The question of whether everything in the universe is in motion has an undeniable answer: yes. Understanding this universal activity requires moving past the everyday idea of movement and embracing a more complex physical reality. Motion is not an absolute state but rather a relationship that depends entirely on the viewpoint of the observer. Across all scales, from subatomic particles to the largest cosmic structures, nothing is ever truly at rest. This continuous state of flux is governed by physical laws that tie together phenomena as disparate as the vibration of an atom and the expansion of the entire cosmos.
The Relativity of Movement
The foundation for understanding universal motion lies in Albert Einstein’s theory of Special Relativity. This theory established that there is no privileged, absolute point of rest in the universe from which all other motion can be measured. Instead, motion is always measured relative to an observer’s frame of reference.
Imagine sitting on a train moving smoothly at a constant speed. To a fellow passenger, you appear stationary, sharing their frame of reference. To a person standing on the platform outside, however, you are moving quickly past them. Both descriptions are equally valid, demonstrating that motion depends entirely on the chosen viewpoint. A frame of reference is an abstract coordinate system used to measure the position, speed, and time of objects.
Physics defines an inertial frame of reference as one that is not accelerating. Objects within it follow Newton’s first law, remaining at a constant velocity or at rest. The laws of physics, including the constant speed of light, are the same within all inertial frames. Therefore, no experiment conducted entirely within a closed system can determine if that system is moving or at rest. This definitively rules out the existence of an absolute rest state for the universe and confirms that all movement is a relative measurement.
Motion within Our Local Group
Moving from abstract theory to concrete examples, the motion in our cosmic neighborhood is governed primarily by gravity. On Earth, we experience multiple layers of simultaneous motion. The planet’s rotation on its axis causes points at the equator to move at approximately 1,000 miles per hour. The Earth is also locked in an orbit around the Sun, traveling at a velocity of nearly 67,000 miles per hour.
Our entire Solar System is also in motion, orbiting the center of the Milky Way Galaxy. The Sun and its planets complete one galactic orbit every approximately 240 million years, moving at around 490,000 miles per hour (220 kilometers per second).
The Milky Way is part of the Local Group, a gravitationally bound collection of galaxies that includes the larger Andromeda Galaxy. These two massive spirals are moving toward each other at approximately 123 kilometers per second. This local motion is driven by their mutual gravitational attraction, distinct from the larger-scale expansion of the universe. Within the Local Group, the Milky Way, Andromeda, and their satellite galaxies orbit a common center of mass.
Cosmic Expansion and Universal Drift
On the grandest scale, the motion of the universe is driven not by local gravity but by the structure of spacetime itself. In the 1920s, Edwin Hubble observed that nearly every galaxy outside our Local Group was moving away from us, with the recession velocity proportional to its distance. This observation, known as Hubble’s Law, is the definitive evidence for the expanding universe.
These distant galaxies are not simply flying away through space. Instead, the space between the galaxies is stretching, carrying them farther apart, much like dots drawn on the surface of an inflating balloon. This expansion affects the entire observable universe and is a consequence of the Big Bang event.
The rate of this expansion is accelerating, a discovery attributed to dark energy. Dark energy acts as an anti-gravitational force, providing a negative pressure that fills space and drives distant objects apart at an increasing rate. Current estimates suggest that dark energy accounts for nearly 70% of the total energy density of the universe, making it the primary driver of motion on the largest cosmic scale. While gravity holds structures like galaxies and clusters together, dark energy dominates motion at vast intergalactic distances.
The Motion of Fundamental Particles
The picture of universal motion is incomplete without considering the smallest scales of matter, where motion persists even in seemingly static objects. Any solid material, such as a table, is composed of atoms and molecules that are constantly in motion. This movement is thermal energy, where the particles vibrate, rotate, and move randomly at speeds that increase with temperature.
Even if an object were cooled to absolute zero, the theoretical temperature at which classical motion should cease, its constituent particles would still be in motion. This residual, unavoidable activity is called zero-point motion, a purely quantum mechanical phenomenon. It is a direct consequence of the Heisenberg Uncertainty Principle, which states that a particle’s position and momentum cannot both be known with perfect precision.
If a particle were perfectly still (zero momentum) at a fixed location (known position), it would violate this fundamental law of quantum physics. Therefore, particles must retain a minimum, non-zero amount of energy, known as zero-point energy. This energy manifests as constant, low-level vibrational motion, ensuring that motion is an intrinsic property of matter at every level.