How much psi are the nitrogen pneumatic gas lift cylinders in a typical office chair? I can't find this information anywhere. How much nitrogen does it take to keep a 200 pound adult up?

I've read somewhere that the greek discovered the electricity first but they just didn't know what to make of it and thought it was just for medicine and were met with a dead end. Do you guys think we have something similar something we don't look at something that could advance us to the next level and we just don't serch in the right place? Maybe we are so busy trying to advance something that is meaningless compared to the thing we don't look at. Or maybe we are so advanced that nothing is slipping through I mean we literally do research about everything would love to know your opinion

If the universe never truly cools and dies, and just goes on forever and infinitely, that would most likely mean that anything that physically can happen will happen, over and over again. Would that not mean that every person who has ever lived and died would one day be revived/reborn on varying and identical Earths? Wouldn't that entail closing your eyes on one lifetime only to open them again an untold amount of time into the future?

If school prepares you for jobs, shouldn't they teach at least half of the states of matter. I get you learn all of them in collage, but if you learn half of them in high school it will make things less overwhelming, right?

Hello everyone,

I’ll be attending community college this fall and am very interested in obtaining an internship at the Department of Energy (DOE) in areas such as High Energy Physics (HEP), Nuclear Physics, or Particle Physics. I have a few questions and would greatly appreciate any advice or insights from those who have gone through the process or have knowledge about it:

1.	Application Process: What does the application process look like? Am I cold emailing professors doing research at the DOE, or is there an official website to apply on?

2.	CCI Application: Is the Community College Internship (CCI) application process different from other DOE internship application processes?

3.	Timing: When is a good time to begin applying for DOE internships?

4.	Preparation: What should I be doing from now until my application to make myself more competitive relative to the pool of applicants? What skills should I learn, and are there any specific personal projects I can undertake to make myself more appealing?

Any advice or tips would be incredibly helpful. Thank you!

why is physics so hard, I am good at maths but I find physics so hard. What mistakes am I doing ? What should be my approach while studying Physics?

Did medieval cosmologists believe that celestial bodies were fed by vapors? I was reading a passage in Paradise Lost that mentions this, but I can’t find much information online.

Milton says in the poem that the moon’s spots were “undigested vapors” and that the moon in turn fed its vapors to higher celestial bodies. I found that there is a geological feature on the moon called the “Mare Vaporum” (vapor sea) but can’t find why it was called that.

The notes in the poem are not very helpful, but they do mention the “empyrean” and celestial fire, which are features of medieval cosmology inspired by Aristotle.

Apologies if this is not the correct place to post this type of question in.

I am a second year undergraduate student who officially committed to studying physics halfway through my first year. I feel that I am behind my peers when it comes to studying physics. Lecture material takes me multiple sittings to barely absorb. Homework is always grueling and takes me two to three times the average amount to complete. I am looking for guidance on how to better study/suggestions for a study schedule.

I try to read the textbook before lecture but that also takes me a very long time and is not sustainable so I give up as the semester progresses. Solving extra problems is ideal to get more used to physics but again, this is not sustainable when I have other classes and commitments to take care of.

How are people able to comprehend lectures and breezily attempt the homework after one go? And also balance other technical/physics classes at the same time. I am so exhausted of getting bad grades, not being able to handle the classes I want at once, and burning out due to not studying correctly/efficiently. I want to do better and enjoy my learning but I need a major change/reset.

Please help with any advice, I will appreciate any guidance you may have.

Asking for Vanessa Carlton: Please explain the physics of 1) what it would take to fall into the sky and 2) whether you could say time was “passing me by” as I fell. Thank you!

yes I know practically we can't reach other universes but we also tend to say that "if we would travel at the speed of light we can reach that galaxy in some "x" billion years" but when I asked a question earlier on this reddit about something else, there people seems to claim that the "gap" between matter is increasing at the rate of the expansion of the universe which is claimed to be faster than light. Then when we say "if we were to travel at the speed of light we could reach that galaxy withing some light years ( say 2.5 million light years )" we can't actually reach it since nothing can travel faster than light and if we even were to travel at speed of light we wouldn't 'technically' reach it as distance between the galaxies is increasing with a rate faster than light....

And one similar question, I have heard about how milky way and another galaxy ( I guess andromeda ) will collide into each other in about 4.5 billion years... then how would they collide if they are being separated with expansion of universe

andromeda approaching milky way

I understand the formula is "qd(E) sinθ". However, what I am confused about is if the dipole in the uniform field rotates 180° as a result of reversing the direction of the field, the torque of the dipole is 0, since sin(180)=0. But how can something rotate due to an external force without any torque?

Can we say a blackhole is a anti-matter blackhole? More specificallu could you have a blackhole consisting of only a particular fundamental particle?

For instance a blackhole that is 99% up-quarks. If would happen if you fed it anti-down quarks?

Summary: In my writing, the Antagonist creates a Flagship capable of interstellar travel. This Flagship houses a weapon, capable of firing a one grain projectile 5% faster than the speed of light. The first test fire of the weapon is conducted past the Kuiper Belt.

Question: As an observer abord the Flagship, what would you see upon and after the weapon's firing test?

My Assumption: When the weapon is fired, it would look like someone had taken an eraser and removed a black strip of void, replacing it with a prolonged, blinding white light. Anyone viewing the event without proper eye protection would be blinded instantaneously and permanently.

Want to learn more about quantum mechanics or even just physics in general. anyone got any interesting/useful books or resources to get?

Hello All,

Im currently trying to create an indoor water circulation system in which the circulating water doesn’t come into contact with plastic. I haven’t been able to find any water pumps without plastic components (but if there is one it would nullify the entire issue) so I believe the best option that I’ve found so far is to use a Venturi to move the water. Now mind you I have very little understand of fluid dynamics and how this principle works, so please forgive my ignorance and apologies if this is not posted in the correct subreddit

In order to pump water continuously, at about 10 gallons per minute to a height of about 1.5-2 meters, how much pressure / cfm would be needed? I’m not sure if pipe/hose volume or diameter are relevant but if so those variables can be quite flexible in this scenario.

I’m ideally searching for the smallest and quietest air compressor possible to move the water as this will be stationed in a kitchen.

If there are missing variables please let me know and I’ll do my best to answer any questions about the situation that I can

Thank you in advance!!!

This axiom is so pervasive it's been adopted as a pejorative. But is it true?

Can we do math and decide how many duplicates are likely for a time ? The ammount of snowflakes globally per year, the average size of snowflakes, the number of molecules in that size, the percentage of those configurations that crystals are able to form. Certainly there is a repeat rate?

I have a degree in physics with a specialization in GTR.

Machine learning is used in gravitational wave data analysis. But I don't know ML.

Any suggestion on where do I start? like books, courses, videos?

thank you.

Gravity si often represented as a hole in 2D. I understand that that "hole" exist in every direction around us and it's impossible to represent it correctly since we don't have (annd probably can't have) a good enough understanding of space and time.

Let's say that i put a weight on an elastic surface. That surface will be deform and "attract" every object near the hole. If i put my arm under the surface and push up it will be deformed the other way and the object will be "pushed away".

If gravity curves the space in a certain direction isn't it possible for an object to chrve the space in the opposite direction and cause antigravity with a repulsive force? The object should have negative mass to create antigravity?

P.S. i'm not good with math, i understands only the concepts of vomplicate physics

Edit: i know that the hole analogy is incorrect. I like the one with the sheet of paper too, you draw a straight line and curve the paper. The line is straight, it's the paper that is curved.

I understand that even this analogy is incorrect and the whole concept is way more complicated

Edit 2: i don't think that antigravity is possible but i'm asking here cause you know physics better than me

A while ago I learnt about relativity (the absolute basics) and I learnt about the derivation of the time dilation formula using gamma. Just to clear things up this is what I learnt.

https://imgur.com/a/hVdteaE

Now, I came across the muon experiment that proves time dilation and decided to try the calculations myself, mainly wanting to understand if instead of the muon experiencing time dilation from the earth's perspective and the earth experiencing length contraction from the muon's perspective, could the calculations match for the opposite?

However, when I used the formula as muontime = earthtime * gamma, I got a time value much larger than expected, meaning more muons would decay rather than what happens where less muons decay. So I used the spacetime interval formula to find the proper time, getting 6.7*10ˉ⁶. muontime = earthtime * gamma got me 1.7*10ˉ⁴, and muontime = earthtime / gamma got me the same exact answer as the spacetime interval formula.

https://imgur.com/a/jErvQcB

I am now confused, as velocity is relative you could derive the gamma equation both ways, so which is correct?

so, the question is already clear from the title

it is as we basically say that the universe is endlessly expanding at so and so rate but what really fills the gap it creates during the process?

if the answer is dark energy/matter then where exactly does the stars planets giant rocks stops forming in the universe if that gap is only filled with dark energy?

I am working through QM1 using Griffiths but I’m concerned that I don’t really have a good understanding of entanglement or decoherence. What follow-up books would you recommend if I’m interested in these topics specifically?

I’m trying to imagine what one of these particles is like up close. It’s tempting to think of them as little spheres - but that’s definitely not the case.

Assuming you shrunk down to a size where you were able to interact with a single proton (for example), what would you actually experience?

Just need some recommendations

I’ve always found it fascinating and remarkably coincidental that the same three properties which describe elementary particles - mass, spin, and charge - are also the three properties which describe black holes. There’s something about the fact that quantum gravity has been such a struggle and yet these objects, which are in essence pure gravity, share a very fundamental property of our quantum world.

As far as we know is it just a coincidence? Is there any research which has or is currently looking at this as a means to further our understanding of (possible) quantum gravity?

I am currently learning about Bragg's Law and its derivation. However, the assumptions/logic behind the derivation seems flawed to me. It is probably likely that I am incorrectly understanding some of the assumptions behind Bragg's Law. Here are areas where I'm confused.

1. My understanding is that incident X-rays are diffracted by atoms on each layer. If that is the case, why do most drawings depict the incident ray as being reflected?
2. I understand that for constructive interference to occur, two waves must meet in phase, meaning that one wave must travel n*lambda more distance than the other wave. However, the Bragg's Law derivations I've seen do not account for the fact that the two waves that interfere can leave the plane at different angle. The derivation only accounts for the difference in distance traveled due to one wave penetrating farther into the crystal, and not the difference in distance traveled due to the two waves leaving their respective planes at different angles. If we account for the latter difference in distance travelled, wouldn't the derivation be different?
3. Furthermore, in the derivations that I have seen, two parallel waves are shown leaving their respective planes. How can two waves that are parallel interfere if they never actually meet?

Overall, I'm just really confused about the derivation for Bragg's conditions, as it just seems incorrect to me. Could you please tell me what I'm misunderstanding or doing incorrectly?

Thank you so much.

Let's say I am standing on a truck which is moving in the +ve x direction with a constant velocity, let's say 10m/s with respect to the ground(inertial frame), I then start start running in the -ve direction with a velocity of 10m/s with respect to the truck(i.e, 20m/s in -x direction w.r.t to the ground) and jumped, would I fall backwards and roll on my back or just fall straight to the ground just standing there?. Answer's with calculations would be appreciated (Ofcourse ignoring air resistance )

Suppose we make an observation for the proton in a H atom. The wave function will collapse and the proton will appear somewhere "random". This means the electron cloud around the proton also "moved" probably. How does the electron "know" it has to move with the proton? What about larger composite systems, e.g. molecules? How do constituent parts of a quantum system (don't think these parts are entangled?) collapse at the same time to the same spot in space?

I recently watched 3Blue1Brown's video on the speed of light in various media, and I found his visualization of EM waves to be really helpful in understanding how waves propagate through a field.

I know that in addition to the wave model shown above, physicists also use virtual particles as a tool for calculating interactions between fields. The question I have is how do virtual particles fit into the wave picture, and to what extent are they real descriptors of what's going on?

Is it possible to disrupt the funnel of a tornado enough to cause it to have reform? Either by piercing the funnel at certain speeds or with sound or a concentrated blast of wind?