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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: automan]
#14504698 - 05/24/11 02:02 PM (12 years, 8 months ago) |
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automan said:
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Dimi said: Also, how is a change in direction not some form of acceleration? Can you explain an example?
Put a ball on the end of a string and spin it at 100rpm. It is infinitely changing direction, but maintaining 100 revolutions per minute. The actual speed of the ball would depend on the length of string, but it would stay the same.
The speed of the ball stays the same, but the velocity (speed + direction) is constantly changing. The ball is therefore accelerating. In fact, the acceleration is equal to v^2/r. The same is true of an electron moving in a magnetic field.
Edited by ChuangTzu (05/24/11 02:12 PM)
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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: automan]
#14504740 - 05/24/11 02:12 PM (12 years, 8 months ago) |
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automan said: I disagree that a curve in space causes acceleration. A change in direction, sure. That's why I think there is a missing measurement in physics. A unit of 4 dimensional space.
You can add as many dimensions you want, but if your theory doesn't add any more predictive power than a 3-space-dimensional model, then it's not worth the extra mathematics. String theory has 11 or more dimensions and it hasn't yet made a single prediction different from general relativity.
2 masses placed into a universe attract eachother and we understand very well in what way they will do that. There is really no explanation of how any of the forces act. Place opposite charges in a universe with nothing else and they will attract each other. What is actually moving them? The force is, nothing more. We postulate force-mediating photons but how does exchange of photons cause an attraction? They just do.
We derive analogies to gain some intuition on how they will act, but this is just a short hand so we can solve some problems with less math or to help us set up the math.
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automan
blasted chipmunk


Registered: 09/18/03
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Re: Gravity and Acceleration [Re: ChuangTzu]
#14504858 - 05/24/11 02:37 PM (12 years, 8 months ago) |
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ChuangTzu said: You can add as many dimensions you want, but if your theory doesn't add any more predictive power than a 3-space-dimensional model, then it's not worth the extra mathematics. String theory has 11 or more dimensions and it hasn't yet made a single prediction different from general relativity.
Trying to understand something better is never a bad thing even if it doesn't improve on the math to accomplish tasks we use today. It may lead to understanding to better solve problems we haven't thought of or needed to solve yet.
-------------------- No, no, you're not thinking, you're just being logical. ~ Niels Bohr
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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: automan]
#14505147 - 05/24/11 03:44 PM (12 years, 8 months ago) |
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automan said: Trying to understand something better is never a bad thing even if it doesn't improve on the math to accomplish tasks we use today. It may lead to understanding to better solve problems we haven't thought of or needed to solve yet.
No, I agree, that's why physicists have jobs.
Though, perhaps, some string theorists shouldn't have jobs--it'd free them up to do more useful work. But that's another topic...
There's nothing wrong with trying to improve your intuition of gravity by any means you can. Eventually you're likely to increase the predictive power of your analogies. I only took issue with the statement that physics is missing something with respect to gravity because a particular analogy is flawed.
While there is always room for improvement, general relativity is pretty damned good and doesn't seem to require or benefit from extra dimensions. There are some frays along the edges which indicate areas for improvement, but the string theorists haven't really shown us that extra dimensions help at all yet.
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Dimi
The Mindful One


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Re: Gravity and Acceleration [Re: ChuangTzu]
#14505262 - 05/24/11 04:09 PM (12 years, 8 months ago) |
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String Theory explains why gravity is such a weak force, as part of it is being "leaked" into extra dimensions. 
Okay, well string theory explains a lot, like merging general relativity and quantum mechaics. There's no reason not to think it's all the same physics. Laws shouldn't be different just because it's super small versus super large.
Thanks for the "ball" example!
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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: Dimi]
#14505431 - 05/24/11 04:49 PM (12 years, 8 months ago) |
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Dimi said: String Theory explains why gravity is such a weak force, as part of it is being "leaked" into extra dimensions. 
Forces have different strengths, I'm not sure why you'd assume that the force of gravity isn't just what it is. Why should it be any stronger? Does string theory offer any way to test whether some of the gravitational force is being "leaked" into extra dimensions? If not, what's the point of discussing it?
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Okay, well string theory explains a lot, like merging general relativity and quantum mechaics.
Has it done this?
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Dimi
The Mindful One


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Re: Gravity and Acceleration [Re: ChuangTzu]
#14506455 - 05/24/11 07:54 PM (12 years, 8 months ago) |
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"Has it done this?", Yes String Theory or M-Theory does explain how quantum mechanics and general relativity are combined.
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Forces have different strengths, I'm not sure why you'd assume that the force of gravity isn't just what it is. Why should it be any stronger? Does string theory offer any way to test whether some of the gravitational force is being "leaked" into extra dimensions? If not, what's the point of discussing it?
The point is, those four forces could be one-in-the-same. Just look at the electroweak force. Weak wasn't added until they figured out at high temps, they were manifestations of the same force.
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DieCommie

Registered: 12/11/03
Posts: 29,258
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Re: Gravity and Acceleration [Re: Dimi]
#14506894 - 05/24/11 09:12 PM (12 years, 8 months ago) |
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Dimi said: Laws shouldn't be different just because it's super small versus super large.
That is an assumption that sounds intuitively good, but for now it is just that - an assumption.
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johnm214


Registered: 05/31/07
Posts: 17,582
Loc: Americas
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Re: Gravity and Acceleration [Re: automan]
#14507481 - 05/24/11 11:05 PM (12 years, 8 months ago) |
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automan said: I disagree that a curve in space causes acceleration. A change in direction, sure. That's why I think there is a missing measurement in physics. A unit of 4 dimensional space. It seems like an object moving at a steady rate would move through a unit of space per rate. Even if that unit of space were stretched long by gravity. That would show as acceleration.
Remember: gravity doesn't just manifest as a curve in space, its a curve in space time. In addition to changing the space, it changes the time, and this accounts for the problem I think I see you observing with the standard analogy of the fabric and bowling bowl. The fabric is space and time, and the curve changes all these dimensions from the flat newtonian form.
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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: Dimi]
#14507599 - 05/24/11 11:31 PM (12 years, 8 months ago) |
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Dimi said: "Has it done this?", Yes String Theory or M-Theory does explain how quantum mechanics and general relativity are combined.
Oh really? Last I checked, it wasn't enough of a theory to explain anything.
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Dimi
The Mindful One


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Re: Gravity and Acceleration [Re: ChuangTzu]
#14508525 - 05/25/11 05:47 AM (12 years, 8 months ago) |
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Oh really? Last I checked, it wasn't enough of a theory to explain anything.
Yes, well I said that assuming the people in this thread know it hasn't been proven to be true yet.
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Simms
Fuckwit


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Re: Gravity and Acceleration [Re: Dimi]
#14508718 - 05/25/11 07:44 AM (12 years, 8 months ago) |
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Dimi said: Laws shouldn't be different just because it's super small versus super large.
A-ha! But are you sure its just that: big vs small?
I think it is more about the structure. How a structure, a group of billion atoms react and how single atoms react. Big difference, because eventually we are not talking about the same object in different scales, we are talking about completely different objects.
Group of atoms-molecules, group of molecules, act as material. But that does not mean that atoms itself are material, they make up material. So, they are not the same thing and assuming that same laws would apply to them is a hasty assumption.
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Dimi
The Mindful One


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Re: Gravity and Acceleration [Re: Simms]
#14508836 - 05/25/11 08:31 AM (12 years, 8 months ago) |
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I get that, as quarks make up atoms and they behave differently than 'material' as well. However, it's my belief that its' all the same physics governing everything, and that we just can't prove it yet, or are incapable of perceiving it.
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ChuangTzu
starvingphysicist



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Re: Gravity and Acceleration [Re: Dimi]
#14509255 - 05/25/11 11:02 AM (12 years, 8 months ago) |
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Dimi said: Yes, well I said that assuming the people in this thread know it hasn't been proven to be true yet.
So you said something that wasn't true because you assumed that the people reading it knew that it was false? You sound like a politician.
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Dimi
The Mindful One


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Re: Gravity and Acceleration [Re: ChuangTzu]
#14509291 - 05/25/11 11:08 AM (12 years, 8 months ago) |
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Okay dude, that was a little harsh. 
I figure everyone knows that M-Theory hasn't been proven. Those ideas were assuming that if it is correct, then those ideas would be right.
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