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sjunky
2008-Nov-10, 07:19 AM
http://deco-00.slide.com/r/1/40/dl/th9GRFq_7T8C6gsNl7U1kuWnnKkzP0CK/watermark


Einstein introduced the concept of 4 dimensional space-time manifold.

My question is
Is there any practical explanation to prove that
the curve is 'Smooth' in inner and outer sides.?

Thanks.

WaxRubiks
2008-Nov-10, 08:06 AM
perhaps you could elaborate..

what does the diagram/picture mean?

david perry
2008-Nov-10, 08:34 AM
perhaps you could elaborate..

what does the diagram/picture mean?

Isnt it obvious? If you put "the powder" on the table and snort it in a line "a" to "b" through the tube shown, you enter a "space-time wrap (sic)".

D

PraedSt
2008-Nov-10, 08:36 AM
LOLl! :D

sjunky
2008-Nov-10, 07:52 PM
Actually I added the table and powder for future reference



As far as my question is concerned This universe is made up of space-time curves, my particular query is 'Are they are smooth in inside and outside
or they are rough' Any practical experiment to prove this ?

PraedSt
2008-Nov-10, 07:59 PM
I can suggest a way to get a better response. Click on that red and white triangle on the top right corner of your original post. This messages the moderates. Ask them politely if they would be kind enough to move this question to the Q&A section. It seems the right sort of question for that, and you'll have greater traffic there.

Also, welcome to BAUT sjunky. :)

sjunky
2008-Nov-10, 08:10 PM
I can suggest a way to get a better response. Click on that red and white triangle on the top right corner of your original post. This messages the moderates. Ask them politely if they would be kind enough to move this question to the Q&A section. It seems the right sort of question for that, and you'll have greater traffic there.

Also, welcome to BAUT sjunky. :)



r u sure ? shall I do that know

thanks.

grant hutchison
2008-Nov-10, 09:24 PM
My question is
Is there any practical explanation to prove that
the curve is 'Smooth' in inner and outer sides.?The curvature corresponds to the varying force of gravity. Since gravity varies smoothly from place to place in open space, the curvature is smooth. A rough "surface" in the spacetime diagram would imply the presence of lots of small local sources of gravity.
There is no "inside" and "outside": in the diagram, we have a 2D curved surface; in general relativity, a 4D curved hypersurface.

Grant Hutchison

ToSeek
2008-Nov-10, 11:31 PM
Moved from Astronomy to Q&A.

sjunky
2008-Nov-11, 05:58 AM
OK we will leave space-time wrap here and discuss about it later on
Now in the picture you are seeing a table with 2 points A & B.

We know that the shortest path is a St.line b/w them.

That is not my question

The table is in space that means no atmosphere implies no disturbance of air,

We would use automatic robot hand instead of Human's to avoid hand shaking.

Now the pen is filled with some powder, and from a certain height above the table the hand will try to draw a St.line with out coming contact to the table.

In idle conditions we will get a St.line as straight as a measuring scale

In reality can we get it ? if the experiment is done in space

If not why ? what would be the reason.?

eburacum45
2008-Nov-11, 07:30 AM
The presence of the table will cause a small amount of gravity (and so will the presence of the 'robot hand'). You can't ever experience the condition of a complete absence of gravity whenever there is something with mass in the vicinity.

Note that it is a misconception that there is no gravity in space; there is gravity alright, especially near a planet, but if you are in orbit you are in freefall, and you feel weightless because you are falling.
http://en.wikipedia.org/wiki/Freefall

sjunky
2008-Nov-11, 07:42 AM
The presence of the table will cause a small amount of gravity (and so will the presence of the 'robot hand'). You can't ever experience the condition of a complete absence of gravity whenever there is something with mass in the vicinity.

Note that it is a misconception that there is no gravity in space; there is gravity alright, especially near a planet, but if you are in orbit you are in freefall, and you feel weightless because you are falling.
http://en.wikipedia.org/wiki/Freefall


so what about St.line

can we draw a St.line b/w those 2 points?

sjunky
2008-Nov-11, 11:01 AM
At the end

can we see a straight line ?

eburacum45
2008-Nov-11, 01:30 PM
No matter how straight you draw the line, it will be immediately affected by the gravity of the table and the robotic hand- so the answer is no. The gravitational effect of these small objects will be small, so it will look pretty much like a straight line- at least at first.

mugaliens
2008-Nov-11, 11:51 PM
Isnt it obvious? If you put "the powder" on the table and snort it in a line "a" to "b" through the tube shown, you enter a "space-time wrap (sic)".

D

Are you sure that's not the space-time warp women enter when they go off to "powder their face?"

antoniseb
2008-Nov-11, 11:59 PM
I'm still in the dark as to what you mean by smooth (or its antonym) for both "surfaces" or your space-time wrap?

Are you asking about Planck-scale variations from smooth? Also how do you define one side of the surface from another?

sjunky
2008-Nov-12, 12:19 PM
I'm still in the dark as to what you mean by smooth (or its antonym) for both "surfaces" or your space-time wrap?

Are you asking about Planck-scale variations from smooth? Also how do you define one side of the surface from another?

I didn't get what you said, a bit clear would help me to explain

Thanks.

PraedSt
2008-Nov-12, 12:40 PM
I didn't get what you said, a bit clear would help me to explain

Thanks.

I think antoniseb is asking is:

1. How are you defining 'smooth'? It depends on what scale you are using. For example, a sandy beach looks smooth from head height, but if you get down to the surface, you notice all the sand grains- a beach is very rough at that scale.

2. About sides, as far as I understand, we're embedded in space-time. Nothing is enclosed anywhere, so there is nothing like an 'inside' and 'outside' surface. There's only one surface.

Ok, I don't know much about space-time, so (2) may be wrong. But that still leaves antoniseb's (1)...

sjunky
2008-Nov-12, 01:15 PM
I think antoniseb is asking is:

For example, a sandy beach looks smooth from head height, but if you get down to the surface, you notice all the sand grains- a beach is very rough at that scale.


antoniseb's (1)...

Exactly, exactly you got my point

I'm asking the characteristics of space-time

Is it appearing like that for our satisfaction or it is something different

How can we deny the existence of medium 'aether' .?

PraedSt
2008-Nov-12, 01:32 PM
Er...how do you get from smooth to aether? :)

Also, 'our satisfaction' is usually not an objective of science. Look at quantum mechanics.

sjunky
2008-Nov-12, 05:50 PM
Er...how do you get from smooth to aether? :)

Also, 'our satisfaction' is usually not an objective of science. Look at quantum mechanics.

OK no aether, we will go ahead with space-time conversation



In idle conditions, can we get a St. line? if not y

antoniseb
2008-Nov-12, 08:52 PM
In idle conditions, can we get a St. line? if not y

Would you be so kind as to write with fewer abbreviations? I'm really not sure what you're asking here. What is an idle condition?

Celestial Mechanic
2008-Nov-13, 01:51 PM
Would you be so kind as to write with fewer abbreviations? I'm really not sure what you're asking here. What is an idle condition?
I'm going to guess that sjunky means "ideal" when he/she writes "idle". :)

antoniseb
2008-Nov-13, 07:59 PM
I'm going to guess that sjunky means "ideal" when he/she writes "idle". :)

You're probably right, but in this context, what is an ideal condition? A massless table and powder? Oh, and what is a Saint line? (or is that Street line?)

DrRocket
2008-Nov-13, 11:19 PM
Einstein introduced the concept of 4 dimensional space-time manifold.

My question is
Is there any practical explanation to prove that
the curve is 'Smooth' in inner and outer sides.?

Thanks.

Your question is a little loose. What is "the curve" ? Curves and surfaces have only one side. There is no "inner" or "outer".

However, to try to address your questin it is perhaps germane that the formulation of space-time is as a smooth manifold, complete with differentiable structure and a Lorentzian metric, on the tangent space.

Celestial Mechanic
2008-Nov-14, 05:16 AM
You're probably right, but in this context, what is an ideal condition? A massless table and powder? Oh, and what is a Saint line? (or is that Street line?)Again, context suggests "straight" line for sjunky's St. line.