stevmg said:starthaus -
I have read Taylor/Wheeler Spacetime Physics the First edition (1962 version) which is easier for a novice to comprehend than the later 2002 2nd edition as the later edition has too many bells and whistles. The First Edition is more to the point. Remember I have no one else around me to even discusss this subject matter with other than this Forum and so digesting the material can get slow.
The third chapter goes into GR. It explains the curvature of spacetime as the source of gravity. What is not explained in any text that I ever read or any comment anywhere is that what would make an object at rest (I know, there is no such thing as "at rest") appear to be pushed (curved worldline)?
Then it dawned on me - every object anywhere has a worldline that is forever growing and hence, other than the old general saying that "everything's in motion" and all frames of reference are relative to each other with no central one favored, there is the motion - presumably all the worldines would be traveling along a geodesic (I guess that's the right term) and there would always appear to be a "force" acting on them as all geodesics are curved.
I didn't have anybody here to tell me that and I never saw it anywhere else. All the 2D analogies which showed by bending a 2D world in a third dimension, objects would appear to be pushed together as they moved (page 184 of this 1st Edition), never showed why they would move in the first place.
In a 3D world, the unseen 4th dimension, time, makes them move (i.e. - the worldline.)
I hope I am correct.
starthaus said:This is a tricky question. To my best knowledge there is one very good vizualization of the effect, it is a series of lectures produced at Caltech by Jim Blinn entitled "The Mechanical Universe".
stevmg said:Thank you for your quick reply. It seems that the more elementary we get (such as what initiates the movement of the parable of the two travelers cited in Spacetime Physics, 1st Edition) the more complex become the answers.
stevmg
starthaus said:This is a tricky question. To my best knowledge there is one very good vizualization of the effect, it is a series of lectures produced at Caltech by Jim Blinn entitled "The Mechanical Universe".
Shackleford said:Hasn't that been the case historically with physics? The more we learn the more complex it becomes and the less we realize we know.
Shackleford said:Hasn't that been the case historically with physics? The more we learn the more complex it becomes and the less we realize we know.
Always remember, that when somebody says 'this is complex', he/she actually is saying 'I do not know'. This custom has come into existence because many people think, that the reason why they do not understand something must be that many factors are involved. In reality, however, it may well be the case that only one rule or one principle may be the cause of the phenomenon under study. Take, for example, the following number sequence:Shackleford said:complex
stevmg said:As described in "Choas" by Gleick.
Actually, I say "I do not know" all the time to my wife...
It is the safest answer. Trust me.
Sometimes it refers to unknowns, but not always. "Complex" can refer to phenomena that are understandable but whose behavior requires a lot of computing power to predict, like the predicting the weather a few days from now on a supercomputer, or calculating the large-scale behavior of a collection of water molecules from basic quantum physics (as was done here). It can also refer to things where understanding the answer requires you to have already gotten the training needed to understand a bunch of background concepts and mathematics that may be far from everyday experience (like the concepts and math involved in general relativity), which may have been the sort of thing stevmg was getting at when he said "It seems that the more elementary we get (such as what initiates the movement of the parable of the two travelers cited in Spacetime Physics, 1st Edition) the more complex become the answers."AdVen said:Always remember, that when somebody says 'this is complex', he/she actually is saying 'I do not know'.
JesseM said:Sometimes it refers to unknowns, but not always. "Complex" can refer to phenomena that are understandable but whose behavior requires a lot of computing power to predict, like the predicting the weather a few days from now on a supercomputer, or calculating the large-scale behavior of a collection of water molecules from basic quantum physics (as was done here). It can also refer to things where understanding the answer requires you to have already gotten the training needed to understand a bunch of background concepts and mathematics that may be far from everyday experience (like the concepts and math involved in general relativity), which may have been the sort of thing stevmg was getting at when he said "It seems that the more elementary we get (such as what initiates the movement of the parable of the two travelers cited in Spacetime Physics, 1st Edition) the more complex become the answers."