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this relates to the dark matter / dark energy and why it is thought that so much of our universe is missing.

 

I have to admit before I pose my questions that I have a strong interest in astronomy but no university or physics background. What I know and understand has come from book. documentaries, talking to others interested in astronomy, and probably to some degree my own interpretation of what I have read and watched. So please if I am wrong in my questioning point out where I am wrong so that I ccan learn rather than shooting me down in a ball of flames.

 

 

If we are to agree that the universe was created in a big bang and that bang has stopped then would it be fair to assume that the universe is shaped like a sphere but with a void in the middle?

as all mater would be traveling apart at roughly equal speeds and the inital shape was spherical that would be a reasonable thing to assume. I do understand that the big bang is not a description of an explosion as we typically understand them but all points of matter expanding away from each other.

 

This begs some serious questions

If there is a void in the middle then can light travel across this void?

Think about this before jumping to the first answer that seems obvious. we are told that space time expanded through inflation as part of the big bang theory. does this mean the universe's shape is spherical or is space dependant on matter or particles being present?

 

If it truly is spherical, then this contradicts the WMAP survey results.

 

If the universe had a void in the middle and light could not travel accross this void then is it possible that this could account for what is considered missing from the universe. If light could not travel across the void then it would have to travel around it. That would mean that light would not travel in direct straight lines but follow the curved surface. That would then infer that measurements taken from distant supernovae would not be the true distance, but the curved distance traveled by the photons.

 

Some of this might seem a bit way out, but it is not intended too. I am simply trying to get my head around the whole big bang thing and why this issue of dark matter / dark energy has recently become the explaination for the missing matter. Maybe its our measurements that are wrong and through that the need to suddenly find a whole lot of matter that does not exist.

Edited by efanton
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you should read this article,

 

discovery magazine

may 2013 issue.

" dark energy

meet the nobel laureates exploring the universe's biggest mystery "

page 38.

 

from what i have gathered so far is it's about the expansion and it ripping the universe apart.

 

3 ending scenario

1 big crunch

2 big rip

3 knife edge

 

on one of the page it has a diagram,

 

it shows,

 

5% normal matter of the universe

24% dark matter of the universe

71% dark energy of the universe

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sorry but I cant afford to buy magazines so will be uable to read that article

 

None of your response considers the potential of voids being a viable option in the universe or the issue that all our measurrement are based on the measurement of light traveling from distant super novae and any poetential void affecting that measurement

 

Surely this is the most important question of the day. Can we trust the measurements of light from distant super Novae?

Is there any definitive proof these measurements are correct. If light can be bent by gravitational lensing, is it possible that distortion of light rays could account for the missing matter?

 

Is it not conceivable that what we are seeing is a distorted view of the universe?

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that article address what you are asking.

 

and also, all i can say is hang out at the grocery store and read the article.

 

and also void is another word for nothing.

 

another thing, there's 3 theories of this,

 

http://www.wetenschap24.nl/.imaging/stk/wetenschap/zoom/media/wetenschap/noorderlicht/artikelen/2010/August/43829136/original/43829136.jpeg

 

http://apod.nasa.gov/apod/image/0603/CMB_Timeline300.jpg

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I do understand that the big bang is not a description of an explosion as we typically understand them but all points of matter expanding away from each other.

The problem, however, is that you're trying to describe it as an explosion. There's no void at the center, since there's no center. Matter (galaxies and whatnot) are roughly at the same place as they were when the universe cooled enough for matter to form billions of years ago. As you say, it's space itself that is expanding, making matter be further away. But that doesn't mean matter itself is flying away from other matter with the expansion. Think of a cake with raisins in it, which you bake in an oven. The raisins aren't actually moving, but since the cake itself is swelling, they will end up further from each other.

 

http://en.wikipedia.org/wiki/Metric_expansion_of_space

http://en.wikipedia.org/wiki/Big_Bang

That would then infer that measurements taken from distant supernovae would not be the true distance, but the curved distance traveled by the photons.

Sure. And with enough curvature, we could be a few light years away from a black hole, which appears to us to be at the other end of the galaxy. However, real distance in that sense doesn't mean anything, since for all practicalities, the actual distance to that black hole has to follow the curvature of space. So regardless if we're trying to observe it or actually travel there, the distance would be "at the other end of the galaxy".
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Well I personally don't belive in the Big Bang theory but if it is true then I imagine that the universe does in fact have a spherical shape. If particles bursted out in all directions then the sphere would be the most logical shape to have arisen.

And I agree that watching distant supernovae isn't a very good way of measring distances but it is the best we got :/

 

 

As you say, it's space itself that is expanding, making matter be
further away. But that doesn't mean matter itself is flying away from
other matter with the expansion. Think of a cake with raisins in it,
which you bake in an oven. The raisins aren't actually moving, but since
the cake itself is swelling, they will end up further from each other.

As far as I interpreted the BB theory: Before it there was no space or time;or matter and energy for that matter. After the zero dimension,infinite density particle exploded into the universe it instantly created the spacetime fabric. So space is already endless and it is actually matter that is moving away from each other (on a cosmological scale(galaxies)) because of "dark energy" (another theory I don't belive(Dark Fluid seems more reasonable))

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As far as I interpreted the BB theory: Before it there was no space or time;or matter and energy for that matter. After the zero dimension,infinite density particle exploded into the universe it instantly created the spacetime fabric.

Then you're interpreting it wrong, and it's no wonder you have a hard time accepting it.

 

There was no "before" the BB, just as there's no north of the North Pole. There was no particle that exploded. Particles weren't formed until the universe had cooled off enough for them to actually be created.

 

https://en.wikipedia.org/wiki/Chronology_of_the_universe#Hadron_epoch

 

what's dark fluid ?

http://en.wikipedia.org/wiki/Dark_fluid
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The problem, however, is that you're trying to describe it as an explosion. There's no void at the center, since there's no center.

Matter (galaxies and whatnot) are roughly at the same place as they were when the universe cooled enough for matter to form billions of years ago. As you say, it's space itself that is expanding, making matter be further away. But that doesn't mean matter itself is flying away from other matter with the expansion. Think of a cake with raisins in it, which you bake in an oven. The raisins aren't actually moving, but since the cake itself is swelling, they will end up further from each other.

 

I fully understand the above. I guess I used unfortunate phrasing to try get my idea accross.

 

Sure. And with enough curvature, we could be a few light years away from a black hole, which appears to us to be at the other end of the galaxy.

However, real distance in that sense doesn't mean anything, since for all practicalities, the actual distance to that black hole has to follow

the curvature of space. So regardless if we're trying to observe it or actually travel there, the distance would be "at the other end of the

galaxy"

 

see what you have done?

You have gone from a 3D visualisation of the universe to a 2D version.

 

Both cannot be correct.

 

let me try get my problem with understanding existing theories accross in a different way.

 

we have the earth and a distant super nova just like the two raisons in a cake being streched apart.

When we look at that supernova we are not looking at it in current time we are looking at where it was millions or possibly billions of years ago. In that time both the earth and the supernova have moved in relation to each other. Yet we use type 1a supernova's as standard candles to measure the distance between. The distance we measure is obviusly not the true distance.

 

we can safely assume that all supernova events did not happen at exactly the same time. Therfore the distances that we assume for two separate supernovae cannot be correct they have been distorted by the expansion.

 

Now like the cake analogy, if expansion is constant, the distance to a supernova occuring closer to us will not be as distorted as one further away. in effect our understanding of the universe's shape has to be totally distorted. The only way that it could not be distorted is that the speed of light also changes with the expansion of the universe.

 

Without being able to accurately measure the distances how can scientist even begin to argue that matter is missing or that there must be dark matter or energy to fill the gap of the missing matter.

 

I find it impossible to believe that the universe exists in a single plane. Everything around us is in three dimensions, how could it even be postulated that the surface of the universe is curved that would imply a totally flat universe, and we know what happened to the flat earth theory.

 

this all leads back to the same issue. How can we be assured that distance measurements are in anyway accurate?

Edited by efanton
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see what you have done?

You have gone from a 3D visualisation of the universe to a 2D version.

I'm fairly sure I didn't. Imagine a 2D universe, let's say a totally flat paper, which you roll up to make the ends meet, effectively creating a wormhole in 2D space. This will work as an analogy that could theoretically be possible in 3D space, folding space to make two points meet, creating a wormhole. But it's important to know folding a paper isn't an exact model of what the 3D space would look like.

 

Another example is gravitational lensing, which you mention yourself. You might have seen the pictures of heavy objects bending space much like a ball would bend a rubber cloth. If you accept the ball on a rubber cloth analogy, which is a 2D visualisation of something happening in our 3D universe, why is folding a paper any more far-fetched? What is heavy objects sinking into, to bend light?

we have the earth and a distant super nova just like the two raisons in a cake being streched apart.

When we look at that supernova we are not looking at it on current time we are looking at where it was millions or possibly billions of years ago. In that time both the earth and the supernova have moved in relation to each other. Yet we use type 1a supernova's as standard candles to measure the distance between. The distance we measure is obviusly not the true distance.

You're right. The size we're seeing right now is not the size of the universe at this very moment.

 

http://en.wikipedia.org/wiki/Observable_universe#Size

we can safely assume that all supernova events did not happen at exactly the same time. Therfore the distances that we assume for two separate supernovae cannot be correct they have been distorted by the expansion.

How are they distorted? Do you mean the fact that they're red-shifted? Then yes, we know they have been red-shifted, which is one of the reasons we know the universe is expanding.

>Now like the cake analogy, if expansion is constant, the distance to a supernova occuring closer to us will not be as distorted as one further away. in effect our understanding of the universe's shape has to be totally distorted. The only way that it could not be distorted is that the speed of light also changes with the expansion of the universe.

Even assuming you mean red-shifted when you say distorted, I'm not following this, so you might have to clarify what you mean.

this all leads back to the same issue. How can we be assured that distance measurements are in anyway accurate?

Same as any other science really. You see something, build a model of it, then test the model to see if it fits. So far, everything fits. It doesn't matter what you or I believe in, or can accept, the models we have now are our best explanation for what we're observing, and they'll be used as such until better explanations emerge. Edited by pwagen
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we can safely assume that allsupernova events did not happen at exactly the same time. Therfore the distances that we assume for two separate supernovae cannot be correct they have been distorted by the expansion.

How are they distorted?

Do you mean the fact that they're red-shifted? Then yes, we know they have been red-shifted, which is one of the reasons we know the

universe is expanding.

 

no I meant exactly what I said. If we measure the distance to two different supernovae our measurements will be distorted.

Both have moved in relation to the earth due to expansion but both measurements are wrong. We have measured where they were millions or billions of years ago. For our measurement to be correct they would both have to occur at the same time and both be at the same distance to avoid the different amounts of distortion for the two separate supernovae by the expansion of the universe over time.

 

 

 

Now like the cake analogy, if expansion is constant, the distance to a supernova occuring closer to us will not be as distorted as one

further away. in effect our understanding of the universe's shape has to be totally distorted. The only way that it could not be distorted is

that the speed of light also changes with the expansion of the universe.

 

Even assuming you mean red-shifted when you say distorted, I'm not following this, so you might have to clarify what you mean

.

I think I expained this above. as both events occured at diferent times the distance to the closer supernova will be less distorted by expansion than the one further away. the scientists are measuring the time it took for the light to travel not the actual distance.

Edited by efanton
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no I meant exactly what I said. If we measure the distance to two different supernovae our measurements will be distorted.

Both have moved in relation to the earth due to expansion but both measurements are wrong. We have measured where they were millions or billions of years ago. For our measurement to be correct they would both have to occur at the same time and both be at the same distance to avoid the different amounts of distortion for the two separate supernovae by the expansion of the universe over time.

If we measure two supernovas going off at the exact same time, with the same red-shift, then yes; we can reasonably assume they went off at the same time in the past, and were, at the time, the same distance from us. Now, if we measure two supernovas going off at the same time, with different red-shifts, it would be equally reasonable to assume they went off at different times, at a different distance from us.

 

We know they are not where they are today as they were when the supernovas actually took place. What you seem to mean by "distortion" seems to be the fact that the galaxies are not where they were when they sent out the light. Which is true. But again, we know that, and can adjust to it. It doesn't change the measurements. We can say "there was a supernova 5 billion light years away", which, as you point out, means the light has traveled for 5 billion years, not that the supernova remains are currently 5 billion light years away from us.

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ok, you seem to understand my point.

 

Now with all our measurements, and thats not many when we consider that we are trying to measure the universe, how can the physical shape of the universe be determined and how has it been determined that so much matter is missing?

Edited by efanton
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ok, you seem to understand my point.

 

Now with all our measurements, and thats not many when we consider that we are trying to measure the universe, how can the physical shape of the universe be determined and how has it been determined that so much matter is missing?

there's 3 theories of this,43829136.jpeg

 

and i'm not sure what missing matter there is.

please explain this.

Edited by krash661
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Now with all our measurements, and that not many when we consider that we are trying to measure the universe, how can the physical shape of the universe be determined and how has it been determined that so much matter is missing?

As far as the shape of the universe goes, I'm not sure. You're probably better off reading up on the details on your own rather than have me feed you information that is pretty likely to be false. But basically, it seems to have to do with how mass bends the universe locally (such as the Sun creating a gravitational field which allows the planets to orbit it), and then looking at how all the mass in the universe bends the universe as a whole. But again, you should probably double-check that one.

 

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question35.html

http://map.gsfc.nasa.gov/universe/uni_shape.html

 

As for dark matter, we've measured stars' movements, basically. Thanks to our understanding of physics, we know how large bodies behave when it comes to orbits and whatnot. A good example is our solar system, which is well understood in that sense. And we know how bodies would behave on a larger scale, such as stars in a galaxy, or even galaxies effecting each other in a galactic group.

 

What we've seen then, is that stars move as though there is more mass around than what we can see (or detect in other ways, such as different kinds of radiation). This suggests there is matter out there that only interacts with other matter by its gravitational influence. This is what's come to be known as dark matter.

Edited by pwagen
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Thanks pwagen you have gone some way to helping me understand what I'm seeking, you help is much appreciated.

 

It still confounds me how the scientist can predict that 24% of the universe is dark matter and 71% of the universe is dark energy.

 

 

Krash, I have seen those diagrams many times. As far as I understand it they are theoretical diagrams to help understand the warping and expansion of space and are not meant to be true representations of the actual physical shape of the universe.

I dont, and I am sure you dont, believe that the universe exists in a single plane as is represented by diagrams 2 and 3.

 

I suppose from all I have read and studied in the last few weeks about this subject there can be no definitive answer to my question at this time. sad.png

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shape doesn't always mean what we think it does in everyday language. for instance a donut is the same shape as a mug and also as a human. in topology all these are the same shape. meaning they can be bent and manipulated into each other. all have one hole.

 

so topologically speaking if we drew a large triangle in space and it resembled what a triangle drawn on, say, the saddle shape then our universe would be saddle shaped. this doesn't mean the actual shape.

 

our universe is thought to be flat and infinite according to WMAP results.

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Stanford University has recorded Leonard Susskind lessons and put them on youtube. I believe the series of lectures on String Theory and M-Theory adress the shape of the Universe. Knowing some calculus does help.

 

Another resource that may help is

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Type 1A supernovae have the same absolute brightness, ie. the infalling mass that converts a white dwarf star to a neutron star occurrs at the same total mass every time, and we can deduce the distance from the apparent brightness. This is the only distance since the 'actual' distance you refer to is meaningless.

 

Space-time is a four dimensional manifold, and as such it can have positive or negative curvature, but it doesn't have to be embedded in another dimension, so I don't know what you mean by the 'void' at the centre of the Big Bang. There is no centre to a positively curved universe because that is not part of the manifold.

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Krash, I have seen those diagrams many times. As far as I understand it they are theoretical diagrams to help understand the warping and expansion of space and are not meant to be true representations of the actual physical shape of the universe.

Absolutely, they're 2D representation of something that describes our 3D world.

 

If you have 12 minutes, I'd suggest you watch "Imagining the Tenth Dimension". I know there are some that think it's incredible unscientific and should be taken off the web for eternity. But for what it's worth, it helped me understand how dimensions relate to each other, which in the end made it possible to understand how a 3D universe can be curved.

 

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shape doesn't always mean what we think it does in everyday language. for instance a donut is the same shape as a mug and also as a human. in topology all these are the same shape. meaning they can be bent and manipulated into each other. all have one hole.

 

so topologically speaking if we drew a large triangle in space and it resembled what a triangle drawn on, say, the saddle shape then our universe would be saddle shaped. this doesn't mean the actual shape.

 

our universe is thought to be flat and infinite according to WMAP results.

 

that is exactly my point Chrispen Evan

 

What I am looking for is the actual phyiscal shape of the universe not the theoretical shape.

 

I did hear at some point there was some sort of project to actually map this in a 3d model but I have failed to find it in my search the web.

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