My granddaughter sends a video:

"My theory is that between atoms the temperature is absolute zero."

Her grandmother and I have no idea what to make of this.

It is most commonly proposed that leptogenesis occurred first, and that heavier baryons were generated only later during baryogenesis. Wouldn't it be more natural for these processes to have taken place concurrently, right from the very beginning? And could this perhaps provide a mechanism for how matter survived annihilation? Has such a hypothesis been studied?

I’m taking a class in solid state physics and am a bit confused on what k actually means in the equation psi(x+R)=exp(ik•R)psi(x). I see how it’s related to energy (like in the Kronig-Penney model) but obviously it’s not a nice bijective correspondence—instead its a pretty nasty transcendental relation that shows one value of k can correspond to many energy levels.

While the relation between k and physical energies is obviously important, it doesn’t really seem like it has clear physical significance—it’s not clear what exactly it means. Obviously by definition it gives the phase shift between other unit cells but it’s not as clear as saying E=h_bar² k² /(2m). Should k just be thought of as parameter or is there an actual physical meaning we can assign to it?

Yeah. I've interested in the physics,science, and technology.
I'm not graduate or study formally in the school or university.(self taught)

If the force is always perpendicular to the velocity, then shouldn't speed increase? There's nothing acting against the velocity direction

can’t seem to add a photo but my phone screen appears rainbow in the reflection of my bathroom wall. see here

it looks just like the view of a phone screen through polarized sunglasses. my hand/etc reflects normally

does this mean the wall material is…. refractive? dielectric? why?

eli5, I’ve never seen a wall do this before and I don’t understand optics

I’ve been developing an idea I call the “Tree Principle.”
The basic thought is simple:
A tree cannot become the seed from which it grew.
Not because we lack the technology to make it happen, but because the tree represents a later physical state in a process that has already occurred.
We can produce another seed.
We can recreate the environment.
We can even create something that looks almost identical to the original.
But that doesn’t mean the original tree has become its former self.
I’m wondering whether this analogy tells us anything useful about time.
If reality is constantly undergoing physical change, could “going back in time” actually mean reversing an enormous chain of changes rather than simply moving backward along some dimension?
And if so, would that make traditional time travel fundamentally different from what we usually imagine?
I’d be interested in criticism of the analogy, especially from people who know more about physics or philosophy than I do.

I recently started searching about the fundamentals of physics since my dream is becoming an instrument scientist. Can you help guys?

My mechanics professor provided us practice questions to study for our midterm. I’m confused about this one:

Your friend is on her way cross-country skiing and has to do 3000 J of work by pushing against the ground with her skis. In addition, friction does -800 J of work on her. With all her gear her mass is 60 kg. Her initial speed was 5 m/s and her final speed is 3 m/s.

a) Calculate the change in kinetic energy of the skier.

Since net work is just change in kinetic energy, this should be really simple. What I don’t understand is the skier doing 3000J of work by pushing against the ground with her skis - wouldn’t that be perpendicular to the displacement? How is it doing work?

I've recently begun studying physics and intend to become an engineer at some point. However I have found myself feeling quite lost when it comes to forces, newton and such. Friction and gravitation makes sense but I find it very difficult to make sense of Newton. Is there a way to make this measurement more tangible? When someone tells me about like a kg, a meter or something alike I get a very clear picture of what that entails but I can't imagine what a newton, 10 newtons or 100 newtons mean.

Thankful for any advice

I know this is probably a stupid question but i’m a 6thform physics student and we just did circular motion and i was curious if it was to do with the angle instead

Searching online I just find articles about differences in sunlight between winter and summer and they only talk about sun angle. I’m sure there must be more to it, perhaps the changed vegetation or air temperature makes a difference?

Ok, so I am watching this Tesla flying car video and i have two questions:

1. As the car leaves the ramp upsidedown, it does not begin to fall. It drives off the ramp and remains level, upside down, while the car is no longer 'sucking'.

2. As the car flips, and starts to land, you can see the underside of the car, and it is all just flat/metal. Would we not see a giant fan underneath in order to generate that kind of suction?

Something about this feels like it doesnt make sense.

I had a theory that the reason an internal combustion engine has to be so inefficient is this. The piston can only extract work from the fraction of the gas’s internal energy stored in linear momentum perpendicular to the piston’s surface.

So as the piston is extracting work from that particular “reservoir,” the only way to extract more work would be if the molecules spontaneously ordered themselves so that, all of a sudden, more of their energy is channeled into that “reservoir.” I.E. to get perfect efficiency, all the molecules would have to spontaneously assume linear motion directly at the piston surface.

And that’s just too improbable, so we never observe it occurring.

I am told this is wrong, because internal energy is re-equilibrated between modes (such as linear momentum) rapidly enough that spontaneous generation of order is not required to do a next increment of useful work.

But the only alternative explanations I’m getting are just, “well, the engine cycle has to produce an entropy increase, so it has to reject heat.” Okay, I get that, that’s a statement of the second law.

But if my original theory is incorrect, what is actually happening at the statistical, molecular level that requires the power stroke of the piston to reject a certain amount of heat each cycle?

Quite odd, I hope the question isn't too dumb lol. Video :)

I know water helps protect against radiation, but we can't have a space station flooded with water... or can we? Would it be possible, or rather, viable to have a layer of water inside a spaceship's hull? In a hypothethical mars mission, all water would be reused for the duration of the mission, but instead of keeping it on a giant gallon all the time, what if we spread it around the hull of the spaceship? Of course, it wouldn't be exposed to the vaccuum of space, but rather inside the hull. If so, how big would this layer need to be to give significant protection against radiation?

When I mean classical determinism system, I mean Newtonian laws of physics, where action A leads to only action B, etc, and we can know what will happen if we know every relevant factor. However reading around, a lot of paper have been published that seems to challenge this type of system, or even redefine it to claiming microscopic effects don't necessarily follow Newtonian law as seemingly predicted in the early 1900s.

The question is why does it seem that way, particularly in quantum studies and is right to say there are strong findings to believe that?

Im used to questions with pi/4,pi/2 but havent done any with pi/3 or pi/6 so should we be dividing the circle into 6 and 12 parts or? So could anyone help with this question.

Two vibrations at right angles to one another are described by the equations

x = 10 cos(5πt)

y = 10 cos(10πt + π/3)

Construct the Lissajous figure of the combined motion.

Plz help as i have my exams coming soon and the professors wont help.

(16M) I want to do a physics project.i want to do it on something new .I want to be a scientist in the future and I want some stuff to put on my cv

I’m currently running a roleplaying game adaptation of the Three Body Problem series. The present situation is that an invading alien fleet flies toward a modern-day Earth. The aliens have identified particle accelerator experiments as the key to humans unlocking quantum technology, and so have sent ahead remote-controlled protons which can accept a collision in an accelerator and then randomly generate results to ruin the data.

To try and get out of this predicament, one of the players asked if they could build a particle accelerator for experiments designed around antiprotons. Is this possible, and what do you think would be possible if all of humanity poured a large amount of resources into researching fundamental physics via antimatter? Thank you in advance for your responses, I barely passed physics in high school and am doing my best 😂😂.

Hello, I am looking for an experienced person, not AI, to help me to understand . I’m working on SHG by frequency doubling. My pump laser has unstable polarisation, and with 9 W injected, I only get 0.8 W of converted frequency. However, with the same assembly but a different pump laser, I harvest 1.5 W in a simple passage. I’m not sure about the impact of polarisation on this result. I measured a PER of 14 dB, but as it is unstable, it is difficult to determine its influence. If anyone has any advice, I am taking a theoretical explanation 🙏

So as someone who's been a fan on the different interpretations of quantum studies and how weird our universe could be base on our new findings challenging our old assumption, I do wonder if in 2026 has there been new physically findings that may suggest potentially interacting or finding the Multiverse or at least a mechanic base on it? Not suggesting we open an inter-dimensional portal but just new findings.

Particularly any findings on the nature of quantum fields and time space and if suggest anything about the multiverse or any similar ideas.

I understand this could be considered philosophy then physics, but most philosophers would tell you interpretation must be built on the findings and studies of physics, not on metaphysical interpretations alone and it's not exactly possible to seperate science and philosophy since both are intertwined.