In Quantum Physics space itself is physical and can be folded and effect by gravity and energy. Ask yourself this question what was before the universe? What is the universe expanding into? The answer is nothing and nothing itself is different than empty space, because space can be measured.
Hey! Nothing can too be measured. I know this because Mueller has a whole lot of nothing on Trump.
“The combination of the 100 PW laser and the XFEL will initiate exploration of the vacuum birefringence, one of the most prominent strong-field quantum-electrodynamic effects, says Ruxin Li, the project leader. Normally a vacuum is thought of as completely empty — but according to quantum electrodynamics, it is actually full of virtual particles that continually appear and vanish.”