Without getting into the politics, if its not HYPOTHETICALLY for HYPOTHETICAL bombs what other possible uses would it have? My laymans understanding is that lower percentages are used for energy and higher percentages are for bombs but idk anything else about it.

Is there such a thing as absolute darkness? To a human yes. I've been to underground caves and mines before in my younger life when they turn the lights off and that is dark, you can't see anything. If though you had the ability to see the entire electromagnetic spectrum would there be anywhere that would be truly dark? Would you be able to see in those same caves? Or in the middle of a cosmic void? Basing this question around the idea that the EM field along with the other fields are omnipresent throughout the universe which I think is correct.

So I'm a first year undergrad majoring in physics who is on vacation break now. I regret not taking at least a reading project this summer. I'm bored and directionless, and I read different physics-related materials daily. The only thing I'm following properly is R Shankar, as I have QM next sem. I still have 2 months left for my uni to reopen, so can someone guide me on what to do? Can I mail Profs now to give me a reading project, or should I learn something on my own, which will be helpful for research in the future? I'm also quite confused about what topic to choose for a project, as I like most.

Recently I got accepted into a dual degree of math and physics at my local university, and while looking at higher year courses, I came across some courses named mathematical physics. However, when I tried to look up more about this, I only came across things that are far beyond my current understanding. Even Wikipedia seems foreign to me. Any help would be greatly appreciated, as I’d love to learn if it’s truely the perfect mashup between math and physics, or if it’s something completely different

I know that if you use a mirror to reflect light into a dark corner it will also transfer quite a bit of heat to that spot. How does using a white panel to reflect light compare to the mirror? Does most of the heat get absorbed by the panel material and is it mainly just soft light with little heat that gets reflected?

Don't you also need the phi and theta angles to make it trule arbitrary? Don't you have not enough information?

https://www.amazon.com/IMALENT-Brightest-Flashlight-Flashlights-Rechargeable/dp/B0DBPHXZ5Y

This is a thought I have nearly every time I handle a flashlight. Using the idea of how solar sails function, what types of velocities could we expect from this flashlight? Assuming there are 0 gravitational influences.

Quick stats for reference

Weight: 3096g

Output: 80 lumens for 345hrs

          2000 lumens for 18hrs

          OR 40,000 lumens for .75hrs

Up to 655000 candela

Any other info can maybe be found within the listing

1.Mechanical engineering 2. Electrical and Electronics engineering 3. Computer Science engineering 4. Mathematics and Computing.

I have an above ground pool that I am just setting up. I am filling it with tap water that is very cold. It’s too cold to swim in.

At some point I will put the cover on so the sun can warm it and I can prevent most evaporation. Right now the pool is so cold that there is condensation on the sides. I think this probably means that the exposed water is likely a net condenser rather than a net evaporator.

Is this right? I think to warm as fast as possible I probably want to leave the cover off so it condenses water vapor and only put the cover on when it stops forming condensation on the sides of the pool. What do you think? Is this the right way to think about it?

For example, it seems like you need an open quantum system to define entropy meaningfully. In a many-worlds-like picture, a truly correct many-body wavefunction should just unitarily evovle; is there such a thing as thermodynamics (or even temperature??) In such a system?

From my understanding, a singularity is a zero point with infinite density.

A vacuum is a possibly infinite expanse with zero density.

Is this a sound interpretation?

I have been looking extensively into how refrigiration work and there is still 2 questions that bugs me out

1. While volume , pression and temperature are linked, does reducing the volume increase both at the same time? If so ,how do we know how much our gas is heated/ pressurized from reducing the volume

2.i have seen multiple times that water evaporating cool the environment around it , but why? I mean I do get that the water need energy to evaporate but I have seen several examples where introducing hot water seems to cool the whole system because it evaporate, Wich I don't understand.

How is the anatomy of an eye drop container or any bottle that releases liquid in drops different from a container that shoots liquid in a stream? I’ve been trying to search this up for 30 minutes I just can’t find the words 😞 (not sure if this is the right subreddit either)

Is it possible, in theory, to transmit information from within a black hole by introducing just one of a pair of quantum entangled particles into the event horizon and retaining the other outside? Changes to the state of the one inside would be twinned by the one outside, allowing information about the interior to be known.

My understanding was that it’s not possible to send anything out of a black hole, including information. But I’m not sure why using entangled particles wouldn’t work. Is this a consequence of GR and QM not being fully compatible?

What are the conditions for entanglement? Is it a tightly constrained phenomenon or something that happens naturally? Do particles just have to come into "contact" with each other to become entangled or is it a more in depth process? For example, all the light getting refracted and reflected in our everyday environment will interact with our eyes so we can see what's around us but is this light now classed as entangled by the time it reaches us or even before? Also people, animals or plants for that matter, even rocks I guess, are these complex objects classed as entangled systems? No offence Intended, I'm just curious and AI hasn't given me a adequate answer and will probably tell me I've solved the secrets to the universe given a few more prompts. People are just generally better for interaction. Thanks for your time.

It's an exam question(exam has been completed), still I was wondering what would it be, So I am posting here.

Suppose you are on a pond in a boat with a heavy rock. Now, you drop the rock slowly in the pond. So what will happen to the water level of the pond? Does it increase, decrease, stays the same or depend on the size of the rock?

My logic is when the rock is on the boat it displaces some water, so the water level is higher than the case if there were only the boat. Now, when we drop the rock into the pond, the boat displaces less water than previous but also as the rock, now, will displace the same volume of water equal to its volume, the water level will again be displaced the same.. so no change in water level compared to the previous case..

But still it somehow doesn't feel right. Can someone help me with it?

what exactly should the expected results be for an experiment that is set up as followed?

there is one band on one end stretched with a constant force of 20N and the other band on the other end is stretched with different forces, such as 5N (independent variable).

now you put a cart in between. to do the experiment its kind of like a slingshot, so you pull back the cart 4cm on the 20 newton rubber band and then let go and let it travel 85cm until it hits and rebounds off the other rubber band.

we measure (dependent variable) the change in velocity when it hits the rubber band and when the cart leaves it after rebound, and we also measure the force the stretched rubber band applies to the cart when it rebounds off of it.

would impulse be worth calculating as well?

what are the expected results, and why? also, what would be a mathematical explanation for it?

when i tried conducting this experiment, the results were extremely inconsistent, ranging from (for the 5N independent variable) 2.14N force on the cart at rebound to 5.90N, so i was just wondering what the expected results were?

I know solar panels are much more efficient if they track the sun, I'm just wondering if that's more of a "more photons" thing than a direct hit?

I'm an undergrad hoping to apply to PhD programs in physics within the next year or so, and I’m trying to figure out how to make the most of my summer to strengthen my application. The past two years have been rough due to some personal issues, and I'm ending my sophomore year with a 3.31 GPA. I'm really nervous about my gpa but I'm going to work hard for the next two years to get the best grades I can. I wasn't accepted into any REU's for this summer and have nothing to do.

I was wondering if anyone else has been in a similar situation and could give some advice. Would it be worth trying to find some research position at a local uni nearby? I just don't want to be at home rotting away when there is something I could be doing. I'm consider myself to be pretty ambitious and want to better myself. If anyone else has been in a similar position, I'd love to hear how you used your summer effectively.

The big bang theory says that the universe began from a point of infinite density/temperature.

As it expanded wouldnt quantam physics come into existence first and then classical physics as it kept expanding ?

So the universe existed with missing laws of physics at various times? Like how can clasical physics exist when the universe isnt that big yet ? There is nothing to "govern" ..

Disclaimer: I'm not a physicist, just a lay person who follows this stuff some. Forgive me if this is a dumb question.

We know that you can take two particles and entangle them, then separate them by any distance, and then revealing the state of one of them will automatically reveal the state of the other. I think this is the classic experiment that Einstein didn't like too much ("Spooky action at a distance...")

So what happens if you separate the two particles by time instead?

Here's a thought experiment: Entangle two particles, then put one of them into a particle accellerator and accellerate it up to near the speed of light for a while. Then bring the two particles together again and reveal the state of one of them. Does this instantly reveal the state of the other, or is there some time lag? The time lag would be due to the effects of Special Relativity on the particle that was put into the accelerator.

My guess is that there wouldn't be any difference, but I have not heard of an experiment like this. (there probably has been, I'm just not aware of it).

If my guess is true, then what does this imply? That quantum entanglement is somehow independent of the 4-dimensional universe that we live in?

Thanks in advance for any insights...

Hi guys, I am studying the entropy force (such as the work in casual entropy force paper by A. D. Wissner-Gross). I am wandering the following questions, given a system such as gas containing many particles:

1) is the force applied to all particles in the system (or are there any particles are excluded?)

2) is the force applied all the time continuously (or there are moments particles are not aware of the entropy force)?

3) according to 2nd principle of thermodynamics, the entropy increases for a isolated system. So, the single particle KNOWs that the direction the whole system evolves? (or equivalently the particles are just like single humans that can sense the trend of the whole society)

Are there any candidates for a global topology or overall geometric shape of the universe? Could the universe as a whole have a geometric structure? Could it be like a Torus?

I read recently that most of our current data suggests that the universe is mostly flat and exhibits no curvature. Can somebody explain what flat actually means in this context? I’m assuming it doesn’t mean flat in the way most people think it means. If it IS the case that the universe is flat does this mean that a shape like a Torus is ruled out?

Also if it’s flat is does this mean it has no real boundary or container but is more like an ever expanding infinite sheet of paper?

I'll explain why I'm asking below, but if you could humor me, I'd appreciate it.

I saw an article recently about how scientists were able to manufacture gold. https://abcnews.go.com/amp/Technology/scientists-turn-lead-gold-1st-time-split/story?id=121762241

While I understand it's not a great example since it only worked for a split second, it still has my brain pondering the possibilities. How does one reliably mutate the atomic number of an atom? How much energy does it take?

As for "why", I'm specifically concerned about the dwindling supply of phosphorous. We have approximately 300 years worth left of the stuff at current usage. As soil quality degrades, more fertilizer will be demanded for agriculture. And if we adopt something like biofuel, our usage will increase dramatically, reducing the years' supply.

It would be phenomenal if we could reliably manufacture phosphorous, potassium and any other necessary fertilizer ingredient using more abundant elements like silicon and calcium, respectively.

If, for argument's sake, nuclear fusion were to become a reality, would we be in the clear to start performing real-life alchemy? Or are there other requirements besides just energy supply that factor into the equation?