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# The edge of space

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I was just wondering if any of the membership here ever considered the questions:

#1; Is the speed of light determined by this universal expansion?

Not according to SR, if it were, the speed of light would not be a constant.

#2; If the universal expansion were slower, would it also be the same for the speed of light.

Again, no because the rate of expansion was slower in the past since it is now said to be accelerating. And I believe it was faster before the slower period that preceeded our current accelerated period.

#3; If this is so, then what happens if the expansion comes to a halt.

If the universal expansion comes to a hault SR says light still travels at the same speed because its a constant. Hence the two are independant.

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If the universal expansion comes to a hault SR says light still travels at the same speed because its a constant. Hence the two are independant.

Uhhh, SR says nothing about expansion. The universe cannot expand, let alone faster than c. GR implies that. Why would expansion be exempt from SP, or GR? Expansion, relative recession, inflation, call it what you will, mass tends to infinity as velocity v (yes even if it is only a relative velocity) tends to c.

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Quote:

Originally Posted by EWright

If the universal expansion comes to a hault SR says light still travels at the same speed because its a constant. Hence the two are independant.

Uhhh, SR says nothing about expansion. The universe cannot expand, let alone faster than c. GR implies that. Why would expansion be exempt from SP, or GR? Expansion, relative recession, inflation, call it what you will, mass tends to infinity as velocity v (yes even if it is only a relative velocity) tends to c.[/Quote]

First of all, your statement has nothing to do with the portion of my post that you quoted. As for the portion of my statement that you quoted, SR does state that the speed of light is a constant. Therefore, whether the universe is expanding or not (which it is), then SR dictates that light must still travel at 186,000 miles per second. If you argue this, you argue the very basis of SR. Everything in SR is based on this assumption.

As for your statement, I can only assume that what we have here is a failure to communicate. You are saying that the universe is not expanding? The universe is indeed expanding and currently it is doing so at an ever accelerating rate. Cosmologists have dubbed the force behind this mysterious acceleration "dark energy" but do not know what it is. (The theory I have mentioned in other posts does account for dark energy as well as dark matter and other mysteries of physics. In addition to correcting for SR.)

As for the potential expansion rate of the universe, it can indeed exceed c. c is limited by the physics of the universe, not the other way around. Alan Guth's inflationary theory, which is widely accepted and a necessary product of the big bang as well as the flatness of the universe and uniformity of the CMBR states that the universe expanded at a rate far beyond the speed of light in its infancy.

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First of all, ... the speed of light in its infancy.

Relax EWright,

I did not mean to get you all riled. We can discuss serious physics you know, I hope.

Any way, don’t get peeved about the response: Yes the speed of light is constant. Remember though, SP is cool, but GR rules.

There is no communication break-down, it is the fact that the physical laws that break-down at the BB that I find unappetizing, forgive me for not swallowing. Yes, I am saying the universe is not expanding and that inflation is not part of the standard model because it has a distasteful false vacuum from the get-go requiring new physics, that’s all. Nothing wrong with that point of view (physics is physics, new physics is not). Maybe I’m too pragmatic, but false vacuums, dark energy, exotic dark matter, I wouldn’t eat it for lunch if you gave it to me for free.

You write "dark energy" but do not know what it is”

I agree. By definition it is unobservable, like most of the other "things" in modern cosmology (sure redshift is real, the CMB is real, and there are light elements in abundance, i.e., more that 15 billion years is required to produce them, so they must have been made premordially, cool)

Where can I find info about your theory, I’d like to check it out, what thread can I go to?

A note on inflation theory: The flat universe idea of Guth is not in accord with general relativity GR. According to GR the universe is non-Euclidean and gravity is everywhere present. How do you (and Guth) figure the universe is flat?

According to Guth, all the matter and radiation visible today in the universe emerged from the colossal energy that was stored in empty space (a more than empty space called the false vacuum) during the inflationary stage. Though, astutely, there is no mentioning from where originated the (negative) energy (the universe, like a virgin giving birth, sprang from nothing). This form of creation ex nihilo he calls the ultimate “free lunch.” But it looses its flavor somehow.

“Grilling, broiling, barbecuing - whatever you want to call it - is an art, not just a matter of building a pyre and throwing on a piece of meat as a sacrifice to the gods of the stomach.” James Beard. (1974)

Inflation is a plight born of scarcity—not enough proof, not enough money, not enough knowledge about what constitutes space, not enough decent food-for-thought, not enough backing from fundamental laws. Inflation does not come close to covering the cost of big bang cosmology, even with food stamps as an add-on. The heat-or-eat dilemma just won’t go away—the universe expands exponentially, temperature drops, heating bills skyrocket, food purchase tumbles, spatiotemporal geometry is limited, and it’s impossible to distinguish, empirically, one inflation model from another (I'm familiar with six versions, from the original scenarion to chaotic inflation, in passing, new new inflation, eternal inflation etc.).

In the past few years the Guth-universe has been a binge and purge kind of place—where, for example, an apprehensive pubescent spends the family lunch money on a Big Mac or a Whopper, even though he knows better. It sounds more like pallid gastronomy than valid astronomy, I know. Healthy options are available.

Coldcreation

GRules

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While on the topic, is it safe to assume that our Universe has a spherical shape?

It is my personal view that the universe in infinite and therefore shapeless. I tend to think our local region, a result of some cosmic event around 13 billion years ago, is spherical.

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Can we please keep our discussions on such complicated subjects as close to the facts and pure english as possible? Your description made me more nausiated than informed.

So you do not agree with inflation, or the 'fact' that the universe is expanding. What then do you attrubute the measurements of its expansion to account for? In otherwords, what cosmological model do you agree with?

And yes, I can account for the source of dark energy as well as dark matter, redefine the workings of gravity, black holes, SR, the mystery of heavy elements in the early universe, the shape of the universe (cosmologists say it is flat; I did not), the cause of the initial expansion of the universe, space beyond the observable universe, etc. I am not posting the lengthy support for these theories for reasons I have already posted.

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Wow! Some ideas are way off base here. The speed of light has NOTHING to do with the rate at which space is or can expand. In fact, physics allows for space to expand at a rate faster than the speed of light. Space is not limited to a speed of less than c by modern physics. It is light that is limited to c, not the expansion rate of the universe that is limited by a produce of itself.

Great post, but Tormod was not implying that the universe expands at c, he was talking about the observable universe, meaning that the range of observation is expanding at c... not that the speed of light had anything to do with the expansion itself.

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Great post, but Tormod was not implying that the universe expands at c, he was talking about the observable universe, meaning that the range of observation is expanding at c... not that the speed of light had anything to do with the expansion itself.

Well it would seem you know Tormod better than I do. If this is indeed what he meant then thank you for the clarification. Though it is not how I read it, or in what way did he misinterpret what I said in his response?

Tormod, care to sound off on this?

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That is how he meant it, and he explained it several times there... that is how I know :)

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Regardless of any imaginable advance in technology, we'll never get to the "Edge" of the universe, due to the constraints placed upon it by the speed of light. Therefore, we can never cross the "edge" to see the universe from "outside", so to speak.

So, this being the case, does it have any meaning to speculate about the "edge" or even the "shape" of the universe?

Speculating on wether the universe curles up on itself has no meaning either, due to the same reason.

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Regardless of any imaginable advance in technology, we'll never get to the "Edge" of the universe, due to the constraints placed upon it by the speed of light. Therefore, we can never cross the "edge" to see the universe from "outside", so to speak.

So, this being the case, does it have any meaning to speculate about the "edge" or even the "shape" of the universe?

Speculating on wether the universe curles up on itself has no meaning either, due to the same reason.

Yes, it does matter if we care to understand it. The shape of the universe is directly related to its ultimate fate. If we don't care to understand things that don't directly influence our lives, why bother spending all the money on things like the Hubble Telescope, WMAP, etc. Which primarily advance our understanding of things. I mean, who's life is really benefited by knowing the CMBR is 13.7 billion light years in the past?

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• 2 weeks later...

My Biggest Concern Is That Of The Big Bang. The Big Bang Would Have Caused The Universe To Expand In All Directions, Therefore The Location Of The Big Bang Should Be Our Main Target. How Do We Find It? Because The Universe Is Expanding In All Directions (and Exellerating) We Will Probably Never Get To See Nor Reach The Edge Of Space. However Locating The Point In Space Where Everything Else Is Moving Away From Will Show Us Where And Tell Us When The Big Bang Took Place . From That Information We Will Know Where It All Started And Have More Clues On Knowing Where To Look For Its Ends!

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How far should we go to reach the edges of Space- our Universe? 15 billion light years?

According to scientists, how will this edge look once we reach it? Everyone can say 'nothing', but how would it feel if we are able to reach it? Is there some sought of barrier?

While on the topic, is it safe to assume that our Universe has a spherical shape?

X^2 + Y^2 + Z^2 - (CT)^2 = 0 ===> Hyperbolic

The universe is expanding at the speed of light. Since noone can exceed the speed of light, it can never be reached.

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My Biggest Concern Is That Of The Big Bang. The Big Bang Would Have Caused The Universe To Expand In All Directions, Therefore The Location Of The Big Bang Should Be Our Main Target. How Do We Find It? Because The Universe Is Expanding In All Directions (and Exellerating) We Will Probably Never Get To See Nor Reach The Edge Of Space. However Locating The Point In Space Where Everything Else Is Moving Away From Will Show Us Where And Tell Us When The Big Bang Took Place . From That Information We Will Know Where It All Started And Have More Clues On Knowing Where To Look For Its Ends!
Everywhere is the point from which the expansion started. Matter is not expanding in space. Space is itself expanding from a point. Everything was once at that point. [if you believe Big Bang cosmology).
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I was just wondering if any of the membership here ever considered the questions:

#1; Is the speed of light determined by this universal expansion?

#2; If the universal expansion were slower, would it also be the same for the speed of light.

#3; If this is so, then what happens if the expansion comes to a halt.

Just a litltle food for thought, what do you think??

( 1 and 2 ) ==> The speed of light is equal to the square root of two factors called the permittivity of free space and the permeability of free space. Basically, the permittivity os free space is how fast an electric field will travel and the permeability of free space is how fast a magnetic field will travel. When you get through all the math and take a good look, the speed of light is determined by the electric charge of an electron. I don't know what caused the Big Bang, but I don't see a connection with the speed of light.

Astronomers seem to thing that the expansion rate of the Universe is accelerating. I don't believe this, however, if it is, then the whole thing needs to be reviewed. General Relativity has the following equation T1 = T2 ( 1 + gt/C^2). Essentially, this equation says that TIME RUNS SLOW IN A GRAVITATIONAL FIELD. Keeping this in mind, here is what I think.

During the first part of the Big Bang, the universe was incredibly dense and the gravitational field would have been immense. In such conditions, time would have run very, very slow.

As the universe expanded, the overall gravitational field became weaker and time began to run faster.

As the universe continues to expand (in the future), the overall gravitational field will continue to expand and time will continue to speed up.

At some point in the future, the expansion will stop and the whole process will start the other way. As the Universe contracts the gravitational field expands and times slows down, etc, ending in a Big Crunch

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Everywhere is the point from which the expansion started. Matter is not expanding in space. Space is itself expanding from a point. Everything was once at that point. [if you believe Big Bang cosmology).

Einstein's field equations show the development of the universe over time. These equations are dependent on initial conditions. Here is an example of initial conditions. Supposed I told you that a car had accelerated 10 MPH and ask you how fast the car is going. Of course you don't know because you don't know how fast the car was going before it accelerated 10 MPH. The speed the car was going before it accelerated is called an initial condition.

Depending on the initial conditions, the field equations give different results. This shouldn't come as a surprise. Indeed, it would be a very large surprise if you could change the initial conditions yet the same answer.

I've never heard of it being done but I suppose you could run the field equations in reverse, however the answer would still depend on the initial conditions.

The seeminyly logical way would be to run the moon backwards, then run the earth / moon combination backward then run the earth / moon / sun backward, etc. As you might notice, the problem becomes more and more difficult as you add more and more factors. This is call the N-Body problem and solutions for more than a few bodies exceed the ability of the world's fastest computers.

nto go

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Bobby, your post, while inherently interesting, appeared to have no connectivity with my own, which you quoted at the outset. What am I missing?

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