Space-time, an uncanny relation
If you are fond of physics like me and even if you're not, you have obviously already heard about the Theory of Relativity.
This theory has been having tremendous success to accurately model most natural phenomena related to light and gravity. Despite this, I've always been uneasy with it to the point where I decided to put it aside and focus on other domains of physics less exotic to me or less mind bending. I'm sure some of you also believe it is a fascinating but unreachable theory too.
The fundamental issue I’ve been having with this theory is related to the core concept of inventing a new "time" concept as well as a length contraction (in an orientation specific to each reference frame). Both these concepts broke my view on what time and space are. Historically, the domain of classical physics had the same skepticism to Relativity but failed to provide an explanation to the phenomena. Those two domains cannot be easily reconciled as they are based on fundamental different perceptions of the same reality.
In my opinion, time and length are essential postulates, a man-made definition that should not be touched. Resorting to challenge the linearity of time or space feels like a failure in the reasoning to me, a mental lens that makes the problem disappear but does neither solve it nor explain it.
Lorentz himself did not believe that the "local time" he created in his own mathematical transformation was existing, he thought of it like a mathematical trick and not a physical reality. This transformation became an essential part in the creation of the Theory of Relativity.
As a reminder, the local time t’ appears in one of the 4 components of the Lorentz transformation while still referring to an absolute time t:
t’ = γ (t - v.x / c2)
In the meantime, modern media have been surfing on the sensational aspects of time paradoxes and space-time distortion. I believe they are living in the realm of “science fantasy”, but who could blame them when this topic sells so well?
Turning point
When scientists of the 19th century tried to measure the speed of light they couldn't find any preferred direction and concluded that the speed of light was the same in any frame of reference. The Michelson & Morley experiment was probably the most critical experiment concerning this question.
This conclusion had a serious consequence: If speed was constant regardless of the reference frame, the only way to explain many phenomena was to introduce a local time where speed would be constant but time would not. Other notions were then also required such as length contraction to fully account for all observations.
A few years ago, while investigating similar topics, I started collecting all the phenomena and experiments related to light and gravity. By doing so, it became more and more probable to me that we might have overlooked some things or jumped to conclusions a bit hastily. Could there actually be an explanation of all these phenomena that did not require warping space and time? Something that could be explained simply instead of time dilation, complex transformations and the Minkowski manifold? Could classical physics actually explain those phenomena? My curiosity was piqued because with this approach I could reconcile with these ideas. If classical physics could be used, instead of using what I consider exotic methods to explain the same phenomena, this would lift the fundamental objection I had.
Along this passionate search for contradictions, I discovered that it was at the heart of the research of the late 19th century and I haven't found any definitive contradiction despite what I’ve been constantly told before. This is why I'm sharing those thoughts with you, hoping to find a well-intentioned contradictor that could highlight incompatible experiments or flaws in the reasoning.
If you're not able to challenge anything, don't worry! Maybe you’ll discover some phenomena by reading this article.
The elephant in the room: Michelson & Morley
This experiment proves that there is no difference in the time light takes to travel in one direction or another. The apparatus was built so that you could orientate two perpendicular light beams in any horizontal direction.
This experiment is of the utmost importance as I reckon it is the root of the divergence of thoughts.
In the end of the 19th century, many famous scientists were trying to figure out if there was some sort of medium on which light was propagating. It was assumed that, if such a medium existed, there would be no chance that Earth would be static on this medium. The Earth is orbiting the Sun, the Sun is orbiting the center of the galaxy, our galaxy is moving through the universe, so, the odds that Earth was perfectly synchronous with this absolute “wind” was absolutely improbable. Therefore, when they saw that no difference of speed could be seen, it directly contradicted the existence of a global and uniformly moving medium.
There was still one possible option though: maybe this medium was dragged by Earth and matter in general, explaining its relative immobility to the planet? To verify this hypothesis, Fizeau tried to measure the difference of the speed of light within moving water. Hoping that, if this medium was indeed dragged by matter, the water in the tube would drag it too. Despite a result demonstrating a partial drag, the scientific community considered this experiment as negative.
The combination of both experiments led to the subsequent conclusion: The speed of light is constant in all frames of reference and therefore, there is no preferred one. A medium on which light propagates doesn't need to exist anymore.
But wait... why do we need to draw the less probable conclusion between the two? Isn't Occam's Razor here to remind us that, of two possible options, the simplest is the most likely?
Why not refining and exploring the other option further:?
The results tell us that such a medium would be static in the vicinity of Earth. Maybe this is a fluid medium dragged along with Earth but not significantly dragged by lighter masses? Let's keep this in mind for later experiments.
More interestingly, the accuracy of the Michelson & Morley experiment happened to be approximately 18 000 km/h. This means that, if the medium was moving relatively to the apparatus with a speed lesser than this accuracy, the apparatus wouldn't be able to detect any effect.
As a useful reminder for later, the speed of an object at the equator is approximately 1 600 km/h compared to the center of the Planet.
So, yes, if the medium, that we will call "Ether" from now on, was moving, it would move at a lesser speed than this accuracy, relatively slow in terms of Astronomy.
Even the authors of the experiments comment that “relative velocity of the earth and the Ether is probably less than one sixth the Earth's orbital velocity”.
The illustration below attempts to represent in a simplified way the notion of the Ether dragged by nearby massive bodies even though the bubble shape is unlikely.
Conclusion:
If such an Ether was existing, it would require for its modeling the following properties:
The below concept map shows the step by step reasoning. I will update it throughout the article.
Stars are not where you see them
Astronomy has been a very important source of data to exercise our physical models and one of the fascinating phenomena related to light is the Stellar aberration.
Imagine you were on a very lonely planet Earth in the Universe, not moving but with a nice background of stars in the sky.
One could position each star in the sky with precise coordinates, right? Right.
Now, let's take this same Earth and give it a motion in the universe, around the Sun, around the galaxy and so on.
This relative movement related to the background creates a very faint but steady phenomenon: all the stars will appear shifted toward the direction of the movement of the planet for any observer on the surface of Earth.
This is a well known phenomenon in astronomy but too small to be detected by the naked eyes. Precise apparatus are needed to observe it.
How could such a deviation of the ray of light from the star to the observer happen?
Well, if you accept that light propagates on a fluid medium, like a wave on the surface of the sea or like sound in the atmosphere and if you remember that it is probable that this medium is dragged along nearby significative masses like a planet, as observed on the Michelson & Morley experiment, there will be a transition zone between the two zones of Ether.
One zone of Ether is bound to Earth and one is bound to the relatively static distant background of stars. This transition creates what is called a rotational component, a bit like the air goes around an obstacle and has to rotate successively along its path to follow this deviation. Ether would rearrange itself around another zone of Ether.
Stokes himself, the famous fluid mechanics scientist behind the Navier-Stokes equations, commented that the stellar aberration would be typically created from such a rotational component in the Ether. He, like many other scientists of the 19th century, were also convinced that Ether existed but he regrettably didn't push his theory further before the very successful theory of relativity appeared.
Conclusion:
If such an Ether was existing, to account for the stellar aberration, it would require the following additional properties:
The concept map therefore updates as follows:
Gyroscopes are so 20th century!
Those of you working on rockets, airplanes or any other similar vehicles will be aware that it is critical to measure precisely their orientation and rotations. For decades, this has been achieved by the means of gyroscopes. A fast and heavy spinning disc that will stay in the same orientation so that you can use it as a very accurate reference orientation. But its weight and its failure mode called “gimbal lock” were calling for a replacement.
That’s where the Sagnac effect came into place!
When you make a light beam travel through a loop, either by using a set of mirrors or an optic fiber, it appears that the time it takes to travel this loop is different in the two directions if this loop rotates. This delay between the two directions creates a measurable interference fringe telling us the rotational speed of the loop.
You then need to attach this fiber loop or mirrors to your vehicle and voila!
In the paradigm of Ether, this phenomenon is explained rather simply. Indeed, as mentioned above, Ether is globally bound to Earth but seems to fail to attach itself to lighter masses. Either because the influence of the nearby Earth is too important compared to the negligible mass of the device (the mirrors or the optic fibers) or because there is a need to exceed a specific mass so that their accumulated actions start shearing the medium, this is still unclear.
Therefore, when the device rotates, it rotates while the Ether does not. Similarly to the behavior of two boats following each other at the same speed on a lake, the wave emitted by the front boat will reach the following boat before the wave emitted by the following boat reaches the front one. This delay between the two waves going in opposite directions then creates the interference fringe in the laser gyroscope that can be measured to deduce the rotational speed.
Conclusion:
If such an Ether was existing, to account for the Sagnac effect, it would require the following additional properties:
The concept map therefore updates as follows:
Clocks on a plane
One of the most frequent objections I heard is the fact we measured, by many different means, the shifting of time on clocks. A shift that was predicted by the Relativity Theory. We indeed sent precise atomic clocks in rockets and planes to observe the offset between the tested clock and a reference on the ground.
This seemed like the definitive contradiction that I was looking for and the final nail in the coffin of the Ether, but wait… how do we measure time again?
There are mechanical clocks that have a mass oscillating on a spring. The mechanical counting of each oscillation mimics the concept of time passing. They are not precise as any variation of temperature, aging of the spring or mechanical variation can change the oscillation and make time apparently shift.
There are also quartz based clocks where the natural frequency of an electrified quartz crystal is sufficiently stable to count its pulses and mimic again the passing of time.
In a sense, we do not measure time itself but we select a source of oscillation that is stable enough so that we can count the cycles and interpret it as time. This is not a measurement in itself but a reproduction of our own definition of time. If there was indeed an item in the universe that oscillated without any single influence of its environment, we could indeed take it as a perfect representation of time. This is what the atomic clocks are trying to achieve.
This is why all those time experiments commonly used atomic clocks. These are based on a MASER, an equivalent of a Laser but that emits microwaves instead of light. Simply put, they excite Hydrogen or Cesium atoms by means of a microwave radiation within a cavity whose dimensions are designed to produce the right radiation compatible with the atom’s natural properties.
Some electronics then try to adjust the optimal frequency that matches the greatest amplification of the signal of these atoms. These devices hope to tune in to the natural microwave frequency of the chosen atom and this is the promise of an extremely stable time measurement.
Let’s now put this device in the paradigm of Ether again and see how it would behave.
By studying just the movement of the resonating cavity through the Ether bound to the nearby Earth, you can notice that there will be a Doppler effect happening within the cavity itself. The rebounding waves are traveling on a static ether but with the cavity walls moving in one direction over the medium. The analogy is again the two boats on a lake.
Using c as the propagation speed of the electromagnetic waves on Ether, if the clock is static with the Ether, the resonating frequency f of the cavity of a length d is:
领英推荐
f = c / 2d
Adding the relative speed ve of the cavity over Ether, this creates a Doppler effect along the axis of motion that can be expressed as following:
f = ( c + v ) . ( c - v ) / ( 2 . d . c)?
Therefore, the tiniest speed of the clock over the Ether leads to the shifting of the resonating frequency of the cavity, leading in turn to the shifting of the clock itself despite its usual extreme precision.
Never run eastward
An illustration of one of these numerous experiments with clocks is the Hafele–Keating experiment where the scientists decided to transport atomic clocks on airliners around the globe. One mission went westward and the other went eastward.
Even though the speed of an airliner is far lesser than the speed of light, the duration of the flights and the precision that can be achieved by the comparison of the clocks to the reference clock that stayed static on ground, some noticeable results were detectable :
Yes, you read it right, the plane flying toward the west had their clocks ticking faster! How could it be that one result was positive and the other was negative ? Typically, if the Ether was static relative to the reference clock, having planes going at any speed in any direction would lead to the onboard clocks showing some delay and never any advance.
To explain this in the Ether paradigm, it would require that there was a speed offset of the Ether on the ground, a tiny wind sufficiently small that the Michelson & Morley experiment couldn’t read it.
Well, fortunately for us, Earth does rotate toward the East at a speed of approximately 1 600 km/h at the equator. This ground ether “wind” would, for instance, offset the previous formula like in the following diagram.
This would likely mean that the Ether is globally dragged by the Earth but struggles to follow its rotation. This would mean that the Ether fluid has a sufficiently weak interaction with matter so that its rigidity (or viscosity) prevents it from being dragged by small masses and the rotation of Earth.
Motion redshift
Let’s leave our clocks a minute and go back into space. Another phenomena observed in astronomy is the redshift of moving objects.
As the universe is expanding, distant galaxies are typically moving away from us at different speeds. We use the fact that light seems to shift toward red colors the faster the objects go away from an observer to estimate their speed. Similarly, we’re able to estimate the rotation speed of galaxies thanks to the fact that the galaxy arms that are moving toward us are slightly shifted toward the blue colors while the arms moving away are shifted toward the red.
If you assume again that Ether tends to stick where the greatest masses are, it means that all along the path between these observed galaxies and us, the observer, the Ether will change speed at some point. Either gradually or more abruptly, this is hard to tell. Regardless of the shape of the speed evolution, the changing of speed of the Ether along the trajectory of a photon will create a frequency shift all along.
Conclusion:
If such an Ether was existing, to account for the shifting of clocks and redshift of light due to motion, it would require the following additional properties:
The concept map therefore updates as follows:
Gravity & clocks
In another group of experiments, a set of atomic clocks were sent on rockets to high altitudes this time. Even though the speed is non negligible in such vehicles, the purpose was to observe the influence of gravity over the clock.
The Gravity Probe A / Vessot Rocket Clock Experiment was one of these and it concluded that time shifted by the sole influence of the intensity of the local gravity thus supporting even further the Theory of Relativity that predicted a time dilation in the gravity well.
But again, similarly to the explanation given for the shifting of clocks due to motion, the clock cavity’s frequency is given by the simplified following formula:
f = c / 2d
It then requires a variable local speed of light c function of the local gravity.
Luckily, a formula providing this dependency can actually be extracted from the Theory of Relativity, where a body of mass M is located at a distance r:
Therefore, if you accept that only the speed of light varies in a gravity well instead of time and space, then the clock shifting can be simply explained.
Of course, it prompts the next question: Why does gravity affect the speed of propagation of light in the Ether??
Relativity does not actually explain this either, it just observes and models this effect.
Gravity redshift
Another well known phenomenon is that colors and electromagnetic waves see their frequency decrease while falling in a gravity well. The frequency of a signal emitted by a GPS actually does shift a little when reaching Earth’s surface as well as any source of light in space observed from the ground.
Similarly to the shifting of clocks, if you assume that the speed of light is impacted by the local gravity, the decrease of this propagation speed along the fall toward Earth’s surface will induce a reduction of the frequency of the signal.
Shapiro delay
Thanks again to Astronomy, we observed that any signal traveling into a gravity well was delayed by a measurable time. For instance a signal sent by Mercury and passing at a distance of four times the sun radius is delayed by 180 μsec on top of the one due to the deviation of the trajectory before reaching Earth.?
Similarly to redshift and clock shifting due to gravity, if you assume that the speed of light is affected as shown in the previous formula, the delays match and there is no need for space time dilation again.
Conclusion:
If such an Ether was existing, to account for the shifting of clocks and delays in a gravity well, it would require the following additional properties:
The concept map therefore updates as follows:
Gravity mirage
Finally, the last phenomenon that I want to highlight to finish the sweep of all the most important ones is the gravity mirage also called gravity lens.
Fantastic pictures taken by NASA show that there is a lensing effect when light travels near a massive object. Potentially leading to stunning deformations like in the following picture.
All the previous explanations on Ether do not account yet for this phenomenon. But if you combine the effect of the reduction of speed in the Ether near a massive object, as described in the previous formula, and if you remember that waves tend to bend toward the zone where the speed is slower, you may account for this phenomenon.
This is the same phenomenon that happens on the waves over the sea. The speed of propagation of those waves slows down in shallower waters near the coast which in turn makes the waves bend toward the slower zone.
Illustrated in a gravity well, the light enters successively slower zones and therefore bends toward the interior of the gravity well until it finally starts exiting the same well and bends toward the exterior while entering faster zones. Similarly to the deviation of light we create in glasses lenses, gravity distorts the view of objects located behind a massive object.
This phenomenon is well described by Snell’s law, also called the refringency law. It explains how the speed of light on two different media affects the deviation of an incident ray of light and is therefore directly applicable in a gravity well due to its progressive change in the speed of light.
Conclusion:
If such an Ether was existing, to account for the bending of light by a gravity well, it would require the following additional properties:
The concept map therefore updates as follows:
Conclusion
Even though I cannot prove the existence of Ether, it seems to me that we might have overlooked its study and finer experiments.
You might be wondering why this is important at all if it provides the same results as Relativity? Well, it does not.
If this was true, and this is a risky extrapolation, it could mean that :
If Ether was indeed existing, by ignoring the study of its fluidity and its precise interaction with matter we would be missing an essential understanding of the natural laws.
I sincerely hope you enjoyed those thoughts and that I managed to put a glimpse of doubt in your mind. I’d be delighted to carry on the conversation with any of you who are interested.
If you want to read further, you can find my dissertation on the topic in this link .
It covers model studies as well as other potentially contradicting experiments not mentioned in this shorter article. And even better, if you can help me find contradictions in a constructive manner, we will be best pals.
For the final word, here is the complete concept map:
Thanks to Caroline Gemming and Guillaume F. for their support on this article.