Moving at light speed

[Buffy]

...he 3d part comes into it by my travelling perpendicular to the plane coordinates of the sphere, up or down I'm supposing they are all the same, I would not cross the centre of the sphere I would now be travelling a perpendicular sphere. So the sphere model you describe is O.k. as long as you realise that any direction you travel in 3d spacetime you are always travelling along the circumference of the sphere.

Start even simpler: you're a 2d person on a table: you know forward-backward, left-right and that's it. if a 3d person puts a glass on the table it "appears out of nowhere" because you have no way of conceiving up-down. Now bend the table around to form a sphere. You *still* have no concept of up-down, so you have no way of conceiving how you could possibly end up in the same place by travelling straight. its all flat to you, and things can only curve in the two dimensions you know, it can't curve "up" or "down" which as 3d people we easily perceive in the balloon the 2d people live on.

 

Keep thinking....

 

Cheers,

Buffy

[Damo2600]

Hey everybody,

 

The model for the universe that Buffy is explaining is thus:

 

Now imagine space as infinite. Any direction you travel you keep on going from your start point at an ever increasing distance: never returning to your start point.

 

Now imagine this doesn't exist: nothing.

 

Now imagine two seconds on a clock. There is no time inbetween these two seconds. You have one second followed by another second. There is a point in the middle with no time duration. Right? Just like the point between two snooker balls that are touching.

 

The second before this point we don't know what existed. Right?

 

Now at this point; time did not exist; space did not exist. At this point in time nothing at all existed.

 

This is different to a point in time that we experience now. The point between this second and the next second the universe still exists. Right?

 

So at this point nothing exists.

 

Then, during the second after this point, 'nothing' exploded in a firey, hot, density. Now it didin't just explode from a point and expand. No. The nothing exploded everywhere within a point and continued to expand. Further to this model the nothing exploded in such a peculiar way that, like the back drops that animators use to save on drawing time, when you get to the end of the universe you are now back at the begining. Due to the expansion however, unlike the backdrops animators reuse, the backdrops are the same images only there is more space between the images.

 

A further peculiarity to this strange explosion of nothing is that if matter hapens to meet, and fall into, a black hole, then, this matter instantly is also residing in another black hole half way between the distance of where the matter is now and in a direct straight line (in any direction mind you) to the same position of where the matter is now.

 

Does anyone have any opinions on this?

 

Damien

[Tormod]

Now imagine space as infinite. Any direction you travel you keep on going from your start point at an ever increasing distance: never returning to your start point.

 

How is this related to what Buffy wrote...?

 

Now imagine this doesn't exist: nothing.

 

Huh? Now I'm confused. What are you trying to say, Damien.

 

Now imagine two seconds on a clock. There is no time inbetween these two seconds. You have one second followed by another second. There is a point in the middle with no time duration. Right? Just like the point between two snooker balls that are touching.

 

Ignore the ticks of a clock. To us time is flowing constantly. There is no isolated moments of time. There is a theoretical "planck time" which is about 10^-43 seconds, which is considered the "smallest quantum" of space, just as the photon is the smalles quantum of electromagnetic force.

 

But there is never "no time". And I don't understand how this relates to how two snookers balls touch.

 

The second before this point we don't know what existed. Right?

 

So I gather you are talking about the Big Bang? Correct, we do not know what existed before the Big Bang.

 

Now at this point; time did not exist; space did not exist. At this point in time nothing at all existed.

 

Time and space as we know it today did not exist. We don't know if something else existed. As we established already, something must have existed.

 

This is different to a point in time that we experience now. The point between this second and the next second the universe still exists. Right?

 

No, this makes no sense. The "before the Big Bang" time cannot be measured by our clocks because time in our universe started at the Big Bang.

 

Now go ask a string theorist about that and they might argue that sure, you can keep looking back beyond the big ban with the same time ticking away...

 

Then, during the second after this point, 'nothing' exploded in a firey, hot, density. Now it didin't just explode from a point and expand. No. The nothing exploded everywhere within a point and continued to expand.

 

No, there was no "nothing". You are convoluting the issue by saying that over and over. And there was no explosion. The energy packet that contained all the energy in the universe today began expanding. That is what happened at the Big Bang. We simply don't know what triggered it, although this is often explained by a "vacuum fluctuation" (which makes no sense if you have no vacuum to begin with).

 

Further to this model the nothing exploded in such a peculiar way that, like the back drops that animators use to save on drawing time, when you get to the end of the universe you are now back at the begining. Due to the expansion however, unlike the backdrops animators reuse, the backdrops are the same images only there is more space between the images.

 

Again, it was not an explosion but an expansion of a packet of energy. The above statement I do not understand.

 

A further peculiarity to this strange explosion of nothing is that if matter hapens to meet, and fall into, a black hole, then, this matter instantly is also residing in another black hole half way between the distance of where the matter is now and in a direct straight line (in any direction mind you) to the same position of where the matter is now.

 

I think you are confusing black holes with (highly theoretical) wormholes.

 

Does anyone have any opinions on this?

 

Of course. My opinion is that you are starting to see that there are lots of different aspects to this stuff - it no longer falls into the heading "moving at light speed". Lots of this stuff has been discussed before, both in the physics/math forum and also in the astronomy/cosmology forum. You might want to backtrack into those forums here at Hypography to see if you can find other discussion, or start new threads so we can separate the topics a bit. Now you are starting to discuss cosmology at a very broad level so it gets very difficult to keep up with all the details without breaking them apart.

[Damo2600]

"This is getting at why its so hard to comprehend. Because its spacetime not space and time, when the big bang "happened" not only was there no space, there was no time either. There was no "outside" for it to "expand into". And hardest of all is the crux of the matter: there's no sphere, there's no edge, its expanding everywhere in every direction. So to answer your question directly, there wasn't anything at the big bang (before, we have no idea, maybe it was finishing a crunch, but we have *no* way of finding out as far as we know), you can't think of it being a "singluarity sitting in a bunch of gas before it went bang.""

 

Hi Tormod,

 

I didn't say it was wrong. I merely stated the model as it was told to me. (Note above comment.) I'm sorry if this is not about 'the speed of light' the subject merely evolved to this point. If not 'physics and mathematics' which field do you think it comes under? I thought physicists were a major part of coming up with big bang models.

 

So it was not an explosion. O.k.

 

Some of your view points, on the big bang, appear to be different to Buffy's. I am interested other people's explanations of this big bang model. Which is why I asked for others opinions...

 

Damien

[Buffy]

...So to answer your question directly, there wasn't anything at the big bang (before, we have no idea, maybe it was finishing a crunch, but we have *no* way of finding out as far as we know), you can't think of it being a "singluarity sitting in a bunch of gas before it went bang.""

I didn't say it was wrong. I merely stated the model as it was told to me. (Note above comment.)

The first part of that sentance I overstated, so it did sound like it was in disagreement with Tormod, but I was oversimplifying and we basically agree: there was not nothing, but there is a kernel of truth to the "there was no time" which is part of the explanation as to why it "expands" in such a strange manner. I think Tormod and I repeated the rest of it the same way.

 

There are a bunch of topics here, and it would be good as Tormod says to break it up, or look around some more and come back. We definitely digressed a bit, but your argument that the galaxies furthest away from the "center" of the universe are moving at the speed of light (which is kind of where we relevantly took this thread) *is* an interesting one to talk about, but it may be useful to discuss the building blocks of this issue elsewhere.

 

Time for the rest of you cosmology fans who've been hiding from this thread to step in and say something... Maddog? C1ay? Hmmm?

 

Cheers,

Buffy

[Damo2600]

I'll wait then to see if there are other people who wish make a comment. In the meantime are you going to comment on my relativity post #77.

 

Thanks

Damo

[Buffy]

My response to your post #77:

But I can use the same example to show that the time dilation is merely appearance. Imagine two towers both 20m in height. One however is on wheels moving toward the other. A top of each tower sits two observers. Each observer has a clock and prior to the experiment all clocks were syncronised. The first observer on each tower flashes a light ray down to the bottom of the tower which is reflected back up to the top of the tower and the observers record their elapsed time. The second observers record the elapsed time of the light rays with regards to the opposite towers. The two towers meet up and all four observers compare results. All of the clocks remain syncronised. The first two observers recorded equal elapsed time for the light rays they observed.

A few complications:

• The folks in the moving tower will experience *real* time dilation. If everyone synchs their chronometers to start, when they check back, the folks in the moving tower will say its 11:00 while the folks in the stationary tower will say its 11:01.
  
• It doesn't matter where the mirrors are to measure the speed of the light being flashed, both sets of observers will record the same speed for light.
  

Its not appearance, it actually happens and folks put synced atomic clocks in an airplane, flew around for a long time and landed and the clocks were different....Strange, but true.

The second observers give equal yet slightly longer elapsed times than the first two observers. The two towers were symetrical and the results were also symetrical. The experiment could also be reinacted with a mirror at half way and the velocity of the tower cut in half. In this case the stationary tower doesn't need to exist. Keep this in mind. The second observer on the first tower observes an event that happens relevant to the first observer on the second tower. Their recorded times are different. However if the second tower is merely a reflection of the first tower then both observers are actually stationary to each other and their respective time frames are exactly the same.

The observers in both cases record exactly the same elapsed time for light travelling the same distance. To the stationary observers, the clocks on the moving tower seem to be moving slower, but they'd see the light beam on the moving tower properly moving at c, even though the remote clocks appear to them to be moving slower *and* the moving observers record the same time! ;)

I understand however that it is much more difficult to discern the illusion if: Qwfwq is stationary in space and I travel at 60km/s ... However all our time frames are actually equal.

We all perceive events as normal. Everyone else is slowing down, but our time frames are not equal. Note with all these examples, there is a notion of the "local frame of reference" (the stationary tower, the airport that the planes with the atomic clocks took off and landed at), that provides a key element of this paradox: there IS a way to say "he was moving and we were stationary." In your example, if the two towers are on parallel tracks, start in the mid point of those tracks, make a full round trip taking a measurement as they are whipping past eachother then meet in the middle again, the full round trip will *cancel* the effect, and it will look like what I think you're trying to argue would be and "illusion" of time dilation. The problem is that the act of *traveling back* cancels out the the dilation, resynching the clocks!

 

Cheers,

Buffy

[tarak]

Just an observation.Although theoretical,the moment we say a body with mass zero,there is no body.

[Qfwfq]

Hi Qfwfq,

 

I didn't quite understand your language clearly enough. I did state that I was happy with the explanation of the Lorentz Transformation. I have been assured that this is empirically correct. I don't have a problem with it. I am getting from your post though that time does not slow down. My clock ticks at the same rate yours does given we are travelling at different velocities. However the illusion created by this universe gives me the impression that events are taking place at different times than they are for you.

 

Is this correct?

I'm sorry Damien if I wasn't clear enough but I can't really know what you understand and don't. I can't follow this whole thread either but I can try to help you. Let's try a specific case:

 

If you consider two people, each at constant velocity, which also means going straight, each will see the other's clock as ticking slower. Which clock is actually going slower? As long as they both continue to travel, both straight at constant velocity, there is no way of experimentally matching up how much time has elapsed for one and for the other.

 

Smart Alec says: "Well then, let's have them depart from each other and then later meet again. If they have each seen less time elapse for the other, so should they when they meet again. But this would be contradictory."

 

It would indeed be contradictory and this is known as the twin paradox. It obviously can't happen, where is the argument wrong?

 

If they departed from each other and later met, they did not both travel straight and at constant velocity. If one of them did, the other clearly did not and will have aged less than the one that did not accelerate.

 

Smart Alec replies: "But, if motion is relative, which one is the one that accelerated?"

 

When I say constant velocity or not accelerating, what I really mean is an inertial frame of reference. Einstein's paper "Zur Elektrodynamik Bewegter Körper", published exactly 100 years ago, is based on the principle of relativity for inertial observers, just like Galileo and Newton had considered it, except for the inclusion of time as a geometrical dimension subject to coordinate transformations like the spatial dimensions. Later Einstein used the principle of equivalence to work out General Relativity, which contemplates more general coordinate transformations, and the earlier work became known as Restricted, or Special, Relativity.

 

In General Relativity there is still the notion of locally inertial frames of reference. Lorentz coordinate tranformations hold, locally, between them.

 

Just an observation.Although theoretical,the moment we say a body with mass zero,there is no body.

I disagree with this. What is meant by there being or not being body? Is an electron a body and a photon not?

[Tormod]

If not 'physics and mathematics' which field do you think it comes under? I thought physicists were a major part of coming up with big bang models.

 

Yes, they do. But cosmology is the overarching field here, incorporating astrophysics, mathematics, theoretical physics and philosophy. When you discuss things like cosmic expansion, black holes, and the Big Bang you are basically discussing cosmological models - which belong in the AStronomy and Cosmology forum.

 

My point was more, try to stick to the original thread and start new threads about the other issues that pop up. I wasn't wiggling my index finger at you. ;)

[Damo2600]

Hi everybody,

 

The point Tarak was trying to make is that outside the singularity you have mention there is no spacetime (as was Buffy's description). So the singularity is weightless and infinitely small. Really it's existence is nothing at that specific point in time (i.e. the begining point before the bigbang). That is why I thought it made more sense that the begining point would be particle-sized. At least this would be something. Another point I would like to bring up is that I'm not sure, I understand, why you can't observe the universe existing within a finite geometric sphere, whilst the cosmological principle doesn't remain true for all observers within that sphere.

 

Can you help me here?

 

--------------------------

 

I don't get an A on relativity then. I saw a question asked on another forum:

 

If light is a constant why do we use two different clock speeds to measure it?

 

The speed of light is the same for both observers yet the distance travelled is observably different. Another way to put it would be the distance travelled is the same, the recorded times are different (i.e the clock speeds are different) and the velocity is equal. A further way of stating it would be the recorded times are equal, the distance travelled is the same yet the velocity is different.

 

So the observer who is standing on the moving tower has a slower clock speed recording the speed of light (travelling to the base of the tower and reflected back up). The observer who is stationary to the embankment has a faster clock speed recording the same light ray. Although light is travelling at a constant speed, moving reference frames that are relevant to a stationary reference frame will actually slow down. IF I am travelling at 50km/s my clock speed is going at a faster rate than an observer travelling at 100km/s. The stationary observer's clock is going faster still. If I am travelling at 100km/s I will observe the all stationary points accoording to me travelling at a slower rate. In this case it is actually it is I who is actually experiencing a slower clock speed.

 

Difficult to grasp.

 

Damian

[Tormod]

That is why I thought it made more sense that the begining point would be particle-sized. At least this would be something.

 

The only problem with this is that it would not have anything to be compared with. We don't have any relative size. It may be infinite seen from our POV 13,7 billion years later but at the moment of Big Bang it may have been large compared to what was before. We really cannot know.

 

It was not nothing, that is all we know. I think we have established that by now. What size this "not nothing" probably has little relevance since we cannot measure it: it was the entire cosmos. ;)

 

Another point I would like to bring up is that I'm not sure, I understand, why you can't observe the universe existing within a finite geometric sphere, whilst the cosmological principle doesn't remain true for all observers within that sphere.

 

The cosmos is most definitely not a sphere. In fact, we cannot completely know the geometry of the universe either, since all we see is the observable parts of it (ie, those areas from which light has reached us yet).

 

I am not sure what you mean with the cosmological principle comment - which principle? In our universe things should look the same to all observers.

[Damo2600]

Hi Tormod,

 

You asked what is the cosmological principle is and then you described it exactly. Now I understand that the view point we see from earth is the same POV you would see if you travelled to each and every galaxy i.e. that the universe is revolving around me (the cosmological principle). I just can't see how this is evident that there is no finite edge of the universe or in another example that if I travel in a straight line that I will not experience open space that does not contain any galaxies. In this open space I would see the final galaxy in the universe revolving around me (the cosmological principle remains intact) beyond that, if I kept travelling, due to infinite red shift all I would see is black basically.

 

I'm not suggesting that this is definitely the case I am simply asking why or if this cannot be a possible reality?

 

Damien

[Tormod]

There is not a single cosmological principle, there are many (probably as many as there are scientists). I assume you are referring to the anthropic cosmological principle, which basically states that the universe has the properties it has because if it did not, we would not be here to observe it.

 

As for seeing the end of the universe from an "outer" galaxy - this is a very difficult question. If there is an "edge" we need to ask "what is outside". C1ay, for example, argued a while back that he imagined space to be infinite, and that our universe is a bubble in infinite space. That is not an uncommon viewpoint.

 

But there would not be galaxies anywhere near the "edge" of the universe. The reason for that is that the inflationary period which happened at the very early stages after the Big Bang created a universe that is vastly larger than what we see. It grew at incredible speeds and it took a relatively long time before matter started to condense into protoparticles, quarks and later into particles. So assuming that we can explain the universe as a 3 dimensional figure, there would be an incredible distance from the "edge" of matter to the "edge" of the universe.

 

My explanation here is just an attempt at explaining something I can't really explain. The universe is not a simple object with a fixed location in space - it is the sum of everything we know and can ever know. We cannot have any knowledge of what is "outside", because what is outside would necessary be a part of our universe...unless the laws of nature were different "there" than "here".

 

Ah...gotta love cosmology! ;)

[Queso]

i heard somewhere that there's a theory that the unvierse splits itself into infinite copies every moment. is this even a valid theory? i know nothing about it, obviously, and it seems far-fetched. anybody know any information about it?

[Buffy]

Tormod's right about there being multiple cosmological principles, but mainstream cosmologists usually capitalize the one I've been refering to as The Cosmological Principle. Some of the others (excerpted from http://relativity.livingreviews.org/Articles/lrr-2004-8/articlesu1.html):

The ancient Indian cosmological principle:
   The Universe is infinite in space and time and is infinitely heterogeneous.
    
The ancient Greek cosmological principle:
   Our Earth is the natural center of the Universe.
    
The Copernican cosmological principle:
   The Universe as observed from any planet looks much the same.
    
The (generalized) cosmological principle:
   The Universe is (roughly) homogeneous and isotropic.
    
The perfect cosmological principle:
   The Universe is (roughly) homogeneous in space and time, and is isotropic in space.
    
The anthropic principle:
   A human being, as he/she is, can exist only in the Universe as it is.

 

Orb: yeah, that's the multiple universes theory and you should prolly start a new thread if you wanna talk about it.

 

Cheers,

Buffy

[Damo2600]

Hi Buffy and Tormod,

 

I see. So all we KNOW of the universe is what we experience within in the hubble limit. So your model of the universe is purely speculation and there is no way to prove or disprove it.

 

Is this right?

 

Damien