Why do we have to make assumptions in science?

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Discussion Overview

The discussion revolves around the necessity of making assumptions in scientific theories, particularly in the context of General Relativity (GR) and the nature of gravity as a curvature in spacetime. Participants explore the implications of these assumptions and the philosophical underpinnings of scientific reasoning.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Meta-discussion

Main Points Raised

  • Some participants question why matter must move into the curvature of spacetime rather than remaining stationary, suggesting that "sitting still" is a specific path in spacetime.
  • One participant explains that the concept of a "world-line" in GR allows for various paths, including stationary ones, but emphasizes that particles do not remain still in spacetime.
  • Another participant introduces the idea of geodesics and the principle of least action, proposing that matter follows paths that optimize certain criteria, although the reason for this optimization remains unclear.
  • A participant acknowledges the influence of curved geometry on the paths of matter and suggests that the geometry plays a critical role in determining these paths.
  • There is a mention of the limitations of mathematical proof in physics, with one participant arguing that certain foundational assumptions must be accepted without proof, highlighting the inherent uncertainties in scientific inquiry.
  • Another participant expresses a need for evidence and mathematical backing for alternative theories presented in the discussion, while recognizing the established evidence for GR.

Areas of Agreement / Disagreement

Participants express differing views on the nature of assumptions in science and the implications of GR. While some agree on the necessity of assumptions, others challenge the completeness of mathematical proofs in explaining physical phenomena. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants note that certain foundational concepts in geometry and physics may not be provable, indicating a reliance on assumptions that are taken for granted. This highlights the limitations of mathematical frameworks in fully explaining the nature of reality.

Forestman
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I know that GR says that gravity is caused by a curvature in spacetime, but why would matter have to move into the curve, why not just site there on the curve.
 
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Forestman said:
I know that GR says that gravity is caused by a curvature in spacetime, but why would matter have to move into the curve, why not just site there on the curve.
Forestman, anything the piece of matter does corresponds to some path in spacetime.
What you call sitting still is one possible path (shall we call the path a "world-line"?)

I'm not saying this is how Nature works, only that this is how it works according to GR.
There is an idea of a nice path----analogous to the shortest distance paths, geodesics, on a curved surface.

Curved geometry (in particular curved 4D geometry) can influence where matter goes by deciding things like shortest distance.

When there are forces and interactions and potential hills, then geometry can still play a role. There will be a Lagrangian and an action integral and (in theory) the matter will want to follow a path that optimizes the action. E.g. a least action path. And the geometry is still a key ingredient.

You could call the physical action integral "bother". And then you could ask a new version of your question: "Why does matter choose the spacetime path with the least bother?"
(which indeed might happen to be a sitting-still type of path from somebody's perspective.)
Why does matter optimize? And depending on how you set it up it might maximize instead of minimize, but always some kind of optimum.
And the answer might be that we don't know why matter chooses optimal or least bother paths.

I hope you get several more answers. It is an interesting question. You might look up action principle on Wikipedia.
http://en.wikipedia.org/wiki/Principle_of_least_action
 
Last edited:
Forestman said:
I know that GR says that gravity is caused by a curvature in spacetime, but why would matter have to move into the curve, why not just site there on the curve.

"Sitting there" at one point in spacetime is equivalent to asking a particle to sit there at a particular point in space and time.

particles don't do that.
 
So what you guys are saying is that since time is bent as well as space an objects world line would be bent towards a massive body. That makes sense. Thanks.
 
A.T. thanks for that, what you said makes a lot of sense to me.

Hey TimothyTang, you have an interesting theory and all, but I would need to see some evidence and math for it. There is a lot of evidence for GR though.
 
My previous post got deleted because I was typing it as the moderator deleted some other ones and I suppose it had nothing to do with the original question anyway. However I think it would be interesting to note in the debate with objects following the "nicest path" in GR that no matter how hard one tries there are certain things that can't be proved by math. I mean that we have to take some things for granted and make a FEW assumptions (they aren't at all outlandish). For instance in basic gemetry there are a few things that have no proof which I can't exactly remember. I think they are a point and 2 other things. All things said it isn't outlandish to make an assumption of what a point is. The point(no pun intended) that I am trying to make is that I believe there is a limit to how far math and physics an go to proving why certain things happen. That isn't to say they can't offer an explanation, but you have to start somewhere and there has to be something that you can't prove that you take for granted based on the evidence you have at hand. Nature doesn't have a limit like that though so we have to make due with what we have to explain it
 

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