4 ms·

Well actually, the Earth clearly isn't round, as anyone who has been near a hill or large body of water can attest. Assuming you're not travelling very far, a

Well actually, the Earth clearly isn't round, as anyone who has been near a hill or large body of water can attest. Assuming you're not travelling very far, a "bumpy Flat Earth" geometry works quite well, and didn't your lecturer tell you physics about using "models that work quite well"? That said, one of the things I've enjoyed about travelling a decent way North-South is how the night sky feels different. I do wonder how many Flat Earthers have had that opportunity.

Koiwai 6y ago
I won't call a basketball 'not round' because it has a rough surface, would you? The highest mountain or deepest canyon on earth are roughly 10 km above/below sea level, compared to the radius of earth it's way smoother than a basketball. As for the flat earthers, you assumed they would accept another concept that stars are very far, if they resides not far above us, that could kinda explain that. For the record I'm not a flat earther, please do not downvote me because of the previous paragraph.
- function_seven 6y ago
  I still stay the Earth is round, but not because of the relative roughness or smoothness of the surface. Oblate spheroids are round in the same way my dinner plate is round!
- j7ake 6y ago
  In the end it depends on what you want to predict from your assumptions that tell you whether it’s okay to assume a ball is round or the roughness matters. Would you call a golf ball round? Depends. If you want to calculate how a golf ball travels upon being hit by a golf club, then you’re going to get more predictive results if you consider the dimples in the golf ball. If you only want to calculate the number of balls you can fit in a bag, by all means ignore the roughness. Just as in the flat earth debate: it’s perfectly reasonable to assume flat earth when planning your bike trip, but the assumption breaks down when you want to fly large distances. For me it is all about knowing which models and abstractions are useful in which contexts rather than philosophising what is “real”.
TeMPOraL 6y ago
Well, actually, Earth isn't just an oblate spheroid either. As you say, it's bumpy. On top of that, it has nonuniform density, which means the gravitational field on its surface isn't that of a perfect sphere (or an oblate spheroid). If we imagine how water would settle if nothing except Earth's gravity and rotation were acting on it, the complex surface that water creates is called a geoid. That surface reflects the nonuniform density of our planet. Here is a pretty heatmap showing the diffrence between geoid heights and oblate spheroid model: https://en.wikipedia.org/wiki/Geoid#Undulation https://en.wikipedia.org/wiki/Geoid#Undulation All of that seems like it doesn't matter, and then (like me over the past month) you want to do something in the GIS space, and then suddenly it does. It is important for accurate mapping and measurement. Of course, nobody has time dealing with this crap (and the shape of the geoid wasn't known until recently anyway), so we cheat - we standardized on a large bunch of region-specific coordinate systems, where one or more points are carefully referenced to geoid or ellipsoid (oblate spheroid) models, and everything else is measured in this local coordinate system.
- slavik81 6y ago
  I've worked professionally with geometrics engineers to correctly display maps and place markers in all the right places. Your description matches my experience. I will say, though. I was surprised at how much you can do with a flat Earth model. It takes a few km to accumulate significant error. For some calculations, it's a valid model... but you do need that accurate reference point to start from.
killtimeatwork 6y ago
Nothing in this universe is really round - "being round" is just an abstract mathematical concept.

Koiwai 6y ago

I won't call a basketball 'not round' because it has a rough surface, would you? The highest mountain or deepest canyon on earth are roughly 10 km above/below sea level, compared to the radius of earth it's way smoother than a basketball. As for the flat earthers, you assumed they would accept another concept that stars are very far, if they resides not far above us, that could kinda explain that. For the record I'm not a flat earther, please do not downvote me because of the previous paragraph.

function_seven 6y ago
I still stay the Earth is round, but not because of the relative roughness or smoothness of the surface. Oblate spheroids are round in the same way my dinner plate is round!
j7ake 6y ago
In the end it depends on what you want to predict from your assumptions that tell you whether it’s okay to assume a ball is round or the roughness matters. Would you call a golf ball round? Depends. If you want to calculate how a golf ball travels upon being hit by a golf club, then you’re going to get more predictive results if you consider the dimples in the golf ball. If you only want to calculate the number of balls you can fit in a bag, by all means ignore the roughness. Just as in the flat earth debate: it’s perfectly reasonable to assume flat earth when planning your bike trip, but the assumption breaks down when you want to fly large distances. For me it is all about knowing which models and abstractions are useful in which contexts rather than philosophising what is “real”.

TeMPOraL 6y ago

Well, actually, Earth isn't just an oblate spheroid either. As you say, it's bumpy. On top of that, it has nonuniform density, which means the gravitational field on its surface isn't that of a perfect sphere (or an oblate spheroid). If we imagine how water would settle if nothing except Earth's gravity and rotation were acting on it, the complex surface that water creates is called a geoid. That surface reflects the nonuniform density of our planet. Here is a pretty heatmap showing the diffrence between geoid heights and oblate spheroid model: https://en.wikipedia.org/wiki/Geoid#Undulation https://en.wikipedia.org/wiki/Geoid#Undulation All of that seems like it doesn't matter, and then (like me over the past month) you want to do something in the GIS space, and then suddenly it does. It is important for accurate mapping and measurement. Of course, nobody has time dealing with this crap (and the shape of the geoid wasn't known until recently anyway), so we cheat - we standardized on a large bunch of region-specific coordinate systems, where one or more points are carefully referenced to geoid or ellipsoid (oblate spheroid) models, and everything else is measured in this local coordinate system.

slavik81 6y ago
I've worked professionally with geometrics engineers to correctly display maps and place markers in all the right places. Your description matches my experience. I will say, though. I was surprised at how much you can do with a flat Earth model. It takes a few km to accumulate significant error. For some calculations, it's a valid model... but you do need that accurate reference point to start from.

killtimeatwork 6y ago

Nothing in this universe is really round - "being round" is just an abstract mathematical concept.