&quot;If we could ascend into that higher domain, we would free ourselves from the straitjacket of ordinary space. We could bend our arm through an extra dimension to reach into a locked safe, or see the insides of a human body laid out before us.&quot;<p>This is often brought up in discussions on 4th dimensions but think about it: For the 4th dimensional being to see inside a closed 3D space, photons from that space should reach its visual organs. From the viewpoint of beings in 3D these photons would be &quot;lost&quot;. This energy discrepancy should be detectable by placing 3D sensors around that space.