How does space get inside of an inflating balloon?

[Silvestru]

This is where multi-verse come in to affect, the realism of a multi-verse is what we are discussing now, if we can imagine several ''balloons'' floating around in a box in darkness, each balloon an isolated system but only isolated by the laws of light. They may view us as a black hole?

 

 

Why a black hole? How did we get back to the black hole again?

 

Scientific method proves for things to expand there has to be more space to expand into, I do not buy into this before the BB was nothing malarkey , evidence suggest otherwise.

What evidence doesn't?(Corrected) No one on this forum suggested that before the Big Bang there was nothing.

"The model describes how the universe expanded from a very high density and high temperature state"

Edited May 4, 2017 by Silvestru

[MigL]

Space, or even the universe ( observable ) is a certain volume.

We can't say anything about that volume unless we assign co-ordinates to it.

These co-ordinates, then, become the MODEL, and we can make analogies between the volume of space/universe and the co-ordinates of the model.

 

We model universal expansion by increasing the number of co-ordinates between events.

We model length contraction/time dilation ( in flat, Minkowsky space-time ) by varying the size of the co-ordinate grid.

We model gravity by differential variation of the ( x,y,z,-ict ) co-ordinate such that there is curvature or warping ( i.e. not flat ).

 

These are all MODELS which are governed by strict mathematics which make predictions that have been tested for the last century,and measured to be accurate to several decimal places. In effect, they are similar to your simplistic balloon with points of light model, which is not accurate at all and cannot be used to make substantive predictions, but is meant as a quick and dirty explanation for children.

 

I suggest you raise your level of discussion above that of a child.

[JohnLesser]

 

Why a black hole? How did we get back to the black hole again?

 

 

Why a black hole? how would you perceive a spec of dust 100m away from you?

 

I would perceive that the spec of dust was reflecting and emitting light but I could not see this, I would perceive that there was this invisible sphere surrounding it that I could not see, i.e a black hole.

[Mordred]

Lets detail GR version of curvature a bit further with two thought experiments.

 

take 2 balls drop them from a height. Plot the rate of fall and direction of fall. Keep track of the distance between the two balls. (assign a variable here called the Kronecker delta function).

 

If there is no gravity or curvature the Kronecker delta will be constant. The distance between the two balls do not change.

 

If you have mass then just as in Newton gravity the balls will fall towards the center of gravity. This will alter our previous parallel freefall paths affecting the Kronecker delta. The two balls will get closer together as they fall.

 

We can now use this to plot spacetime curvature. (using the freefall paths of two or more objects in parallel. The kronecker delta gives us our devitations from the parallel paths (intrinsic curvature due to mass )

Edited May 4, 2017 by Mordred

[Silvestru]

Why a black hole? how would you perceive a spec of dust 100m away from you?

 

I would perceive that the spec of dust was reflecting and emitting light but I could not see this, I would perceive that there was this invisible sphere surrounding it that I could not see, i.e a black hole.

 

That is for sure not the definition of a black hole and I would not perceive a spec of dust as such.

A black hole is actually doing the opposite of "reflecting and emitting light"

[JohnLesser]

These co-ordinates, then, become the MODEL, and we can make analogies between the volume of space/universe and the co-ordinates of the model.

 

These co-ordinates are the point sources, without these point sources XYZt could not be used. But to be honest, I would not need coordinates to land a rocket on mars.

[Mordred]

You need the math and coordinates to predict where the moon will be and shorten your flight time.

 

The universe doesn't care how we measure it.

Edited May 4, 2017 by Mordred

[Strange]

This is where multi-verse come in to affect, the realism of a multi-verse is what we are discussing now, if we can imagine several ''balloons'' floating around in a box in darkness, each balloon an isolated system but only isolated by the laws of light. They may view us as a black hole?

 

 

The universe outside the observable universe is still part of our universe. The "multiverse" idea is quite different (and has no evidence).

 

 

 

Scientific method proves for things to expand there has to be more space to expand into,

 

I don't see why. The big bang model doesn't say that.

 

 

 

I do not buy into this before the BB was nothing malarkey , evidence suggest otherwise.

 

There is no theory that says there was nothing before the universe.

[JohnLesser]

Lets detail GR version of curvature a bit further with two thought experiments.

 

take 2 balls drop them from a height. Plot the rate of fall and direction of fall. Keep track of the distance between the two balls. (assign a variable here called the Kronecker delta function).

 

If there is no gravity or curvature the Kronecker delta will be constant. The distance between the two balls do not change.

 

If you have mass then just as in Newton gravity the balls will fall towards the center of gravity. This will alter our previous parallel freefall paths affecting the Kronecker delta. The two balls will get closer together as they fall.

 

We can now use this to plot spacetime curvature. (using the freefall paths of two or more objects in parallel. The kronecker delta gives us our devitations from the parallel paths (intrinsic curvature due to mass )

I do not understand where we get gravity curvature from, things seemingly fall to the ground in a straight line, a linear force. What are you saying is curved?

 

[Strange]

Believe it or not the darkness you see between distant bodies is actually daylight. There is just nothing to see that is reflecting or emitting light.

 

 

This is actually a very good point. Analogies can only highlight a limited number of ideas. In the balloon analogy these are:

 

1. You can have something with a limited size (the surface area) without a boundary/edge.

 

2. Everything moves away from everything else as the area expands.

 

But you have to:

 

A. Expand the idea from 2D to 3D (not easy)

 

B. Remember that the balloon does not exist (there is no "substance" that galaxies are stuck to)

 

C. Remember that there is no inside or outside "the balloon"

[JohnLesser]

 

 

The universe outside the observable universe is still part of our universe. The "multiverse" idea is quite different (and has no evidence).

 

 

I don't see why. The big bang model doesn't say that.

 

 

There is no theory that says there was nothing before the universe.

Things certainly change over time, either that or I am slipping through parallel dimensions lol.

 

I was told this on other forums before.

[Pugdaddy]

The volume of space is changing as a function of time. Space in not expanding, it is being created everywhere at once.

[Strange]

I would perceive that the spec of dust was reflecting and emitting light but I could not see this, I would perceive that there was this invisible sphere surrounding it that I could not see, i.e a black hole.

 

 

Just because you cannot see it does not make it a black hole.

 

A black hole has a very specific meaning related to the curvature of space-time (or the amount of mass within a volume). It is not just something you can't see.

[MigL]

What does your 'perception' have to do with anything ?

You don't seem to have a clue as to what a Black Hole is.

You use simplistic analogies and try to draw valid conclusions from them.

So simplistic, that a whole branch of Physics needs to be explaned to you before you finally concede.

 

Then you move the goalposts and/or skip to a totally new subject about which you have lots of misconceptions and only simplistic familiarity.

[Strange]

But to be honest, I would not need coordinates to land a rocket on mars.

 

 

I think you would. Otherwise you wouldn't know where Mars is, you wouldn't know where it is going to be and you wouldn't know what direction your rocket was going.

[Mordred]

I do not understand where we get gravity curvature from, things seemingly fall to the ground in a straight line, a linear force. What are you saying is curved?

 

What is curved is the Kronecker delta function. This is your tidal force due to a point mass source. (center of gravity).

 

Try this take a piece of paper, a compass and a pencil.

 

Start with coordinate for center of gravity. Draw a line at every degree from that point. You just plotted the freefall path of falling objects to a center of gravity.

In other words you just mapped gravity.

 

In non curved space ie Flat space there is no center of gravity so no deviation in the distance between the freefall paths of two or more falling objects.

 

Kronecker delta stays constant (linear)

Edited May 4, 2017 by Mordred

[JohnLesser]

 

 

 

But you have to:

 

A. Expand the idea from 2D to 3D (not easy)

 

B. Remember that the balloon does not exist (there is no "substance" that galaxies are stuck to)

 

C. Remember that there is no inside or outside "the balloon"

Yes you understand well, that is exactly why the balloon analogy is a terrible analogy because of the skin of the balloon, that is why I like to use an inflating ghost.

[Strange]

I do not understand where we get gravity curvature from, things seemingly fall to the ground in a straight line, a linear force. What are you saying is curved?

 

 

What we perceive as gravity is the curvature of space-time.

 

Imagine two parallel lines that stretch from the past into the future. Each line represents a different location in space. As you move along your line (as time passes) the two lines will stay the same distance apart and you stay in the same (relative) spatial position.

 

Now, if there is some mass present on the other line, then this will cause a curvature of space-time and the lines will no long be parallel but will curve towards one another. As you move forward one your line, you will move towards the other line; i.e. towards the mass. You will interpret this as the force of gravity making you fall towards it.

[Mordred]

Use the raisin bread for a better 3d analogy though no analogy is perfect.

 

 

What we perceive as gravity is the curvature of space-time.

 

Imagine two parallel lines that stretch from the past into the future. Each line represents a different location in space. As you move along your line (as time passes) the two lines will stay the same distance apart and you stay in the same (relative) spatial position.

 

Now, if there is some mass present on the other line, then this will cause a curvature of space-time and the lines will no long be parallel but will curve towards one another. As you move forward one your line, you will move towards the other line; i.e. towards the mass. You will interpret this as the force of gravity making you fall towards it.

Exactly

[JohnLesser]

 

 

I think you would. Otherwise you wouldn't know where Mars is, you wouldn't know where it is going to be and you wouldn't know what direction your rocket was going.

I can see mars with my eyes like I can see the local shop, have you ever heard of steering ? I do not need coordinates to direct myself to a location I can see.

Use the raisin bread for a better 3d analogy though no analogy is perfect.

 

Exactly

Yes the raisin bread is not a bad one, but it still puts in solidity where space has none.

[MigL]

You 'can get to Mars without co-ordinates' ?

 

Co-ordinates are like a map, or street signs.

You couldn't even get to Pittsburg without such co-ordinates.

[Pugdaddy]

Raisin Bread is not a good analogy. It suggests that space is expanding. Space is being created.

[JohnLesser]

You 'can get to Mars without co-ordinates' ?

 

Co-ordinates are like a map, or street signs.

You couldn't even get to Pittsburg without such co-ordinates.

If you can see it you don't need coordinates, it is a bit like shooting a gun, aim and shoot, if you could steer the bullet you would never miss.

 

 

Defining destination by coordinates is a bit different, this is for when you can't see the destination, other than that point and ''walk''.

 

A guided missile is different to a bazooka.

Edited May 4, 2017 by JohnLesser

[Mordred]

Now what curves under the FLRW metric.

 

[latex]{s^2}=-{c^2}d{t^2}+a{t^2}[d{r^2}+{S,k}{r^2}d\Omega^2][/latex]

 

[latex]S\kappa.r= \begin{cases} R sin.r/R &k=+1\\ r &k=0\\ R sin r/R &k=-1 \end {cases}[/latex]

 

Again we are plotting the parallel paths of light. null geodesics/worldlines.

 

However in this instance the density varies over time. This equates to your expansion history over time and how it affects the worldlines of light.

Raisin Bread is not a good analogy. It suggests that space is expanding. Space is being created.

You don't create volume nor volume change.

If you can see it you don't need coordinates, it is a bit like shooting a gun, aim and shoot, if you could steer the bullet you would never miss.

 

 

Defining destination by coordinates is a bit different, this is for when you can't see the destination, other than that point and ''walk''.

 

A guided missile is different to a bazooka.

Yes but GR does more than plot the path to an object. Your also plotting how mass affects time.

Edited May 4, 2017 by Mordred

[Pugdaddy]

According to Dr. Nima Arkani Ahmed it is. Scroll to minute 37.