The Apple Didn't Fall
“Professor Marshal, what causes gravity?”
“Let's see, you're Troy aren't you?” The professor was always amused by the new freshman and their naive ideas of science. “The fact is, we don't know. No one has ever proposed a reasonable hypothesis that is consistent with all the things we can observe.”
“Yeah, but” Troy blurted in the time honored way that made the professor wince, “the textbook says, scientific laws must be true, universal, and absolute. They're the cornerstone of scientific discovery, because if a law ever did not apply, then all science based upon that law would collapse.
“If we don't know what causes it, doesn't that mean that all of science is based on an assumption?”
“Okay, normally we wouldn't have time to talk about such frivolous things as the validity of scientific laws, but since this is the first day, maybe a discussion will help me to get to know you better. If we're going to have a discussion though, let's do it right, by defining our terms. Newton's law of universal gravitation states that every massive particle in the universe attracts every other massive particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. We can measure the acceleration of a falling object like Newton's apple and it's 32 feet/second squared.”
At this point, Troy put up his hand, but the Professor ignored it. “When we observe the planets and moons in the solar system, it's obvious that there's a force holding them in their orbits, otherwise, by another of Newton's laws-of-motion, they would fly off into space.”
Becoming impatient, Troy began waving. With a sigh, the Professor finally acknowledged him, “Yes, Troy?”
“I think we understand the basic grade school stuff.” Troy looked around to see if any of the other students objected. “What we don't know is how they determined what the mass is of the sun or the moon. There are three unknowns in the equation, the mass of both objects and the force required to maintain them in orbit. You can't solve the equation for all three at the same time.”
Slightly more impressed, the Professor elevated the age at which his lecture was aimed. “Of course, we can't prove what the mass is, but each planet or moon is affected by more than one object. The earth, for example, revolves around the sun and the moon revolves around the earth. Each of the three affects the others. So we don't have just one equation with three unknowns, we have three equations with four unknowns.”
With a smile, Troy sprang his trap. “But how do you know the unknowns are the mass? Has there ever been an experiment where the mass of both the objects drawn together by gravity were measured directly? What if the unknowns in the equations represent something else other than the mass? How could we tell?”
“Actually, we couldn't tell, but no one has ever suggested any other property of the planets or moons that could be responsible,” the Professor answered blithely.
“What about the electrical charge of a body? If the charges are opposed, they'd exert the same kind of force,” Troy offered, refusing to let go.
Without so much as a by your leave, another student jumped in, “That's a really stupid idea. What about all the stuff that's neutral, it'd all go flying off into space.”
“Let's see, according to the seating chart, you'd be Charlie? Is that right? OK, Charlie, let's see if Troy can explain why that wouldn't happen,”
Like a kid in a candy shop, Troy burbled, “It's simple really. In an electric field created by a plasma, there isn't anything that's neutral. On earth, there is a voltage between the earth and the sky of about 100 volts every 6 feet so your head is negatively charged with respect to your feet and that field exerts a force. In the air, electrically charged particles can move around so the field we can measure is changing all the time. But in the solid body of the earth, the charges are fixed, so the positive charge would be greater and greater towards the center of the earth.
“The Neutral Charlie is talking about is where an atom has the same number of electrons as it does protons, but it doesn't really exist because the protons are in the nucleus and the electrons are on the outside. That allows the electrons of one atom to be attracted to the nucleus of another when they are closer to it and is what allows atoms to bind together into molecules.
“Even if you did have a neutral atom, it would still be attracted to an atom that didn't have enough electrons to balance its protons. But we aren't talking about an apple being attracted to the ground, that is very different than the effect of gravity. The force would have to be an attraction between everything on the surface of the earth and an accumulation of positive charge at the center of the earth. Isn't that right?” he ended looking smug.
“That's a good, Troy, but there's another reason why an electric field couldn't cause the effect of gravity.” the Professor resumed his condescending tone, “the force generated by an electric field is 10 to the 36 th power times more powerful than gravity and its force varies inversely to distance while gravity varies inversely in proportion to the square of the distance. That really is a very big difference. No matter where you are in an electric field, the force it generates is always the same.”
And then Troy asked the question that turned the world upside down. “So, under what conditions would the force of an electric field be indistinguishable from gravity? What if the field isn't uniform? What if the electric charge on the earth varied in an inversely proportional way according to the square of your distance from the center?”
Once again Charlie interrupted, “but then you're right back where you started from. Mass would simply be defined as being the property of a particle responding to the electric field instead of a gravitational field. It would still be mass, so nothing would be different.”
With a troubled look on his face the Professor responded, “Actually, if Troy's hypothesis was right, it would indeed turn the world upside down. The law-of-gravity is a law only if it is always true. If the force of gravity is caused by an electric field, the field could change and the law-of-gravity wouldn't be a law. The sun wouldn't be a nuclear furnace, black holes couldn't exist and the big bang didn't happen. For your sake Troy, I hope to God you are wrong, because, if not, you've just destroyed the life's work of more people than Galileo.”
