The Universe, who is fascinated by that?

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#1621179 2-Sep-2016 09:02

Seeing as it's a space thread, a bit off topic but anyway...

An "anomaly" on SpaceX launch pad:

Oops - there seems to be an "anomaly" with getting the youtube link to work.

Here's a direct link: https://www.youtube.com/watch?v=_BgJEXQkjNQ

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tdgeek

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#1621185 2-Sep-2016 09:14

Fred99:

Seeing as it's a space thread, a bit off topic but anyway...

An "anomaly" on SpaceX launch pad:

Oops - there seems to be an "anomaly" with getting the youtube link to work.

Here's a direct link: https://www.youtube.com/watch?v=_BgJEXQkjNQ

On topic as I see it. Zuckerberg is angry, lost his satellite, this is hardly without risk

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#1621190 2-Sep-2016 09:17

joker97:

tdgeek:

joker97:

tdgeek:

joker97:

It's not expanding within a larger construct. The whole construct is expanding. Space-time is expanding. Other dimensions are not directly involved, only the 4.

So, the universe is finite, glad we got that settled. I agree that the universe is the whole construct, so if its expanding it cannot by definition be infinite

You said it's not known.

Correct. You said its infinite, yet you say its expanding, which means it cannot be infinite. I was being mildy sarcy!

My belief is that space is space, its always existed. In fact you can't talk of space existing, as the content is what exists. Space is seen as something that can be made, i dont believe that. I'd also not call space a noun, a thing. What is a thing is things

It doesn't matter what I think or what you think, but that the fact that Hawking can't explain it.

In my statements I always try to state the current most commonly accepted standings. I thought the current thought was it was infinite, but maybe not. You can do all sorts of mathematical functions on infinity. I did that in Uni but I can't remember any of them now!

Here I quote my source ... I don't know how the science of it works let me see if I can find out

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#1621191 2-Sep-2016 09:20

this guy thinks it's infinite but cannot support it

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#1621195 2-Sep-2016 09:26

Fred99:

Seeing as it's a space thread, a bit off topic but anyway...

An "anomaly" on SpaceX launch pad

How much CO2 and small harmful particles did that release?

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#1621196 2-Sep-2016 09:27

tdgeek:

I saw the ballon example as not of the universe, but how galaxies etc move away from themselves and everything else due to expansion. The surface of the ballon is convenient to show the outer rim galaxies, but the content of the universe exists inside the sphere.

Is the expansion equal velocity? I think it is, with minor variations, cannot recall. If so, then the centre outwards, at that speed for 13.8 billions years should be empty?

Last point. If the Universe is spherical and expanding out from the big bang, it would be the same as the Earth, travel in one direction (well, its not really) and you end up home again. Except the expansion dispels that theory although the principle applies.

I think you may be interpreting the balloon analogy differently than was intended. I think you are looking at the 3D balloon as a representation of the 3D universe expanding, viewing it from a point outside the universe within some sort of larger 3D space. With this interpretation the universe would absolutely have to be spherical and finite with a defined centre.

However, I think the analogy was intended more like this: One dimension has been removed so we can better understand the concept. So by removing one dimension, our 3D universe is represented by the 2D surface of the balloon - thus everything in the universe is expanding at the same rate, and there is no centre.

My personal extra interpretation is that the surface of the balloon is a 2D construct that is curved within 3 dimensions. So by adding the missing dimension back, we have a 3D universe curved within a 4th physical dimension.

I may be way off with my last point, but to me it seems to be a natural progression of the analogy.

I'm not well versed enough with the theory (and definitely not with the maths) to posit whether it is likely to be correct. I'm just trying to explain how I understand the analogy to work. I'm sure others can correct any part I am misunderstanding.

EDIT: For clarity (I hope).

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#1621224 2-Sep-2016 09:50

It is a shame we cant post math symbols and equations. I have found once one learns the physics symbols used, that the formula become easy to understand (although I still have to work hard with tensors). It is much easier to explain a formula than it is to try and describe what the formula represents.

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#1621227 2-Sep-2016 09:54

Paul1977:

I think you may be interpreting the balloon analogy differently than was intended. I think you are looking at the 3D balloon as a representation of the 3D universe expanding, viewing it from a point outside the universe within some sort of larger 3D space. With this interpretation the universe would absolutely have to be spherical and finite with a defined centre.

However, I think the analogy was intended more like this: One dimension has been removed so we can better understand the concept. So by removing one dimension, our 3D universe is represented by the 2D surface of the balloon - thus everything in the universe is expanding at the same rate, and there is no centre.

My personal extra interpretation is that the surface of the balloon is a 2D construct that is curved within 3 dimensions. So by adding the missing dimension back, we have a 3D universe curved within a 4th physical dimension.

I may be way off with my last point, but to me it seems to be a natural progression of the analogy.

I'm not well versed enough with the theory (and definitely not with the maths) to posit whether it is likely to be correct. I'm just trying to explain how I understand the analogy to work. I'm sure others can correct any part I am misunderstanding.

EDIT: For clarity (I hope).

Bingo! This is what I have been trying to say. Thanks for clarifying it. I have no idea if this is correct either, but it is the one I can come closest to comprehending.

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#1621243 2-Sep-2016 10:01

Paul1977:

tdgeek:

I saw the ballon example as not of the universe, but how galaxies etc move away from themselves and everything else due to expansion. The surface of the ballon is convenient to show the outer rim galaxies, but the content of the universe exists inside the sphere.

Is the expansion equal velocity? I think it is, with minor variations, cannot recall. If so, then the centre outwards, at that speed for 13.8 billions years should be empty?

Last point. If the Universe is spherical and expanding out from the big bang, it would be the same as the Earth, travel in one direction (well, its not really) and you end up home again. Except the expansion dispels that theory although the principle applies.

I think you may be interpreting the balloon analogy differently than was intended. I think you are looking at the 3D balloon as a representation of the 3D universe expanding, viewing it from a point outside the universe within some sort of larger 3D space. With this interpretation the universe would absolutely have to be spherical and finite with a defined centre.

However, I think the analogy was intended more like this: One dimension has been removed so we can better understand the concept. So by removing one dimension, our 3D universe is represented by the 2D surface of the balloon - thus everything in the universe is expanding at the same rate, and there is no centre.

My personal extra interpretation is that the surface of the balloon is a 2D construct that is curved within 3 dimensions. So by adding the missing dimension back, we have a 3D universe curved within a 4th physical dimension.

I may be way off with my last point, but to me it seems to be a natural progression of the analogy.

I'm not well versed enough with the theory (and definitely not with the maths) to posit whether it is likely to be correct. I'm just trying to explain how I understand the analogy to work. I'm sure others can correct any part I am misunderstanding.

EDIT: For clarity (I hope).

Ok, so you say the balloon surface is the Universe, its 2D. Ok, no centre, agree.

So, whats inside the balloon? Nothing as the Universe is only on the surface?

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#1621280 2-Sep-2016 10:51

tdgeek:

So, whats inside the balloon? Nothing as the Universe is only on the surface?

My interpretation is that the area inside and outside of the balloon is a 4th physical dimension that our 3D universe resides within. I guess this allows for theoretical wormholes etc by squeezing the balloon so two points of it's surface touch each other.

I'm not sure how the idea of time as a dimension fits into this, as that then makes it a 5 dimensional model (and apparently there may be 6 more dimensions after that!).

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#1621298 2-Sep-2016 11:18

How do you treat infinity in arithmetic?

Infinity - Infinity = what

Are two separate infinities the same size?

Can you even have two separate infinities? One infinity should spatially preclude a 2nd infinity existing?

Or can infinities nest like Russian dolls?

After all everything should fit in an infinity?

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#1621349 2-Sep-2016 12:32

Paul1977:

tdgeek:

So, whats inside the balloon? Nothing as the Universe is only on the surface?

My interpretation is that the area inside and outside of the balloon is a 4th physical dimension that our 3D universe resides within. I guess this allows for theoretical wormholes etc by squeezing the balloon so two points of it's surface touch each other.

I'm not sure how the idea of time as a dimension fits into this, as that then makes it a 5 dimensional model (and apparently there may be 6 more dimensions after that!).

4th dimension. Hmmm. If the universe is that skin I guess the thickness of it is the distance between how far light has travelled for 13.8 billion years, and the inner skin is how far hard matter has travelled?

If so, the inner is part of the universe also, but its completely void as everything has travelled away from the big bang. and that shows the universe is not infinite. But it is IMO still the sheer except it is empty space, devoid of matter and light

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#1621369 2-Sep-2016 12:53

It seems to be generally accepted that the Universe is expanding. In that case I don't see how it can be infinite. I think what confuses people is that space is also expanding, not just the distances between stuff in it. The Universe is not expanding inside a larger volume, like a container of some kind that it is filling up, but it is the expansion. This is hard to grasp. I still see this as the multi-dimensional balloon model, with the centre everywhere on the surface and nothing 'inside'. The reason you can't travel around the sphere and end up back where you started is that the expansion happens faster than you could move at the speed of light, so you would never be able to complete a circumnavigation.

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#1621380 2-Sep-2016 13:06

For the dimensions it is typically phi(x,y,z,t) in euclidean geometry (sometimes called xyzt space). Where t = a point in time (the bit that many people forget about). It can also have a magnitude which can mean talking about all of the points inside the space rather than where the space is relative to something else.

In space-time, the other concept worth knowing about is a minkowski space. Other things are momentum vectors and wave vectors and a thing called lagrangian mechanics.

Much of it though is just geometry, so I find something like khan academy useful for refreshing the basics.

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#1621481 2-Sep-2016 15:47

tdgeek:

4th dimension. Hmmm. If the universe is that skin I guess the thickness of it is the distance between how far light has travelled for 13.8 billion years, and the inner skin is how far hard matter has travelled?

If so, the inner is part of the universe also, but its completely void as everything has travelled away from the big bang. and that shows the universe is not infinite. But it is IMO still the sheer except it is empty space, devoid of matter and light

By removing a dimension to represent the universe as the surface of the balloon it would have no thickness (if you mean the thickness of the rubber, which you may not). In the real world the rubber has depth, but for the purpose of the analogy it does not.

I'm not sure how you would represent how far light has traveled since the Big Bang. I guess it would be the circumference of the inflated balloon?

The air inside and outside the balloon would not be considered part of our 3 dimensional universe.

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