# I Space Time sketch

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1. Dec 14, 2015

I've been wondering, space time is supposed to be consists of one dimensional string as described in the string theory, but how exactly does space time looks like since it is invisible to us. Is it possible to get a sketch of such one dimensional strings?

2. Dec 14, 2015

### Simon Bridge

As usual, we make models to represent things that are otherwise invisible.
A 1D string is sketched as a line as usual. You will find lots of examples online and in books on string theory.

3. Dec 14, 2015

Right but string theory is a theory, isn't there an actual way to test space time and make it visible?

4. Dec 14, 2015

### Simon Bridge

Depends what you mean by "visible".
You can show that the behaviour of objects in space and time is consistent with a particular model we are interested in.
Ferisntance - the various demonstrations of general relativity show that this geometric treatment of space and time works.

5. Dec 14, 2015

There is length contraction to have a more definite shape of this behavior, but most of the time you move at a straight path.

6. Dec 14, 2015

### Simon Bridge

When you jump you dont move along a straight path through space with time.
Some experiments probing the geometry of space time involve light rays ... eg. with gravitational lensing.
But you still have not said what you mean by "visible".
Considering yr last comment, it would help to know your education level too.

7. Dec 14, 2015

I graduated from university back in 2009 with a B.S. degree and currently working. Visible as of showing what this one dimensional string would look like, I know it is too small to see, but the general direction would maybe be in a certain direction or shape, and if there is a way to make these string visible to see? Gravitational lensing would be showing space and time curvature in a much wider sense.

Last edited: Dec 14, 2015
8. Dec 14, 2015

Last edited by a moderator: May 7, 2017
9. Dec 15, 2015

Sorry, after reading more I think the article more focused on the attosecond laser pulse structure than the space time structure. Let me know if I'm wrong. It's a pretty cool concept though, sigh.

10. Dec 19, 2015

### Simon Bridge

afaik there is no phenomena that can show that string theory is underlying the physics we currently know in the same sense that gravitational lensing shows that general relativity underpins Newtonian gravitation and motion. If there were, the string theory would have been confirmed.

11. Dec 19, 2015

Well I am thinking of tracing out the structure that's made up of the one dimensional strings in the 3 dimensional world. Based on special relativity described in Wikipedia here it is believed that spacetime follows a one-dimensional curve. I can be misreading it. So if it is possible to trace out such a structure, let it be a whirlpool or some flow of direction it would be interesting to visualize it.

Last edited: Dec 19, 2015
12. Dec 19, 2015

### Hornbein

I think he means that a stationary point looks like a line in spacetime.

13. Dec 20, 2015

### Simon Bridge

A point in 3-space traces out a 1D curve, over time, called a "trajectory"... you probably don't find this mysterious.
In 3+1 space-time, a point is called an "event" - related events trace out 1D curves in space-time called a "world-line".
The simplest worldline is where the event is stationary wrt the observer - in which case it is a straight line up the ct axis.
The concept "follow a curve" does not apply to space-time: it is the mathematical framework that we use to do geometry in.
http://preposterousuniverse.com/grnotes/grtinypdf.pdf [Broken]

Last edited by a moderator: May 7, 2017
14. Dec 20, 2015

Well, we apply the 3D cartesian structure to space time. I think space time is of a different structure, so I'll leave it at that. I can provide an explanation, but it would be a bit of self speculation. On top of that I do not have a correct structure of space time either, so I thought sketching it would get me the correct structure.

15. Dec 21, 2015

### Simon Bridge

Look up "geometry of space time" ... we would generally say that space-time is non-euclidean, but it is usually represented on cartesian space-time diagrams. Its just that the space-time 4-ball does not look like a euclidean 4-sphere. You can see this if you just do it in 2D, where one dimension is time (ct), and plot all the points where the space-time length is 1. ie. If you put y=ct then you are plotting $x^2-y^2=1$.

Apart from that, "flat" case, the precise geometry will depend on the situation.
... and what is observed depends also on what the observer is doing.

We dont have to use cartesian coordinates, for instance the geometry in the link is more usefully expressed in spherical-polar coordinates. More generally, space-time geometries get represented in a coordinate-independent form.

You should probably get used to the way space-time gets described before starting down your own path.

Last edited: Dec 21, 2015
16. Dec 21, 2015

My idea of spacetime would be something more like a curved one dimensional string. Although these geometry does look interesting surrounding any spherical mass. Even if space time is not around a spherical mass it should still exhibit some type of one dimensional structure that cannot be seen but still can be found by the present day technology. The test which we conducted for a warped space time is this. Although it is assumed that without a spherical mass or black hole the spacetime is still "flat", which is contrary to my belief, that they should behave more like a curved string. For a curved string it should be visible to the human eye like a jumbled wire, but for some reason it is invisible.

17. Dec 21, 2015

Well, I don't have to prove the structure to attempt to discover it right?

18. Dec 23, 2015

Anyone else thinks if space time has a shape and if there is a way to test it?

19. Dec 23, 2015

### Simon Bridge

The shape of space-time is a well established concept in physics ... you seem to be using the words to describe something else which is unclear right now.

What do you mean by "dimensional structure"? Can you provide an example?

20. Dec 23, 2015

Well space time is not a standard 3 dimensional cartesian structure, that I am sure of. Imagine a cube made out of blocks like a Rubik's cube here. If I have a figure of myself in one of the "block", then my figure is supposed to repeat itself for a standard cartesian structure does in all of the blocks (27 blocks in a Rubik's cube, so that would be 27 figures). You might ask, why is the figure repeating, right there is only 1 figure, but the repeating structure of space time, or what space time can contain shows the duplicate of the figure by 27 times. So the only way for the figure to "not repeat itself" in these blocks of space time, is that every single block of space time structure must be different from each other and continuous. We represent this differences in the space time structure with a "number" for distance. But how the space time structure differ from each other remains unknown, thanks to various resources I was able to come to this conclusion. So what kind of structure is space time if it is "not" a 3 dimensional cartesian structure, I can't really say, my best guess is a structure that is different in every direction so that allows space time to hold different things within, else the figure would just repeat itself in every length. Keep in mind the space time structure changes from length contraction in relativity, so it might contain a "shape" with minimum and maximum value. You can do a lot of things with a minimum and maximum value.

21. Dec 23, 2015