Have you heard about the Pioneer anomaly? Over the years since the two Pioneer space probes were launched, they have drifted off their expected flight path. Other satellites and probes have experienced other anomalous gravitational effects that have yet to be explained.
One researcher believes he may have solved part of the riddle. But as this article says, according to Newtonian laws of motion, these spacecraft should not be so far off course, even with the effects these scientists have apparently discovered which, at most, might account for 30% of the drift. The other 70% remains unknown, and not even their theory can explain the ways other probes have been affected.
"We would expect the two spacecraft to follow Newton's law of gravity," Dr. Turyshev said, "but they in fact fail to confirm Newton's law. If Newton is wrong, Einstein is wrong too."
I was thinking of the Pioneer Anomaly when I wrote Everything We Know is Wrong, which was just published in the May edition of Nature Physics. Because stories in the Futures series are limited to 950 words, I wasn't able to go into detail about the theory behind the story. So I'll try to explain it here.
First let me say I'm no physicist, so take it for granted that I'm oversimplifying things.
The story began one cold January morning when it occured to me that the weather we were experiencing was unusually cold, but it would have been perfectly normal weather for a higher altitude. That led me to think, perhaps global warming could be explained in terms of altitude, or more precisely, a shrinking or expanding atmosphere.
So what could cause the entire atmosphere to shrink or expand? Gravity, but only if gravity were not constant.
But of course, gravity is constant. So I asked myself, "Self, how do we know gravity is constant?" Because we can measure it and compares those measurements to a long history of data. Gravity never changes. But if it were changing in tiny, gradual increments over say a period of decades or a century, would we notice? Wouldn't we just recalibrate our instruments to account for the anomaly? Wouldn't we doubt ourselves before we doubted gravity? The only way we could detect variable gravity is by using a tool we couldn't recalibrate, like, for instance, a distant space probe. If gravity were not constant, our distant space probes wouldn't be flying as expected. And that appears to be what is happening.
So what would cause gravity to fluctuate? Electricity fluctuates. Magnetism fluctuates. Electricity and magnetism are linked forces - move a magnet through a coil of wire and you create electricity. Move an electrical current through a coil of wire and you create magnetism.
But gravity stands alone, right? And the source of gravity has never been explained. You can't make gravity, and you can't make it disappear. It has no comparitive force, the way electromagnetism does. Or does it?
What if there were a force or energy that, when an object is moved through it, generates gravity in that object? Lets call it Ether, in a nod to fringe science. And what if a moving gravitational field generates Ether? Just like magnetism and electricity, gravity and ether would be variable according to velocity, mass, atomic structure, and all kinds of other conditions.
Because gravity is such a weak force at small scale, it is easiest to study it at the cosmic scale. Here we have all these large celestial bodies moving through space generating Ether, which in turn affects gravity, but in any relatively small celestial area, such a solar system, where most of the gravitational sources move in defined pathways, the gravitation constant would seem relatively constant. Changes to it would be small and gradual for the most part. But the solar system is also moving, oscillating up and down through the plane of the galaxy, and therefore, through areas of greater and lesser gravitation/ether density. So periodically you would see larger, more dramatic changes in gravity.
But even if gravity did change, we'd be unlikely to notice it, because we assume gravity is constant. If gravity were not constant, it literally would change everything we know about the universe. We could no longer trust any of our observations about anything beyond our very small piece of the universe. Jim Morrison said, Out here in the perimeter, there are no stars. Out there in the depths of space, gravity could be wildly different than it is here at home. And rather than doubt the gravitational constant, we would be coming up with ever more exotic physics to explain things that don't make sense. When the simplest explanation, that gravity is not constant, would not only explain many things that don't seem to make sense, like Jupiter-sized planets orbiting stars at Mercury distances, it would also explain things like the Pioneer Anomaly and global warming and ice ages and the extinction of wooly mammoths and dinosaurs (i.e. they didn't disappear, they just got smaller and turned into birds, because a change in gravity selected for smaller animals) and why we have earthquakes on December 26th.
But of course, if you accept the idea that gravity might not be constant, you also have to accept the idea that we can't know anything about anything except our own small corner of the universe.
So my story isn't just about variable gravity or about ways you could detect a change in gravity if it were variable, it's also about whether we'd be willing to accept that everything we know is wrong.