Flat universe paradox

[commander_keen]

I am taking astronomy class as one of my GE in college. From what I understand, our Universe is <i>almost</i> flat. That means that it's expansion should slowly start to decrease over time. If that is the case, then why is our Universe doing the opposite and increasing in expansion velocity over time?<br /><br /><b>Is</b> the Universe flat, or is that outdated information? The astronomy teacher at my school said that at one scale, our universe is expanding, but on an extremely larger scale its actually slowing down. That makes absolutely no sense to me so if anyone has a better answer please explain. <img src="/images/icons/frown.gif" />

 

[kmarinas86]

http://en.wikipedia.org/wiki/Cosmic_inflation<br /><br />Cosmologist have a lot of problems:<br />http://en.wikipedia.org/wiki/Galaxy_rotation_problem<br />http://en.wikipedia.org/wiki/Dark_energy<br />http://en.wikipedia.org/wiki/Dark_matter<br /><br /><font color="yellow">The astronomy teacher at my school said that at one scale, our universe is expanding, but on an extremely larger scale its actually slowing down.</font><br /><br />I think you or the teacher got this in reverse. The space between the galaxies is expanding faster than the matter is expanding - so the theory goes.<br /><br />That the universe is flat is implied by Big Bang cosmology, the observed baryonic mass of the Universe, and how the Cosmic Background Radiation is thus interpreted.<br /><br />It is the Big Bang cosmology which impiles that the universe is flat. This is a case where a theory implies the <i>interpretation</i> and <i>correlation</i> of the data. If the Big Bang cosmology is not the "truth" then we should be free to examine other possiblities other than a flat universe.<br /><br />A flat universe implies that dark matter and dark energy fulfill the requirements needed for "Omega=1" which also implies their existence. Galactic Rotation curves and current interpretations of gravity imply dark matter. It is a physicist's ideal for the amount of dark matter and dark energy that molds our galaxies to be such that Omega=1. Negative pressure necessarily affects the geometry (and curvature) of space-time in the same way how positive pressure does. Current physics assumes that negative pressure can coexist with positive pressure in the form of a cosmological constant which permeates all space. Sure

 

[harmonicaman]

I think the flat universe model is merely the result of flawed (or incomplete) attempts to mathematically model the universe - but don't tell your professor I said that!<br /><br />I believe you have to make an intuitive leap and see the universe as not just flat, but as a point; a <i>singularity</i>! At this point in the distant past (about 15 billion years ago by some estimations) time and space were created and are growing within the singularity. <br /><br />The universe is still a point, but time and space are being created inside of it with no end in sight.<br /><br />BTW - There are many diverse models of the universe around which enjoy varying amounts of acceptance, you'll have to decide for yourself which ones merit the most serious consideration... <img src="/images/icons/rolleyes.gif" />

 

[neutron_star69]

1. isnt a singularity in a black hole?<br />2.so does that mean our universe is in a singularity of a black hole?<br />3. and how can there be no end to a singularity?

 

[harmonicaman]

1. Black holes do not form the kind of "Singularity" postulated by BB theory. In my opinion the term "Singularity" should not be used when discussing black holes as it leads to confusion and is not properly descriptive of what is going on within a black hole. <br /><br />2. Our universe is occurring within a Singularity. The universe contains billions of black holes which are merely very dense concentrations of space/time.<br /><br />3. The creation of time and space within the singularity seems to be a never ending process...

 

[a_lost_packet_]

A singularity is a point at which things degenerate into mumblygook. For instance, in an equation, it is the point at which an equation breaks down. In a classic black-hole, it is the point at which explanations cease to account for the point of time which can not exist within the larger "whole" of time. For social dynamics, a singularity is that point in time/evolution of a thing in which the process around it breaks down.<br /><br />So, if the Universe resides within a "singularity" what is the definition of that singularity that you use? If a singularity, by definition, is a portion of an unexplainable, degenerated system, what system is being used to define your singularity? (Honest question as to your definition of "singularity.")<br /><br /> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>

 

[harmonicaman]

When we peer far into space (and also back in time), we are looking at a smaller and smaller universe; we then postulate that if we could just see far enough back in time, we would see the point of our origin. From every location in the universe, this "Singularity" (or point of origin) is the most distant object you can see in every direction. <br /><br />The "Singularity" for BB theorists is the point where space/time first came into existence.<br /><br />In the case of black holes, we just don't have a clear understanding of the physics that govern them. For BHs to be called "Singularities" just leads to confusion because they are not at all related to the "Singularity" from which our universe originates.<br /><br />Black holes are only called "Singularities" because we haven't discovered the correct mathematical formulas to properly model them.

 

[neutron_star69]

so what you are trying to say is that our universe started from a singularity and it began to expand? well where did the singularity come from?

 

[commander_keen]

Some kind of space-time foam. In quantom theory, 'empty' space is actually full of energy. Particles are going in and out of existence all the time. Therefore some postulate that the universe was created when one particle was created and somehow didnt disappear and destroy itself, and instead expanded to what we have today. Something out of nothing. Its the ultimate free lunch!

 

[neutron_star69]

that makes no sense. a particler cant be made from nothing

 

[commander_keen]

The last one was a jab. Remember what I said earlier: space technically isnt empty. It is full of energy.

 

[harmonicaman]

Where the Singularity came from (and the expanding space/time which is our universe) is a philosophical question for which we have no answers. Hawking has some interesting ideas, but even he has trouble going all the way back to the beginning!<br /><br /><br />For the BB purists here are a few tenets of our belief system: <img src="/images/icons/rolleyes.gif" /><br /><br />1. We know that the Singularity was <i>always there</i> because it is the point where <i>time</i> began! <br /><br />2. The singularity cannot grow or expand because there is no "There" for it to expand into; space and time are being created <i>within</i> the Singularity - that is the only place it can go! (Note that if the Singularity itself were expanding, space would appear totally different to us. We would see where we came from and where we are going; in our universe we only can see where we came from - in every direction.)<br /><br />3. There concept of existence outside of the Singularity has no meaning; the expanding interior of the Singularity contains everything in the universe - period!<br /><br />

 

[nexium]

According to widely accepted theory the rest of the Universe does not know what is happening in our galaxy or any other galaxy and won't find out for millions to billions of years, because information does not travel faster than light. I would therefore conclude that even relatively close portions may be accelerating expansion while other parts are slowing expansion or even contracting. Just because that condition is possible, does not mean it is happening, nor should we conclude that our assumpions conscerning what we observe are correct. Neil

 

[neutron_star69]

so harmonicaman, what would happen if you escaped the singularity (if at all possible)? you couldnt progress further because you say there would be nothing to go to so what would happen?

 

[trisco]

I think that if you could escape the singularity you would in effect <i>increase</i> the singularity because you wouldn't be able to expirience it without space/time. In that case did you really escape the singularity?

 

[neutron_star69]

yeah but he says nothing is beyond a singularity, so you would escape to "nothing". so what could there possibly be beyong a singularity?

 

[harmonicaman]

<b>Neutron -</b><br /><br />I believe you could escape the singularity by exceeding "c" (the speed of light). The "Edge" of the universe is right in front of your nose, if you could just go fast enough to reach it...<br /><br />...and of course there's the big question of what you would find on the other side!

 

[nojocujo]

That would be dependent on the curvature of the universe. You still wouln't be able to reach the edge of the universe in the current model. In a closed model you would eventualy circumnavigate the universe due to gravity just as the earthi s falling towards the sun.

 

[trisco]

could our universe be a singularity in another universe like a black hole is a singularity in our universe?

 

[neutron_star69]

ive thought of that. Our universe could be like a proton in an atom of a hydrogen in a drop of water a dog drinks in another univer. And so on and so on.

 

[neutron_star69]

universe*

 

[harmonicaman]

<b>Nojocujo -</b><br /><br /><i>"You still wouln't be able to reach the edge of the universe in the current model. In a closed model you would eventualy circumnavigate the universe due to gravity just as the earthi s falling towards the sun."</i><br /><br />I would argue that our universe is both open <i>and</i> closed, depending on your perspective. The open universe will create time and space for infinity, yet it is enclosed within the Singularity. The universe has no "Edge", yet the edge is right in front of our nose at "c" (the speed of light).<br /><br />Since time and space are being created at "c", if you could just go beyond the speed of light (faster than time and space are being created), you would find yourself beyond the "Edge" of the universe.<br /><br />I believe this is one of the fundamental reasons why it is so difficult to reach and exceed "c"; to do so would mean going over the "Edge" and leaving the universe behind!

 

[trisco]

what I was talking about above was: many people think that black holes are doorways <i>to</i> other universes, what if the doorway <i>is</i> another universe. maybe our universe is just a black hole in another universe and the dark energy is the stuff we suck out of that universe.

 

[kmarinas86]

<font color="yellow">what I was talking about above was: many people think that black holes are doorways to other universes, what if the doorway is another universe. maybe our universe is just a black hole in another universe and the dark energy is the stuff we suck out of that universe.</font><br /><br />why? just because it sounds cool? we can hardly find planets so how are we supposed to discover different universes which are even harder to find?

 

[nojocujo]

Harmonicaman<br /><br />I didn't say perspective defined whether the universe is open or closed. There are three models open, static or closed. It is an assumption that spacetime is created at "c" . During inflation spacetime creation far exceeded "c". I don't see why deflation wouldn't allow that also. But you would still have the edge of the universe in front of your nose whether flat or curved.