r/AskPhysics

The first derivative of position is velocity, the second is acceleration and the third is jerk. But what does this actually mean? I can kind of understand that it would mean the rate at which the acceleration increasing, but in what scenario would this be a thing that is useful to measure?

This may sound like a dumb question but it’s one I’ve thought a lot about. I wanted to know if theirs a specific reason why light speed is what it is, why couldn’t it be faster or slower? Or is it just a complete coincidence that it happened to be that speed and there’s no reason behind it?

So I’ve read about lagrangians a lot, did some practice problems, and it all still seemed sort of mysterious and arcane to me . In my head I was doing that thing where I just solved the problems with no intuition as to how it applied to reality, but now I think I get what Lagrangians are doing, and I’m embarrassed at how obvious it sounds. But just in case I want to check to make sure I’m not misleading myself.

Basically, how I understand if, there are 2 ways of looking at a system: equations of motion and Lagrangians. I’m sure there are more but there are at least 2.

Equations of motion look at the current state and ask what happens next. So, an object with momentum in the x direction will, after an infinitesimal amount of time passing, move an infinitesimal amount to the right.

Now, this obviously only allows certain series of outcomes. Situations where an object flies around the sun at twice the speed of light and then instantly halting for no reason won’t happen under Newtonian physics, for example. And Lagrangians are a way of assessing whether or not they comply with the laws of physics by looking at the path, so to speak.

Basically, I have always been concerned by how equations of motion deal with completely different quantities to Lagrangians and their “action”, and I never got how they connect, but now I think I do. Equations of motions are bottom up recipes for constructing paths that a system can take, and Lagrangians are ways of assessing if the paths are valid, in a kind of top-down way. And the Euler-Lagrange equation lets you swap between them. For every recipe, there is a corresponding assessment to see if it was made with the right recipe, and vice versa.

Apologies if this is heavily poetic language, talking about recipes and stuff. I’m trying to build an intuition - someone once told me that I’d eventually learn how to think in terms of Lagrangians, and this is where trying to do that led me, and I’m not confident it led me to the right place.

Not sure the right terminology, but it seems like they are using the moons gravity to turn themselves around and head back for earth. Will they feel any degree of force on their bodies as this turn occurs. I feel like the answer is no, but I can't explain why that would be.

I’ve been studying physics for a while now, and I’m starting to wonder how it changes over time for people who stick with it long-term.

On one hand, I feel like you build intuition—things like forces, energy, and motion start to make more sense naturally. But at the same time, the topics seem to get way more abstract and math-heavy (like moving into things beyond basic mechanics).

For those who’ve studied physics for years:

Does it actually feel easier because of experience?

Or does it just get harder, but you get better at handling it?

When did it “click” for you, if it did?

Do advanced topics feel more intuitive or just more confusing?

I’m curious whether physics ever feels “simple,” or if it’s always challenging in a different way.

A few theories seem to suggest an even split across the universe, but it appears the only matter we really observe outside of a few molecules created in a lab, are all normal matter.

Why haven't we observed more in the universe?

Looking at standard diagrams for Free Neutron Decay, it expels an Electron and an Electron Antineutrino. Neutrons are supposed to be 2 down-1 up quark though, and in an unstable nucleus a Proton can "eat" an Electron to become a Neutron. (there is also rare Proton Decay, where a Positron and Neutrino are ejected to become a Neutron, but thats radioactive stuff)

So, in theory, isnt the Neutron creating an Electron to let off excess energy? where is the Positron?

or, even stranger, do we potentially have the structure of a Neutron incorrect? Ive tried googling this for weeks and never find any discussion on this part of the topic(or the positron question). Please help me out here

I’ve heard that the sun gets blocked from the window, and the window gives it an SPF 30 effect.

Can I get tan through a window?

I’m not sure exactly where to put this information but I’d like to write this somewhere just to see who has what to say about it as nobody I speak to is interested or informed on the matter

While researching alchemy, esotericism, symbolism, philosophy, spirituality and religion I have come to a question and answer myself but would like a professional opinion.

If 1 dimension + 1 dimension = 2 dimensions does that prove 1x1=2 as well? And by extension 1x0=1?

I was then thinking about a circle as a 1 dimensional unit in a 2 dimensional space. I think a circle is visible in a 2 dimensional space because i actually does have 2 dimensions.

A seen + unseen. A matter + spirit/frequency/vibration.

A metaphor being that as you can draw a circle or shape on paper you can turn the page over to reveal its other side being the unseen element.

It can also be explained using the concept of time as a 1 dimensional unit having a front and back/seen and unseen but being 1 unit containing two seperate dimensions within it.

I think 0 is the first dimension making our 1d actually the 2nd dimension and 2nd dimension the 3rd and so forth.

If a dot is drawn on a piece of paper it is already 2 dimensional not a single dimension. If it can be seen it is already in a 2 dimensional space otherwise you couldn’t see it.

If you multiply 1x1 in a single dimension it requires the 1 to be in 2 places at the same time. Is that possible? Or does that imply already that they are two seperate units being multiplied to make another unit?

Any input would be great. What are your thoughts?

I can go further into how I came to this conclusion but it’s a bit longwinded but I can explain in depth my thought

process.

Any idea where I should post this if not here as it keeps being rejected.

Thanks

Why does steam come out of my cup of hot chocolate even though it’s not at 100 degrees Celsius?

If positive potential difference is applied between cathode and anode, the electrons emitted per second reach reaches a constant value for increasing voltage? But isn’t there an electric field between cathode and anode?? Will electric field be enough to pull electrons from cathode on its own?? Sorry if this a dumb questions

Suppose you’re traveling fast enough somehow to notice a blue shift in the spectrum of light coming at you from your destination star. Would your calculation of your velocity from that blue shift match your calculation of your velocity based on distance traveled per unit time as measured by fixed reference points (other stars with little proper motion) before you took dilation of your time unit into account, or after?

This Artemis II mission has gotten me very curious about the relative positions of the earth, moon, and sun during the drive-by. I’ve been scouring the internet for animations or images, but ones that include where the spacecraft, earth, and moon are relative to the sun at the exact moments of observation are so few and far between. I couldn’t find any for Apollo 13’s mission either! Why is that?

I've been thinking about how dark matter interacts gravitationally but not electromagnetically. Suppose a hypothetical car with a powerful engine could accelerate to 0.9999c through a region of space with typical dark matter density. Would the dark matter impart any noticeable drag or gravitational perturbation on the car's trajectory? Since dark matter doesn't interact via the electromagnetic force, the car's atoms would pass right through it, but gravity would still act between the car and each dark matter particle. Over a long travel distance, could these tiny gravitational tugs accumulate into something measurable? Alternatively, would the car's high speed cause dark matter to effectively appear as a sort of weak wind due to relativistic effects?

I'm curious if there's any theoretical framework that describes how a massive object moving at relativistic speeds through a dark matter halo would behave differently than it would through ordinary matter. Thank you.

If there was a ring that went let’s say around the equator of the earth, and ignoring material constraints and all the other things that come with this question. If the ring was constructed to be equidistant from the ground at all points around its circumference (like 300 feet or something like that), would it appear to be floating?

Just curious lol

Consider an “island” at an orbital altitude of 1000 km travelling at 3.08 km/s.  The island is stationary over a point on the Earth.  Obviously the island will not orbit there, but  immediately deorbit into the Earth.

What force would it take to “hold” the island in orbit stationary over a point on Earth?

My thinking is as follows.  I expect I’ve got something wrong, so any comments welcome!

At geo sync orbit (36k km)
Orbital speed 3.08 km/s
Gravity 0.2217 m/s^2

At 1000 km altitude
Orbital speed 7.35 km/s
Gravity 7.5 m/s^2

The orbital speed difference is 7.35 km/s(1000) - 3.08 km/sec(geosync) = 4.27 km/s
The gravitationsal difference is 7.5 m/s^2(1000) - 0.2217m/s^2(geosync) = 7.3 m/s^2

The geo sync speed balances 0.2217 m/s^2.  So, I need to be applying and upward force that provides an acceleration of 7.3 m/s^2, or about 70% of 1G.

Δy = 1/2 At ^2? Assuming no wind resistance and a starting speed of 0 m/s? Sorry if I’m wrong I’m new to physics

was just wondering, since non newtonian fluid becomes solid with force, but water is also said to act as "a solid" (like hitting the ground) from high enough - is every liquid a non newtonian fluid, depending on the scale of force?