Professor Dave's 10 Things...

Hey all,
I'm sure this has been asked before but can any FE-ers respond to this video point by point disproving Professor Dave?

Also if you have to do it with the presupposition that gravity does not exist, please provide your evidence for why gravity does not exist with a replicable/reviewable source so we are all on the same page 





Just curious as to how FE-ers see Dave's videos and respond to the information he presents. He is quite rude but still makes valid points

You should list all his points. No one wants to do your homework for you.

If you aren't willing to even put in the effort to list what the points are, why should anyone put in the effort to respond to it?
Did you even put in the effort to search for this video?
Literally copying and pasting the URL into the search will get you a few threads.

e.g. this one:
https://www.theflatearthsociety.org/forum/index.php?topic=82146

Did you bother reading through that thread to see what people have said?

But this is just a crappy video to try to make fun of FEers; and has several incorrect statements.

e.g. point 2 is the most BS claim of his.
He claims that 8 inches per mile squared is wrong, and claims that it is a parabola which in no way represents Earth.
He suggest people learn basic math, while entirely failing to understand basic math himself (although I suppose the math he is objecting to is slightly more complex).
He also complains that people post it with no explanation of how it works or why.

Yet what does he do? He posts a formula with no explanation of how it works.
He accepts that formula should be h=r*(1-cos(s/2r)).
But this is wrong.
This is the formula for a bulge between 2 points, rather than the drop from one to another.

If you want the drop, that would be h=r*(1-cos(s/r)).
This is from simple trig.
Construct a right angle triangle as shown:


s is the arc along Earth.
h is the drop.
r is the radius
The angle at the centre (in radians) is s/r.
The vertical distance along the purple line before the grey bit which is h is r*cos(s/r).
i.e. h=r*(1-cos(s/r))

But this math is hard, using a trig function. You can't easily do it in your head.
Fortunately, there is a way to approximate it.
for a small value of x, cos(x) ~=1-x^2/2
So sticking that into the above we get:
h=r*(1-(1-(s/r)^2/2))
h=r*(1-1+s^2/(2*r^2))
h=r*s^2/(2*r^2)
h=s^2/2r

Notice how this is the parabola he objects to.
We can also put in some values to get a simple number we can use of the form:
h=(k*inches/mile^2)*s^2.
Where s is a distance in miles and h is a height in inches.

So the value we need to calculate is (miles^2/inch)/2r
Putting in Earths radius as 3963.19 miles, this gives us:
(mile/inch)/(2*3963.19).
Putting in 1 mile = 63360 inch, this gives us:
63360 / (2*3963.19).
That is 7.99356.....
or roughly 8.

This is how the 8 inches per mile squared comes to be.
And this IS valid, at least as a good approximation.

But in reality, considering you want to talk about the height of a distant object which might be obscured, you really want a different triangle, this one:

You still have the angle as s/r, but now you have:
cos(s/r) = r/(r+h)
(r+h)*cos(s/r) = r
r*cos(s/r)+h*cos(s/r) = r
h*cos(s/r) = r-r*cos(s/r)
h = r*(1-cos(s/r))/cos(s/r)
You may notice that is the same as the above, but with an extra factor thrown in, 1/cos(s/r).
That means we can still apply the small x approximation, and we get this:
h=(s^2/2r) / (1-(s/r)^2/2)

And then we can make another approximation. As s/r << 1, ((s/r)^2/2) <<1, so (1-(s/r)^2/2) ~= 1.

For example, if s was 100 miles, that would be 0.99968. That means the drop would be slightly larger, but by a negligible amount.

So not only does he use the wrong triangle, to get the wrong formula out; he also uses the wrong distance; and is entirely incorrect with his claim that the 8 inches per mile squared is wrong.

And for a valid comparison, he should have used this image:

The red line is a circle (with a radius of 1), the green line is a parabola, specifically 1-(x^2)/2.

But of course, if he did that you would see quite good overlap.

With them being so horribly wrong about that, and you not bothering to mention that, why should anyone care about the rest?

Hey all,
I'm sure this has been asked before but can any FE-ers respond to this video point by point disproving Professor Dave?

Also if you have to do it with the presupposition that gravity does not exist, please provide your evidence for why gravity does not exist with a replicable/reviewable source so we are all on the same page 





Just curious as to how FE-ers see Dave's videos and respond to the information he presents. He is quite rude but still makes valid points

Fun fact: assigning Professor or The Science Guy to your name doesn't make you more brilliant. It just makes you a self-important asshole. Titles are assigned by other people.

I've seen this guy automatically pop up on my "next video" autoplay whenever I play flat Earth videos. Almost as though Youtube wants to propagandize me.

Not responding to any of his points, nor will I watch his videos. You can call me dumb or wrong or whatever all you want.

But the fact that this goofball gives himself a title makes him a hard pass. Along with the "debating flat Earth without using science" person. If you understand that the process of knowing things is science, then you should understand how fallacious that idea is. If you aren't using science in your RE theory, what are you using? Folklore?

I am bulmabriefs144, Smasher of Testicles.  You see? Titles are ridiculous.

You should list all his points. No one wants to do your homework for you.

If you aren't willing to even put in the effort to list what the points are, why should anyone put in the effort to respond to it?
Did you even put in the effort to search for this video?
Literally copying and pasting the URL into the search will get you a few threads.

I apologize, didn't realize that skimming a <20 minute video was so horrible, here are his 10 points
1. Gravity is real and objects experience freefall at 9.8 m/s² instead of just buoyancy and density (which are scalar products, not vectors)
2. 8 in/mi² and why that doesn't exist/work
3. Water does not simply "find its own level" but instead conforms to the shape of a globe (and basically explaining this)
4. Our atmosphere is next to a vacuum because it's a space vacuum not a vacuum cleaner
5. How/why water can stick to a spinning ball (uses water droplet in the shape of a sphere to justify)
6. Moonlight isn't "cold"
7. River's can't flow uphill and curvature versus elevation
8. How the Earth is closer to the sun during winter and how sunlight hits the Earth

And his last two points are pretty much nonsense but basically: FErs believe in scientism yet don't use science and that it is unreasonable to say that all RErs are indoctrinated when FErs tend to regurgitate similar incorrect information

I actually tried to find some of these tried but idk maybe I'm inapt at searching on this site

But this math is hard, using a trig function. You can't easily do it in your head.
Fortunately, there is a way to approximate it.
for a small value of x, cos(x) ~=1-x^2/2
So sticking that into the above we get:
h=r*(1-(1-(s/r)^2/2))
h=r*(1-1+s^2/(2*r^2))
h=r*s^2/(2*r^2)
h=s^2/2r

I'm confused, where does this approximation come from? Why is this approximation inherently correct for our purposes? I feel like there's a big gap there and maybe I missed it/misunderstood.

Quote from: SouthBeastGamingFTW on October 28, 2023, 11:49:27 AM

Hey all,
I'm sure this has been asked before but can any FE-ers respond to this video point by point disproving Professor Dave?

Also if you have to do it with the presupposition that gravity does not exist, please provide your evidence for why gravity does not exist with a replicable/reviewable source so we are all on the same page 





Just curious as to how FE-ers see Dave's videos and respond to the information he presents. He is quite rude but still makes valid points

Fun fact: assigning Professor or The Science Guy to your name doesn't make you more brilliant. It just makes you a self-important asshole. Titles are assigned by other people.

I've seen this guy automatically pop up on my "next video" autoplay whenever I play flat Earth videos. Almost as though Youtube wants to propagandize me.

Not responding to any of his points, nor will I watch his videos. You can call me dumb or wrong or whatever all you want.

But the fact that this goofball gives himself a title makes him a hard pass. Along with the "debating flat Earth without using science" person. If you understand that the process of knowing things is science, then you should understand how fallacious that idea is. If you aren't using science in your RE theory, what are you using? Folklore?

I am bulmabriefs144, Smasher of Testicles.  You see? Titles are ridiculous.

I agree, he's not exactly the ideal person but regardless he discusses scientific fact. I outlined the points so perhaps now you would like to respond? Any good conspiracy theorist would

I apologize, didn't realize that skimming a <20 minute video was so horrible, here are his 10 points

The point is that it takes you no effort at all to post a link to the video, so you shouldn't expect people to respond. Especially when it has already been posted before.

If you want a discussion, you should at least put in some effort yourself.
Literally all it took me was searching for the url of the video.

1. Gravity is real and objects experience freefall at 9.8 m/s² instead of just buoyancy and density (which are scalar products, not vectors)
2. 8 in/mi² and why that doesn't exist/work
3. Water does not simply "find its own level" but instead conforms to the shape of a globe (and basically explaining this)
4. Our atmosphere is next to a vacuum because it's a space vacuum not a vacuum cleaner
5. How/why water can stick to a spinning ball (uses water droplet in the shape of a sphere to justify)
6. Moonlight isn't "cold"
7. River's can't flow uphill and curvature versus elevation
8. How the Earth is closer to the sun during winter and how sunlight hits the Earth

1 - Saying gravity is real, without evidence, doesn't really help the discussion.
FEers have a variety of claims for why things fall, including things like universal acceleration.
But buoyancy is a vector.

2 - dealt with above.

3 - No, it finds its level, with that level being a equipotential surface. This is not intrinsically flat or globular. But yes, level on a globe is round. So this is really just point 1 re-hashed. Why do things fall.

4 - It's more that the atmosphere has a pressure gradient derived from gravity, not what kind of vacuum it is.
If you break a hole in the ISS, the atmosphere will go out.

5 - A stationary droplet doesn't help with the spin.
Representing it as angular velocity or rotation period, as well as appealing to the much larger mass of Earth is also quite dishonest.
If you want to do it properly you need to show how angular velocity, tangential velocity and size relate to the force.
And for a simple model, an ball made of a material with the same average density of Earth will have the same ratio of gravitational attraction to the ball vs force required to maintain circular motion, as Earth does when rotated at the same angular velocity.

8 - Who made that argument?

I'm confused, where does this approximation come from? Why is this approximation inherently correct for our purposes? I feel like there's a big gap there and maybe I missed it/misunderstood.

Do you mean the small x approximation for trigonometric functions, or the 8 inches per mile squared?

The small x approximation comes from the taylor series expansion.
i.e. f(0) + f'(0)*x+f''(0)*x^2/2 + ...
or the sum from i=0 to infinity of fⁱ(0)*x^i/i!
where fⁱ is taken to be the ith derivative.
For f(x)=cos(x),
f'(x)=-sin(x),
f''(x)=-cos(x),
f'''(x)=sin(x),
f''''(x)=cos(x).

cos(0)=1, and sin(0)=0.
This means the terms will start as:
1 - 0*x - 1*x^2/2 + 0*x^3/3! + 1*x^4/4!, and so on.
Which ends up being:
1 - x^2/2! + x^4/4! - x^6/6! and so on.
if x is small, i.e. x~=0, or |x| << 1; then x^4/4! << x^2/2!, so that term can be ignored, as can higher order terms.
This gives us the approximation cos(x) ~= 1-x^2/2
Likewise, sin(x)~=x and tan(x)~=x.

The 8 inches per mile squared comes from that approximation.

We can also use that next term to get an idea of the error.
Due to the alternating nature of the taylor series expansion, each term will "over correct".
That means the error is at most x^4/4!.

So remembering that x is s/r, and that we multiply by r, that means the error will be at most r*(s/r)^4/4!
=s^4/(24*r^3)
We can also remember that the approximation is s^2/2r.
That means the percentage error will be [s^4/(24*r^3)]/[s^2/2r] =  s^2/(12*r^2)

Using metric for simplicity, with Earth having a radius of 6371 km, a distance of 100 km gives a drop of 785 m, and a maximum error of 16 mm.
The actual error, calculated using their formula but corrected to s/r is 16 mm. That is 0.002%. And I suppose given that I should say it is 784.806 m when using the approximation and 784.790 when using cos). The rounding I did was more significant than the error of using the approximation.

If we cut it down to 10 km, the drop is 7.85 m (or 7.848061 m), with an error of 0.002 mm or 0.00002%

At 500 km, it is still only a 0.05% error. But at 1000 km it is a 20% error.
So unless you go to extreme distances s^2/2r works well.

Quote from: Space Cowgirl on October 28, 2023, 01:12:59 PM

You should list all his points. No one wants to do your homework for you.

Quote from: JackBlack on October 28, 2023, 03:43:03 PM

If you aren't willing to even put in the effort to list what the points are, why should anyone put in the effort to respond to it?
Did you even put in the effort to search for this video?
Literally copying and pasting the URL into the search will get you a few threads.

I apologize, didn't realize that skimming a <20 minute video was so horrible, here are his 10 points

It's not that scanning a video is so horrible, it is that you wanted someone to have a debate with a video instead of you. People have been coming here doing that sort of thing for years. It's kinda boring, and never really creates a good discussion. Anyway, welcome to FES! lol

I am bulmabriefs144, Smasher of Testicles.  You see? Titles are ridiculous.

Finally, I found a quote to add to my signature