The discussion centers on the nature of forces described by Newton's third law, specifically why the forces are equal and what underlies this equality. Participants explore theoretical implications, philosophical questions, and the foundational aspects of Newton's laws.
Participants generally do not reach a consensus on the underlying reasons for the equality of forces. Multiple competing views remain, with some focusing on the philosophical implications while others emphasize the empirical basis of Newton's laws.
Participants note that the discussion touches on the limitations of physics in addressing "why" questions, which may lead to philosophical considerations rather than scientific explanations. The conversation also reflects on the potential for alternative theories if definitions of action and reaction were to change.
James Gordon said:I am not a physics expert or a math expert, but I do not see this question answered by searching with Google. The opposite forces described by Newton's third law, why are they equal? Why does not the pushed on object push back 1/2 as much, or 2.3% as much, or some other value than exactly the same as the force applied to it. What actually causes the forces to be equal?
Orodruin said:If you look at Newton's laws as fundamental, they are equal because the third law says so. This is how science works, you give a hypothesis which gives testable predictions and then you test it. The third law has been very well tested and so we conclude that it is a good description of how the world works.
If you want to consider the conservation of momentum more fundamental, then the third law is a consequence of momentum conservation (in the other viewpoint, it is the other way around).
Unfortunately, physics is not in the business of answering the "Why?" question.James Gordon said:Answering that it works because it works does not seem to address the why of my question. There is a why behind all things and I do not see that answered.
SteamKing said:Unfortunately, physics is not in the business of answering the "Why?" question.
Physics, as Orodruin stated, tests experimentally various hypotheses which are offered about how the universe works. Answering the "Why?" question often leads one from the scientific to the philosophical.
Newton's Second and Third Laws of Motion both offer testable hypotheses about motion. If experiments show that these hypotheses did not accurately describe how bodies move, then these laws would be replaced by different ones, and the process starts over.
SteamKing is saying that physics only cares about "how universe works?" not "why does it work that way?", so any "why?" question is out of physics. If you want to know why universe works the way it does, you shouldn't study physics but philosophy. But if you want to stay in physics, you should get used to it. That's part of understanding physics!James Gordon said:At this point it sounds like the answer is in fact "I don't know."
Shyan said:That's not a correct. SteamKing is saying that physics only cares about "how universe works?" not "why does it work that way?", so any "why?" question is out of physics. If you want to know why universe works the way it does, you shouldn't study physics but philosophy. But if you want to stay in physics, you should get used to it. That's part of understanding physics!
Shyan said:SteamKing is saying that physics only cares about "how universe works?" not "why does it work that way?", so any "why?" question is out of physics. If you want to know why universe works the way it does, you shouldn't study physics but philosophy. But if you want to stay in physics, you should get used to it. That's part of understanding physics!
So the proper way of saying it is, physics doesn't care about "why?" questions, so for a physicist its a choice to care about them or not. But if s\he does care, then s\he's thinking about something other than physics.
Your problem is that you think there is an action and then there is a reaction and so the situation seems asymmetric to you. But its not like that. Maybe its just bad wording. The situation is completely symmetric between the two objects. Otherwise how can you say which force is action and which is reaction?!James Gordon said:Fair enough, HOW is it that the opposite forces are equal, and not another ratio-relationship? I think you are misreading my usage of why, or perhaps I should use the word how, that really seems like a semantic issue. Regardless, how is it an object does not push back with half or a third the amount of force, instead of equal force?
Shyan said:Your problem is that you think there is an action and then there is a reaction and so the situation seems asymmetric to you. But its not like that. Maybe its just bad wording. The situation is completely symmetric between the two objects. Otherwise how can you say which force is action and which is reaction?!
Let me explain how this is different from answering a "why?" question. In this explanation, I observe the nature, the way objects interact. I realize the symmetry and make my laws somehow that they respect this symmetry. So its just that I'm modifying my laws so that they work, then I say they're correct because they work.
Why do you think things should be asymmetric? Do you have a definition that tells you which force is the action and which is the reaction?James Gordon said:What is the cause for things being completely symmetric between the two objects instead of an action and a reaction? This is still the crux of my question.
Shyan said:Why do you think things should be asymmetric? Do you have a definition that tells you which force is the action and which is the reaction?
Note that I'm not telling you're wrong. If you can define action and reaction somehow that in every problem you can identify them, and then propose laws with that asymmetry that agree with experiments, then you have proposed an alternative theory to Newton's, just because it works!
James Gordon said:I certainly don't have the expertise or talent to outdo Newton. But it is not that I think that things should be asymmetric, I am trying to understand how it is that they are not. What is the nature of this relationship that makes it as such?
Yep... No one is disputing that.James Gordon said:At this point it sounds like the answer is in fact "I don't know."
James Gordon said:Answering that it works because it works does not seem to address the why of my question. There is a why behind all things and I do not see that answered.