What is velocity, one of the major concepts we learn in physics? What place does it occupy in our lives? Where is mankind in the universe in terms of velocity? Why is it important to understand velocity?
In order to find answers to these questions, let's consider ourselves sitting at home after a long, tiring day. Are we aware that we are moving very fast even at a moment when we seem to be resting? When we travel by bus, we are motionless from the standpoint of a sitting passenger, yet have a velocity compared to an outsider standing on the sidewalk. The trees lining the road seem to be going backwards, but they are fixed to the ground with no speed. Therefore, velocity is relative and we in fact move at different speeds while sitting at home depending on the objects of reference. We have a zero velocity relative to our guests sitting with us on the couch, but have various speeds compared to the center of Earth, the moon, the sun and the center of the Milky Way galaxy. Not only us, but all existence in the universe has a movement, or oscillation. This movement is usually in the form of a revolution for objects of important mass and as a vibration for particles with smaller masses.
The shining celestial bodies of the cosmos rotate around themselves like whirling dervishes. They revolve around other heavenly bodies or around their common center of gravities, such as pilgrims revolving around Ka'ba in Mecca. The gravitational force set in the universe pulls all objects towards each other. This gravitational force indeed pulls all masses together; however, it is counterbalanced by the motion of revolution given to grand heavenly bodies. As a matter of fact, everything is moving: a solar system with its planets, moons, and comets; the Milky Way galaxy, along with billions of stars, nebulas, galaxies, interstellar dust, gas clouds, and other celestial objects… all are moving in a giant rotating motion like a carousel. In this article, you are going to find some of the scientific findings of our revolving planet, the sun, and the universe, and how some verses in the Qur'an sound miraculously relevant to them.
The Earth's motion
First of all, we have a velocity stemming from the Earth's rotation. People living on the equator travel approximately a thousand miles per hour in reference to the center of the globe due to this rotation. While people on the poles never gain any distance over 24 hours, people on the equator travel nearly 23,800 miles! Inside a plane, because we move at the same rate as the plane, we cannot feel its speed. In a similar way, since we move at the same rate as Earth, we cannot feel the globe's movement.
There are many benefits associated with the Earth's rotation. The delineation of day and night, atmospheric jet streams, oceanic currents, and similar events rise from the rotation of Earth around its axis. For instance, it causes the warm water currents of the Gulf Stream to reach England, generating a warm and rainy climate.
There are verses in the Qur'an that point to the globular shape of the Earth and its rotation around its axis and revolution around the sun:
"He has created the heavens and the Earth with truth. He wraps the night around the day, and He wraps the day around the night. And He has made the sun and the moon subservient (to His command), each running its course for a term appointed (by Him). Be aware! He is the All-Glorious with irresistible might, the All-Forgiving." (Az-Zumar 5)
Yet another verse furthers this point:
"It is He Who has created the night and the day and the sun and the moon. Every one (of such celestial bodies) floats in its orbit." (Al-Anbiya 33)
The verb "wrap" is usually used for round objects, and the perpetual arrival of day and night are only possible with a circular planet. The Earth's rotation leads to different days, on the micro level, and different seasons, on the macro level. The Qur'an concisely summarizes all these physical events with the simple phrase, "wrap the night around the day."
The Earth's primary motion is around the sun. We are roughly 93 million miles away from the sun and we make this orbit, which is nearly 584 million miles, every 365 days. According to the center of the sun, our average velocity on this orbit is approximately 66 thousand miles per hour.
In addition, other planets travel around the sun via different orbits and speeds, each moving on a separate plane. For a moment, it is significant to visualize the sun, which is more than a million times larger than Earth, with its planets and other viscera revolving around it via no visible bond between them.
The movement of the sun
As stated earlier, when we travel on a bus, we observe the trees and buildings near the road going backwards even though we are the ones moving. In a similar way, we see the sun as revolving around us, though in fact the Earth is the one moving. In the Qur'an, the chapter of Al-Anbiya, the verse reading, "each running its course," is about the creation of the sun and moon, clearly pointing to their movements. Unfortunately, the verse that reads, "A(nother) clear sign for them; And the sun runs the course appointed for it for a term to its resting-place, for the stability of it(s system)…" (Ya Sin 38) was misunderstood as the sun revolving around the Earth. However, we know today that our sun is one of a couple hundred billion stars in the Milky Way galaxy. As such, it both rotates around itself and revolves around the center of the Milky Way galaxy, and confirms the miraculous declaration of the truth in the verse.
In addition, the sun also has a secondary movement inside the local star cluster towards a certain direction. We can explain this with an example: the atmosphere is in motion along with the Earth. Each particle and particle set that makes up the atmosphere not only moves right and left, but also has a total revolution around the Earth. The sun behaves in a similar way within the star cluster and around the center of the Milky Way.
How are we going to define the velocity of the sun? We can determine the sun's speed by referencing a constant point depending on the average velocity of stars in the section of the galaxy that we inhabit. The sun, according to a local constant point, travels towards the shiny Vega star in the Lyra constellation with an average speed of 43 thousand miles per hour.
Apart from their individual movements, the stars in our galaxy also revolve around the galactic center. The velocity of this movement depends on the star's mass and its distance to the galaxy's center. The sun completes one loop inside the Milky Way galaxy every 225 million years. It has completed a total of 20 tours around the galaxy's center since the Earth's creation. Our Earth, which moves along with the Sun, travels around the galaxy's center at nearly 492 thousand miles per hour.
The motion of the Milky Way galaxy
Our galaxy is one of the billions of galaxies in known space. Galaxies are the biggest known structures. The universe expands and galaxies move away from each other, conforming to the meaning of the verse, "And the heaven, We have constructed it mightily; and it is surely We Who have vast power, and keep expanding it" (Adh-Dhariyat 47). Our galaxy, along with nearby galaxies, is pulled towards the Leo and Virgo constellations. The cause of this attraction is not understood yet.
Since all galaxies are moving, how can we determine the velocity of the Milky Way galaxy? As is known, the entire universe is filled with cosmic radiation as a remnant of the Big Bang. When this radiation is taken as a reference, the Milky Way travels at around 1.3 million miles per hour.
At the moment, when we think we are sitting in place, we are actually moving around the center of the Earth, sun, our local star cluster, the center of the Milky Way galaxy, and also moving away from other galaxies. We have velocity in relation to all of these movements. The revolution of the universe is also a fact verified by the Divine word: "I swear by the heaven ever-revolving" (At-Tariq 11).