I know some optics basics and how fresnel lens work on macro level, but I can't comprehend what would happen if a lens with thickness let's say of 550 nm is created (via photolithography or some other dark magic) - how will the light (solar or ideal blackbody radiation) behave? Would the lens focus only 550nm wavelength light, how it looks to human eye, can this be used in any practical application?

P.S I would like if you give me some sources where I can read more about optics and light behavior on such small scale

The basic experiment is pretty easy and straightforward. Pull hot water into a syringe, remove air bubbles and then block the hole and pull the plunger back -> it'll start to boil despite being nowhere near 100°C, way below quick pasteurizing temps, because the low pressure allows boiling at way lower temps.

I was curious if that physical effect alone could sterilize the water anyways despite being way lower than typical pasteurizing temps (temp levels the bacteria care about), because boiling the water in cells sounds...not a good time if you're a cell.

If you're not familiar with what I'm trying to say, watch this vid: https://youtube.com/shorts/1e5M8QmNb7Y

It's a straightforward show and tell about water boiling at hot-ish temperature just because of the very low pressure.

I'm just curious if that has any effect on microorganisms (I'd assume so, I don't like getting boiled from the inside - but idk for sure). Could be interesting for temperature sensitive compounds if that works, but idk

Or are the fundamentally different concepts?

When you have a convex lens and you change the focal length the image at some point flips. What happens in-between? How does the image distortion into being upside down? When I try it it seems to bend around itself and I cannot make sense of it.

As the universe expands how does the new space come into being? What is happening?

A while ago, I discovered that my intuitive way of thinking about time already had a name: eternalism. Until now, though, I hadn’t taken the time to explore what’s been written about it.

I’d love recommendations for books, papers, essays, or anything else that would make for a good read. I’d just love to dive into this rabbit hole. Critical perspectives are welcome as well.

Do you guys have any reference for workbooks like MIT physics workbook? I want to practice on semi-deep conceptual stuffs more than the calculation but calculations are good to. The MIT workbook is really good and not shallow and just want to know if you know other workbooks similar to MIT's. Also, I recently saw a physics statics problem which is the overhanging rectangular boxes, do you guys know how to solve that using the concept of the center of mass?

I like physics and plan to get a PhD in physics; I’ve spent hundreds if not at least a thousand dollars on physics and math textbooks. My goal was to get a PhD in physics and, hopefully, a research position at a university, or anywhere, really. The problem is, I’m starting to get interested in biology.

What kept me passionate about physics in the beginning was the constant curiosity. It started with pop science and then I started taking it more seriously. The more I understand, the less curious I am of course. I feel like there’s no drive to study because I feel like I’m wasting my time.

I have my own thoughts on this but wherever i search, it keeps returning the opposite conclusions/recommendations.

Induction coil: donut shape, so only outer layer of triply cookware directly above the coil is heated.

Form your answer 1st, then read my thoughts below.

I think disc bottom pan has more uniform heat distribution. The side walls conduct less heat, so the disc stays hotter even till the edge of disc than edge of base in fully clad pan, in which heat gets conducted away to walls. Fully clad walls increase surface area that is hot, therefore also the heat loss to the surroundings.

So my conclusion is, when food mostly touches only base, disc bottom is better, (in case of pans), when food touches walls of the cookware, fullyclad is better, as even walls heat the food, so food has to be stirred less. In discbottom pots, food is heated from cookware only at the base, the rest of the food cooks mostly via steam from food below.

Could wormholes ever allow time travel? I'm curious about the physics behind it.

I'm not a physics expert, but I've been curious about wormholes and whether they could theoretically connect different points in space and time.

I understand that wormholes are hypothetical, but I'm wondering:

- Is traveling to the past theoretically possible through a wormhole?

- What are the biggest scientific problems with this idea?

- Is there any serious physics behind it, or is it mostly science fiction?

I'd appreciate explanations, including corrections if I've misunderstood something. I'm here to learn and have a genuine discussion.

A thought came in my mind and I just wanted to know.

I understand this but I wanted to know if anyone has done it. Ik this is not the subreddit for this question but I was awakened by this question, so yeah here I am. Thanks

I wasn't sure of a good way to ask the question in the title.

I know when we see the moon we can see it as different colors because of Rayleigh scattering and various other factors, but why is it when I take a super zoomed in picture of the moon on my phone the moon appears to be off-white and grey?

Even though my is zoomed in the light is traveling the same distance to my camera lens, is the color being automatically corrected or is there more to it than that?

for context, I go to UCSD and study physics here. I am a senior who has already taken all of the necessary classes to graduate except for one lab that will be done this quarter, 3rd year I was taking about 5 classes each quarter solely for physics. That came at the cost of me taking a french G.E. in my 4th year, but I digress. I am currently in a graduate level mechanics class, and have taken more than enough physics electives to complete my major. I have a 3 point something GPA. taking the GRE is simply not within my budget if I enjoy eating food everyday (200 dollars is a lot for a test and some application fees are REALLY expensive), which sucks but that's simply how it is. I'm not asking about the world's leading programs, small fish in an ocean of talent and whatnot, but do I have a shot at getting into a decent one?

Hello everyone. I set up the classic experiment where you place two metronomes on a moving platform (on rollers, in this case, soda cans)

It seems no matter how I start them they sync in antiphase. I know that that should be possible but antiphase is an unstable steady state if I remember correctly. I cannot for the life of me understand why they are never syncing in phase.

I even derived my own (albeit, idealized) equations of motion for the system and simulated it, they synced in-phase, so I don't understand what's the issue now. Any suggestions on what could be going on?

My derived system if curious (latex):

\theta_i'' - \mu\left(1 - \frac{4\theta_i^2}{\theta_0^2}\right)\theta_i' + \omega_i^2 \sin(\theta_i) = -\frac{x''}{l}\cos(\theta_i), \quad i = 1, 2, \ldots, N \\
x'' + \frac{c}{M_{\text{eff}}}x' = -\frac{ml}{M_{\text{eff}}} \sum_{j=1}^{N} \left[ \theta_j''\cos(\theta_j) - (\theta_j')^2\sin(\theta_j) \right]

So I came across two questions where sin^(wt) in the 1st question is being called periodic as well as executing shm whereas in the 2nd question it is being called as periodic only. What’s right and what’s wrong? I mean I asked ai and at first it said that I would be only periodic and when I told it that the ans says otherwise it came up with some explanation I couldn’t understand

Picture: Here

A bodybuilder (red) sits on a chair and let person 1 sit on his lap. The body builder hold onto this person. Then, person 1 let person 2 sit on his lap and then hold onto them. Then, person 2 let person 3 sit on his lap and the hold onto them. This cycle continues until an arbitrary number n of people. Every person uses force F such that the person they hold onto does not fall.

Assume that the chair can't be broken, every person have the same weight, build, and the people can be represented as a square with 1/4 of its part gone. Also that they all put the force at the same place.

If every person sitting on someone's lap is sitting with distance k from the stomach, is there a general equation to calculate the force that the bodybuilder have to exert such that the system is in equilibrium? Or better yet, an equation where we can find the force needed for some person numbered p where p is less than n?

​

I have been trying to understand electromagnetic waves, but I am unable to connect the mathematical representation with what actually happens in real life.

As far as I understand, EM waves don't really have a visible “look,” but there should be some physical orientation of the electric and magnetic fields in space, which we represent using sine and cosine functions. What I don't understand is why a wave is represented by a sine function in the first place. Why does it vary like that, and what is actually happening physically?

For example, the electric field produced by a charge decreases as we move farther away from it. So, shouldn't the graph show a decreasing curve as the distance increases? How does a sine function fit into this picture?

In another video, I saw that the sine function represents the strength of the electric or magnetic field. For example, if we consider a time interval from 0 to 2, during the positive half-cycle, the field goes from zero to a maximum value and then returns to zero. During the negative half-cycle, the same thing happens, but in the opposite direction.

If this is correct, does it mean that a charged particle placed at a fixed point experiences an increasing force as the field approaches its peak, followed by a decreasing force, and then a reversal in direction during the negative half-cycle?

But then, why does the field vary like this in the first place? If the source is at a fixed location, shouldn't the field simply decrease as we move farther away from it? I think I might be confusing the variation of the field with time and its variation with distance, but I'm not able to understand the difference intuitively.

What I really want to understand is how an electromagnetic wave actually travels through space. If it travels in a sinusoidal form, what is the physical intuition behind that? Is the sine curve just a way of representing how the field changes, or is there a reason the field naturally varies in this particular way?

I know these might sound like basic questions, but I don't want to just learn the equations without understanding what they actually mean physically.

I’ve been doing assignments lately, but I think I’ve been doing all of them wrong so is that what the final average velocity is?

A friend told me about a paper on an experiment where 3(?) people individually performed a measurement on a superposition and all got different but verifiably correct results. He couldn't remember the title of the paper, though. Does anyone know it?

Since electricity is generated when a magnet and a coil are moved closer together or further apart, can we generate electricity by placing a massive magnet and a coil in space and using the expansion of the universe to increase the distance between them?

I thought resistance was correlated to how thick the wire is, and what material you're using. Thin aluminum is worse than thick copper right? Yet my book says it's Volt ÷ Ampère

Please tell me if I'm wrong, and why in an easy-to-understand way please! /Gen

Given that these correlations cannot be mere coincidence, and that information cannot travel faster than light, how do these two electrons "know" about each other and maintain their correlation?

See this video of me demonstrating. In words, here's what I'm doing. I cover my mouth and nose with my hands, like I'm covering a sneeze the unsanitary way. Then, I whistle. As I whistle, I flutter one of my hands, so I'm quickly slightly opening and closing the cavity created by my hands. I start with a high-frequency whistle, and I slowly slide the whistle down in frequency as I flutter my hand.

At high whistle frequencies, the heard pitch is steady. But at one specific frequency, the heard pitch wavers with the flutter. In other words, when my hands are closed, I hear one pitch, but when my hands are open, it's a slightly different pitch. The same thing happens if I start low and slide up: the pitch is steady except at that one whistle frequency.

What's going on here? I feel like it has something to do with the wavelength of the whistle relative to the size of the cavity, but I don't think it's resonance, because the tone you hear isn't the cavity resonating, like blowing across a bottle. The tone you hear is just the whistle. So why does it change with an open or closed cavity? And why only at that specific frequency?

Hi everyone! I have been wondering for a while now if it would be possible travel into the future (if the future is already pre-determined) and how would that happen scientifically?

And what about multi-verses would that be a possibility too or are all of these theoretical?

Thank you guys for indulging in my curiosities! I appreciate you all. Have a good day or night yall! (^u^)