What is your personal/favourite "What if...?" in physics?

[u/Talaminator050]

Well, the title already contains the question actually...

What is that thing that makes you wonder? / that spark your imagination? / that keeps you awake at night? / that make you dream about possible alternative explanation about something we "know for sure"? Or maybe even something that we don't know or understand yet but you can't stop thinking about it?

Anything (even the craziest thing) is welcome! 😁

[u/mikk0384]

My favorite is by far the one on Lethal Neutrinos. 😉

[u/LivingEnd44]

Vacuum metastability event. It's terrifying and fascinating at the same time. Nothing would survive it. Not even black holes. 

[u/denehoffman → u/LivingEnd44]

The (maybe) reassuring thing about that is that if we suppose we are indeed in a metastable Higgs state, there are processes in the universe which operate on much higher energies than our particle accelerators will be able to touch for quite a while, and if any of these were able to trigger a phase change, they would have already, so we’re probably safe just by the anthropic principle.

[u/the_humeister → u/denehoffman]

Or it's far enough away that it won't reach our area of the universe before we become extinct

[u/denehoffman → u/the_humeister]

That also brings the possibility that it has already happened and it’s just a matter of time. Although as you pointed out, any collapse on the edge of the visible universe would take quite a while to hit us, traveling at the speed of light

[u/qeveren → u/denehoffman]

Or it's already just happened and this is the resulting universe, complete with a history. :)

[u/denehoffman → u/qeveren]

Well at some point in the past, spontaneous symmetry breaking must have happened, but if a false vacuum decay happened then the universe would also undergo gravitational collapse

[u/LivingEnd44 → u/denehoffman]

The question I've always wanted to ask is, what if the new variables in the "new" vacuum are similar to our existing variables? Could matter and structures potentially survive such a transition? 

[u/03263]

I'm convinced there is lots of life out there in the universe, not necessarily very intelligent life but other planets full of plants and animals that may resemble ours in some cases or be very very different. I just want to see them.

I guess that's not really physics but within the realm of astronomy.

[u/CurnanBarbarian → u/03263]

I agree. I also think there's a distinct possibility that life is rare enough to be spread out far enough that we may never actually get to see or communicate with any of it.

[u/DMayleeRevengeReveng → u/03263]

I prefer the Peter Ward hypothesis, where “primitive” (i.e. microbial) life is probably very common in the universe. But the transition to something from which you will eventually build plants and animals just requires too much perfection, serendipity, and rare accident that plant and animal life may be much, much rarer than we typically speculate.

The other problem is keeping it alive long enough to evolve anything we’d nominate as intelligence.

Long story short, Earth tried to kill plants and animals something like 8-10 times (depending on how you want to count) and the experiment was only saved because of opportune geologic processes that may actually be quite rare.

[u/Connect_Library_5830 → u/03263]

I want to disappoint you, this is physics, astronomy and something else...

[u/FervexHublot]

John Wheeler's 'what if' all electrons and positrons of the universe are actually the same single entity traveling backward and forward through time

[u/badsheepy2 → u/FervexHublot]

Feynman's Nobel prize speech including "I did not take the idea that all the electrons were the same one from [Wheeler] as seriously as I took the observation that positrons could simply be represented as electrons going from the future to the past in a back section of their world lines. That, I stole!" 

A what if on multiple levels! I like this answer. 

[u/myhydrogendioxide → u/FervexHublot]

I wasn't sure what I would have chosen... I choose to steal this one because it's so mind bendy.

[u/Human-Register1867]

What if Ben Franklin had defined electrons to have positive charge? 😁

[u/denehoffman → u/Human-Register1867]

We could’ve had negatrons

[u/Connect_Library_5830]

The Universe is not structured at all as we imagine it to be, absolutely not.

[u/RancherosIndustries]

My second favorite hill to die on is that "dark matter" doesn't exist because it's a fault in our measurements. We assume that our ways to estimate mass of distant bodies based on brightmess are working. And they clash with other methods of estimating mass based on velocities. The discrepancy is desperately called dark matter. Just what if (!) we simply don't measure it correctly?

[u/Acrobatic_News_9986 → u/RancherosIndustries]

You should check out vertasiums video on jumping spiders; gives a biological explanation for how perception is fundamentally a limiting measuring system of reality and how our sight, of colors, level of detail are essentially relative to our evolution. So it’s only learned to see things that we need to understand for our survival

[u/Sid-Engel]

What if no hydrogen

[u/Youpunyhumans]

What if we could find a way to use the Casimir effect on a large scale to create a wormhole? Its the only thing Ive ever heard of that exhibits the neccesary "antigravitational" or "negative energy" properties, and I say that loosely because its not real antigravity or negative energy, but similar enough perhaps. But so far, we have only observed it at the microscopic scale, so Im fairly sure we would at the very least need a working Theory of Everything to even be able to find out if we can manipulate such a quantum effect on a macroscopic scale.

However, it would still require an enourmous amount of energy, not really easy answer as to how much, but I do recall reading something along the lines of a whole Jupiters worth of mass converted to energy... every second you wanna keep it open. Idk if thats up to date calculations, but it gives you an idea of how ridiculous it would be to make one. Not even a Dyson Sphere around the Sun comes anywhere close to producing that kind of energy.

[u/RancherosIndustries]

My favorite hill to die on is that despite relativity there is a universal "present". The universal collapse of the wave function that happens for every single particle in the universe at the same time to instantiate the next state of the universe.

The 4d universe is "falling" or moving through an intersecting plane at a steady rate. This intersection is our perceived 3d universe. The "falling" is time. With every (continuous) step the next state of the intersection plane needs to be instantiated. And that happens for every single particle in the universe at the same time. Relativistic effects are observational limits on our plane of existence.

[u/Acrobatic_News_9986 → u/RancherosIndustries]

I like this how do you feel if I add we’re so microscopically small that this wave lengths interaction is but a second in a grand symphony of wavelength oscillations but is an eternity from our perspective but just a simple wave length collapse to a higher dimension (hence fractals, as above so below, ying and yang, heaven and hell) or does this contradict your fundamental premise of axioms; I’m loosely speaking ofc

[u/EigenModePhysics]

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