We often feel stationary, but we are participants in a complex cosmic dance. Our perception of motion is relative, making it challenging to grasp the incredible velocities at which we constantly travel through space. We are moving through the universe at speeds that defy everyday experience, a journey involving multiple layers of motion, each adding to our overall cosmic velocity.
Our Spinning Planet
Our initial layer of motion comes from Earth’s rotation on its axis. The speed of this spin is not uniform; it varies with latitude. At the equator, Earth rotates at approximately 1,037 miles per hour (1,670 km/h). This speed gradually decreases towards the poles. For instance, at 45 degrees latitude, the rotational speed is about 733 mph (1,180 km/h), becoming effectively zero at the North and South Poles.
Despite this rapid rotation, we do not feel the motion. This occurs because everything on Earth, including our bodies, the atmosphere, and oceans, moves along with the planet at the same constant speed. We are in sync with Earth’s spin, so there is no relative motion to perceive.
Orbiting the Sun
Beyond our planet’s spin, Earth orbits the Sun. Our planet travels at an average speed of about 67,000 miles per hour (107,000 km/h) around our star. This constant velocity is crucial for maintaining Earth’s stable elliptical path, preventing it from falling into the Sun or drifting into space.
Earth’s orbital journey covers roughly 584 million miles (940 million km) in one year. While the orbit is an ellipse, the speed remains consistent, ensuring our planet continues its predictable revolution. This orbital speed translates to approximately 1.6 million miles (2.6 million km) traveled each day.
The Solar System’s Galactic Movement
Our solar system, including the Sun and all its planets, moves through the Milky Way galaxy. The entire solar system orbits the center of the Milky Way at approximately 490,000 miles per hour (220 km/s). This velocity is necessary to complete one full revolution around the galactic center.
Even at this speed, a single orbit, known as a cosmic year, takes about 225 to 250 million years. The Sun is situated in one of the Milky Way’s spiral arms, the Orion Spur. This movement highlights the vast scale and dynamic nature of our galaxy.
Our Galaxy’s Journey Through Space
The Milky Way galaxy is in motion, traveling through the universe relative to other galaxies and the cosmic microwave background (CMB). Our galaxy moves at roughly 1.3 million miles per hour (600 km/s) relative to the CMB. The CMB serves as a universal reference frame, representing the leftover radiation from the early universe.
This movement is not random; the Milky Way, along with other galaxies in our Local Group, is being pulled towards larger concentrations of mass, such as the Great Attractor.
Why We Don’t Feel the Motion
Despite these speeds, we do not perceive the sensation of motion due to fundamental principles of physics, primarily inertia and constant velocity. Our bodies possess inertia, meaning they resist changes in their state of motion. When an object moves at a constant speed in a consistent direction, we do not feel that motion directly. We only feel motion when there is an acceleration, which is a change in speed, direction, or both.
Consider being a passenger on an airplane flying smoothly at a constant speed. Even though the plane travels hundreds of miles per hour, you can walk around the cabin, pour a drink, and feel stationary. This is because you, the plane, and everything inside are moving together at the same velocity. Similarly, on Earth, the planet’s rotation and orbital motion are so consistent and smooth that we, along with the atmosphere, are carried along without any perceptible sensation of movement. Our inner ears, which detect motion, are designed to sense changes in acceleration, not constant velocity. The forces involved in Earth’s movements are too small to be sensed by human perception.