Gravity is Bunk!!!
- Thread starter DaN K. StAnLeY
- Start date
-
- Tags
- gravity
As Reality Check said, expanded space and contracted space are both examples of deformed space.
sol invictus
Philosopher
- Joined
- Oct 21, 2007
- Messages
- 8,613
No. "Deformed space" simply means space that isn't flat. If that's hard to imagine, think about a stretchy, flexible surface (the infamous rubber sheet). Start with it stretched across a drum head, and cover it with a regular pattern of dots. Now picture what happens to those dots if you tighten the screws on the drum (they move apart), or loosen them (they move together), or if you poke your finger into the surface (they do something more complex).
All those are examples of how a two-dimensional space can deform. According to general relativity, very similar things can happen to spacetime (with three space and one time dimension).
Isn't contracted and expanded space still flat, provided it's contracted or expanded evenly—like in your drum example?
Ziggurat
Penultimate Amazing
- Joined
- Jun 19, 2003
- Messages
- 61,634
Yes, flat space can (in principle) expand or contract while still remaining flat.
Unless something has happened between page one and where this is located, the simplest point is: if the simple illustrations of how gravity works/exists and of how rotational forces work/exist do not make sense to you AND you do not understand/follow the math, you are pretty much up the creek and can either accept that these are proven whether they make sense to you or not - or you can assume that all the things that depend on them and/or are a result of the fact that they do exist are just made up.
This is not a put-down - different minds work different ways. But it is the heart of the problem.
This is not a put-down - different minds work different ways. But it is the heart of the problem.
Ok.
Then my "Yes, sometimes"–answer stands. Some, but not all, contracted space is deformed. Some, but not all, deformed space is contracted.
Bjarne, if you want a more informative answer than that, I think you need to be more detailed on what you're actually asking about.
portlandatheist
Illuminator
- Joined
- Jun 9, 2007
- Messages
- 3,725
The rotation does have a very real effect in the opposite vector of gravity. This is why the radius of the earth is different from pole to pole than it is through the equator.
according to wiki:
Equatorial radius 6,378.1 km
Polar radius 6,356.8 km
That's a difference of 21.3 km that I believe wouldn't be there had if there was no rotation.
according to wiki:
Equatorial radius 6,378.1 km
Polar radius 6,356.8 km
That's a difference of 21.3 km that I believe wouldn't be there had if there was no rotation.
Just thinking
Philosopher
- Joined
- Jul 18, 2004
- Messages
- 5,169
If I recall, and please correct me if I'm way off, if the Earth had a rotational period of 2 hours instead of 24, we would fly off the equator ... or pretty much just float freely above it. That's not all that great of an angular velocity.
Last edited:
sol invictus
Philosopher
- Joined
- Oct 21, 2007
- Messages
- 8,613
There's a bit of confusing terminology there. Yes, space can remain flat while it stretches/contracts, so long as it does so uniformly in a very specific way (for example, in "spatially flat" cosmologies). But during such periods, spacetime isn't flat. Making separation between space and time is sensible only under very special circumstances.
That sounds at least roughly right, yes. The acceleration due to rotation increases like the square of the period, and even with a 24 hour period the rotation decreases ones effective weight by .4% or so at the equator versus the poles.
Last edited:
W.D.Clinger
Philosopher
According to my calculations, a rotational period of 2 hours would cut our weight in half (at the equator). To become weightless, we'd need a rotational period of just under an hour and 25 minutes.
Will
Will space-time be flat once space has stopped stretching/contracting, or is it still deformed?
alexi_drago
Graduate Poster
- Joined
- Oct 2, 2006
- Messages
- 1,353
In the rubber sheet theory, what is the shape of the sheet at the centre of a mass placed on it?
sol invictus
Philosopher
- Joined
- Oct 21, 2007
- Messages
- 8,613
Spacetime could be flat if the stretching occurred in the right way and then stopped. But would be very difficult to make that happen, because if there's any mass or energy around it causes the stretching rate to continue to accelerate.
It's not a theory, it's an analogy. In gravity in 2 spatial dimensions (plus time), a mass causes space to fold into a cone with the mass at the tip. So in that case the space actually is flat except on top of the mass (any 2D surface you can make out of paper without tearing it or folding it is flat).
In the more interesting case of 3+1 dimensions the space is curved even away from the mass. There are various ways to express that curvature, but basically the radius of curvature scales like some power of distance from the mass.
Cool. I realise that totally flat, non-deforming space would be very difficult to realise, but I wanted to check that I'd understood the principle.
Bjarne
Philosopher
- Joined
- Oct 6, 2009
- Messages
- 5,075
Here in the Earth’s orbit around the Sun, - space bend / deforms
The Sun (matter) is the cause to that happen.
Billion km. away from the Sun the same thing happen: Space bend / deform because of the Sun.
What really happens here?
What is “bended” space or “deformed space” ?
We can say that the Sun (matter) have some kind of “contact // connection” with space right?
I mean because of matter causes space to: “bend” / “deforms”
How can matter billion of km away from the source (matter) bend space?
What happen?
Is matter contracting space?
Does space have some kind of “density” that can deform / bend / “””contract”””” ?
Or how is it possible to understand “bended” or "deformed" space?
The Sun (matter) is the cause to that happen.
Billion km. away from the Sun the same thing happen: Space bend / deform because of the Sun.
What really happens here?
What is “bended” space or “deformed space” ?
We can say that the Sun (matter) have some kind of “contact // connection” with space right?
I mean because of matter causes space to: “bend” / “deforms”
How can matter billion of km away from the source (matter) bend space?
What happen?
Is matter contracting space?
Does space have some kind of “density” that can deform / bend / “””contract”””” ?
Or how is it possible to understand “bended” or "deformed" space?
Last edited:
I'm not sure how much of it can be understood non-mathematically. If someone else here could give a clear, intuitive explanation, I'd be very happy, since I haven't heard one yet.
Bjarne
Philosopher
- Joined
- Oct 6, 2009
- Messages
- 5,075
Imaging you was the sun, you would now "bend" space 100 billion km away from you, - or 1.000.000.000.000.000.000.000.000.000 etc...... km away
How would you do it ?
Well it's easy isn’t it >> “Bended / deformed space is in reality contracted space. What the Sun (or matter does) is to contract space.
Does that not sound acceptable?
Last edited:
I don't know. I haven't read general relativity yet, so I can't say if that is an accurate way of describing it. Hopefully some more knowledgeable posters can answer your question.
Reality Check
Penultimate Amazing
No it does not.
Contracting space does not produce any force on an object moving in it. If you have contracting space then a straight line in that space remains as a straight line, objects still move in a straight line and Newton tells us that there is no force acting on them.
"Bended / deformed space" does produce a force on an object moving in it. Mass curves ("deforms") spacetime so that movement along a straight line in spacetime becomes a curve. This curvature in movement is a change in direction of the velocity of an object. This is an acceleration. An acceleration on a mass is described as a force (F=ma). We call that force gravity.