The shape of Earth

[Jehanne]

Or (perhaps, And):

https://en.m.wikipedia.org/wiki/Archimedes%27_principle

[downbeatplumb]

Depends on how solid the rubber, but if it is less dense than the medium it is surrounded by then it will float. 

Using the displacement of liquid to measure the volume of a stone? Not sure how that proves Newton's theories about perpetual motion, you might want to explain that a little more.

Same goes for using fire to suck up liquid into a vacuum.

Yes, precisely. If it is less dense than the surrounding medium, it will float. Why? because at that point the force of buoyancy is larger than that of gravity.

Now, take a ball that is more dense than water. it will sink. But how much will it weigh in the water? The answer is the weight outside of the water minus the weight of the water that would occupy that volume.

The same happens in air: the weight of anything (rock, balloon, etc) will be the weight outside of the air minus the weight of the air for that volume.

In the case of the rock, the weight outside of the air is much larger than the weight of the air, so it sinks. For a balloon, it is less, so it floats.

Now, why is there a weight outside of the air?

https://www.youtube.com/watch?v=E43-CfukEgs

[Fake Messiah]

"Did you also catch Mount Everest with the telescope? Considering that it is the highest mountain in the world it should be seen everywhere, but it's not because the Earth is round." - Fake Messiah. 

Why do we have telescopes? Why can't we just see every star anytime we want to? Is it possible that there is a limit to how much light our eyes can gather and discern? Can you perceive an ant crawling along the ground from more than 300 feet away? If you were standing at one end of a football field would you be able to see a cockroach walking along the other end-zone? Or would you need aid? What about a sound? Would if somebody shot a gun from more than a mile away? Now would if that gun were suppressed? Would you still hear it? Or would you need a device to help you hear something that far away and that quiet?

Ah, what a big fat nonanswer. He is actually comparing the biggest thing in the world, Mount Everest, to a cockroach.
If the world was flat you could see mountains like Mount Everest up in the sky from anywhere in the world, if not by the naked eye, then with a telescope, but you can't. If you are on flat land, all you see is flatness all the way to the horizon.

[Jehanne]

The gravitational field/pull on a flat Earth would also be vastly different!

[Fake Messiah]

Jehanne, that is too complicated for him.

1. What is gravity? How do you know that mass pulls on mass? I have observed that what goes up must come down based on buoyancy and density. Why does a stone sink and why does a helium balloon defy gravity?

You know, there are other forces that affect objects, it's not just gravity.

[zebo-the-fat]

Jehanne, that is too complicated for him.

1. What is gravity? How do you know that mass pulls on mass? I have observed that what goes up must come down based on buoyancy and density. Why does a stone sink and why does a helium balloon defy gravity?

You know, there are other forces that affect objects, it's not just gravity.

You can do an experiment (probably not at home!) where a very sensitive strain gauge can measure the attraction of two large masses towards each other. (Large masses, but still tiny when compaired the whole planet, which is why you need very sensitive equipment, but it has been done)

[BrianSoddingBoru4]

@h311inac311

 What is gravity? How do you know that mass pulls on mass? I have observed that what goes up must come down based on buoyancy and density. Why does a stone sink and why does a helium balloon defy gravity?

(Bold mine)

This was determined and demonstrated more than 200 years ago. If you would read up on the history of science, you wouldn’t need to ask such inane questions.

Boru

[The Grand Nudger]

Most of the questions have been elementary to middle school level. My boys are doing units on this stuff right now. Now, trolls trolling - and ofc troll knows most of this at least vaguely, but the thrust of the trolls questioning implies that they probably didn't actually -do- these science experiments when they were at that grade level...which is why they were unaware of how trivially easy demonstrations of this stuff was...and that's not uncommon in the us at all.

[HappySkeptic]

No-one is this scientifically illiterate. He is either a poster case against home schooling, or a troll.

[h311inac311]

"Did you also catch Mount Everest with the telescope? Considering that it is the highest mountain in the world it should be seen everywhere, but it's not because the Earth is round." - Fake Messiah. 

Why do we have telescopes? Why can't we just see every star anytime we want to? Is it possible that there is a limit to how much light our eyes can gather and discern? Can you perceive an ant crawling along the ground from more than 300 feet away? If you were standing at one end of a football field would you be able to see a cockroach walking along the other end-zone? Or would you need aid? What about a sound? Would if somebody shot a gun from more than a mile away? Now would if that gun were suppressed? Would you still hear it? Or would you need a device to help you hear something that far away and that quiet?

Ah, what a big fat nonanswer. He is actually comparing the biggest thing in the world, Mount Everest, to a cockroach.
If the world was flat you could see mountains like Mount Everest up in the sky from anywhere in the world, if not by the naked eye, then with a telescope, but you can't. If you are on flat land, all you see is flatness all the way to the horizon.

Is air a thing that can block light? 
Is air a thing that can redirect light? 
If not then you'll have to explain to me again why I can see a city skyline from across more than 60 miles of curved water. And, who knows, maybe you could see Mt. Everest from extreme distances, assuming there are no obstructions. Why not try pointing a high-powered laser at it?