How can an object in a vacuum slow down at a rate not explainable by gravity?
A few years ago I read about the Pioneer Anomaly, which is the observed deviation from predicted trajectories and velocities of various unmanned spacecraft visiting the outer solar system, most notably Pioneer 10 and Pioneer 11. Yes, they are still experiencing some sunward acceleration due to the sun's gravity outside the heliopause, but they are both slowing down slightly more than expected. As I continued reading, I found out that these are not the only mystery — there is also the flyby anomaly, wherein spacecraft that transit over Earth's polar regions (rotational AND magnetic) experience an acceleration rather than a deceleration…this is very similar to the Pioneer spacecraft's deceleration relative to the Sun. But then I noticed something in the first reference above: "The magnitude of the Pioneer effect is numerically quite close to the product of the speed of light and the Hubble constant", and the writer notes that the significance of this is not known.
So now we have three observations: the Pioneer anomaly, the flyby anomaly, and the interesting degree of the Pioneer effect. To these I added another anomaly, the galaxy rotation problem, which notes that the arms of spiral galaxies, from just outside the central bulge to the edge of the galaxy, spin at an almost constant speed…and according to Newtonian physics, such masses traveling at such speeds would tend to fly away and escape from the galaxy.
I realized that there must be some kind of spatial boundary just outside the heliopause, and close to masses such as Earth…and wondered if perhaps there was such a boundary outside spiral galaxies preventing the ejection of stellar masses orbiting the central bulge so fast that that the centripetal force should eject them from the galaxy. What would possibly explain such boundaries? At first I considered that perhaps the consistency of the fabric of space itself was not constant, that space itself was 'lighter' in proximity to masses…which would have explained to some extent the anomalies above, but left a nagging question: what would happen to the speed of light from extrastellar sources? That, and what would this mean to the current search for Dark Matter and Dark Energy?
So I spent several months ruminating over that issue, and last night (in the shower, of all places), it came to me: what if the fabric of space was stretched in proximity to masses? What if a kilometer of space in near-earth orbit did not match with a kilometer of space in interstellar regions? If this were true, then when the Pioneer craft exited the Solar System, they did not experience additional sunward acceleration (or, in more understandable terms, 'slow down'). No, instead the Pioneer craft were traveling precisely as many kilometers per hour as they should have been…but the kilometers they traversed were shortened. To observers here on Earth, the Pioneer craft appeared to slow down more than they should have, but if I'm correct, their velocity did not change more than it should have due to stellar gravity!
This would also explain the 'flyby anomaly', the apparent acceleration of spacecraft near Earth, for as they neared our planet, the fabric of space in close proximity to Earth became ever-so-slightly stretched…and — to Earthside observers — accelerated more than expected. But as with the Pioneer craft, the spacecraft near Earth did not experience an unusual change in acceleration — instead, they were traveling just as many kilometers per hour as they should, but those kilometers of space were being stretched by their proximity to Earth.
Now here's where things get interesting…because if my "Elastic Space" theory (hereafter referred to as "ES") pans out, then the positions of visible stellar objects are as we see them, and are just as far away as they appear to be…but the light that traveled from those objects had to travel further (to the view of Earthlings in a gravity well) than we had previously understood, because while the light was still traveling at 300,000 kilometers per second, each kilometer was slightly shorter than we expect them to be. In other words, all interstellar light that reaches us here has traveled many more kilometers than we expect…and are significantly more redshifted than they should be.
In 1929, Edwin Hubble proved that the velocity at which various galaxies are receding from the Earth is proportional to their distance from us. The farther away the galaxies are, the more quickly they are accelerating away from us. But ES shows that this is not the case after all, because the more distant the galaxy, the more 'shortened kilometers' the photons from that galaxy has had to traverse, and those photons will be significantly more redshifted than the apparent distance of that galaxy would warrant.
And there's another piece of the puzzle that I alluded to earlier — the observed Pioneer effect was numerically equivalent to the product of the speed of light and the Hubble constant. I think that fact has now become significant.
According to Wikipedia, "dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most popular way to explain recent observations and experiments that the universe appears to be expanding at an accelerating rate…In the standard model of cosmology, dark energy currently accounts for 74% of the total mass-energy of the universe" The major proof of the existence of dark energy is the apparent acceleration of galaxies as evinced by the observed redshift of those galaxies. However, ES shows that the actual redshift of those galaxies is significantly less than the observed redshift.
Dark matter was a harder nut to crack. Again, according to the Wikipedia, "In astronomy and cosmology, dark matter is a theoretical form of matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy could account for the vast majority of the mass in the observable universe." How could ES explain dark matter? Could the apparent elasticity of the fabric of space account for the dark matter's apparent gravitational effects on visible matter? Perhaps, because a large portion of the evidence for dark matter is the galaxy rotation problem mentioned earlier in this article.
With ES, the fabric of space is stretched to some extent everywhere within the volume of a star's heliopause, and more so near any planets therein. Stars and planets have mass that is easily measurable by today's instrumentation. However, if the space within the heliopause is stretched, effectively making a bubble of stretched space within the surrounding vicinity of interstellar normal (non-stretched) space, then would that make the volume of the heliopause lighter, or effectively less massive than would be predicted by current models? Perhaps, for as weak as the Pioneer effect and the flyby anomalies were, if such differences were applied to the entire volume inside a heliopause, the total effect on that volume, on that bubble of stretched space, might well explain the gravitational rotation problem and put the issue of dark matter to rest.
In all honesty, ES may well turn out to be a manifestation (or extension) of "frame-dragging", first predicted by Einstein's Theory of General Relativity. Frame-dragging predicts that the rotation of an object would alter space and time, dragging a nearby object out of position compared with the predictions of Newtonian physics.
Is there a way to test ES? I don't know yet. Perhaps if we could measure the observed velocity of the light from a known source as it travels near a massive object and is slightly warped by that object such as happens with gravitational lenses. If the light travels more quickly than expected — after allowing for the curvature of the measured volume of space — then that might be considered proof of ES. Another way might be to send a very high-speed object between two major masses — say between the Earth and the Moon — and measure changes in apparent velocity along the path of travel.
Most new theories give rise to as many questions as answers, and here are other questions that ES raises:
1 – How would ES affect the flow of time?
2 – How might violent stellar events affect and be affected by ES?
3 – Does ES infer that stars are not at the presently observed distance, but are actually at the observed distance slightly modified (probably somewhat diminished) by the Hubble constant?
I know that I am not a physicist by any means. Nor am I in any way qualified to presume to knock the life's work of Edwin Hubble and that of thousands of other physicists and astronomers, famous and not-so-famous. It is better to assume that I am wildly inaccurate in my observations and conclusions, and to remind myself the danger inherent in a little knowledge. But who knows? Maybe I hit on something, the layman's physics equivalent of winning the lottery. I expect to receive scorn, derision, and perhaps a little pity from those who do know far more about physics than I will ever learn…but maybe I'm right! Time will tell.