Thanks to gravity, the earth does fall. It is actually in a constant state of falling since it is in orbit around the sun. This gravitational pull that the sun has on the earth is useful since it stops earth from catapulting into space. Gravity means that objects are not just drawn to the thing that has the stronger gravitational field, they are also literally falling towards the source of the gravitational pull. Since gravity, as a force, is caused by mass, it follows that the sun is the centre of our solar system; it is the heaviest thing in it, therefore all of the planets in our solar system orbit it. Because all of the planets orbit the sun, they are also literally falling towards it. But being in orbit around something also means that you are spinning around it.
Because of the sun’s immensely huge mass and therefore just as immense gravity, its gravitational pull and field cause all of the planets to ‘fall’ towards it. This is the exact force and action that causes orbiting around a large mass. So, unlike the question suggest, the earth is literally falling towards the sun thanks to its gravitational pull.
But all this talk about ‘falling’ sounds quite sinister and suggests that we will eventually actually fall into the sun and burn up. Yes, the earth is being drawn to the sun due to the sun’s huge mass and its immense gravity, but there are other forces at play too. The earth is not just affected by the sun’s gravity, thus moving in one straight direction towards the sun.
The earth is also moving sideways thanks to its sideways momentum. Thankfully, for the sake of us not falling into the fiery sun, the earth has a lot of sideways momentum.
In effect, the earth is actually constantly falling towards the sun, deeper into its gravitational pull, but it always misses. In layman’s terms, the earth is literally falling towards the sun and missing it.
To describe this action more scientifically, you could say that the earth has a ‘closed trajectory’. This doesn’t just describe earth’s orbit around the sun, it can also be used to describe anything orbiting a larger object with a greater mass and therefore gravitational pull. It really is just a fancy way to say that something is perpetually falling and specifically towards something.
It is so important to our life on this planet that we orbit the sun. As mentioned before, if we did not orbit the sun, the earth would be wildly out of orbit thanks to our own axis spin and would end up somewhere potentially uninhabitable for our life on earth.
Similarly, earth’s tilt on its own axis, as well as the specific way that we orbit the sun, causes the seasons on earth. It takes around 365 days to orbit the sun, this also makes our seasons possible, and the sun able to get to parts of the world at different times of the year in different ways.
This is important for reproduction inn nature: animals rely on the seasons to produce offspring in the most opportune times of the year to ensure their survival chances. That is just one example of why earth ‘falling’ towards the sun is so important and integral to our survival as living organisms on earth.
So, why does earth not actually fall into the sun? Well, since earth’s sideways momentum is strong enough to ensure that we do not fall into the sun, and all of the other planets in our solar system have not fallen in either, it is safe to say that the reason we have not is because of earth’s own mass.
Objects with lesser mass like asteroids etc. have fallen into the sun because they are not heavy enough to have a strong sideways momentum that keeps them from falling into the sun. A way to picture this is imagining a small asteroid coming towards earth. Since earth is a larger object than the asteroid, it is falling towards earth thanks to gravitational pull.
If the asteroid is large enough to have a sideways momentum that can complement the earth’s pull, then the asteroid will miss. And you can guess what would happen if the asteroid did not have its own sideways momentum.
A father of physics, Isaac Newton, had a very interesting though experiment to explain this idea of something falling towards something in space. This idea was so profound that it still rings true today.
Newton’s cannonball thought experiment has you imagine the tallest place on earth, a place that you could fire a cannonball from that would encounter no obstacles if it made it the whole way around the earth. This thought experiment is already very interesting, but the explanation of it is even more so.
Once the cannonball is fired at a certain speed (you can pick the speed), the earth’s gravity is pulling on it, causing it to fall towards earth. Depending on the speed that the cannonball is fired at, it will strike the earth thanks to the earth’s gravitational pull.
This same effect will happen for a lot of the speed options that you choose, the cannonball striking the earth further away from the point it was fired at thanks to its sideways momentum in relation to the earth’s gravity.
But if you fire the cannonball at just the right speed, theoretically, the cannonball will orbit the earth. As strange as this sounds, the whole point of Newton’s thought experiment was to show that things will orbit a larger object mass based on its speed travelling in another direction.
The cannonball is still falling towards earth, just like the shots before, but it will not strike the earth, because the earth is actually curving away faster than the ball is falling. So, just like the earth constantly falls and misses the sun, the cannonball will perpetually fall and miss earth. That is, until it comes back to the point where it was fired from in Newton’s thought experiment.
The point of Newton’s cannonball thought experiment is to show that orbits are simply objects travelling sideways at a pace just fast enough that they do not strike the source of the gravity. In simpler terms, this means that an orbit just shows that a smaller object with lesser mass will need to be travelling at a certain sideways speed in order to avoid striking the planet or larger mass object that is pulling it in by its gravitational field.
Now you can just zoom out and apply this to the question at hand: why the earth doesn’t ever fall. Imagine that the cannonball is earth and the earth is the sun. Earth is simply travelling fast enough in one direction to avoid falling into the sun. falling into and falling towards are two different things.
Both are dependent on gravity, but falling into would suggest that the object does not have enough sideways speed to orbit the larger mass object.
Newton’s cannonball thought experiment is relatively easy to wrap your head around. Funnily enough, this is also exactly how satellites work. In order to get something to orbit the earth or any other planet, it just needs enough sideways speed to ensure that it will miss the earth.
This is exactly how the earth misses the sun, because it has enough sideways speed to accomplish a closed trajectory. In Newton’s thought experiment, this is exactly what he is saying would happen to the cannonball: it would reach the perfect speed to orbit the earth. And in doing so, the cannonball is falling towards earth perpetually.
This concept of falling into something with larger mass is not exclusive to outer space or our solar system’s giants. In fact, every object in the universe is falling constantly.
Think about how we are stuck to the earth’s surface when we walk. That is because life evolved to fit the level of gravity that the earth produced. As humans, we are accustomed to this gravity, in fact, we were built for it. So, when you jump on the spot, you always land back to earth because you are falling towards it.
Just like the earth is constantly falling towards the sun, you are constantly falling towards the earth whenever you are not in contact with it. If you zoom out even further, the sun in our solar system is also constantly falling towards the center of the galaxy in exactly the same way. Everything falls into something bigger than itself. This is basic gravity.
But why do we not feel this falling motion? The answer is that we do experience this falling motion, but we just do not notice it easily. The distance between things in space also makes a difference in these scenarios. Since humans on earth are so far away from the sun, our falling motion around the sun can also feel like a straight line.
The reason that we cannot feel this movement around the sun is because you actually cannot feel constant speed along a straight line. Even though the earth’s orbit around the sun is not a straight line, our distance from the sun makes it feel that way. Again, if we zoom out further, the solar system that we are part of is falling towards the center of the galaxy.
But this galactic center is so unattainably far away from us that the constant speed is close to a straight line on human scales. But we are in fact orbiting it on a curved trajectory. The only reason that we can’t feel this curve is because of the distance. This is the same reason we cannot feel the curved orbit around the sun as humans on earth.
So, if we bring back the original question: Why doesn’t the earth ever fall down? We can now answer this. The reality is that the earth is always falling. Thanks to the gravitational pull of the sun, a larger mass object than the earth, we are perpetually falling towards the sun.
This is what we have to thank for our seasons on earth, the light hours in the day, and the life that has evolved on the planet. But the reason that we don’t outright fall into the sun because the earth has its own sideways speed and movement that acts in a way with the sun’s gravity to produce a line of orbit.
The best way to explain this motion of the earth orbiting the sun is by using Newton’s cannonball thought experiment, in which the cannonball is fired from the highest point on earth and the speed of the cannonball determines whether it will strike the earth or whether it will fall into the earth’s orbit. Just like the satellites that orbit earth today.
