Gravity is Disappearing

Gravity is Disappearing

by Damon Nomad


Newton's Simple World

You remember from high school physics, Newton proved gravity existed. Damon Nomad is crazy.

What did wily old Isaac really prove and what did he say about the source of gravity?

He kind of pulled the wool over our eyes by offering us a simple view of the world. Things behave pretty much like the world we experience. It explains billiard ball collisions, the path of a baseball flying through the air, and even the motion of the planets. Well actually, this last piece has some problems when you take a close look. Newton's world was a little too simplified. It is so appealing and comfortable, a rigid view of a fixed three-dimensional space and a universal cosmic clock ticking. Just like you see when playing a game of billiards in your game room.

In Newton's day, the raging argument of science was about the planets and their celestial motion. He worked it out, creating calculus along the way with a stroke of intuitive brilliance. Newton said there must be a force responsible for this motion, an attractive force between objects, gravity (F_g ).

F_g = G (m₁ x m₂) / R²

G is a constant; m₁ mass of object one; m₂ mass of object two and R is the distance between the objects. In a tour de force, using this basic starting point Newton calculated the motion of the moon about the earth and the planets around the sun. So it seemed back in 1700.

He confided in his closest friends; a dirty little secret. He had no idea where the gravity came from, he said he would leave that to the realm of God. But the calculations were brilliant!

Whispers started when problems emerged as astronomers observed Mercury's orbit. Isaac's predictions seemed to be off; we will not go into the details.

Initially, Newton and his supporters said there was an easy explanation. A missing planet too small to observe Vulcan; would make the math work. Yes, Star Trek fans, Vulcan. We all know that is the only place you will find planet Vulcan. For the general public, things were good with the world of gravity for nearly three hundred years. Then a real radical thinker showed up, we all know him, the crazy hair and brilliant peaceful eyes.


Einstein's Four-Dimensional Space-Time

Now you remember. Damon Nomad is crazy. It was Einstein, he proved what gravity was. It's not as simple as Newton's view, something about the curvature of space time. Maybe you don't really understand it; but all of the books and television shows, say the proof is convincing. He used his theory to predict the bending of light from distant stars and gravity waves.

Kindly ole Grandpa Albert is like Newton; he had a dirty little secret as well. It's a little harder to discover, we have to do a little digging.

Einstein said that space and time were inseparable; we live in four-dimensional space-time. Gravity results from the curvature of space time. Further, the curvature is due to the presence of mass or energy. That is the essence of his explanation, known as general relativity. It's difficult for us to understand because the effects do not show themselves in our everyday world and to understand it, involves some very complex mathematics.

He got there in two steps; special relativity then general relativity. We can kind of wrap our minds around what he did with some simple mental images. Then we will get to the bit he swept under the rug.

In special relativity, he said space and time were not separable and time was not universal. There are many books with excellent descriptions. Here is a classic simple explanation of what Einstein was saying about time.

Imagine a man on a speeding train and he is sitting in front of a large window. A pulsing intense light on the table in front of him is his clock. The pulses are triggered by a precise mechanical pendulum; one flash every time the pendulum reaches the low point. It's driven by a nuclear battery and never slows down; in essence, it is a perfect clock.

You are sitting at a train station next to the track, as this train races past on a dark moonless night. You have the ability to see the light pulses for thousands of miles on an immense flat plain You notice the light pulses are getting further and further apart as the train gets further away. Because the light has to travel further to reach you each moment. The man in the train has seen no change in the behavior of his clock; ticking away the same as before. Time is not a universal absolute. We sit on a spinning earth, whirling in orbit around the sun, everything in the universe is in motion. Einstein's first great insight for special relativity; time is relative. The only absolute is the speed of light.

Einstein said time and space are inseparable, four-dimensional space-time together making up the fabric of the universe. We have difficulty thinking in four dimensions, so let's use a three-dimensional space-time analogy. Imagine, a billiard table where the surface is a grid like a piece of graph paper. The x and y coordinates of the grid represent space. Let's plot out a billiard ball collision in Newton's world. You trace out lines for the movement of the balls. You put tick marks along each line for the seconds to track the movement in time. It works fine for billiard balls, even if it's a little awkward to track the time.

Einstein draws the picture differently. Imagine time as a third dimension rising up from your two-dimensional graph paper. A 3-D rectangular space filled with a grid; the vertical direction is time. Use your imagination it's not so hard to picture. Now you trace out the movements of the balls on a line moving along the x and y grid; but also rising above the surface. One three-dimensional point (x,y,t) for each second. This is a two-dimensional space-time plot. Einstein's math did the same thing for three-dimensional space and time. Forget about trying to visualize it, no one can.

Einstein knew he was stuck by the limits of special relativity. It did not work for accelerating frameworks and gravity is like acceleration. He needed a grander theory and that took a long time. When he finally got done, with general relativity, he had a workable model that would explain gravity.
In four-dimensional space-time, gravity is represented by the curvature of space-time. Objects and light follow this curvature. This magnificent theory predicted the precession of mercury without the fake planet Vulcan. It predicted black holes, the bending of light, and gravity waves. Gravity arises from the curvature of space. The degree to which space is curved is determined by the mass of the objects in space or the amount of energy. Looks like the problem of gravity was solved.

Well, there was a problem when new observations showed that the universe was expanding. His wonderful mathematics predicted a static universe. It was easily accommodated by the introduction of the gravitational constant. Which he later realized was a horrible mistake, because of new observations about the expansion. This is the bit he swept under the carpet but that is a bit of a side plot. There was a more troubling problem that he was wrestling with from the pesky world of quantum mechanics.

Since observations proved the universe was expanding, Einstein was worried about what would happen with his theory when things got small. If the universe is expanding, it must have been smaller and smaller further and further back in time. When the universe was about the size of atomic particles, his theory fell apart and the equations exploded into infinities. Infinities are the death of any physics theory, the sign that something is wrong or missing.

General relativity could not explain the behavior of the subatomic world. Einstein did not know how gravity worked in the subatomic world and we are all made of subatomic particles. He spent the last twenty years of his life trying to solve this problem. Literally, on his deathbed, he was trying to work it out with pen and paper. He was constantly bickering with the quantum physicists about their world. What did they have to say about gravity?


Quantum Physics and Gravity

Quantum physics has its own quirky back story, but it has been proven repeatedly in experiments. Results that defy our real-world expectations, because we live in a macro-world. This branch of science does not track back to Newton; it is a much newer science starting in the twentieth century. The seminal works of the Schrodinger wave equation and Dirac's modifications, predict the dual nature of particles as both waves and particles, their location cannot be precisely known and they can tunnel through barriers. It is a strange world; we can explore that story another time.

There are four fundamental forces of nature. For the sake of brevity, quantum science has been used to predict the electromagnetic force, the strong and weak nuclear forces inside the atom. It is a master of the small world and the small universe where general relativity falls flat.

What does it have to say about the fourth force, gravity? Nothing. Get a group of quantum physicists together and ask them. They will all stare at the ground. They ignore gravity and curved space! If they don't their equations, blow up in their faces. That's right quantum mechanics has no gravity!


Precipice
So here we are decades into this debacle and there are no answers. General relativity can not explain gravity in the small world and quantum mechanics ignores gravity. We are all made of atoms, so where does gravity come from? Like I said in the beginning, none of our greatest scientific minds knows where gravity comes from.

We need a new hero to come forward. Unify the world of the small and the large and save us from annihilation.