The discussion centers on the nature of force and its propagation, specifically whether forces are instantaneous or travel at the speed of light. Participants explore concepts related to gravitational effects, mechanical forces, and the implications of these ideas in different physical theories, including Newtonian physics and general relativity.
Participants express multiple competing views on whether forces are instantaneous or propagate at the speed of light, particularly regarding gravity. The discussion remains unresolved, with differing opinions on the implications of these ideas in various physical theories.
Some arguments rely on specific interpretations of physical theories, such as Newtonian mechanics and general relativity, which may not be universally accepted. The discussion also touches on philosophical aspects of time and reality, indicating a complex interplay between scientific and conceptual understandings.
PhDorBust said:Is force instantaneous or does it travel at the speed of light, and why?
Like is the gravitational effect felt on us by the sun immediate or does it take 8 minutes or so to be realized?
PhDorBust said:Is force instantaneous or does it travel at the speed of light, and why?
Like is the gravitational effect felt on us by the sun immediate or does it take 8 minutes or so to be realized?
creepypasta13 said:why would it not be instantaneous?
That is a common argument used against general relativity by those who do not understand it. If that is all there was to general relativity that argument would be correct. However, there is more (a whole lot more) to general relativity than a finite propagation time for gravity. Other terms such as frame dragging nearly cancel the effects of frame dragging. For example, for planets far from the Sun and moving at relatively slow speeds compared to light speed it looks very much like gravity does propagate instantaneously. This is not the case for Mercury. That general relativity explained a known defect with the Newtonian explanation of Mercury's orbit was one of the reasons general relativity won the day over Newtonian mechanics.Pierre007080 said:Gravity is instantaneous. If it were not there would be a "drag" factor on any rotating body because the force would be acting behind the radius line.
This is meaningless nonsense.Because mass absorbs space the support between two masses is removed and the effect is instantaneous.
As DH already said, this simlistic logic is wrong. It assumes that a field can only contain information about the position of the source during emission. But a field can also contain information about the velocity of the source during emission.Pierre007080 said:Gravity is instantaneous. If it were not there would be a "drag" factor on any rotating body because the force would be acting behind the radius line.
No it isn't. It is a human word used to describe a natural phenomena. Time exists whether we are here to observe it or not.pgardn said:Time is a human construct.
russ_watters said:No it isn't. It is a human word used to describe a natural phenomena. Time exists whether we are here to observe it or not.
No, the arrow of time is a consequence of thermodynamics. It is also built into the laws of the universe.maverick_starstrider said:The arrow of time may be a human construct.
Yeah, we really can. You guys are arguing against the definition of science here. The whole point of science is to explain/understand natural phenomena. That is - things that exist in nature, whether we are here to observe them or not.Gear300 said:We can't really be sure whether something is a human construct or not. Even reality, despite how paradoxical it is, is something we take as common sense and for granted.
russ_watters said:No, the arrow of time is a consequence of thermodynamics. It is also built into the laws of the universe.
russ_watters said:? In that wiki article there are 7 "arrows of time" listed and 6 of them are consequences/manifestations of the thermodynamic arrow.
Since that article doesn't mention Sean Carroll, it doesn't really say anything about what you are talking about...
russ_watters said:Yeah, we really can. You guys are arguing against the definition of science here. The whole point of science is to explain/understand natural phenomena. That is - things that exist in nature, whether we are here to observe them or not.
If we define a "year" to be something other than its current definition, that doesn't make the sun any younger or older.
We can say anything, but that doesn't mean it makes any sense... could you explain what you mean?Gear300 said:Couldn't we say that we take for granted what 'natural phenomena' is?
russ_watters said:We can say anything, but that doesn't mean it makes any sense... could you explain what you mean?
To perhaps jump ahead, science requires the assumption that our senses or our God aren't screwing with us. Is that what you are getting at?
Applied to time, we measure time based on physical processes such as the oscillations of a cesium atom. Are you saying that if humans weren't here, the number of times a cesium atom oscillated since the sun formed would be different?
Gear300 said:We can't really be sure whether something is a human construct or not. Even reality, despite how paradoxical it is, is something we take as common sense and for granted.
russ_watters said:Yeah, we really can. You guys are arguing against the definition of science here. The whole point of science is to explain/understand natural phenomena. That is - things that exist in nature, whether we are here to observe them or not.
If we define a "year" to be something other than its current definition, that doesn't make the sun any younger or older.
russ_watters said:We can say anything, but that doesn't mean it makes any sense... could you explain what you mean?
To perhaps jump ahead, science requires the assumption that our senses or our God aren't screwing with us. Is that what you are getting at?
Applied to time, we measure time based on physical processes such as the oscillations of a cesium atom. Are you saying that if humans weren't here, the number of times a cesium atom oscillated since the sun formed would be different?
Gear300 said:No...I'm just saying things might be like that...then again, even if humans weren't around, the number of oscillations just might be the same. But how do we know which side is true?...and if we were to go even deeper, we probably wouldn't be able to define truth too well either...though I take it that many would say that this goes beyond science. I'm not taking any sides, I'm just saying that both of those options are possible.
maverick_starstrider said:This thread is heading for a shift in folders.
So what?Phrak said:Rocks are hard and water is wet. The consensus in discussions of physics as a science is that we are assume an independent reality. This is not a know, but an assumption, that we should be using in common.
Possible or not, none of that is useful. The fact of the matter is that science, as currently conceived, works. So all this idle speculation about god screwing with us really isn't useful in describing reality.Gear300 said:No...I'm just saying things might be like that...then again, even if humans weren't around, the number of oscillations just might be the same. But how do we know which side is true?...and if we were to go even deeper, we probably wouldn't be able to define truth too well either...though I take it that many would say that this goes beyond science. I'm not taking any sides, I'm just saying that both of those options are possible.