https://en.wikipedia.org/wiki/Equivalence_principle#Tests_of...
Every experiment anyone has ever tried has come up empty. The equivalence principle is a postulate (Einstein's "happiest idea") that underlies General Relativity, making it essential to test.
(Source: This is literally what I do for a living.)
To a high degree of approximation, Einstein's predictions are very, very correct. We are trying to look very carefully at Nature because we don't think we have the whole story.
It is possible that Einstein is exactly right. If so, we would never be able to describe the four forces of Nature with one unified theory. Today, we need two theories to describe everything we see -- the quantum-mechanical/particle-physics description of the Standard Model and gravity. There is no quantum-mechanical fuzziness in the mathematics of gravity, and there is no hint of the differential geometry of gravity in the mathematics of the Standard Model. The aspiration of almost every fundamental-physics physicist is to find a way to either simplify the Standard Model or connect it with gravity.
If the return on investment seems insufficent, know, too, that the technology we develop to push the boundaries of knowledge has important spin-offs. GPS is impossible without corrections from both special relativity and general relativity. The instrumentation we develop to make gravitational experiments possible on earth requires the development of new classes of seismometer [1] that may open new understanding of Earth's dynamics and allow better chip-fabrication instrumentation. The instrumentation developed to test gravity in space is also being used to measure the movement of mass (i.e. ice and water) on Earth's surface [2].
Even more important is the training we provide to students. Just as athletes train in the gym to get stronger, confrontation with the hardest known technical problems provides an efficient path for students and young faculty to become proficient at the entire range of modern measurement science. Alumni from our group have not only gone on to fancy academic positions, but also helped to redefine the kilogram, designed upgraded digital calipers used by tens of thousands of people worldwide, built key components of a major quantum-computing company's infrastructure, and more.
The people who work on these kinds of experiments are making a fraction of what they could make in industry. We are doing it for love, not money, and the returns to society are myriad.
[1] https://arxiv.org/abs/1707.03084 [2] https://gracefo.jpl.nasa.gov/
The problem is researchers are far more likely to express their interested in X to the public - quite right - since that must be their passion for the significant focus required to follow that path. This is what the public find so unintuitive, we need to focus on X to benefit from Y, although we don't know what Y is, but it has the potential to be far more useful than anything more direct.
Reminds me of the more literal explanation in a letter by Ernst Stuhlinger at NASA in response to a similar question:
https://www.forbes.com/sites/startswithabang/2017/10/26/even...
I am sorry to hear that - it will be a loss for Eöt-Wash.
I appreciate your comments in general, but I feel that this point needs to be tempered. Yes there are corrections due to SR and GR effects in GNSS, but they tend to get lost in the morass of the least squares residuals compared to all the other much bigger effects, like clock errors, orbital errors, ionosphere delays, etc, etc.
http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
"There is an interesting story about this frequency offset. At the time of launch of the NTS-2 satellite (23 June 1977), which contained the first Cesium atomic clock to be placed in orbit, it was recognized that orbiting clocks would require a relativistic correction, but there was uncertainty as to its magnitude as well as its sign. Indeed, there were some who doubted that relativistic effects were truths that would need to be incorporated [5]! A frequency synthesizer was built into the satellite clock system so that after launch, if in fact the rate of the clock in its final orbit was that predicted by general relativity, then the synthesizer could be turned on, bringing the clock to the coordinate rate necessary for operation. After the Cesium clock was turned on in NTS-2, it was operated for about 20 days to measure its clock rate before turning on the synthesizer [11]. The frequency measured during that interval was +442.5 parts in 10^12 compared to clocks on the ground, while general relativity predicted +446.5 parts in 10^12. The difference was well within the accuracy capabilities of the orbiting clock. This then gave about a 1% verification of the combined second-order Doppler and gravitational frequency shift effects for a clock at 4.2 earth radii."
It makes sense that offset corrections can be handled by a lumped model, as any relativistic corrections on timescales longer than an orbit will be constants of the satellite orbit. Making sub-orbit-duration corrections might require a model that captures more of the relevant physics.
By "financialization," I mean deciding which research projects get funding based on their expected measurable results, i.e., based on some rate of return that can be estimated today. If a research project can lead to more citations soon, or slightly better products soon, or lower costs soon, etc., it will get funding. Otherwise, it will not.
As a consequence, research projects with uncertain payoff but potentially transformational long-term benefits are... neglected.
:-(
It's all right to decry financialization of research, but it is a very difficult problem to solve.
People who have dedicated their life to science should get more than 20%. Say, 50%: "Spend 50% of money/time/people on the funded project, 50% however you want."
I think my 50/50 idea would work quite well. Scientists still would have to demonstrate and justify the value of near-term projects to get funding, but would also get the resources they need to fund long-term projects with impossible-to-estimate present value.
Personally, particle physics irritates me because I don't believe in particles... It's all vibrations, man :)
It's the industry that's keeping talented people out by giving them mundane or bullshit jobs, and not leaving any space for long-term research and vision.
Yeah, instead of understanding the universe and core applications we could have more BS gadgets...
For two important reasons:
1. as a species we must maintain technical capability to perform certain types of experiments - only way to 100% be sure we do this is by re-doing those experiments periodically
2. the fact that the "laws" of physics are fixed in any sense of the word, or that there even are such things as "laws of nature" is at its core a very very likely but UNPROVEN ASSUMPTION... we should always be open to the possibility that we live in a much stranger universe than we imagine and that the laws of physics themselves could vary and that we mush have capability to re-discover the new/changed laws, or to poke deeper at meta-laws
Also (2) is not as much lunacy as it sounds considering that the most likely (in the sense of "mathematically probable" considering the math of probability and information, not in "what we can determine experimentally with our primitive capabilities") setup from our universe models is more like we're in an N-th level "simulation" (a simulation in a simulation ... etc.) maybe running on a something like a "Boltzmann brain" in hell knows what soup of multiverses...
We may live insignificantly short lives and be practically meaningless on a grander scale, but if we dare the play the game of "guessing the laws of the universe" on a large scale, we shouldn't have the arrogance to assume that what we measure and deduce on an insignificantly small space-time volume in our ant-farm corner of the universe actually holds up directly through longer stretches of time and space!
Otherwise we're not really doing science, we're adherents to the religion called scientism, and we're not truly honestly rational, but merely praying in the church of rationalism! These are very very different things!
Just look what humanity was able to do in the Space Race with "computers" less powerful than an ordinary standard wristwatch of today: going to the moon, surviving there and coming back. Today? If it were not for SpaceX, the US would not have a path to access to its own manned transfer capability.
If we do not use abilities, we lose them. Knowledge gets forgotten, data bit-rots, machinery rusts apart.
This is more of a statement of how little computing power is needed for rudimentary space travel. The technology itself was quite advanced, just in other aspects than raw computing power.
General relativity should be tested and verified in energies and conditions where it has no been tested yet, because it's likely that there is crack there somewhere.
Many those military research projects mentioned in the article are pure crackpot science. They search where it easy to search and reasons to do so are usually based on misunderstandings of existing theory.
It is extremely difficult for modifications of gravity to simultaneously fit the cosmic microwave background, big-bang nucleosynthesis, galactic rotation curves, and the Bullet Cluster. The safe bet these days is on some sort of non-baryonic dark particle (which is why so many people are looking for them). Most other loopholes are closed or in the process of being closed.
The coming decade or two should have something significant to say about dark matter. We will either discover its nature or severely constrain its properties through a plethora of varied experiments and searches.
It's a bit like exploding an apple and measuring all the bits that fly of and missing some bits. Whilst we do not know what the apple looked like initially, we are from our measurements, trying to reconstruct that apple.
How convinced are we that their is dark matter and not a case of how we have measured things so far. Hence, differences in results based upon how we measure are evident, whilst many are close to the same, they just don't exactly match up - hence - dark matter theory.
How likely is it that dark matter as we know it - does exist?
Of course you are risking that he eventually proves your hover board is impossible.
https://www.pnas.org/content/112/24/7426
PS: you need to understand how gravity is derived to manipulate it's propagation. Since the mechanisms are very stable due various reasons, only a very good understanding of many processes will allow you to design an experiment that works. I have adopted a very fringe physics model that is unified and explains more using less assumptions. From this perspective I can tell you that contemporary physics is so far from understanding, that most likely we will not see anything in this direction, before we fully trashed our planet.
Never could have come up with such a brilliant theory, took me a year to understand it. Now I understand 137 ^^