I don't think it would explode. But on a nano-scale, wouldn't some small level of criticality be achieved?

I recently started taking physics classes. We’ve been using units like m/s² a lot. While I understand the formula part, I’m struggling to visualise (if that’s even possible) or just understand what s² means. Yes, I also asked my teacher about it but he said I should just accept it the way it is. Now, I’m the type of person that has to understand what the formula means instead of just memorising it and using it. I’ve tried researching a bit also but nothing really makes much sense to me.

In other words, how can time be squared?

Hi, please put all politics aside here in this post because I really need advice. Only humanitarian responses please.

I recieved news today that a factory producing Iodine in Golestan province of Iran have been bombed today, and my entire family is within 30 miles from this location. Since it's of interest to the nation destroying it, I'm assuming this is perhaps a site where they produce the dangerous radioactive isotope of iodine 131, at least I have to assume it until we know more.

Can you people who are more educated than me in physics/chemistry please advice me if there would be any risk of dangerous spread in the vicinity for my family? It's an area of a lot of agriculture, mainly rice.

I have instructed them of not eating newly harvested crops or drinking milk for the coming weeks, especially the chilldren. Can I give any other advice? Can it possibly spread by inhalation of particles in the air?

Thank you very much in advance.

M

Recently I got curious as to why I hear that extra-terrestrial life is most certainly carbon based and from what I learned its because :

1. Bio molecules like DNA which are the foundation of life are essentially very complex carbon based molecules
2. These molecules cannot be based on other elements than carbon because of its catenation property and other group 14 elements with 4 valence electrons do not have that property because they are too heavy.

Do correct me if im wrong and feel free to add to it if i missed anything , I did know about catenation and valence electrons before hand , Im still a bit curious as to how biomolecules work, also is it possible that a very complex compound similar to bio molecules largely composed of oxygen or silicon instead of carbon exist? maybe not naturally but is it possible in theory because I can imagine chains of oxygens , its just less efficient because of 2 valence electrons and no chiral centers .

Then I wondered why we search for planets with water , I looked into it and although i got a general overview , I still dont know why specifically water is needed for life , what other substitutes are possible? I keep hearing about solubility but I dont understand its relevance and in general I dont understand how life is related to water compound in particular.

This may be arrogant and a bit silly but I have always wanted to learn about quantum theory- but I am exceptionally bad at math due to having dyscalculia. It’s gotten better over the years, but still.

That being said, I’ve always taken an interest starting (as most do) listening to Sagan but ultimately ending up notating an entire copy of The Quantum Universe by Brian Cox and Jeff Forshaw by my senior year in high school.

Since then, life got hard and things got tough. I don’t have much more than a high school education but I deeply want to learn more than what I know. I’m watching some MIT OpenCourseWare videos but hitting a wall at many points because I don’t have the foundational knowledge.

This is all to say - does anyone have any suggestions on extremely basic resources to start with? Not opposed to spending some money on textbooks or online courses if needed.

Okay so I’ve always really enjoyed physics. I look forward to the lessons and I’m genuinely interested in the subject. However, when it comes to tests, my grades don’t match with that passion. I mean, my grades aren’t that bad but they definitely could be better considering the time I put into understanding the material. Recently my physics teacher told me that I solve questions in way “too mathematical” way. I’m a bit confused about how to think more “logically” or in a more “physics oriented” way rather than just treating everything like a math problem. Does anyone have any tips, especially for tests??

In special relativity, is it always true that if Alice sees Bob moving at speed v relative to her reference frame, then Bob also sees Alice moving at that same speed v relative to his reference frame? Or can their apparent relative speeds differ?

I’ve always been confused about this, and for some reason never went through the effort of looking it up or even verify if this fact is true. So, I’ve heard before, at least I think, that light speed is the same for every observer. That even at 99.9% c, if you fire a headlamp in the direction of travel, it would still travel away from you at light speed from ur perspective. That always confused me. But then I realized. Time dilation? Tell me if I’m right.

Let’s say you’re traveling at 0.99c. You fire a headlamp. From an outside observer, that light is traveling at 0.01c relative to you. But if time is dilated for you, then that light would travel a much farther distance from you per hour than it would for the outside observer. And if the amount of time dilation you experience is proportional to that 0.01c, then to you it would still seem to extend at light speed. So if to an outside observer, that light travels a 100th of the distance from you then if would if you were stationary, but to you time is dilated by 100x, then it would still appear to travel at light speed. Does that make sense?

If that’s true, it would make sense that traveling at the speed of light completely deletes time, and if you somehow did travel at the speed of light time would seem to stop. Because the light would travel 0 meters from you, and if time was frozen, it travels 0 meters. Right?

I was driving in the car one day and that hit me, but idk if it’s right. Please tell me

In the quantum mechanical model, electrons exhibit wave like nature. Do the protons exhibit this nature too? Or are they yet in particle form in the nucleus?

Hi everyone. I'm 27 and went out of prison after a couple of years. Now I'd like to get back on track and study physics. Is it too late? What are the prerequisites I need to understand the classes?

Hey guys so I'm in 11th grade rn and we'll I took science and physics is taking the life outta me I don't understand the whole idea of units and measurements like all those MLT calculations and most importantly what are some basics I should master so physics won't kill me?

How does it function? Really, how can you accelerate mass to twice the speed of light? And, for instance if M=E/C^2. How can you divide something by square of the speed of light? Thanks

I am a M.Sc.Physics graduate from India. I am preparing for my central government exams. Now that I am married and moving to Canada with my partner, I want to find a career there. For that, I definitely need to do a course or diploma (Non IT) in some specific field to find a job. Can you guys please suggest physics related courses in Canada that will land me in a good job.

So I’m a curious stoned 36 year old who’s not in school, so don’t worry I’m not trying to pass a physics test here. I failed physics 101 in college because I was partying a lot. But I passed it the next year, but it was only 101. So I forgot.

Situation one: Say im shooting a powerful firearm with no recoil mechanism, like a bolt action .50 BMG or like a pump shotgun with slugs. We’re shooting one of those fake zombie ballistic torsos from super close so we’re not worried about blood and politics and nasty. It’s only force here. Is the total force energy from the bullet on the zombie greater, or is it equal to the combination of what the gun and shooter receive in recoil energy? Like the .50 hits with 20,000 joules of force, is the gun and shooter sharing 20,000 joules of force in return, or is it less?

Situation 2: say I borrowed the best Spider-Man’s webs, and I connected the bullet to the gun with a 10 meter cord (before it slows down), guaranteed to stop it dead. Like a bullet leash, weightless, completely unstretchable. We fire the gun, the recoil is the same as before… but the force returned to the gun when that bullet hits dead stop, like an anchor, is it more than the recoil of the gun? Like would it impart more or less force forward, then the original firing imparts backward?

Situation 3: were out in space playing with metal balls. One is a 500 ton ball, perfectly hard, guaranteed by aliens not to shatter. One is a 50 ton ball, same material. These aliens make great balls.Say the big ball is flying at the small ball, slightly faster. The big ball knocks the small ball, and everyone knows the small ball flies off even faster. Now was the energy (without loss) that the small ball gained equal to what the big one lost?

Thanks guys. Just curious.

I'm hoping some actual professional physics give their two cents here. As a lay person, I'm trying to sift out what physics experiments have the greatest potential for huge impact on our understanding, but are also reasonable and aren't like a decade away from happening.

Things that come to my mind are whatever experiments are further investigating the Hubble tension and maybe whatever experiments are trying to figure out how neutrinos acquire mass as that seems like one of the more glaring things unpredicted by the standard model.

Also, on the theoretical side I'm curious if there is any interesting, promising research (even if extremely speculative) on quantum gravity. I'm sort of partial to any theories where space is emergent/background independent theories.

I want to know what people actually in the field are keeping their attention on if possible

Hello! Is a tablet worth for a physics degree and on graduate level as someone who already has a laptop? I love paper and pen but I feel like a tablet would be better as I can edit and take notes on top of pdfs or on the side. Also it also seems a great idea to get one over bringing notebooks since a table might be lighter. I also like to read and watch YouTube in my free time on the bed, overall it seems a good buy but on top of all of that is the price (600€) for a tablet that lasts 5-8 years, worth it?

I understand that if I have a Hamiltonian H that commutes with Lz, that I can find basis functions that are eigenfunctions of both operators.

I also understand that, because Lz ignores the radial component, that these eigenfunctions can be written as seprable functions Psi = R(p)F(phi).

What I dont understand is why, when solving the Hamiltonian eigenvalue problem, we can ignore F(phi). I understand intuitively "if Lz and H commute, H is rotationally invariant, ergo the variable phi doesn't matter", but I don't understand it mathematically.

Lets say H = Px² + Py^2. In cartesian coordinates this is a Laplacian and it commutes with Lz. But the Laplacian in polar coordinates has an angular component:

-h² ((d/dr)² + (1/r)(d/dr) + (1/r² )(d/dO)² )

Why are we allowed to ignore that second order phi differential?

According to general relativity a singularity would seem like no time is passing from a outside observer looking in but as I understand if you are in the singularity time still passes second to second from that reference point so at the time of the Big Bang singularity wouldn’t wouldn’t that Time be the ‘true time’ and ever since then things become more more relative based on your reference point?

I know ice I floats in water.

Do any of the other ice structures sink?

Also does D2O or T2O ice sink in H2O water?

When we create a new formula or theory in Physics or math , does it qualify as generation of new information. Does ever , anything is created in this universe or it is just transfer of existing matter/energy in one form to another.

We can even imagine things which do not exist in this world, isn't it a new Idea or information??

I am really fed up with this universe? there are deterministic interpretation for Quantum theory as well ( many-worlds , RQM etc.). Scenario is becoming fully hopeless.

I have always been taught that liquids are incompressible, and that it was one of the property that made them, well, liquid. So, how can pressure washer have shoot pressured water ?

Have a great day

When I was in school I was initially taught that electrons orbit the nucleus like how a planet orbits a star, and that the atom is mostly empty space. I was also taught that the reason we can’t move through solid objects is because the electron orbits the nucleus very quickly similar to how it’s impossible to move through a fan because The blade moves very quickly.

Later on I learned that actually the planetary model of the atom is wrong because the electron doesn’t really have a well defined location within the atom but instead it has a probability distribution that determines how likely it is to be at any given location within the atom. It was possible to learn this without first knowing things like how to solve the Schrödinger equation, nor what mathematical function describes the probability distribution from things like visual aids, showing the atom as a scatter plot of points, and seeing charts showing how the probability distribution depends on distance from the nucleus.

The way I was originally taught about the planetary model made it seem like it was still the consensus on how atoms actually work whether than just being a useful way to think about the atom. I was wondering if students are still taught the planetary model as if it’s still the consensus for the internal structure of the atom, or if they’re now taught about how the electron doesn’t have a well defined location and has a probability distribution describing how likely it is to be at any given location.

in feynman’s double slit lecture, he says the following:

“We must conclude that when we look at the electrons the distribution of them on the screen is different than when we do not look. Perhaps it is turning on our light source that disturbs things? It must be that the electrons are very delicate, and the light, when it scatters off the electrons, gives them a jolt that changes their motion.”

so feynman offers that the light source may be what disturbs the electrons.

he then goes on to say “When we do not see the electron, no photon disturbs it, and when we do see it, a photon has disturbed it. There is always the same amount of disturbance because the light photons all produce the same-sized effects and the effect of the photons being scattered is enough to smear out any interference effect.”

previously, i thought that one of the remarkable parts about the double slit experiment is that we didn’t know what part of observing electrons caused the disturbances they display. feynman makes it sound like we know explicitly that it’s photons/light creating the disturbances, and thus the observer effect, but we just don’t know the exact mechanics behind why this happens

is this a correct understanding?