Flat earth theory has been in the news because of B.o.B.‘s tweets on the topic, and his subsequent track called Flatline.
I thought he was probably trolling or ‘avin’ a laugh but the ongoing earnestness makes me think he has “self-radicalised” with online bullshit.
Interestingly enough, the Flatline song also indicates Holocaust-denial. I say it is interesting because the other celeb who has prominently come out as a Flat-earther (Tila Tequila) is the author of “Why I Sympathize with Hitler”, so perhaps there is some kind of intersection set there. Fairly low n, though, I admit.
So: what are the simplest ways to show that the earth is round, without a bunch of fancy equipment? There’s all kinds of evidence but for some people a simple test that they can do themselves is best. It seems they don’t trust pictures taken from space.
1/ Watch a departing ship sink below the horizon
For this to work, you’d need a telescope or a good set of binoculars, you’d probably want a fairly low elevation, and it would need to be a large ship. The ship will vanish from the bottom up. Calm seas and low haze will help.
If you’re on the shore with your eye level at 1.7 m ASL, and watching a ship sail away, then when it is 13 km away you will see 5 metres bitten off the bottom. At 16 km away, 10 metres.
https://www.youtube.com/watch?v=dV0h68YU0iQ
2/ Check the stars at various latitudes
This one is not so good because it will require someone to travel and to make observations. (For reasons past understanding, there are people who get massively worked up about issues but are not willing to make a bit of effort to find out more about them.)
Take the flat-earthers at their own terms, use their own maps, in deciding where to take the observations. Most of them use a map centred on the north pole with Antarctica as a ring around the outside. Polaris (α Ursae Minori) is best to use because it is always basically at the same elevation above the horizon. So over a few days you’d show them Polaris at their home in Idaho and they’d observe that it was always about 45 degrees above the horizon at any time. Then you’d take them on a road trip (apparently they don’t trust observations involving aircraft) down to Panama (south, even by their maps) and they’d see that Polaris is only about 10 degrees above the horizon. So far these observations could be consistent with a flat earth because they believe the stars are relatively near.
Then you’d take a cruise south from Panama (there’s no road connecting Panama and South America). Night by night Polaris would get lower in the sky and by the time you got to Peru, it would be gone.
You could do this at other latitudes using other stars but Polaris is good because it takes the rotation of the earth out of the picture and doesn’t require a lot of trigonometry.
3/ Shadow of the earth on the moon
Regardless of the orientation or time of day, when the earth casts a shadow on the moon, it always has the same apparent radius.
The weakness of this one is that it requires the listener to a) think about the geometry a bit and b) accept that the lunar eclipse represents the shadow of the earth on the moon, rather than some intrinsic change happening at the moon.
4/ Call someone you trust in another time zone, ask if the sun is up.
In the era of instant long distant communication, this might be the simplest thing. It doesn’t involve anyone doing anything out of the ordinary. B.o.B. can be at home in Georgia an hour after the sun has gone down, and call a trusted friend in LA.
I suspect that none of this will work because (shrugs) some people just decide what they want to believe and don’t want to consider any arguments deeply.
Ideas such as examining shadows in different places don’t work because a) they think the sun is nearby and b) they don’t do maths.
Any other notions?
