There are 4 fundamental forces known at this time. In order of strength from weakest to strongest are gravity, weak force, electromagnetic force, and strong force. The weak and strong forces act only on an atomic scale. Something needs to be less than 0.000000000000001 meters for an interaction to happen with those forces. We really don’t see them do anything with our eyes but they are what hold atoms and subatomic particles together.
With our eyes we are familiar with gravity causing things to fall. We are also familiar with magnets pushing or pulling things. Interestingly gravity is by far the weakest force. The magnetic force is over 20,000,000,000,000,000,000,000,000,000,000,000,000,000,000 (should be 40 zeroes) times as strong as gravity. Gravity while doing so much for us is also a strange force that is the most weakly understood-we don’t know what particles cause it. The best explanations have been performed by Einstein who helped resolve the effects of gravity on light. But unlike the other forces which can be tied together, gravity seems unique. This is why it is a great target for flat earthers. It is also unexplainable in a flat earth model and so must be explained away.
First of all, a force is something that causes acceleration or change in velocity of an object. That change in velocity could be a change in speed like 35mph to 40mph (or 30mph to 25mph). It could also be change in direction like turning left. The equation physicists use is:
F(total) = m*a [Total Force = mass * acceleration]
I write F(total) because the acceleration an object really experiences depends on the entire total force applied to it. A person pushing a ball forward will accelerate it only if something is not pushing back.
The simple formula for gravity is:
F(g) = G * m1 * m2 / r2 [Gravity = Gravitational Constant * mass 1 * mass 2 / distance from center of gravities squared]
The gravitational constant (6.67408 × 10-11 m3 kg-1 s-2) is a ratio that was measured and refined over years of measurement. Much like the constant pi which describes the ratio of a circle’s diameter to its circumference. Mass 1 could be any object. In our scenario we will consider the mass 2 to be the earth. Along the surface of Earth, within a reasonable amount of error, all objects are the same distance from the center of the earth. If you combine our two previous equations you would have this:
m1*a = G * m1 * m(earth) / r2
You can simplify the equation and remove m1 from both halves by dividing both halves of the equation by m1 to get:
a = G * m(earth) / r2
The really neat thing about this equation is it means an object’s acceleration with respect to the gravitational pull of earth is related to G (a constant), Earth’s mass (a constant), and the distance an object is from the center of Earth. That means that if you drop two items, and they are only acted on by gravity, they will fall at exactly the same rate of acceleration.
This has been done by dropping similarly shaped objects like an orange and a bowling ball and seeing them hit the ground at the same time from very high distances. It seems not to work for something like a feather and a bowling ball, but this is because of air resistance which slow’s the decent of the feather. However, if you put any two objects in a vacuum (such as a feather and a coin) both will fall at the same rate of acceleration.
The center of mass is more important than where individual objects are. So for example, the planets don’t really revolve around the sun. They revolve around the center of mass for the solar system minus the planet’s mass. It is actually really very close to the sun because the mass of the sun is so much greater than the other planets.
If a person is within a hollow sphere of uniform density, in the precise middle, the person would not accelerate. The force of gravity would be equalized by each particle pulling him a different direction. Interestingly, because gravity is stronger the closer two objects are, it doesn’t really matter where inside that sphere a person is placed. All the gravitational forces will equalize to 0.
The weight of an object is the amount of force the ground has to push up to prevent an object from falling through the earth. An apple sitting on a scale is not moving. The Earth is trying to accelerate the apple toward its center; however, the ground pushes back to prevent this with exactly the same amount of force in the opposite direction so that the sum force on the apple equals zero. When we measure something’s weight we are in fact measuring this upward force which is called the normal force.
Okay now that we understand the basics of gravity, it is easy to see why gravity would not work in a flat earth. The mass of Earth is tremendous compared to any object whether it the Earth is flat or spherical. The weight of an object on a spherical earth is the same as long as it is at the same altitude. On a flat earth with an edge, this is not the case. An object on the edge of the planet is further from the center of mass than an object in the center of the plane. Additionally, the direction of gravitational pull would always be toward the center of mass. So an object would be pulled more horizontally, the closer it was to the edge of the planet. Since none of these things happen, gravity cannot exist as described by Newton or Einstein with a flat Earth.
Instead of rejecting the flat Earth theory, flat Earth theorists reject gravity and propose different mechanisms for objects to fall. Fortunately, there are multiple ways to check these proposed mechanisms. First, the author of this article goes straight for helium balloons.
A balloon filled with helium will indeed rise in a world with gravity. The balloon has a low density and rises in the atmosphere until it reaches air of the same density. Gravity is pulling on the balloon and prevents it from reaching outer space.
The force causing the balloon to rise deals with differences in pressure. The amount of force pushing on any side of the balloon varies with the density of air. Air pressure decreases at higher altitudes (this allows water to boil at a lower temperature in the mountains than at the ocean. While the difference in air pressure on the bottom of the balloon vs the top of the balloon is minor, the additive effect across all of the surfaces causes the balloon to rise.
For all objects (helium balloons, books, bricks, and feathers), Earth’s gravity pulls the object toward the center of the planet. The actual acceleration of the object depends on the sum force on the object. In the case of a brick, no significant force pushes on the brick to slow its decent to the ground. In the case of a feather, the high surface area creates friction with the air to slow its fall. In the case of a helium balloon, the air pushes the balloon sufficiently to force it upward (the mass of the balloon is very low compared to the mass of the air displacing the balloon). I believe in the case of the balloon rising, we agree on the general principle of buoyancy. The difference is gravity explains why the air near the ground is more dense than the air higher up; more massive objects are pulled harder by the force of gravity and in the case of fluids, able to displace less dense air upward. At higher elevation air is thinner because there is less gravity to hold it tightly packed together. In a flat earth model without gravity, less dense air is just above more dense air because that is how it works. Even considering the buoyancy as a fact of nature without gravity, why does air not gradually disappear from Earth, continuing to rise without limit?
The linked article asks: “For, if such attraction existed, why does not the Earth attract the rising smoke which is not nearly so heavy as the apple? The answer is simple – because the smoke is lighter than the air, and, therefore, does not fall but ascends.”
If gravity were to act on a single particle of air, the force exerted would be significantly less than the apple. Therefore, other forces can play a roll in the elevation of low density, hot smoke allowing it to rise. Air particles are so light that the electromagnetic force between molecules of air caused by the electrons on their surface would be significantly greater than the force of gravity. This even forces air to uniformly fill whatever vessel it is placed within. The truth is, the Earth does attract the rising smoke with gravity. If the Earth did not attract air, we would have no air to breathe.
Some of the next cited articles are full of errors. Newton’s laws of gravity were proved false in certain extreme circumstances by Einstein. Einstein’s law of general relativity therefore cannot hinge on the work of Newton since it disproved his theory in these extreme situations: 1) light can “bend” around very massive objects, 2) the measurements of time and distance can be different depending on the observer as objects approach the speed of light, and 3) gravity exerts a greater pull than expected by Newton for close orbits like Mercury. In general, Newton’s laws work pretty well without as complicated math, so we rely on those for most things. Einstein’s principles are, however, used to power things like GPS which would not be possible with Newtonian physics alone.
Next the essay asks: “Now, even if gravity did exist, why would it cause both planets to orbit the Sun and people to stick to the Earth?”
This seems easy enough. Gravity does not cause things to fall. It causes things to accelerate. As explained, acceleration is any change in speed or direction. So if a car turning left in a circle at constant speed, the car is constantly accelerating left. Gravity of the sun is accelerating the Earth in such a way that it keeps turning, but with enough velocity not to fall into the sun. It is actually doing the same thing to each person on Earth, but in comparison to the amount of force we experience from the sun, the Earth’s is much greater because our distance is tiny in comparison:
F(earth) = G * 80kg * 5.972 × 10^24 kg / (6,300,000 m)^2 = 803N
F(sun) = G * 80kg * 1.989 × 10^30 kg / (150,000,000,000 m)^2 = 0.47N
The Earth’s gravitational pull on a person is roughly 1600 times greater than the sun’s gravitational pull. This is why a person sticks to the Earth and does not get sucked into the sun.
Next the article asks why does the cannonball fired form a parabolic curve? Why does the cannon not continue indefinitely?
This is also simple. The cannonball is fired by a force. As long as that force is being applied it will continue to accelerate in the direction of the force. A rocket is an example of a projectile similar to a cannonball that can sustain a force after it is fired and continue accelerating. Since no force is acting on a cannonball after it is fired, it does not accelerate any longer, air resistance slows its velocity, and the gravity of Earth accelerates it downward. In fact, since acceleration is constant, gravity would predict that the velocity would decrease at a steady rate and the shape of the projectile’s arc would be a parabola (if acceleration = constant, then velocity = constant * x +different constant, and height = constant * x^2 + differenet constant * x + another constant — the latter is the exact definition of a parabola).
Article: “If the sun is pulling with such power at the earth and all her sister planets, why do they not fall down upon him?”
Hopefully, this can make sense now. Just as a car can turn to the left without forming a spiral if the acceleration and velocity are properly placed. The Earth (and moon since it is technically our center of mass circling the center of mass of the solar system) has reached a stable orbit over a long period of time. Lots of material has fallen into the sun. Lots of material has escaped the solar system. The solar system is in a relatively stable period of time.
Next, “Furthermore, this magnetic-like attraction of massive objects gravity is purported to have can be found nowhere in the natural world.”
Just to name the easiest examples, Mercury, Venus, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, and Pluto are all massive spheres that stick to an orbit around the massive sphere called the sun. No other force is known to cause their orbits. No other force is required to explain their orbits. Most of these planets even have moons which orbit them in the same fashion. This can be observed with a telescope. It takes a little time, but if you are diligent, you can map out the paths of the moons around these objects yourself. You will even be able to see the phases of their moons which look like our moon’s phases.
Science has even developed ways to measure very small gravitational. Henry Cavendish did so in a paper published in 1798. Anyone can repeat this experiment which would not work with buoyancy alone.
Next, “How is it that “gravity” is so strong that it can hold all the oceans, buildings and people stuck to the under-side of the ball-Earth, but so weak that it allows birds, bugs, smoke, and balloons to casually evade its grips completely!? ”
I believe this is already addressed. Gravity is actually very weak, but always acting. Birds and bugs are able to fly because they push the air with their wings. Smoke rises because it is less dense than adjacent area and air pressures force it upward. Similarly with balloons.
Next, “How is it that “gravity” holds our bodies clung to the under-side of the ball-Earth, but yet we can easily raise our legs and arms, walk or jump and feel no such constant downward pulling force? ”
Even in the flat earth without gravity, our arms would be falling constantly because they are more dense than air (even when we are standing on the ground). Regardless, legs and arms fall when you do not fire your muscles. When walking the ground is felt beneath a person’s foot. When a person jumps, he cannot miss being pulled down. Fortunately gravity acts on each of a person’s molecules, providing only a miniscule force on each atom so that people do not have to feel constantly pulled down.
Next, “How is it that “gravity” can cause planets to revolve elliptical orbits around a single center of attraction?”
Ellipses require only one focus to cause their course. Planets move in elliptical orbits because in fact they accelerate toward the center of mass. If a planet orbited the sun in a perfect circle, every turn would be to the left without forward or reverse acceleration. As would be expected the planets do not orbit in perfect circles. As they approach nearer to the sun, the acceleration adds speed and the planet moves more quickly. As the planet moves away, it is pulled in reverse, slowing the speed. The force of gravity being related to the radius squared in fact allows gravitational force to increase and decrease to keep planets in constant orbit. The fact that the speed of Earth orbiting the sun increases and decreases allows it to not move into the sun. (To be addressed later, the Earth’s seasons have less to do with the nearness or farness of the sun as it does to the tilt of the Earth allowing more sun to shine on part of the Earth)
Next, “We are asked by the Newtonian to believe that the action of gravitation, which we can easily overcome by the slightest exercise of volition in raising an hand or a foot, is so overwhelmingly violent when we lose our balance and fall a distance of a few feet, that this force, which is imperceptible under usual conditions, may, under extraordinary circumstances, cause the fracture of every limb we possess?“
Gravity accelerates objects downward. Gravity is weak, but provides constant acceleration so that the farther one falls, the faster velocity becomes. The flat earth explanation, “whereas the definition of weight already given does, for a body seeking in the readiest manner its level of stability would produce precisely the result experienced” seems to imply infinite acceleration. Acceleration can be measured, and it is always the same for falling objects of different densities when other forces are eliminated.
Next, “Even if the centripetal (inward pulling) force of gravity did exist, which it does not, the centrifugal (outward pushing) force of the ball-Earth’s supposed 19 mile per second spin would also exist and have to be overcome, yet neither of these opposing forces have ever been shown to have any existence outside the imaginations of heliocentric “scientists.””
The force of this centripital effect is in fact how spinning was measured for the earth. First though, the Gravitron produces a maximum speed of 24 rpms which produces 3 times the force of gravity. In order for the earth to produce a similar force, it would need to spin at 860,600,000 miles per hour which is quite faster than 1000 miles per hour. In fact, to produce the same force, Earth’s day would need to be 2.5 seconds. A common example of this involves driving in a car. If a car turns sharply, the occupants will be slung to the side more aggressively than if it turns on a large arc. The speed matters too, but you cannot consider the force without speed and arc of rotation. People really only feel acceleration. If a person’s body is not accelerating (as in a car traveling 60mph), he feels nothing. When he turns, slams on the brakes, or hits the gas, he feels the acceleration. The acceleration a person feels is equivalent to standing in a Gravitron that takes one day (24 hours) to fully rotate. This would be a terrible amusement ride.
Next, ““The attraction of gravitation is said to be stronger at the surface of the earth than at a distance from it. Is it so? If I spring upwards perpendicularly I cannot with all my might ascend more than four feet from the ground; but if I jump in a curve with a low trajectory, keeping my highest elevation about three feet, I might clear at a bound a space above the earth of about eighteen feet; so that practically I can overcome the so-called force (pull) at the distance of four feet, in the proportion of 18 to 4, being the very reverse of what I ought to be able to do according to the Newtonian hypothesis.”
I am quite unsure what this means. I think this is saying that if the author jumps straight up he can jump 4 feet. And if he jumps forward at 3 feet he can jump 18 feet forward. This is possible with gravity. When jumping forward, a person will come downward. Forward jumps can be any distance from 0 feet to 29ft 4.25in. This of course depends on the forward velocity/acceleration which has very little resistance in comparison to the downward acceleration. Interestingly, if you measure the length of time to jump forward or vertical it depends only on the maximum height of the jump. So if a long jumper reaches 20 feet attaining 2.5 feet in altitude; the jump lasts the same amount of time as if he jumped vertically.
Now on the tides and attraction of the moon: “If the Moon is only 2,160 miles in diameter and the Earth 8,000 miles, however, using their own math and “law,” it follows that the Earth is 87 times more massive and therefore the larger object should attract the smaller to it, and not the other way around. ”
Earth (5.972*10^24) is 81 times more massive than the moon (7.347*10^22 kg). By the law of gravity every mass attracts every other mass. The earth attracts the moon and the moon attracts the earth. The earth attracts a person on the surface of the planet and the person attracts the earth (though the latter is very little).
The moon’s gravitational force on the surface of the ocean would cause tides. Overall the force of the moon on the entire earth is 1.98 x 10^20 N. On say Lake Michigan which contains 1.3×10^15 gallons of water, a force of 1.6×10^11 N would be expected. The force to accelerate 1 liter of water 10m/s^2 is 10N. Even small lakes and rivers vary with the moon’s gravitational pull. The effect will always depend on the distance the moon is from a particular body of water, the size of that body of water, and what the adjacent land mass is shaped like. Inland lakes like the Great Lakes in the United States experience tides.
Next, “It is affirmed that the intensity of attraction increases with proximity, and vice versâ. How, then, when the waters are drawn up by the moon from their bed, and away from the earth’s attraction,–which at that greater distance from the centre is considerably diminished, while that of the moon is proportionately increased–is it possible that all the waters acted on should be prevented leaving the earth and flying away to the moon?”
Again, the pull of the Earth on the water is significantly greater than the pull of the moon. The water is pulled toward the center of mass which is still within the Earth even when the moon is opposite the earth. It is in fact still 1700 km beneath the Earth’s crust. The phenomenon is what produces the weaker net effect of gravity on the water that allows it to swell.
Just to try to lump NASA into this: “NASA together with Boeing have been perfecting so-called “Zero G planes” and “Zero G maneuvers,” which are able to produce weightlessness at any altitude. Aboard modified Boeing 727’s specially trained pilots perform aerobatic maneuvers known as parabolas. Planes climb with a pitch angle of 45 degrees using engine thrust and elevator controls, then when maximum height is reached the craft is pointed downward at high speed. The period of weightlessness begins while ascending and lasts all the way up and over the parabola until reaching a downward pitch angle of 30 degrees, at which point the maneuver is repeated.”
Weightlessness happens on the descent when the plane and passengers are all in free fall, not during the ascent. This happens because the plane is accelerating to the ground at 9.8 m/s^2 (the acceleration gravity causes). The passengers then have the appearance of weightlessness within the plane which looks stationary. If the plane was not there, the passengers would be sky diving and just falling to the earth. However, the example raises the question: since the air pressure inside the cabin is either what we breath normally or less dense, why do passengers not fall to the ground? With the difference in air density, the flat earth model would force the passenger to the ground because as the author states: “for a body seeking in the readiest manner its level of stability would produce precisely the result experienced.”
The weightlessness experienced by astronauts in space looks similar because the space shuttle and International Space Station are in free fall toward the earth with enough forward velocity so as to stay in orbit.
The author feels he is onto something, “Without gravity, people cannot stand upside-down on a ball-Earth! Without gravity, the Earth and planets cannot be revolving around the Sun! Without Newtonian gravitation, Einsteinian relativity, Copernican heliocentricity, and the entire Big Bang ball-Earth mythos cannot exist and falls to pieces.”
No one stands upside down on a ball earth. Up is relative. Einsteinian physics replaced Newtonian physics. Newtonian physics still get taught because they work most of the time and are easier to comprehend. Copernican heliocentricity predates Newton. It stands on its own and is based on the observation of the motion of planets. Gravity then helped explain how this works. The Big Bang theory came into existence because the stars are moving away from each other. Maybe the neatest idea out of the Big Bang theory is the entire universe started as a single point. Because that one point was the center of the universe, everywhere must be the center of the universe. That puts Earth right where the author wants it to be.
Then the author draws unrelated conclusions: “[Gravity] a theory perfectly outrageous and opposed to all human experience, it follows that, unless we can trample upon common sense and ignore the teachings of experience, we have an evident proof that the Earth is not a globe”
Gravity came about after the proof was established that the Earth is a globe revolving around the sun. To disprove the latter might disprove gravity, but not the reverse. Even so, gravity is fairly easy to comprehend and works flawlessly.
A very neat concept indeed: “‘That which attracts every thing toward every other thing.’ That does not tell us much ; and yet the little it does tell us is not true; for a thoughtful observer knows very well that every thing is not attracted towards every other thing . . . The definition implies that it is a force; but it does not say so, for that phrase ‘mutual action ‘ is ambiguous, and not at all convincing.”
One of the things that perplexed Albert Einstein about the force of gravity was that it was indistinguishable from acceleration. Meaning that a person in a constantly accelerating spaceship with no windows would feel the ground under his feet. If he did not know he was in a space ship, he would think he was in a room on a planet. No experiment he performed could distinguish between a room in a gravitational field or an accelerating room. Differently, if he was in any other field (such as an electromagnetic field) an experiment could distinguish what was going on outside the room. This is why even though gravity works, it is still the least understood force. The best definition is now that an objects mass tells space and time how to be shaped and the shape of space and time tells a mass how to behave.
The difference between the Flat Earth Theory and Gravity is that Gravity produces things that can be tested. If you chose to and had precise instruments: you could travel a great distance above the earth and measure the acceleration of a dropped item, then compare it at sea level. If Flat Earth Theory is true, the object would accelerate faster in the low air density. If Gravity exists, it would accelerate more slowly.
Lots of other things can prove gravity is true. You could measure the attraction of two small masses as described above and performed over 200 years ago. You could even just look up at the sky. If the planets and moons are luminous bodies (not reflecting light from the sun), why do they cast shadows on each other as if being shined on by the sun? The effects of gravity have allowed the prediction of the Uranus before it was known to exist. Maybe just look through a telescope and measure the period of the orbiting bodies. If this could be done in the 1600s, this could easily be performed now.
In contrast, there is no test for the Flat Earth argument other than: stuff falls.