What is the best response to the reasoning that a dog on a spaceship will be Lorentz contracted relative to the Earth?

The reasoning that a dog on a spaceship will be Lorentz contracted relative to the Earth is not sound because Lorentz contraction is a phenomenon that depends on the relative motion between observers. Specifically, Lorentz contraction occurs for objects moving at significant fractions of the speed of light as viewed from a stationary reference frame.

In the context of a dog on a spaceship, if we consider the spaceship to be moving at a high speed relative to an observer on Earth, the observer on Earth would measure the spaceship (and the dog within it) as being contracted in the direction of motion. However, from the perspective of the dog inside the spaceship, it would not perceive itself as being contracted. The dog would measure its own dimensions as normal because it is in its own rest frame, where no contraction occurs.

Therefore, the assertion made in the reasoning misinterprets how Lorentz contraction applies in different reference frames and overlooks the fact that each observer perceives length according to their motion relative to what is being observed.