Consider a sphere. Since a sphere has a consistent shape, no matter where on it you stand, you have exactly the same amount of sphere under you. (Imagine an ant walking around on a crystal ball. From the insect's point of view, the only indication of movement would be the fact the ant is moving its feet—the shape of the surface would not change at all.) A sphere's center of mass is in the center of the sphere, which means gravity will pull anything on the surface of the sphere straight down toward the center of the sphere. This will occur no matter where on the surface the object is located.
78) From Anchorage, Alaska at an elevation of 102 feet, on clear days Mount Foraker can be seen with the naked eye 120 miles away. If Earth were a ball 25,000 miles in circumference, Mount Foraker’s 17,400 summit should be leaning back away from the observer covered by 7,719 feet of curved Earth. In reality, however, the entire mountain can be quite easily seen standing straight from base to summit.
122) Quoting Allen Daves, “If the Government or NASA had said to you that the Earth is stationary, imagine that. And then imagine we are trying to convince people that 'no, no it's not stationary, it's moving forward at 32 times rifle bullet speed and spinning at 1,000 miles per hour.' We would be laughed at! We would have so many people telling us 'you are crazy, the Earth is not moving!' We would be ridiculed for having no scientific backing for this convoluted moving Earth theory. And not only that but then people would say, 'oh then how do you explain a fixed, calm atmosphere and the Sun's observable movement, how do you explain that?' Imagine saying to people, 'no, no, the atmosphere is moving also but is somehow magically velcroed to the moving-Earth. The reason is not simply because the Earth is stationary.' So what we are actually doing is what makes sense. We are saying that the moving-Earth theory is nonsense. The stationary-Earth theory makes sense and we are being ridiculed. You've got to picture it being the other way around to realize just how RIDICULOUS this situation is. This theory from the Government and NASA that the Earth is rotating and orbiting and leaning over and wobbling is absolute nonsense and yet people are clinging to it, tightly, like a teddy bear. They just can't bring themselves to face the possibility that the Earth is stationary though ALL the evidence shows it: we feel no movement, the atmosphere hasn't been blown away, we see the Sun move from East-to-West, everything can be explained by a motionless Earth without bringing in all these assumptions to cover up previous assumptions gone bad.”
In general, we at the Flat Earth Society do not lend much credibility to photographic evidence. It is too easily manipulated and altered. Many of the videos posted here to "prove a round earth" by showing curvature will show no curvature or even concave curvature at parts. The sources are so inaccurate it's difficult to build an argument on them in either case. Furthermore, barrel distortion and other quirks of modern cameras will cause a picture to distort in ways which may not be immediately obvious or apparent, especially without references within the picture. Photographs are also prone to distortion when taken through the bent glass of a pressurized cabin as well as atmospheric conditions on the outside. With this litany of problems, it's easy to see why photographic evidence is not to be trusted.

Regarding the "traveling at the same speed" idea. When in an aircraft, two people can toss a ball to each other. From the POV of those Inside, the ball is moving at normal ball tossing speed. From the POV of those outside, the ball is being gently tossed to over 500kph and the catcher catchers it without problem. If this is the "everything on the planet moving at the same speed" idea in action. Which does make it possible to travel in either direction.

79.) The remark is common enough that we can see the circle of the Earth if we cross the ocean, and that this proves it to be round. Now, if we tie a donkey to a stake on a level common, and he eats the grass all around him, it is only a circular disc that he has to do with, not a spherical mass. Since, then, circular discs may be seen anywhere – as well from a balloon in the air as from the deck of a ship, or from the standpoint of the donkey, it is a proof that the surface of the Earth is a plane surface, and, therefore, a proof that the Earth is not a globe.
96.) If we refer to the diagram in "Cornell's Geography," page 4, and notice the ship in its position the most remote from the observer, we shall find that, though it is about 4,000 miles away, it is the same size as the ship that is nearest to him, distant about 700 miles! This a an illustration of the way in which astronomers ignore the laws of perspective. This course is necessary, or they would be compelled to lay bare the fallacy of their dogmas. In short, there is, in this matter, a proof that the Earth is not a globe.
The Sun, as he travels round over the surface of the Earth, brings "noon" to all places on the successive meridians which he crosses: his journey being made in a westerly direction, places east of the Sun's position have had their noon, whilst places to the west of the Sun's position have still to get it. Therefore, if we travel easterly, we arrive at those parts of the Earth where "time" is more advanced, the watch in our pocket has to be "put on" or we may be said to "gain time." If, on the other hand, we travel westerly, we arrive at places where it is still "morning," the watch has to be "put back," and it may be said that we "lose time." But, if we travel easterly so as to cross the 180th meridian, there is a loss, there, of a day, which will neutralize the gain of a whole circumnavigation; and, if we travel westerly, and cross the same meridian, we experience the gain of a day, which will compensate for the loss during a complete circumnavigation in that direction. The fact of losing or gaining time in sailing round the world, then, instead of being evidence of the Earth's "rotundity," as it is imagined to be, is, in its practical exemplification, an everlasting proof that the Earth is not a globe.
11) A surveyor and engineer of thirty years published in the Birmingham Weekly Mercury stated, “I am thoroughly acquainted with the theory and practice of civil engineering. However bigoted some of our professors may be in the theory of surveying according to the prescribed rules, yet it is well known amongst us that such theoretical measurements are INCAPABLE OF ANY PRACTICAL ILLUSTRATION. All our locomotives are designed to run on what may be regarded as TRUE LEVELS or FLATS. There are, of course, partial inclines or gradients here and there, but they are always accurately defined and must be carefully traversed. But anything approaching to eight inches in the mile, increasing as the square of the distance, COULD NOT BE WORKED BY ANY ENGINE THAT WAS EVER YET CONSTRUCTED. Taking one station with another all over England and Scotland, it may be stated that all the platforms are ON THE SAME RELATIVE LEVEL. The distance between Eastern and Western coasts of England may be set down as 300 miles. If the prescribed curvature was indeed as represented, the central stations at Rugby or Warwick ought to be close upon three miles higher than a chord drawn from the two extremities. If such was the case there is not a driver or stoker within the Kingdom that would be found to take charge of the train. We can only laugh at those of your readers who seriously give us credit for such venturesome exploits, as running trains round spherical curves. Horizontal curves on levels are dangerous enough, vertical curves would be a thousand times worse, and with our rolling stock constructed as at present physically impossible.”
It is a well-known fact that clouds are continually seen moving in all manner of directions - yes, and frequently, in different directions at the same time - from west to east being as frequent a direction as any other. . Now, if the Earth were a globe, revolving through space from west to east at the rate of nineteen miles in a second, the clouds appearing to us to move towards the east would have to move quicker than nineteen miles in a second to be thus seen; whilst those which appear to be moving in the opposite direction would have no necessity to be moving at all, since the motion of the Earth would be more than sufficient to cause the appearance. But it only takes a little common sense to show us that it is the clouds that move just as they appear to do, and that, therefore, the Earth is motionless. We have, then a proof that the Earth is not a globe.
Light travels at a finite speed, with the speed depending upon the medium. With mirages, the medium is air. In air, the speed of light is only slightly less than it is in a vacuum, and the speed of light in air depends upon the temperature of the air. Simply put, the speed of light is slightly greater in warmer air than it is in cooler air. In physics, we usually express this behavior reciprocally as the index of refraction, n:
"By actual observation," says Schoedler, in his " Book of Nature," we know that the other heavenly bodies are spherical, hence we unhesitatingly assert that the earth is so also." This is a fair sample of all astronomical reasoning. When a thing is classed amongst "other" things, the likeness between them must first be proven. It does not take a Schoedler to tell us that "heavenly bodies" are spherical, but " the greatest astronomer of the age" will not, now, dare to tell us that THE EARTH is - and attempt to prove it. Now, since no likeness has ever been proven to exist between the Earth and the heavenly bodies, the classification of the Earth with the heavenly bodies is premature - unscientific -false! This is a proof that Earth is not a globe.
Another point concerning timezones, the sun, and Earth: If the sun was a “spotlight” (very directionally located so that light only shines on a specific location) and the world was flat, we would see the sun even if it didn’t shine on top of us (as you can see in the drawing below). Similarly, you can see the light coming out of a spotlight on a stage in the theater, even though you—the crowd—are sitting in the dark. The only way to create two distinctly separate time zones, where there is complete darkness in one while there’s light in the other, is if the world is spherical.
If the Earth were a globe, there would, very likely, be (for nobody knows) six months day and six months night at the arctic and antarctic regions, as astronomers dare to assert there is: - for their theory demands it! But, as this fact - the six months day and six months night - is; nowhere found but in the arctic regions, it agrees perfectly with everything else that we know about the Earth as a plane, and, whilst it overthrows the "accepted theory," it furnishes a striking proof that Earth is not a globe.

What if the earth was a sphere in inverse? I'm no scientist but I found this discussion by accident and it challenged both beliefs in me. There was a ride at a local amusement park that was cylindrical and would start spinning with the floor eventually falling out beneath us. We would stay attached to the sides. Eventually they would slow the spinning down and we would loosen up from the wall. Is it possible that the Earth envelops the sun, moon, stars and "outer space" as we know? That everything we know is inside as opposed to outside our world we know and experience? Very interesting subject nonetheless.

We read in the inspired book, or collection of books, called THE BIBLE, nothing at all about the Earth being a globe or a planet, from beginning to end, but hundreds of allusions there are in its pages which could not be made if the Earth were a globe, and which are, therefore, said by the astronomer to be absurd and contrary to what he knows to be true! This is the groundwork of modern infidelity. But, since every one of many, many allusions to the Earth and the heavenly bodies in the Scriptures can be demonstrated to be absolutely true to nature, and we read of the Earth being "stretched out" "above the waters," as "standing in the water and out of the water," of its being "established that it cannot be moved," we have a store from which to take all the proofs we need, but we will just put down one proof - the Scriptural proof - that Earth is not a globe.
Every man in his senses goes the most reasonable way to work to do a thing. Now, astronomers (one after another - following a leader), while they are telling us that Earth is a globe, are cutting off the upper half of this suppositious globe in their books, and, in this way, forming the level surface on which they describe man as living and moving! Now, if the Earth were really a globe, this would be just the most unreasonable and suicidal mode of endeavoring to show it. So that, unless theoretical astronomers are all out of their senses together, it is, clearly, a, proof that the Earth is not a globe.

In " Cornell's Geography" there is an "Illustrated proof of the Form of the Earth," A curved line on which is represented a ship in four positions, as she sails away from an observer, is an arc of 72 degrees, or one-fifth of the supposed circumference of the "globe" - about 5,000 miles. Ten, such ships as those which are given in the picture would reach the full length of the "arc," making 500 miles as the length of the ship, The man in the picture, who is watching the ship as she sails away, is about 200 miles high; and the tower, from which he takes an elevated view, at least 600 miles high. These are the proportions, then, of men, towers, arid ships which are necessary in order to see a ship, in her different positions, as she "rounds the curve" of the "great hill of water" over which she is supposed to be sailing: for, it must be remembered that this supposed "proof" depends upon lines and angles of vision which, if enlarged, would still retain their characteristics. Now, since ships are not built 500 miles long, with masts in proportion, and men are not quite 200 miles high, it is not what it is said to be - a proof of rotundity - but, either an ignorant farce or a cruel piece of deception. In short, it is a proof that the Earth is not a globe.
69.) Mr. Lockyer says: "The appearances connected with the rising and setting of the Sun and stars may be due either to our earth being at rest and the Sun and stars traveling round it, or the earth itself turning round, while the Sun and stars are at rest." Now, since true science does not allow of any such beggarly alternatives as these, it is plain that modern theoretical astronomy is not true science, and that its leading dogma is a fallacy. We have, then, a plain proof that the Earth is not a globe.
143) People claim that if the Earth were flat, with the Sun circling over and around us, we should be able to see the Sun from everywhere all over the Earth, and there should be daylight even at night-time. Since the Sun is NOT 93 million miles away but rather just a few thousand and shining down like a spotlight, once it has moved significantly far enough away from your location it becomes invisible beyond the horizon and daylight slowly fades until it completely disappears. If the Sun were 93 million miles away and the Earth a spinning ball, the transition from daylight to night would instead be almost instantaneous as you passed the terminator line.
16) The experiment known as “Airy’s Failure” proved that the stars move relative to a stationary Earth and not the other way around. By first filling a telescope with water to slow down the speed of light inside, then calculating the tilt necessary to get the starlight directly down the tube, Airy failed to prove the heliocentric theory since the starlight was already coming in the correct angle with no change necessary, and instead proved the geocentric model correct.
 3) The natural physics of water is to find and maintain its level. If Earth were a giant sphere tilted, wobbling and hurdling through infinite space then truly flat, consistently level surfaces would not exist here. But since Earth is in fact an extended flat plane, this fundamental physical property of fluids finding and remaining level is consistent with experience and common sense.

136) Many people think that modern astronomy’s ability to accurately predict lunar and solar eclipses is a result and proof positive of the heliocentric theory of the universe. The fact of the matter however is that eclipses have been accurately predicted by cultures worldwide for thousands of years before the “heliocentric ball-Earth” was even a glimmer in Copernicus’ imagination. Ptolemy in the 1st century A.D. accurately predicted eclipses for six hundred years on the basis of a flat, stationary Earth with equal precision as anyone living today. All the way back in 600 B.C. Thales accurately predicted an eclipse which ended the war between the Medes and Lydians. Eclipses happen regularly with precision in 18 year cycles, so regardless of geocentric or heliocentric, flat or globe Earth cosmologies, eclipses can be accurately calculated independent of such factors.

In the past 60 years of space exploration, we’ve launched satellites, probes, and people into space. Some of them got back, some of them still float through the solar system (and almost beyond it), and many transmit amazing images to our receivers on Earth. In all of these photos, the Earth is (wait for it) spherical. The curvature of the Earth is also visible in the many, many, many, many photos snapped by astronauts aboard the International Space Station. You can see a recent example from ISS Commander Scott Kelly's Instagram right here:
135) Not only is the Moon clearly self-luminescent, shining its own unique light, but it is also largely transparent. When the waxing or waning Moon is visible during the day it is possible to see the blue sky right through the Moon. And on a clear night, during a waxing or waning cycle, it is even possible to occasionally see stars and “planets” directly through the surface of the Moon! The Royal Astronomical Society has on record many such occurrences throughout history which all defy the heliocentric model.