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Forces that are invariant under Galilean spacetime rescaling $\mathbf x' = \lambda \mathbf x$, $t' = \lambda^2 t$

Consider a force of the form $$ m \ddot{\mathbf x}(t) = -k\frac{\mathbf x(t) - \mathbf x_0}{|\mathbf x(t) - \mathbf x_0|^d}. $$ For what values of $d$ is this force invariant under the Galilean ...
9 votes
2 answers
744 views

Can Galilean transformation be derived from length invariance?

Given length invariance in Euclidean 3D space between two inertial frames:$$ds^2=ds'^2$$ Can Galilean transformation be derived like Lorentz transformation derived from space-time interval invariance?
2 votes
1 answer
69 views

What is actually meant when it is said Scalar is invariant?

As far as i know a quantity is called invariant if it satisfies some specific transformations. Now,Suppose a body is moving with velocity $\vec{v}$ as measured from the lab frame.Its non-relativistic ...
2 votes
1 answer
976 views

Newton's theory of gravity is covariant under Galilean transformations

We know from classical mechanics that the gravitational field equation for the scalar potential takes the form $$\nabla^2\phi=4\pi \rho,$$ where $\rho$ is mass density (which, can depend on time and ...
0 votes
1 answer
1k views

How length is an invariant in Euclidean space?

The special theory of relativity shows that intervals are invariant under Lorentz transform in the Minkowski space -time. But how can we prove (any postulates or theory) that the length is an ...