On 12/21/2017 11:06 PM, agrayson2...@gmail.com wrote:
On Friday, December 22, 2017 at 4:46:10 AM UTC, Brent wrote:
On 12/21/2017 4:22 PM, agrays...@gmail.com <javascript:> wrote:
On Thursday, December 21, 2017 at 11:03:53 PM UTC, Brent wrote:
On 12/21/2017 2:04 PM, agrays...@gmail.com wrote:
On Tuesday, December 19, 2017 at 8:51:51 PM UTC, Brent wrote:
On 12/18/2017 11:44 PM, agrays...@gmail.com wrote:
Invariants are always the important things in
physics because they are what we can have
intersubjective agreement on.
Brent
*IIUC, the field equations are covariant, which means
coordinate system independent. *
Right. Covariant means that something that changes in
such a way that invariant things remain the same. So
vectors components transform covariantly so that they
keep the vector physically the same.
*Isn't Newton's Law of Gravitation also coordinate
independent? That is, if we use Newton to calculate the
planetary orbits, won't we get the same results in
different coordinate systems? *
Right.
*
If Newton's Law of Gravitation is covariant -- that is,
coordinate frame independent -- I'd expect it to to be
invariant between inertial frames, but I don't believe it
is. That is, I don't think a LT between inertial frames will
leave the form of the law unchanged. How do you resolve this
problem? TIA, AG
*
Don't use a Lorentz transform between frames in a Galilean
invariant theory.
*OK, So why didn't Einstein do what he did for classical
mechanics which is not Lorentz invariant, and directly modify
Newton's Law of Gravitation? AG*
(a) I don't read minds, and especially not Einstein's and (b) I
don't know what "directly modify" means.
Brent
*He changed (= directly modified) the laws of mechanics to make them
Lorentz invariant. So why can't that be done for Newton's Law of
Gravitation? Does that law work for any inertial frame? AG*
Newton's gravity is a field theory. It implies an infinite speed of
changes in the gravitational field. That wasn't consistent with
relativity. What you're calling "directly modified" was just local
mechanics, not fields.
Brent
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