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In a previous thread, the OP asked for answers at the "I" (i.e., undergraduate) level to the following question:
S/he received a variety of contradictory answers, and the discussion may have been hindered by attempts to present more sophisticated mathematical ideas as the appropriate level, resulting in some imprecision and confusion. I'm starting this thread so that we can have a discussion at a higher level of precision.
My answer to the OP's question is that the question states a common, historically-based misconception. The laws of physics *can* be the same in noninertial frames, if we write them in a certain way.
First some historical context. Einstein's original interpretation of relativity, when he created it a century ago, was in some ways hazy and incorrect, which is perfectly understandable since the theory was in its childhood. His original formulation of SR gives a prominent role to frames of reference, but it is now understood that the notion of a frame of reference is optional, and frames of reference play no foundational role. Einstein's original description of GR was that it generalized SR to noninertial frames. This is not the way modern relativists describe the distinction. The distinction is now understood as one between flat spacetime and curved spacetime. Unfortunately, many popularizations still state the distinction according to Einstein's original incorrect understanding.
The laws of physics can be stated in ways that do not require the introduction of the notion of a frame of reference. If one wants to adopt a frame of reference, then these statements of the laws of physics can be interpreted in terms of a particular frame, and it makes no difference whether the frame is inertial or noninertial.
Historically one of the most important examples was Maxwell's equations. One way of stating Maxwell's equations is as follows:
##\nabla_s F^{rs} = 4\pi J^r##
##\nabla_{[q} F_{rs]} = 0##
Here the electromagnetic field tensor F, the four-current J, and the covariant derivative ##\nabla## are all tensors, meaning that these equations remain valid under any diffeomorphism. The indices are abstract indices, so these equations make no reference to any coordinate chart. They can also be specialized to a particular coordinate system by replacing the abstract indices with concrete indices. The concrete-index versions are valid, for example, in Minkowski coordinates, which are the coordinates of an inertial observer. They are also valid in Rindler coordinates, which can be interpreted locally as the coordinates of a uniformly accelerated frame of reference.
Also on this topic: https://www.physicsforums.com/threads/distinction-between-special-and-general-relativity.827721/
Krishankant Ray said:According to the postulates of Einstein theory, laws of physics are same in all inertial frame. What about non- inertial frames? Why they can't be same in non-inertial frame?
S/he received a variety of contradictory answers, and the discussion may have been hindered by attempts to present more sophisticated mathematical ideas as the appropriate level, resulting in some imprecision and confusion. I'm starting this thread so that we can have a discussion at a higher level of precision.
My answer to the OP's question is that the question states a common, historically-based misconception. The laws of physics *can* be the same in noninertial frames, if we write them in a certain way.
First some historical context. Einstein's original interpretation of relativity, when he created it a century ago, was in some ways hazy and incorrect, which is perfectly understandable since the theory was in its childhood. His original formulation of SR gives a prominent role to frames of reference, but it is now understood that the notion of a frame of reference is optional, and frames of reference play no foundational role. Einstein's original description of GR was that it generalized SR to noninertial frames. This is not the way modern relativists describe the distinction. The distinction is now understood as one between flat spacetime and curved spacetime. Unfortunately, many popularizations still state the distinction according to Einstein's original incorrect understanding.
The laws of physics can be stated in ways that do not require the introduction of the notion of a frame of reference. If one wants to adopt a frame of reference, then these statements of the laws of physics can be interpreted in terms of a particular frame, and it makes no difference whether the frame is inertial or noninertial.
Historically one of the most important examples was Maxwell's equations. One way of stating Maxwell's equations is as follows:
##\nabla_s F^{rs} = 4\pi J^r##
##\nabla_{[q} F_{rs]} = 0##
Here the electromagnetic field tensor F, the four-current J, and the covariant derivative ##\nabla## are all tensors, meaning that these equations remain valid under any diffeomorphism. The indices are abstract indices, so these equations make no reference to any coordinate chart. They can also be specialized to a particular coordinate system by replacing the abstract indices with concrete indices. The concrete-index versions are valid, for example, in Minkowski coordinates, which are the coordinates of an inertial observer. They are also valid in Rindler coordinates, which can be interpreted locally as the coordinates of a uniformly accelerated frame of reference.
Also on this topic: https://www.physicsforums.com/threads/distinction-between-special-and-general-relativity.827721/
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