What am I observing?

[JohnLesser]

Howdy, when I look at the night sky and between the stars I observe a black back ground , what am I observing?

 

Do I observe a ''roof'' with ''spotlights'' in, an edge of space?

 

 

Or do I observe just the lack of bodies reflecting light?

[J.C.MacSwell]

Howdy, when I look at the night sky and between the stars I observe a black back ground , what am I observing?

 

Do I observe a ''roof'' with ''spotlights'' in, an edge of space?

 

 

Or do I observe just the lack of bodies reflecting light?

You are looking at radiation that has redshifted out of your visible spectrum due to universal expansion since it was sent, and toward some that is delayed to the point it will never arrive. So you are unable to observe anything in those areas of the sky.

[JohnLesser]

You are looking at radiation that has redshifted out of your visible spectrum due to universal expansion since it was sent, and toward some that is delayed to the point it will never arrive. So you are unable to observe anything in those areas of the sky.

I think you just said , that the ''light'' that reflects or is emitted from bodies in this visible ''dark'' area is too weak to be converted into a visual picture in our brains by time the ''light'' reaches us?

 

Is this what you said as such?

Edited March 20, 2017 by JohnLesser

[Strange]

The light is both too faint and it has been shifted out of the visible range.

 

There are only a finite number of stars and galaxies that can be seen. The amount of light from them falls off, roughly speaking, with the square of the distance (a galaxy 4 times as far away will be 16 times fainter). I say roughly, because there are other factors such as the type and age of the galaxy, intervening gas and dust clouds, etc.

 

Note that most of this light is not reflected but is generated by stars like our sun. The only objects (visible to the naked eye) that reflect light are the moon and 5 planets.

[JohnLesser]

The light is both too faint and it has been shifted out of the visible range.

 

There are only a finite number of stars and galaxies that can be seen. The amount of light from them falls off, roughly speaking, with the square of the distance (a galaxy 4 times as far away will be 16 times fainter). I say roughly, because there are other factors such as the type and age of the galaxy, intervening gas and dust clouds, etc.

 

Note that most of this light is not reflected but is generated by stars like our sun. The only objects (visible to the naked eye) that reflect light are the moon and 5 planets.

I understand we need telescopes to see further away. I have read that space is expanding, can you please explain what is meant by expanding ?

 

Does it mean that the visual bodies are moving away from our observation and that the distance of the space between observer and body is increasing/expanding? or does it mean something else?

Edited March 20, 2017 by JohnLesser

[StringJunky]

I understand we need telescopes to see further away. I have read that space is expanding, can you please explain what is meant by expanding ?

 

Does it mean that the visual bodies are moving away from our observation and that the distance of the space between observer and body is increasing/expanding? or does it mean something else?

The distance between groups of objects, those that exceeds about 200mlyrs between groups, are moving apart i.e. space is being created between them. At 200mlyrs, gravity is too weak to resist the expansion. Wherever you are in the universe, as the observer, everything beyond that distance is moving away from you.

Edited March 20, 2017 by StringJunky

[JohnLesser]

The distance between groups of objects, those that exceeds about 200mlyrs between groups, are moving apart i.e. space is being created between them. At 200mlyrs, gravity is too weak to resist the expansion. Wherever you are in the universe, as the observer, everything beyond that distance is moving away from you.

I am sorry but your post is a bit confusing, what do you mean space is being created between groups of objects? To me you sound like you are saying new space is made rather than the existing space between bodies is expanded when the bodies move away from each other into more space.

Is this what you meant to say?

[StringJunky]

I am sorry but your post is a bit confusing, what do you mean space is being created between groups of objects? To me you sound like you are saying new space is made rather than the existing space between bodies is expanded when the bodies move away from each other into more space.

Is this what you meant to say?

WRT to the objects in question, they are not moving any different than they normally do. They are not experiencing any extra acceleration due to the expansion. There is new volume, or space, between the objects which is moving them apart. An oft used analogy is the surface of a balloon. Pick two points on it and they will move apart during inflation but at each point they are still motionless; forget about any reference points outside of the surface of the balloon.

[Strange]

I am sorry but your post is a bit confusing, what do you mean space is being created between groups of objects? To me you sound like you are saying new space is made rather than the existing space between bodies is expanded when the bodies move away from each other into more space.

Is this what you meant to say?

 

 

I don't think there is any real difference between those descriptions. Space isn't "stuff" so it isn't created in that sense. But expansion means that things move apart (on large enough scales) and so there is more space between them.

[JohnLesser]

 

 

I don't think there is any real difference between those descriptions. Space isn't "stuff" so it isn't created in that sense. But expansion means that things move apart (on large enough scales) and so there is more space between them.

This is my last post I can do today because of new member post limitations so please forgive me for any belated replies after this post.

 

True , space is not ''stuff'' , however there is a huge difference in the statements,

 

 

 

There is new volume, or space, between the objects which is moving them apart.

 

Stringjunky is saying that there is a new volume of space and sort of suggesting that the space between the moving bodies ''grows''.

 

 

However after the earlier conversation of what do I observe when looking between the distant visual bodies, it was explained I do not observe anything because the ''light'' is too diminished by time it arrived to me or red shifted in science terminology, this confirming there is space and light beyond the last visual bodies. In view of this information the expansion of space I asked about must be the later statement by myself and the expansion simply being a distance increase between bodies making a greater length of existing space between two observers rather than trying to give space physicality like the balloon analogy which is suggestive of a Physical surface expanding into nothing , however nothing in the balloon analogy has strangely got a circumference that is outer of the balloons surface, suggesting expanding into more space, because after all things generally need space to expand into or else they become compressed if there is an equal and opposite force.

 

Is my understanding of the ''expansion'' correct?

[StringJunky]

This is my last post I can do today because of new member post limitations so please forgive me for any belated replies after this post.

 

True , space is not ''stuff'' , however there is a huge difference in the statements,

 

 

 

 

Stringjunky is saying that there is a new volume of space and sort of suggesting that the space between the moving bodies ''grows''.

 

 

However after the earlier conversation of what do I observe when looking between the distant visual bodies, it was explained I do not observe anything because the ''light'' is too diminished by time it arrived to me or red shifted in science terminology, this confirming there is space and light beyond the last visual bodies. In view of this information the expansion of space I asked about must be the later statement by myself and the expansion simply being a distance increase between bodies making a greater length of existing space between two observers rather than trying to give space physicality like the balloon analogy which is suggestive of a Physical surface expanding into nothing , however nothing in the balloon analogy has strangely got a circumference that is outer of the balloons surface, suggesting expanding into more space, because after all things generally need space to expand into or else they become compressed if there is an equal and opposite force.

 

Is my understanding of the ''expansion'' correct?

The balloon analogy is very limited in what it describes. i was using it to show the increase in distance between objects, yet none of them feel they are moving in their own frame. Space is 'created' between them. Note: space is not made of anything but there is more space between the objects. It's a pretty difficult idea to translate ithe 2D of the balloon analogy into 3D and you really need to understand the maths of the subject to properly understand what cosmologists are actually talking about. It can't be done in pictures and words properly; they can only give a rough approximation.

[Strange]

Is my understanding of the ''expansion'' correct?

 

 

Hard to say; that was one very long and convoluted sentences there!

 

You are correct that there are stars and galaxies beyond those we can see. The limited range we can see is called the "observable universe". Beyond that is the rest of the universe, which may just be very large or it may go on for ever.

 

The balloon analogy is flawed in many ways, which as you say, implies physicality. It also uses a 2D surface as an analogy for 3D space, which a lot of people struggle with. It also implies a finite universe.

 

So, one important thing to note is that the "observable universe" in the balloon analogy is a circle around "our" galaxy containing all the galaxies that we can see. There are further galaxies beyond that. (Every galaxy has its own observable universe, and they all overlap.)

 

The other useful point the balloon analogy makes is that the universe could be finite but have no edge: the surface of the balloon has a finite area but there is no edge to it.

 

Finally, all these descriptions ("expanding space", space growing", "space being created", "distances increasing", etc) are just different metaphors to describe what the theory (i.e. the mathematics) describes. They all have the potential to confuse or mislead in slightly different ways!

[mistermack]

As far as I can make out, cosmologists are arguing that space is expanding, but they have absolutely no idea how or why.

It's just something to say, to match the observations. But there's nothing I've heard of in physics that explains how space between objects can be increased, without a source of acceleration.

If we don't know something, I think it should be made clear or it just leads to confusion.

 

We don't even know WHERE the extra space is added.

It can't be that the existing space is just getting bigger, because that would make everything bigger, and there would be no way of detecting it. So it seems that space between matter gets bigger, but particles don't grow.

Maybe it leaks in from other dimensions.

[StringJunky]

As far as I can make out, cosmologists are arguing that space is expanding, but they have absolutely no idea how or why.

It's just something to say, to match the observations. But there's nothing I've heard of in physics that explains how space between objects can be increased, without a source of acceleration.

The expansion is a continuation of inflation from the BB. Dark energy causes the acceleration.

 

 

 

We don't even know WHERE the extra space is added.

Everywhere, but it manifests where gravity is too weak to overwhelm the expansion.

 

 

It can't be that the existing space is just getting bigger, because that would make everything bigger, and there would be no way of detecting it. So it seems that space between matter gets bigger, but particles don't grow.

The weak force, strong force and electromagnetic force overwhelm the expansion, so everything stays the same size.

 

Edit: corrections.

Edited March 21, 2017 by StringJunky

[JohnLesser]

As far as I can make out, cosmologists are arguing that space is expanding, but they have absolutely no idea how or why.

It's just something to say, to match the observations. But there's nothing I've heard of in physics that explains how space between objects can be increased, without a source of acceleration.

If we don't know something, I think it should be made clear or it just leads to confusion.

 

We don't even know WHERE the extra space is added.

It can't be that the existing space is just getting bigger, because that would make everything bigger, and there would be no way of detecting it. So it seems that space between matter gets bigger, but particles don't grow.

Maybe it leaks in from other dimensions.

Space is beyond the observable Universe as mentioned, there is no extra space that is added from my understanding, the expansion is just the space between the bodies is lengthening by the velocity of the bodies travelling into more space. The bodies themselves providing the observation by emitting light , the more distance away the body travels the more the visual Universe ''grows''. However it is not growing in a sense of new space but rather new observed space.

 

 

Hard to say; that was one very long and convoluted sentences there!

 

You are correct that there are stars and galaxies beyond those we can see. The limited range we can see is called the "observable universe". Beyond that is the rest of the universe, which may just be very large or it may go on for ever.

 

The balloon analogy is flawed in many ways, which as you say, implies physicality. It also uses a 2D surface as an analogy for 3D space, which a lot of people struggle with. It also implies a finite universe.

 

So, one important thing to note is that the "observable universe" in the balloon analogy is a circle around "our" galaxy containing all the galaxies that we can see. There are further galaxies beyond that. (Every galaxy has its own observable universe, and they all overlap.)

 

The other useful point the balloon analogy makes is that the universe could be finite but have no edge: the surface of the balloon has a finite area but there is no edge to it.

 

Finally, all these descriptions ("expanding space", space growing", "space being created", "distances increasing", etc) are just different metaphors to describe what the theory (i.e. the mathematics) describes. They all have the potential to confuse or mislead in slightly different ways!

Thank you for more or less confirming my understanding is correct. However I feel I must correct you, the 2D example of the surface of the balloon is a 2D example from an outer observers viewpoint but if the observer is inside the balloon , a central observer , the balloon example becomes 3D. I personally believe that a finite Universe is an impossibility, I also believe a visual Universe is finite by the replies to the opening post.

 

 

 

You are correct that there are stars and galaxies beyond those we can see. The limited range we can see is called the "observable universe".

 

Would you say that observation is finite?

Edited March 21, 2017 by JohnLesser

[Strange]

As far as I can make out, cosmologists are arguing that space is expanding, but they have absolutely no idea how or why.

 

 

Only in as much as we don't know the how or why of anything. But in fact we have a theory that explains gravity extremely well (General Relativity) and the same theory explains the expansion of space.

 

 

 

But there's nothing I've heard of in physics that explains how space between objects can be increased, without a source of acceleration.

 

Here is a good overview: http://math.ucr.edu/home/baez/einstein/

 

 

 

It can't be that the existing space is just getting bigger, because that would make everything bigger, and there would be no way of detecting it. So it seems that space between matter gets bigger, but particles don't grow.

 

That's about right. The distance between things increases. This is not apparent locally because things are held together by gravity and/or electromagnetic forces.

 

 

 

Maybe it leaks in from other dimensions.

 

How can "distance" leak?

Thank you for more or less confirming my understanding is correct. However I feel I must correct you, the 2D example of the surface of the balloon is a 2D example from an outer observers viewpoint but if the observer is inside the balloon , a central observer , the balloon example becomes 3D.

 

In the analogy, we are only concerned with 2D observers on the 2D surface. In the analogy there is no 3D balloon; there is no inside (or outside).

 

 

 

I personally believe that a finite Universe is an impossibility, I also believe a visual Universe is finite by the replies to the opening post.

 

We have no way of knowing if the universe is finite or infinite so, I suppose you can believe whichever pleases you (there seem to be about as many people who believe it must be infinite). But the only scientific answer is "we don't know".

[StringJunky]

 

Thank you for more or less confirming my understanding is correct. However I feel I must correct you, the 2D example of the surface of the balloon is a 2D example from an outer observers viewpoint but if the observer is inside the balloon , a central observer , the balloon example becomes 3D. I personally believe that a finite Universe is an impossibility, I also believe a visual Universe is finite by the replies to the opening post.

 

Consider yourself on the surface. It is the only plane that exists - no vertical, no depth - and you are 2D too with no height; all you can do is look along and around the plane of the surface.

Edited March 21, 2017 by StringJunky

[JohnLesser]

 

 

. But the only scientific answer is "we don't know".

What if we did know but did not know we knew it?

 

I would think we could certainty conclude an infinite space with quite a degree of accuracy by thinking about it and the details involved. I of course am not a scientist, but to me something that is finite suggests there is an end to it, so what could we possibly perceive is at the end or after the end?

 

Do we imagine after space there is a ''solid'' like structure or do we imagine more space? from the earlier replies you have already told me that there is more space beyond the observable universe which leads me to believe this continues forever or the only other possible conclusion is back to the ''solid'' like structure. The question then arises what would be after this ''solid'' like structure which I could then only presume more space. I could repeat this question an infinite amount of times and I am quite sure I would never reach an end.

I do not find the answer of there is nothing beyond this to be any sort of answer unless we were looking at nothing in the sense of just space , ''made'' of nothing.

Consider yourself on the surface. It is the only plane that exists - no vertical, no depth - and you are 2D too with no height; all you can do is look along and around the plane of the surface.

A finite or infinite plane?

[Strange]

That is the main point of the balloon analogy. Or the surface of the Earth: finite but with no boundary and nothing beyond it.

[StringJunky]

A finite or infinite plane?

As strange said.

[JohnLesser]

That is the main point of the balloon analogy. Or the surface of the Earth: finite but with no boundary and nothing beyond it.

So when it is said that space is expanding and there is nothing beyond it, are ''they'' saying that nothing is really just the lack of knowledge beyond the visual universe but not necessarily saying that there is nothing there?

[Strange]

So when it is said that space is expanding and there is nothing beyond it, are ''they'' saying that nothing is really just the lack of knowledge beyond the visual universe but not necessarily saying that there is nothing there?

 

 

You need to distinguish the visual universe (usually called the observable universe) from the whole universe.

 

The observable univers is a sphere with a diameter of about 93 billion light years that contains everything we can see. Beyond that, the rest of the universe is assumed to be pretty much the same. It is is either very large or infinite. In both cases, there is not thought to be any edge or boundary, and therefore nothing "beyond" or outside.

[JohnLesser]

 

 

You need to distinguish the visual universe (usually called the observable universe) from the whole universe.

 

The observable univers is a sphere with a diameter of about 93 billion light years that contains everything we can see. Beyond that, the rest of the universe is assumed to be pretty much the same. It is is either very large or infinite. In both cases, there is not thought to be any edge or boundary, and therefore nothing "beyond" or outside.

Thank you for the clarification, of course if the Universe was infinite it would be impossible for something to be outside because of the infinite part, there would be no outside or ''beyond''.

 

You say the Universe is a sphere, is this because of the earlier discussion and that between the stars we can observe nothing because light has a radius of diminish?

 

Are you saying from a multiverse perceived view, ''outer'' observable universes would observe our observable Universe to be liking to a light sphere?

[Strange]

Again, the *observable* is a sphere (centred on us - every point in the universe has its own visible sphere around it).

 

The shape of the whole universe is not known. But if it is spherical then it must be very large because it is measured to be geometrically "flat". Or it could be smaller with a different topology (shape) such as a torus.

[JohnLesser]

Again, the *observable* is a sphere (centred on us - every point in the universe has its own visible sphere around it).

 

The shape of the whole universe is not known. But if it is spherical then it must be very large because it is measured to be geometrically "flat". Or it could be smaller with a different topology (shape) such as a torus.

I understood the observable Universe is spherical because of the isotropic nature of ''light''. I think you may of misunderstood my question.

 

 

In thought to my original question, what am I observing between the stars at night? I am possibly observing other observable Universes (light spheres) but can not see them because the light from them is too red-shifted.

 

Is this what you are saying to me?

Edited March 22, 2017 by JohnLesser