The earth is constantly falling, but will never reach the ground

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

29 December 2024

Some one recently asked me why the earth doesn’t fall. I responded with a question: “Fall where?”. He replied, “in the space”; to which asked, “Where in space?”. Unfortunately, he did not respond to my last question.

In a recent discussion, I pointed out that the so-called “Artificial Intelligence” is actually no intelligent at all! In my book, intelligence is not about answering questions; it about asking questions. One of my teachers used to tell us that there are no stupid questions, only stupid answers.

The question above can only be asked by an intelligent being. Indeed, Isaac Newton who is one of the most intelligent persons in the history of mankind, asked the same question many centuries ago. He was sitting under an apple tree at Cambridge University and one of its fruits fell on the ground next to him, or so the fable goes…

He looked at it and wondered: “Why did the apple fall to the ground?” Then he looked up in the sky, saw the moon and asked, “Why isn’t the moon falling?”. He had just finished developing his three laws of motion, the first of which was that an object stays at rest or in uniform motion at constant velocity unless acted upon by an external force.

So, he concluded that there must be a force that caused the apple to move towards the ground – he called it “gravity”. But if gravity pulled the apple to the ground, why is it not doing the same to the moon?

After some thought, he realised that the motion of the moon around the earth counters the pull of gravity. In other words, the moon is constantly falling to the earth, but because of its orbital motion, it can never reach the ground.

The same can be said of the earth: it is constantly falling into the sun, but due to its orbital motion, it never reaches the “ground”. Knowing the distance to the sun (about 150 million kilometres) and the time it takes to go round once (365.25 days or 8,766 hours), it is easy to calculate the speed at which the earth is falling. It is 107,461km/h.

And the sun is also falling to the centre of the Milky Way galaxy, but it will never reach there. The sun revolves around the galactic centre at about 828,000km/h. At this speed, it takes about 230 million years to complete one revolution. It has gone round only once since the first appearance of dinosaurs.