Reality → Energy → Motion → Cosmic motions
Earth circles the Sun at a speed of 30 km/s, 90 times the speed of sound [1] . The Sun, together with the planets and neighboring stars, revolves around the center of the Milky Way at a speed of 230 km/s, 8 times faster than Earth around the Sun [2] . The Milky Way and other galaxies of the local group move relative to each other at speeds of maybe up to 1,000 km/s [3] . Remote galaxies and superclusters move away from each other, the faster the greater their distance, with speeds up to (or even exceeding?) the speed of light [4] . Still, when looking at the sky, all stars and galaxies appear to be fixed objects, due to the huge distances involved [5] . It took precision measurements with modern telescopes, spectrographs, and spacecrafts to detect the remote motions and large-scale structure of the universe.
Earth's average orbital speed can be easily calculated from the orbital period and the distance to Sun. A more accurate computation would have to consider that the orbit is elliptical and the speed varies accordingly.
The orbital speed of the Sun around the Milky Way's center is derived from observations of the stars' movements that indicate an orbital period of about 220 million years and a distance to the galactic center of 28 000 lightyears. The inferred rotational speed of 230 km/s differs from the speed computed on the basis of visible mass distribution and Newton's law of universal gravitation. The discrepancy is one of the main reasons for the assumption of dark matter.
The relative velocities between galaxies of the local group vary greatly due to the strong impact of gravitation at short distances. Small galaxies commonly circle a large galaxy, with increasing speed as they approach and eventually merge. Two large neighbor galaxies may also fall through each other, e.g., the Milky Way and the Andromeda galaxy are assumed to 'collide' in 4 billion years (due to the huge voids between stars, the probability of stars crashing is minimal).
The distance to the nearest stars is about 5 lightyears. At that distance, the arc of one degree is about a trillion kilometers. At an assumed speed of 100 km/s perpendicular to the line of sight it takes nearly 3 centuries for the closest stars to travel that arc, or move their observed position by one degree.