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.

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

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?

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?

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

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

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

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

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?

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.

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?