Today’s concepts of space and time trace back to Albert Einstein’s theories of relativity. In special relativity, he derives relations of how a “moving observer” experiences space and time with respect to an “observer at rest”. In general relativity, he derives relations of how mass and energy are affecting space and time. Both theories have been very successful, but fail to solve fundamental mysteries such as competing values of the Hubble constant, dark energy, the wave–particle duality, and quantum entanglement. Here we show that this failure is due to prioritizing a primary observer: Einstein’s relations are valid only for a “system at rest” or a momentarily comoving reference frame. There is no superordinate reference frame in which all observers (“at rest” and moving) are treated alike. In what we call “Euclidean relativity”, we replace Minkowski spacetime (MS) with Euclidean spacetime (ES). We claim that an observer’s reality is formed by projecting ES to 3D space. The major benefit is: ES is a superordinate frame which is not limited to individual observers. It even gives us a Theory of Everything. Matching the symmetry simplifies physics! Alternative models of Euclidean relativity run into paradoxes as they claim reality to be in ES. Our theory profits from two concepts: “distance” (space and time in one) and “wavematter” (electromagnetic wave packet and matter in one). Time is a subordinate quantity: covered distance divided by the speed of light. Wavematter is a generalized concept of energy: Waves and particles are the same thing (energy), but seen from two perspectives. Length contraction, time dilation, acceleration, and gravitation are geometric effects.