to undergo whatever process made it explode.

    An infinite amount of matter would have an infinite amount of gravity therefore could never separate.

    No, no. No-one believed in that kind of thing then. Einstein believed the universe was completely stationary, had existed for all of time and would continue to exist for all of time. Ironically, though, his own theory said the universe should ventually collapse in on itself under its own gravity. Unable to accept this, he added a 'cosmological constant' to his equations that kept the universe static. When cosmology got off the ground, he referred to this blatent fudge as 'my biggest blunder', a famous quote, and proof he never looked in the mirror cos quite obviously his biggest blunder was his choice of barber. So - no - Einstein held out against any kind of expansion or contraction until he hadn't any choice but to accept it.

    They certainly do. In fact they are at the opposite ends of the frequency spectrum.

    I've yet to hear of another reason.

    Well, it wouldn't. That's the point. But you were supposing that FTL travel causes you to go back in time. Well, in ship 1's frame of reference, ship 2 is travelling at 1.8 times the speed of light.
     
  7. May 7, 2005 #6
    Then you'd have a photon appearing out of no particular reason (or better said, out of nothing) in your own time frame, considering you were observing those particles prior to the change of quantum state.
    Also, are you suggesting that photons may be an information-carying medium?
    And I would really like to know why two particles cannot be in the same state simultaneously (this sheds new light: the photon which you speak of would have to leave the state-changing particle and reach the second particle and all this prior to the first particle's change so there wouldn't be two identical quantum states simultaneously - it's like foresight, lol - I hope you understand me here).

    I think I'm lacking knowledge here: isn't motion the cause of frequency lowering?
    And if so, then the photon inside expanding space is not moving, thus it shouldn't lose energy (it's like carying the photon on a plate - it is not moving, you are).

    I can't understand your words; and what's FTL?

    I still consider it time travelling: From the accelerating twin's perspective, time for the stationary twin should run faster (say, when one second passes for the first twin, two will have passed for the stationary one - thus, he will seem to be in the future, won't he?)

    About observation,
    I have a hunch that this was set as a scientific epistemology.
    I mean, that single particle could have been moving, it's just that the scientist can't decide whether or not it really is.

    About the perfect reference frame (or whatever is its name): Couldn't scientists find out a place where if they were there, they could be in total rest - and thus decide an absolute speed for particles?

    Isn't it necessary for energy to occupy space?

    I don't see it that way.
    Let's imagine that that infinite primary chunk of matter were composed of different types of particles with different "amounts" of gravity.
    The overall gravity of this infinite primary chunk of matter would be infinite, but if we go down to particle level, then it wouldn't be so - thus, the particles would be able to break apart.
    It's also very clear that it must be so if you believe that our real Universe is infinite (I know I don't); infinite amount of gravity, yet particles are still able to roam freely.

    He argued for a stationary Universe prior to the confirmation of Big-bang hypotheses. When those hypotheses were confirmed (the recession of galaxies, etc), Einstein changed his equations - so I guess he was compelled to agree with the Standard Model because of the undeniable proof.

    P.S. If it weren't for his hair, he wouldn't have been so famous today (lots of people know him, yet they don't have the smallest clue about what he has done).

    As I've stated before, I believe the motion of the particle to be the cause of lowering of frequency. If the particle is carried by the expanding space, then it means that it is doing absolutely nothing - it's just being carried - how can it lose energy without cause?

    I see clearly now. :) Thanks for all the information.
    P.S. Excuse my grammar mistakes.
     
  8. May 7, 2005 #7

    Chronos

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    You need to read more about GR. You are attaching strings to hooks that do not exist.
    Think the pauli exclusion principle.
    Faster than light.
    So what's your point?
    The scientists will never agree which of them is 'stationary'. That is a fundamental concept.
    No, energy creates space.
    Report back after taking a Physics 101 class.
    It doesn't lose energy, it gets time dilated.
     
  9. May 8, 2005 #8
    Thanks Chronos. To expand on a couple of Paul's questions:

    No, that could not happen. Perhaps I chose a bad example, and it was pure supposition anyway, so take it with a pinch of salt. The photons would not appear out of nothing - they would appear to us (taking a forward-only time view) to have always existed. Also, in that bad example of mine, one photon wouldn't do it. There would need to be another going forwards in time that coincidentally changed direction in time at the same point in time and space. To us it would just appear to be one photon reaching each of the entangled pair at the same time. Like I said, take it with a pinch of salt. I know next to nothing about entanglement, but this was a possibility we had been discussing on another thread.

    Of course. Radio, television, mobile phones... in all cases the information-carrier is photons.

    Like Chronos said, it's the Pauli exclusion principal. I can't tell you WHY this is true, and in fact I got my head bitten off for trying on another thread, but it is fortunately so. Said principal also hammers another nail in the primordial atom theory I guess. There's no problem with photons occupying the same sapce, I believe. It's all down to spin or something. Don't ask me.

    Being a beginner to quantum theory, I cannot give you a quantum explanation for the Doppler effect. You have to let go of your earth-based notion of motion. Yes, a receding (to us) galaxy is in motion relative to us, but this perceived motion is caused by the expansion of space in between. For all I know, all motion is due to space being expanded and contracted by energy, forces, what you will. Now imagine a constant ray of light between two galaxies with a given wavelength such that it appears static. As the space between the two galaxies expands, that ray of light gets stretched and so the wavelength increases. If that's too simplistic (and inaccurate), think about the constancy of the speed of light. Imagine a charge oscillating up and down. This oscillation corresponds to the oscillation of energy density in a wave, and the time it takes to complete one oscillation is the period, which is also the period of the wave. As the speed of light is constant, the wavelength of light is associated to its period. If the source begins to recede with the charge still oscillating with the same period, then the charge is further away from its starting point during one position in its period than another, hence the wavelength increases. This is the Doppler effect, and without it we may never have known about the expansion of the universe at all (we also wouldn't have speed cameras so it's a mixed blessing).

    Ah, you're previous description of time travelling suggested particles moving backwards in time. Here, both bodies move forwards in time, but at different rates. More time will have passed for one observer than the other, so yes when the traveller returns he will seem to have travelled into the future - but we all do that anyway! But yes, he will have done more so than his twin.

    Moving where? Relative to what? It really makes no sense to describe something in an empty universe as moving when there is literally nothing to move towards or away from. It's like asking whether an atom is a solid, liquid or gas - motion is a property of emergence and is entirely relative.

    I'm afraid not. There will always be something moving towards or away from you (as at the very least the universe is expanding) and so it would be equal true to say that you are moving towards or away from it. No such place exists. There are no special points in space.

    The amount of matter in the universe is strictly finite, hence no problem. However, there is the question of why gravity isn't working as hard as it should be - the expansion of the universe should slow down not speed up. All sorts of theories. Gravity is cumulative and, as Newton will tell you, works in such a way that the total gravity of an aggregate of smaller objects can be conceived as that of one big object from its centre of mass. So 17th century physics that are still the bees knees say no.
     
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