Why do I believe the Earth is a globe?
I ran into this snippet of conversation the other day, in which one person was saying why he believes that the Earth is a globe, and the other person was saying why he's on the fence about the whole globe/flat issue.
I'll start by saying that I'm 100% convinced that the Earth is a globe. What does it mean to be 100% convinced? It means I'd eagerly bet my entire life savings that the Earth is a globe. I have no doubts on this count.
However, I believe it's useful and important to think about why I believe these things. The Globe-Earth Theory is a particularly fun one, because I don't actually run into first-hand evidence of it very often! Sure, there are very many things in my life which depict a Globe Earth, but they're not really evidence.
So, do I have any real first-hand evidence? First, I've traveled all over the world and I have experienced things such as jet lag, inverted seasons in the North/South hemispheres, sunrise at an absurdly early hour in London in June. These things corroborate the Globe Earth story to me, but I'll be honest: I have not actually worked out the math to see if they all sort out properly.
Second, I've spoken via Skype with people on the other side of the world from me. When it was nighttime there, it was daytime where I was. Again, the flat-earthers probably have an answer about why this doesn't quite prove the Globe Earth Hypothesis, but I'm pretty happy with it myself.
But I'm really interested in debunking this. Samuel Birley Rowbotham was an English man in the 19th century who publicly promoted the idea of a Flat Earth. Publicly, and apparently, lucratively. My reading of his Wikipedia article leaves me with the impression of a good old fashioned snake oil salesman. Apparently one of his public reasons for supporting the Flat Earth Hypothesis was that the Bible said so.
Fundamentally, I'm not here to attack the man's character, however suspect it may have been. If I can't debunk his arguments, I shouldn't be betting my life savings against him. This link is an excerpt from Rowbotham's book Zetetic Astronomy, where he tries to obfuscate us all into believing in a flat earth. In particular, in this section, he's trying to convince us that a ship's hull disappearing over the horizon before its mast is merely a simple optical illusion.
From what I can make out, his argument goes like this:
- When an object is very far away, the human eye can't make out details on it.
- A ship's hull is a "detail" of a ship.
- Thus, when a ship is very far away, the human eye can't make out its hull.
He supports his argument with a bunch of official-looking drawings, like this one:
See? Obviously an illusion!
It appears to me that he's saying because the human eye can't distinguish details at a distance, that of course it can't distinguish the difference between the hull and the horizon and the two get mushed together. That's a fair first pass, and maybe it would even be convincing to someone who hasn't tried this themselves.
How might we disprove his argument? Disproving stuff is what science is all about. When you think something might be true, the first thing you need to do in science is figure out how you might show that it's false. Let me ask you a question: what if we had a device that let us magnify distant objects, so that we could distinguish details at a distance? If Rowbotham's argument is correct, and we viewed a distant ship through such a device, the hull should simply reappear. Rowbotham's argument is that we're suffering from a lack of visual acuity; let's just improve our acuity and see what happens! If only we had such a magical magnification device...
By Alex Shunkov and formatted by Bcjordan [CC BY 3.0], via Wikimedia Commons
Oh right, we've had telescopes in our lives since the 17th century! It should be trivial to get a telescope, look at a ship whose hull has disappeared, and it will reappear through the telescope if Rowbotham is right.
Folks, I've done this myself. I live in Santa Barbara, CA, and there is a huge amount of freighter traffic through the Santa Barbara Channel. We see big container ships passing through all the time, and the more distant ones have a missing hull. When I look at them through my binoculars, the hull is still missing. In fact, it's missing the exact same amount as it was before I magnified it! This is why I don't believe Rowbotham's argument for a second. His argument simply doesn't hold up to closer scrutiny.
Discussion Question: As I thought this through, I asked myself if all this matters. The details of my life don't seem to be affected greatly by my knowing the true shape of the Earth. Does it matter whether we believe in a Globe Earth or a Flat Earth?
You'd loose your entire savings if you took that bet.
On what points do you disagree with my assessment of Rowbotham's argument?
I think he's just joking :p
There is no evidence to support your statement. :)
The mind of a conspiracy theorist must be a hell of a thing. I have this picture that it's what happens when healthy skepticism goes completely out of control, to the point that they're more willing to believe the ramblings of some 19th-century charlatan than a calm and sensible rebuttal.
nice post
LOL, thanks for the giggles. :)
First article on 'flat-earth' (or so :p) that I like!
It's an interesting topic. I sorta looked into it about ten years ago, but pretty much dismissed it for reasons you gave.
I found this article on that very interesting.
Yeah, I try pretty hard not to treat the Bible as a science textbook.
Nice article.
Daytime/night-time is a prime evidence in my opinion.
If the Earth was flat, there would be no time difference.
Experiment for flat Earthers: take a flashlight in a dark room and aim it at the pizza from above. The entire pizza will be alight at the same time. So would be Earth it if was flat.
On a first pass, I don't know how you get past that one.
I vaguely recall some ancient theory about the sun being very close to the hypothetical flat earth (I want to say something like 100 km), and moving across the surface relatively quickly. I think the guy even worked out quite a bit of math to show how it could be a self-consistent theory.
So to make the pizza thing work, the flat earther would need to make the flashlight very small and very close to the pizza. Even then, it would never be darker than dusk anywhere on the pizza. Accounting for that would turn into a very bizarre convoluted nightmare. But maybe I'll have to read more Rowbotham to see how it can be explained. :)
Meh, we have hours and hours of video from the Space Station. To imagine that it was all filmed while diving towards the ground at one g in an Airplane, means that the airplane must have started near the orbit of Jupiter. Once you admit that we can go that far in an airplane, the Flat Earth seems inconsequential.
But I grew up in the Cocoa Beach area. I've talked to dozens of Astronauts and my dad was a NASA engineer, neither of which group can hold their alcohol or keep a secret.