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This is relatively easy to answer: As an old saying goes, you best learn from your mistakes – and you’ll never do the same mistake twice. Success is always nice, but in my experience, most knowledge can be gained from failed experiments. When you publish these “flops”, you avoid other people repeating the mistake. So, revealing the technical flaw in the LHC some time ago finally confirmed that no particle can exceed the speed of light.
Since we depend on signals to evaluate any theory there are limits to this which we will not overcome. Entanglement is one example where we are able to write down corresponding equations which work every time, but understanding what’s going on is a different story. Another topic would be ideas about a multiverse. Most cosmologists are pretty sure that there must be other universes “out there” (some even say parallel to our’s), but I’m sure we will never actually “see” them, i.e. get any signal from them. Last, but not least: Will string theory ever turn out to be string physics, given the scales involved? Fortunately, there is a strong hint at a cosmological string which has been revealed by the HST, based on an extremely clever idea.
Finding something that has eluded us since nearly a century is less likely every day. Moreover: Since the HST has found about 10 times as many galaxies as previously accounted for (some “real” dark matter), and considering much more deeply the workings of “dark energy”, which works in analogy with gravity, plus looking at working theories of modified gravity (like MOND) there are lots of clues disfavouring dark matter (although it was a stroke of a genius at the time).
Looking at national budgets and their management, you’ll see and understand pretty quickly that no nation, not even the larger ones, could afford to set aside a billion dollar fund (per year!) for a single project. You need to consider building time, in-service support and, finally, the dismantling (i.e. the so-called life cycle costs of a project).
The LHC comes to mind, which represents the currently achievable top of the scale in particle physics (and data evaluation). Then, in astronomy, the James Webb Telescope is bound to expand our view and knowledge of the cosmos, also a collaboration. Clearly, the further the technology develops, the more expensive these scientific probes become, which makes a collaboration necessary; we couldn’t do without.
Well, just try to solve the complete (!) equations by hand and you’ll see pretty soon that you’ll run into problems. Even with numerical relativity it took some time and more sophisticated technology (both hard- and software) to finally come to some templates which are solutions of individually defined merging black holes. More templates, including neutron stars and mixed versions (BH – NS) and a larger bandwith of the involved masses are yet to come.
Visualizations are a key to understanding an otherwise complex subject. So, even when I studied maths, I used to transfer an equation to the corresponding curve (and do some curve analysis with it), which enhanced understanding significantly. Same thing with relativity (both): Understanding why we don’t experience effects of velocity or varying gravity gets much easier when you draw a simple graph which lets you see immediately what’s going on.
Yes: From what I’ve heared here, we are supposed to give up EVERYTHING we thought we have understood so far, and in addition, we were able to describe our world with it’s constants and laws quite nicely, We cannot and should not give up everything, without even replacing it with some appropriate equivalent. After all, it is my understanding that our “classical” physics should be the “limit” of string theory, pretty similar to Newton’s gravity being the limit of Einstein’s relativity (in a nutshell).
Right now I’m getting the impression that strings could be the last fundamental “thing” in our world – but what ARE strings? So far, there has not been an answer to that.Probably more basic: Are the “fundamental” constants we think of – c, h and G – still fundamental? If not: are physical laws, which “govern” any change of a status, fundamental or are we going to loose that as well?
One of the fundamentals of our world might be that very energy that always has driven what we call space, beginning with the (trans-)formation (creation) of energy to space (in 9 spatial dimensions). Beginning with the inflationary phase of the Big Bang and continuing at a lower level today, energy transforms into space, still driving the universe apart, time being one of the intrinsic properties of space itself, which might be called “reactivity” of space, i.e. defining the smallest possible action, which we know as Planck’s constant.
It is possibly not a natural progression; I’d like to think of it as an ongoing struggle, the ongoing fight to either confirm or falsify a theory. In addition, it needs corresponding characters to do so. The perhaps most interesting “fight” might have been that between Einstein and Bohr about quantum physics, where Einstein agreed in principle, but thought the theory was incomplete. The struggle can only continue with enough scientific education and some experience – and that, in my view, is a looming danger.
A year ago I would have considered ways to develop a stronger collider, especially looking at new technologies to do so (eg. laser collisions). This year, the pandemic has imposed limitations especially on the financial sector, leading to focussing significant financial ressources on the immediate medical needs as well as covering commercial and humanitary ones. Consequently, my idea would be to hold our breath with collider development, making as much use of the LHC as possible, while thinking about new technologies. Among the field of technology, the IT sector needs to be thought about as well, given the limits of data to be processed with the LHC.even today.
You can hardly leave theoretical physicists alone !! What happens if you do is something I call “run-away-maths”, leaving out any connection to experiment and/ or observation. Best evidence ? Have a look at current articles in the Cornell “arxiv”, eg. in the sections “Cosmology…” and “General Relativity and Quantum Cosmology”; pick any – you’ll hardly find answers to fundamental (or sophisticated) questions about Nature.
Of course, any experimentalist needs his/ her fundamental background to work with; assumptions alone don’t really help.Anyway, I’m still looking for “negative mass” – and perhaps there is an answer in this very course ?! The equation might be a single one, but it will unlikely be “elegant” (by elegant I think of Einstein’s E=mc² or even his EFE, having in mind that there are lots of shortcuts for each term). Probably the best reason to see it this way is shown right here in the lecture by the 2 shown Langrangians. Examining each element you might come to the result that the equation is indeed a single one describing all of particle physics – but in its entirety by no means elegant.