Let’s clarify: I am not advocating a flat earth theory here. After my last blog, there seems to be a knee-jerk reaction to a binary opinion. This seems to go along the lines of if you are questioning the idea that we are a sphere flying through space, then you must be a flat earther. I have found a little bit of a strange response to a straightforward question. The other exciting aspect of the responses is that they completely disregard the many other theories about Earth and its position in space.
To be clear, the question I am trying to answer is, how can we prove that we live on a sphere? When I was asked this question, I struggled to answer it. Like many, I had accepted it without question. Yet, when pushed, I saw little evident proof of something that seems accepted without question. After I had failed to answer the question for the person asking me and for myself, it was over a beer with my brother and a friend that I found a possible answer. I was discarded as a flat earther by my friend. My brother was willing to engage and had a fascinating observation.
I should explain that my brother was an artillery officer for many years, so he is well-versed in hurling large pieces of metal through the air to arrive at a particular point on the earth accurately. He observed that if the world were not a sphere, none of the shells he fired would have hit their target. This was because when calculating the shell’s trajectory, an adjustment is applied for the earth’s curvature when calculating the specifics for firing a shell to the target. I was intrigued.
It turns out that the Navy first started to adjust their firing trajectories for the earth’s curvature. It was well understood that the trajectory of the shell out of the gun barrel had to be calculated by considering air resistance. This would change depending on the air pressure (basically a measurement of the density of the air), prevailing wind, shell weight and a lot more. Even with this calculation, the shells would land past their target. It was not until the earth’s curvature was included that they started to hit their target.
That was that, then. Our human prowess at destruction and blowing things up has proven that the Earth is a sphere. But then it struck me that if a shell travelling 15 miles needs to be adjusted in its trajectory to hit a target, why can we not see this if we look closely? We should be able to observe this phenomenon in plenty of places.
But first, I wanted to understand the magnitude of the adjustment in the curvature. That should be pretty simple maths; as you know, I am always up for some maths. In this case, I will spare you the details, mainly because they have been laid out in detail by others. Applying a bit of Pythagoras theorem, the answer we get is as follows:
What does this mean to you and me? I plugged this into a spreadsheet, and with the earth’s radius at 6371km, the result is that there should be a curvature effect of just under two meters at a range of five kilometres. At seven Kilometers, it is about four meters. In my mind, this should be observable, but the issue is that the point of observation is important. We are only looking for a 2 ~ 3-metre deviation. The most accessible place to observe this would be at sea.
I started to scour the internet for some evidence; it did not take too long.
The photograph above is of the Thornton Bank wind farm taken from the coast of Belgium. It is approximately 27km from the coast, so if we assume a spread of the turbines from 27km to about 35 km, the curvature would be approximately 55m at the closest point and just under 100m at the furthest point. The wind turbines are approximately 100m tall (sorry, I do not have a good source for this). That is what I see in this photograph.
Well, that is a relief. But it leaves me even more curious about the clock in Prague. More on that next time.