[cobaltoxide]

> Is it possible to compress space?

The geodesic distance between inertial test masses increases and decreases.

Colloquially we say that space has stretched and compressed.

Geodesic distance can be measured by the time it takes light to travel between the points.

Inertial test masses can be simulated by hanging them from fine wires (LIGO) or by setting them up in an orbital constellation (LISA).