The 10th Dimension (Physics!)

My background is not in physics, but I found this video to be relatively straightforward. I ask the physics people (Almagest, Tak, others?) to watch it and tell me if this is a pretty good representation of very high-level physics theory.




No I do not know why the forum isn't formatting it correctly. Make it fixed please, Galt!

Format for embedded video link is:

{flash(x,y)}<direct link>{/flash}

Sub brackets for braces obviously. x,y=425,350 works well.

URL link from clicking:

https://www.youtube.com/watch?v=HvgwR9ERCBo&NR

Direct link:

https://www.youtube.com/v/HvgwR9ERCBo&NR

So:

Interesting video btw. I hadn't heard it explained this way before.

My current understanding is that string-theory in a sense predicts too much. Its testable hypotheses also are beyond our current grasp energetically. So while it might explain a few things, right now it is mathematical gymnastics and not science.

Curious to hear input from the actual physicists on the forum...

I found a BBQ frito in my couch today

It was good

Peanutbutter wrote:

Make it fixed please, Galt!

Sorry, the red name was taken away a couple of months ago.

>.>

Watched the video.

This is fun as a brain game but nothing else that I can see. The first 2 dimensions only exist in calculations and to use their existence to relate in some way to "2D entities moving through the 3rd dimension" and then extrapolate that out to a list of dimensions is silly. The highest physics class I took was only 2 semesters in college so maybe it makes me a physics hillbilly but I just don't see the point.

Grak, I know the format. The forum posting tools even do the formatting for you. A series of [youtube] tags will format to [flash] tags on post, and even when I explicitly put [flash] tags the board wouldn't format them and I got a big empty space where the vid should have gone. It just was broken but it's apparently fixed now.

But w/r to the contents, I'm curious to see what the grad students (Tak at entry-level, Almagest finishing up his doctorate) think of it, too.

I fixt it.

In physics land, the actual conceptualization of how the large number of dimensions play out is not really emphasized. It's just a number in an equation (usually referred to as degrees of freedom), and whatever number makes the equation work, that's how it is. Especially considering this number changes depending on what theory you're talking about, coming in and saying, "This is how we conceptualize 10 dimensions and there can't be any more" seems kinda silly.

I'd agree with Galt that it's an interesting video in brain exercise, but from a physics point of view, I would have to describe it as inane.

Of course, I took one string theory class two years ago and have forgotten most of it.

Yay physics!

Well, M-theory has 11 dimensions of spacetime, including time, so I don't know how he can say there are only 10 maximum dimensions of spacetime, including time. The way I understood it, there is time and then 10 dimensions of space, but all but three of the space dimensions are curled up in a very contrived manner so that we can't see them.

Also, a cylinder is still a two-dimensional object, even though it has curvature in the third dimension. You don't get another dimension by curving something. If what he said was true, we live in four dimensions, since the universe has curvature in the fourth dimension of space.

Tak wrote:

Also, a cylinder is still a two-dimensional object, even though it has curvature in the third dimension. You don't get another dimension by curving something.

Like I said, maybe I'm a physics hillbilly but I don't see how that is agreeable. In terms of 3D space bending in the 4th is the "bending" in the 4th dimension referring to time dilation due to gravity? Is that the basis for the idea of 2D objects bending in the dimension "above" their current dimension? If so I don't see the point of any of it. It all still seems like a flawed way of relating the physical world with time in some sort of functional way. Between the inconsistent units of measurement and the use of fictional objects to explain other dimensions seems like a big bowl of nothing to me.

When you take a two dimensional space and bend it in the third dimension, all you are doing is redefining how points in your space connect to each other. If you can't actually travel in the 3rd dimension, you still live in a 2-dimensional space. If you're in a flat, 2-dimensional world, and you have a triangle, the sum of it's angles will be 180 degrees. If you go off in one direction, you can go in that direction forever. If you live on the surface of a sphere, which is still a 2-dimensional object, since you can't move up or down, the sum of the angles of a triangle will be greater than 180 degrees and if you walk in one direction, you'll eventually come back to where to started. The difference between these two space-structures is how adjacent points connect. A resident of one these geometries wouldn't be able to tell the difference between them just by looking around, since they can't see in the 3rd dimension - it's not really there, just a mathematical construction. They could tell the difference between the geometries by drawing triangles and carefully measuring they're angles.

In our universe, we have three dimensions of space and one of time. Ignoring local curvature, the universe could have three possible geometries, it could be flat, just like a flat 2-dimensional surface, it can have positive curvature, like the surface of a 4-dimensional sphere, or it can have negative curvature, which doesn't have a true 2-dimensional analog, but it's kind of like a saddle-shape. We can think of this curvature as existing in the 4th dimension, but there isn't really a 4th dimension, since we cannot actually move through it. The 4th dimension is a mathematical construction with no basis in reality that we use to describe how adjacent points in space connect.

Now, you can think of four-dimensional spacetime, but this is not the same as a space with 4 dimensions. Time is intrinsically different, in that when you look at distances in spacetime, space distances essentially give positive contributions and time gives a negative contribution. What the dude in the video did was attempt to construct a spacetime with 3 space dimensions and 6 time dimensions. String theory has 9 or 10 space dimensions and 1 time dimension.