Feature of theory

Space-time

Energy-time

Reality

Remarks

Relativistic mass: $m=\gamma m_0$

-

+

+

Time dilation = f(direction)

-

+

+

Hafele-Keating experiments

Hamiltonian: $E={\left(m_0^2{c}^4+c^2{p}^2\right)}^{\frac{1}{2}}$

+

+

+

Derived in Hestenes’ calculus

Time dilation (clock slowing)

+

+

+

All experiments

Speed c = c' (in all frames)

+

-

-

Michelson-Gale experiments

Length Contraction

+

-

(-)

Unmeasured, unlikely

Time dilation (symmetric)

+

-

-

GPS experiments, etc.

Velocity Addition Law

+

-

-

Cannoni

No preferred frame

+

-

-

Michelson-Gale experiments

Past-present-future

+

-

(-)

Unmeasured, unlikely 4D

Twin paradox

+

-

-

Barn/pole paradox

+

-

-

Grandfather paradox

+

-

-