Our world may be a giant hologram

[martu]

I disagree. While I do think that whatever the field, the bar for following along the simpler cases isn't that high at all (and this is definitely one of those), and within the capability of any reasonably bright person, what one finds intuitive largely depends on experience. Thus, it's simply not reasonable to expect that any fairly bright person would find things intuitive without experience in background concepts.

What we have in this thread is a good example, actually--someone proficient in high-school coordinate geometry should have absolutely no trouble of making the intuitive leap to a 3-sphere once it is described to them, and in hindsight would actually regard it as more or less a trivial step. On the flip-side, I wouldn't be at all surprised that someone that avoids mathematics finds it absolutely mind-boggling, regardless of intellectual ability in other areas of life.

In other words, intuition generally adapts fairly well if you just do the homework, but expecting things to be intuitive without such work is just plain silly.

Yes absolutely I agree, I was alluding more to the idea that something, let us take for example QM, will never be intuitive to us. My phrasing was poor, apologies.

What I hope is that someone can do for, say, the behaviour of the very small what Einstein did for spacetime, use simple to follow analogies and models so that we (the non physicist) can understand fully. 100 years ago this idea was revolutionary and obscure now it is ordinary, why can’t I assume the same will happen for the Quantum world? Or can I?

 

[sol invictus]

I think you are wrong about this, if the 4th dimension isn’t time what is it?

I wasn't talking about "the" 4th dimension. I was saying that one way to define a 3-sphere is to embed it in 4 flat Euclidean dimensions, just as Vorpal did. Because people have trouble conceptualizing intrinsic curvature, it's just easier to imagine it that way - as a "surface" in a flat space. It's a mathematically valid procedure, but that doesn't mean it has much to do with the real world.

And what do you mean by ‘time – it’s fixed’?

skeptigirl kept asking what the geometry of the universe is at a given (fixed) time.

Do you mean that things aren't accelerating? Because if they are then time has to be taken into account.

Just set time to something - i.e. consider the universe as it is, was, or will be at some definite time. First understand that, then think about the time dependence.

 

[INRM]

martu,

There's positive energy (energy, mass), and there's negative (potential) energy in the form of gravity.

Eventually in an infinite amount of time the two would negate each other. If you had an infinite amount of positive and negative energy though...

 

[martu]

I wasn't talking about "the" 4th dimension. I was saying that one way to define a 3-sphere is to embed it in 4 flat Euclidean dimensions, just as Vorpal did. Because people have trouble conceptualizing intrinsic curvature, it's just easier to imagine it that way - as a "surface" in a flat space. It's a mathematically valid procedure, but that doesn't mean it has much to do with the real world.

Ok sorry I missed that, though I often get confused talking about the physics I do have a maths degree so I find the maths intuitive.

skeptigirl kept asking what the geometry of the universe is at a given (fixed) time.

Just set time to something - i.e. consider the universe as it is, was, or will be at some definite time. First understand that, then think about the time dependence.

OK so we 'freeze' time and this is our t=0 for the purpose of our observations and it also gives us the starting state of our system. Then we let the clock tick, we let everything move, and watch.

 

[martu]

martu,

There's positive energy (energy, mass), and there's negative (potential) energy in the form of gravity.

Eventually in an infinite amount of time the two would negate each other. If you had an infinite amount of positive and negative energy though...

What is the difference between these two types of energy that they require an (arbitrary) label denoting positive and negative? Is it attraction\repulsion?

 

[Ziggurat]

What is the difference between these two types of energy that they require an (arbitrary) label denoting positive and negative? Is it attraction\repulsion?

It does indeed come from the fact that gravity alone has an attraction between like charges.

One way of dealing with potential energies is to calculate all of them in terms of energy stored in fields (with zero fields anywhere being our reference zero potential energy). Basically, you integrate the square of a field over all of space, and you get an energy. That squaring is important: it's why the potential energy in two like electric charges placed near each other is more than the potential energy if those charges are far apart. But gravity works the other way around: the integral is larger when the potential energy is lower, because it's attractive for like charges. Hence, gravity has negative energy under this definition.

 

[Roboramma]

Why would one think their wasn't a 4th dimension?

Sorry - a fourth spacial dimension.

 

[martu]

It does indeed come from the fact that gravity alone has an attraction between like charges.

One way of dealing with potential energies is to calculate all of them in terms of energy stored in fields (with zero fields anywhere being our reference zero potential energy). Basically, you integrate the square of a field over all of space, and you get an energy. That squaring is important: it's why the potential energy in two like electric charges placed near each other is more than the potential energy if those charges are far apart. But gravity works the other way around: the integral is larger when the potential energy is lower, because it's attractive for like charges. Hence, gravity has negative energy under this definition.

Thanks understood and thank you INRM for clarifying in the first place.

 

[martu]

Sorry - a fourth spacial dimension.

Isn't time a spacial dimension just one we can't 'see'? Like the 3rd dimension is spatial to us but to a 2D critter it is an abstract idea. I thought this was why time slowed down the faster you go, you were travelling through time in a way sort of like catching it up.

 

[Skeptic Ginger]

....



I think Emperor’s clothes is a bit harsh, the one thing you can say is that the maths works which at least gives the Emperor some underwear.

I'll go for the underwear option. And I'll even add perhaps the emperor's underwear functions as clothes I don't recognize, like some girls wearing boxers as outerwear.

I hope it is clear:
I make no claims to know what I am talking about.
I do, however, retain the right to say, "sounds good but there's this little problem".
Could be the problem is on my end, or it could be (albeit much less likely) on the other end. But there is something wrong with having to use a 2D model to model the 3D shape of the Universe. It's not the same as modeling the unseen dimensions here. We can see 3Ds. We shouldn't have to use a substitute model. And the 3D model, expanding raisin bread, has a center and an edge.

 

[Roboramma]

Isn't time a spacial dimension just one we can't 'see'? Like the 3rd dimension is spatial to us but to a 2D critter it is an abstract idea. I thought this was why time slowed down the faster you go, you were travelling through time in a way sort of like catching it up.

This is getting silly. I'm talking about another spacial dimension beyond the ones we experience everyday. Call it a 4th spacial dimension, call it a 5th dimension (after time), the point is it doesn't need to exist, but is useful for conceptualizing the curvature of the universe.

 

[Roboramma]

I'll go for the underwear option. And I'll even add perhaps the emperor's underwear functions as clothes I don't recognize, like some girls wearing boxers as outerwear.

I hope it is clear:
I make no claims to know what I am talking about.
I do, however, retain the right to say, "sounds good but there's this little problem".
Could be the problem is on my end, or it could be (albeit much less likely) on the other end. But there is something wrong with having to use a 2D model to model the 3D shape of the Universe. It's not the same as modeling the unseen dimensions here. We can see 3Ds. We shouldn't have to use a substitute model. And the 3D model, expanding raisin bread, has a center and an edge.

I think the problem is that the universe is non-euclidean, but only to such a small extent that we can't actually build a model of that.

Imagine 2d beings living on a sphere. Could they make a 2d model to show the curvature of the sphere? No.

Similalry we live in a curved 3d universe, not a euclidean universe. But we can't experience that curvature. One way to think about it is that it's curved into a 4th spacial dimension (but this dimension doesn't have to exist).
You can't make a model of a curved 3d structure inside of 3 dimensions. I mean, how do you make a model with triangles whose angles don't add up to 180 degrees?

Or, maybe you can, but it would be extremely difficult to do so.

I think you could probably make a decent computer simulation, but note that this doesn't allow you to see the structure from the outside, only the affects of the structure from the inside.

 

[Skeptic Ginger]

I think the problem is that the universe is non-euclidean, but only to such a small extent that we can't actually build a model of that.

Imagine 2d beings living on a sphere. Could they make a 2d model to show the curvature of the sphere? No.

Interesting.

Similalry we live in a curved 3d universe, not a euclidean universe. But we can't experience that curvature. One way to think about it is that it's curved into a 4th spacial dimension (but this dimension doesn't have to exist).
You can't make a model of a curved 3d structure inside of 3 dimensions. I mean, how do you make a model with triangles whose angles don't add up to 180 degrees?

Or, maybe you can, but it would be extremely difficult to do so.

I think you could probably make a decent computer simulation, but note that this doesn't allow you to see the structure from the outside, only the affects of the structure from the inside.

I'll have to contemplate this for a bit.

 

[INRM]

Well when I said positive energy I meant energy levels that have a value greater than zero; when I said negative energy I meant energy levels that have a value less than zero.

For the total energy of the universe to be zero you would have to have one unit of negative energy for every unit of positive energy.

Energy tends to flow from higher levels to lower levels. Since negative energy is less than zero, positive energy would logically flow in such a way to reduce the negative energy.

Of course if there is as much positive energy as negative given enough time they would completely neutralize equalling zero. There is no violation of conservation of energy either.


INRM

 

[meow]

From this article at New Scientist:






I can almost wrap my brain around this, but one thing I am confused about is the Planck length. I had always understood the Planck length to be the smallest unit of distance that could ever be measured, due to the nature of light. But this article makes it sound as if the Planck length is the smallest unit of distance period. No half a Planck length, even if you can't measure it.

It's most likely that I am just not understanding the concept correctly, but it seems to me that if there is an actual, physical, smallest distance, that you would have to travel over that distance instantly, otherwise at some point you would have gone half of the 'shortest' distance.

Anyway, I thought this article was pretty neat! What you guys think?

i think it's fascinating. wouldnt surprise me in the least.

http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html?full=true

 

[meow]

ya know, i really think our world IS a giant hologram.

 

[meow]

i need 5 more posts till i can use an avatar. what a silly rule that is.

 

[Soapy Sam]

I'm going to predict that the hologramic universe will become the woo concept of 2009 .
Gone will be the word "Quantum" from all looney advertisements, replaced by various spellings of hologram((m) ((at)ic(al))).