/r/AskPhysics

Photograph via snooOG

/r/AskPhysics exists to answer questions about physics.

  • Questions should be relevant, and answers should be on-topic and correct.

  • We don't condone cheating on school work, and homework questions should be handled according to these guidelines.

  • Incivility will not be tolerated.

  • If your question isn't answered in a day, you can post it in the Tuesday thread in /r/Physics (unless it's homework-related).

See also:

How to use LaTeX?

First, you will need to install one of the recommended add-ons. To include an equation typeset in LaTeX in your post, put the LaTeX code between [; and ;].

[;i\hbar \frac{\partial}{\partial t} \Psi = \hat H\Psi;]

/r/AskPhysics

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1

Relativistic mass of an electron from a quasar?

Greetings. I’m a first-time poster with a very, very basic knowledge of physics.

I’m reading about quasars. If electrons get blasted to 99% light-speed, what would the e-‘s relativistic mass be?… Or am I misunderstanding the concept? Is there a simple equation to calculate how mass changes w/ velocity change?

0 Comments
2024/05/20
13:39 UTC

0

Terrence Howard: A New Model?

Science definiton: the systematic study of the structure and behaviour of the physical and natural world through observation, experimentation, and the testing of theories against the evidence obtained.

Posted because a lot of people are automatically saying he is wrong without studying or researching what he is saying.

His book with his theory. https://tcotlc.com/

He's saying that there are two types of mathematical models, and he explains his theory in his book and website as above.

All you can do is study what he has said and test it, that is what science is, but you can only do that by changing your current thinking of maths.

If anything it will be an interesting scientific challenge.

2 Comments
2024/05/20
13:28 UTC

2

Nuclear carpet bombing…

Very sorry if this isn’t relevant, I’m aware that it’s probably borderline at best, my apologies in advance, so here goes:

Assuming an old school “Fat Man” type A-Bomb, what would happen if nuclear bombs were dropping with the same kind of intensity as conventional bombs on an area?

Would there be cumulative effects from multiple explosions (like the firestorm phenomena associated with incendiary carpet bombing)? Would there be any kind of unique effect or would it just be a standard blast but covering more area?

Not for any particular purpose, was just a weird intrusive thought that is nagging at me.

Cheers

1 Comment
2024/05/20
13:17 UTC

2

What are currently the biggest discrepancies between our best theoretical predictions and actual measurements?

This can also include measurements which can be explained with one specific parameter set in our best accepted theories but those parameters will yield an error for some different kind of measurement (so we need two different parameter sets to accurately model the two observations using the same theory)

Also, "big" can either be a big value discrepancy, or a "big problem" that there is a discrepancy at all.

Hope the question is clear, if not I'll try to clarify better.

6 Comments
2024/05/20
12:45 UTC

2

Modeling a Kick with Physics Integral

Hello, I was trying to calculate the amount of force generated at the end of a roundhouse kick (i.e. the highest point), using integral calculus and physics. How would I be able to set up an integral, or multiple integrals to help me calculate the amount of torque generated through the motion of a roundhouse kick. I think that it has something to do with angular momentum but I'm not too sure. Please help me, thank you.

1 Comment
2024/05/20
12:42 UTC

0

Terrance Howard

Everything he is saying makes sense! If everything is 3 dimensional then how are there any straight lines. The circle of life is real!…Hell Tesla knew what he was talking about but free energy is not a consumers market! Think people need to give Terrance and his ideas more thought!

5 Comments
2024/05/20
12:30 UTC

1

Why is there movement in the universe instead of stillness ?

4 Comments
2024/05/20
12:29 UTC

0

Could pangaea have been the solid shell of the earth with a smaller diameter that broke up because of expansion of the matter inside of it?

Disclaimer: I am very interested in physics but am a complete novice. Though I'm a little embarrassed to ask I have a thought that's been brewing and wanted to see whether people smarter than me can dispel it!

One day I was thinking of dark matter vis-a-vis universe expansion, and I started wondering if perhaps dark matter expands at a different rate than the matter we can currently measure, and that made me wonder if the dark matter interwoven in all things somehow affected the space between said standard matter on Earth and caused pangaea to break apart... I know that's probably an amateurish notion, but even if it isn't anything groundbreaking like that, maybe it was something less wild like the gases or other components inside the earth expanding to cause the break up?

My searches haven't turned up any theories about pangaea being an outer shell that's been broken up, but that makes a lot more sense to me than it having been a huge mass on one part of the planet (why would it form that way?) which then broke apart and migrated around?!

Any thoughts?

6 Comments
2024/05/20
11:44 UTC

1

Can't completely understand Electro/Magneto-statics

Hey, I'm a first year EE student that's taking some electrostatics classes right now. I've been having this problem even after weeks of daily studying, but I can't wrap my head around such theoretical concepts. I can solve any questions that ask for the curl, divergence, electric field etc. but I have no idea about questions with interpretation. I can't wrap my head around concepts like what flux, divergence or the gauss law actually are. I've watched tons of lectures and read multiple books for understanding, but it's still too abstract. Is this normal? What can I do to understand better. Not sure if this question belongs to this sub but I wanted to give it a go because I'm genuinely clueless about what to do.

1 Comment
2024/05/20
11:44 UTC

1

Is spacetime quantised?

Has there been any physical experiment or thought experiment that tried to prove or disprove that spacetime or only time or only space are not continuous or quantised?

One can think energy and time are conjugate to each other. Energy comes in packets but time does not?

Similarly, momentum and space (position) are conjugate. So is space also quantised?

Please don't judge me. Lol. This question may not be well thought.

4 Comments
2024/05/20
11:38 UTC

1

Does the Penrose diagram with the black and white holes mean there's another parallel universe for every single black hole out there? Or is does every black hole in the universe share one singularity? Am i making any sense?

4 Comments
2024/05/20
10:56 UTC

1

Strange QFT Interaction terms

Hi everyone! Currently studying for my QFT finals. I came across two different interaction lagrangians whose vertexs I haven't been able to find. I was hoping somebody could help!

The first is of the type L = k*phi*partial(phi) (for a Complex Scalar field).

My problem here is that I don't understand what exactly the psi inside the 4-derivative is doing there. Is that a new field defined w.r.t the other one? Or maybe it's the same, but the interaction depends on the momenta of the field?

The other one is something like this, for Dirac fields: adjoint(psi)*P_R*psi. I know that P_R is the right-handed chiral projector, but it can be rewritten as a sum of two terms (1+gamma^5)/2. So, how many vertices are there? Just one with P_R as the interaction matrix? Or should I split them and work with two different vertices?

Thanks everyone!

2 Comments
2024/05/20
10:17 UTC

0

Universe question

Hello together

I have seen a video which makes me afraid. I am honest I have panic attacks, ocd and anxiety. I question myself „Is my husband really my husband I met years ago?“

I know it’s rationally nonsense but if you suffer anxiety it is really hard to calm and I am unable to take naps.

So if a physicist could look and tell something about it „like it is impossible because ….“ , it could help.

Can anyone please refute this theory.

Thank you all and please don’t laugh.

https://vm.tiktok.com/ZGeCmJvRL/

8 Comments
2024/05/20
09:41 UTC

1

A car and a brick wall

Here's the scenario. The are two vehicles of equal weight and equal construction. Vehicle A is travelling at a significantly faster speed than vehicle B. Both vehicles crash into a brick wall but because of vehicle A's higher speed it goes through the wall while vehicle B comes to an immediate stop.

Who do you think is more likely to survive?

I believe that it would be the person in vehicle A because instead of coming to an immediate stop it is spread out over a longer time.

This makes me think that there is a zone where depending on your speed you will mostly likely die.

3 Comments
2024/05/20
09:36 UTC

4

What are some interesting physical interactions to view in thermal vision?

Have just got hold of a high definition thermal imaging camera. Was wondering what interesting interactions would be interesting to see through that perspective.

I was thinking maybe metal balls hitting together, things like that.

5 Comments
2024/05/20
09:33 UTC

1

Not sure I quite follow Noether's theorem

I always read that momentum is conserved because the laws of physics dont depend on position, and energy is conserved because the laws dont change over time. However momentum wouldnt be conserved if the laws were not also time invariant, and energy would not be conserved unless the laws were also position invariant. What am I missing?

2 Comments
2024/05/20
08:53 UTC

1

Calculate wall radio signal attenuation

Hello Everyone

For a university project i'm trying to calculate the attenuation of two different radio frequencies going through walls. I found the "Beer-Lambert Law" which seems very promising to make an approximation.: P(d) =P0*e^(-ε'*d) with ε'being the Absorption coefficient, P0 the input and P(d) the output power with a wallthickness of d.

My Problem is that i can find ε' values but not a formula for it including the wavelength/frequency of the signal. Is there a better formula to make an approximation based on the frequency or do you know a formula for ε' ? I mean i'm aware that this is probably not possible without any measure values or constants.

Thank you in advance

4 Comments
2024/05/20
08:10 UTC

2

Internal forces and mechanical equilibrium

Can there be unbalanced internal forces on a particle inside a 'system' which is said to be in mechanical equilibrium.

For example: In a system of two planets revolving around each other, the gravitional force between them acts as an internal forces of the system. And there is no other external force acting on the system from anywhere else. Can this system be said to be in mechanical equilibrium?

1 Comment
2024/05/20
08:01 UTC

0

[QUESTION] If all particles are massless, how is there gravity?

Recently I was in a discussion here with a person I took to be a physicist. I was saying that my understanding of gravity as elucidated in the Special Theory of Relativity was that mass causes a distortion in local spacetime, and objects of lesser mass get trapped in that distortion, giving the appearance that the object of greater mass is exerting a force on the lower mass object.

I think the cliche illustration of this is having four people each holding one corner of a bed sheet, which represents spacetime, and pulling the sheet taut, then having another person let a basketball, representing a planet, roll to the center of the sheet, which then sinks downward, depicting the local distortion of spacetime that we call gravity.

The redditor I was speaking with, however, explained that mass is something of an illusion, because all particles are actually massless, and what we think of as mass is simply, if I understood him, the aggregate kinetic energy of all the subatomic particles that make up an atom.

If I'm still on target at this point, I believe that E = mc2 is another way of saying this, or is related to it.

So:

  1. if it is literally true that there is no such thing as mass, then what is it that causes the distortion in local spacetime that we call gravity?

  2. Further, if the different planets, moons and the sun in our solar system each cause a local distortion in spacetime, but they actually have no mass themselves, how do they 'tug' on distant bodies, as in the Three Body Problem?

  3. Although I am not intimately familiar with the details, I know that since the James Webb Space Telescope went up, there have been re-evaluations as to the rate at which the universe is expanding (Hubble Constant, Hubble Tension, influence of dark energy), and I think I've heard some astrophysicists saying there may not have been a Big Bang--and even that the universe may not be expanding. Either way, isn't a central factor in calculating the rate expansion of the universe the amount of mass in the universe? Like the traditional question of whether the universe would end in a Big Freeze or a Big Crunch, wasn't that essentially about whether the energy from the Big Bang that started the expansion sufficient to overcome the combined gravity of all that matter or not? So again, if the matter does not actually have any mass, meaning it does not have gravity in the aforementioned sense, isn't this whole question turned on its head?

I'd be grateful to any physicists here who'd be willing to help out this avid physics enthusiast, layman though I am. ;-)

8 Comments
2024/05/20
07:52 UTC

0

proper time and relativistic time?

is this correct: time interval between two events measured by an observer who is ate rest relative to the events is called proper time, while the time interval between the same two events measured by an observer moving relative to the events is called relativist time?

1 Comment
2024/05/20
07:43 UTC

0

Something happens to window when my finger gets close

Saw that moisture was forming when my hand gets close to the glass on the bus and can’t find an explanation or think of one myself

0 Comments
2024/05/20
06:57 UTC

1

Confusion about chain rule

For the multivariate function pressure, p=p(x,y,z,t), if we hold t constant and look at an x-z slice (y also held constant), then the differential of pressure is:

dp = ∂p/∂x dx + ∂p/∂z dz

And if we choose to do partial differentiation wrt x, then we can find our equation by dividing through by ∂/∂x:

(∂p/∂x) = ∂p/∂x + ∂p/∂z (∂z/∂x)

My question is, given how we’ve defined pressure and its independent variables, should not ∂z/∂x be 0? z and x should be independent from one another

18 Comments
2024/05/20
06:38 UTC

2

Higgs and mass of electron

Hi All, I understand that the mass of an atomic nucleus is mostly due to the binding energy of quarks through E=mc2. In the case of a mass of an electron (and I guess a quark), I read many times that it is the feature of interactions of quantum fields. I guess in the case of an electron, it would be some fancy interaction between Higgs field and electron field which gives rise to mass. I do not need to understand the details of this, and it is certainly beyond my level. However, there is one aspect of this topic I would like to conceptually grasp. Is it fair to say that electron's rest mass can be calculated from the energy of interaction between electron field and Higgs field (also through E=mc2)? Thanks!

3 Comments
2024/05/20
06:24 UTC

2

Speed necessary to run on water

I read an article where the author gave an extremely rough estimate of the necessary velocity an average human would have to achieve to run on water. They just used an estimated volume of water that could be displaced to generate thrust and the mass of the person. The question is: how do you get from the force that needs to be generated (the force of gravity) to the speed, since we don't know how fast the water is moving? Could you estimate the stride length, allowing the use of energy conservation?

0 Comments
2024/05/20
05:58 UTC

0

Solution and method to this problem?

"Two parallel wires are at a distance of 2m one from another. Knowing the first wire has a current of 30A going up, find the irection and intensity of a current that travels through the second wire in sucha way as to maintain stable a third wire, found at 5Ocm from the second one and travelled by a continuous current goung up." The solution should be 6A.

0 Comments
2024/05/20
05:42 UTC

4

I came across some arguments from a flat earther online. As physicists, how would you respond to these?

"Standing bodies of water do not display convexity on the surface and cannot support stress."

"Now, if standing bodies of water can display convexity then please show me or tell me an experiment I can do where I can measure a standing portion of water at rest that is higher at one end than the other? At what scale does the water begin to change its physical behaviours and why? Physical demonstration please and not just your words. Reality is objective, and your words are not going to change anything. What you are saying goes against all observation and experiment."

"In order for a gas to be at measurable pressure it needs some form of containment. In order for gas to be at pressure at all, especially when coexisting next to a near perfect vacuum, it needs to be contained by some sort of solid barrier."

"Gravity has no mechanism to induce objects into motion or cause acceleration. The current stance within science suggests that large bodies can bend space and time by virtue of their own mass. Space and time are conceptual non tangible privations and cannot be warped or bent. It's theoretical nonsense designed to support a wider narrative that supposedly only exists outside of Earth's reference frame."

"We can see way too far for the Earth to be a sphere of 24,000 miles circumference. The way in which the horizon rises to eye level contradicts the geometry of a sphere that should be deviating down and away from you at every point on the surface. At high enough altitude, you should be able to look "down" at the Sun, however no one has ever looked down at the Sun because we don't live on a sphere."

"No sphere is perfectly spherical but all spheres deviate downwards from every other position relative to a starting point. That is basic geometry, and it is inescapable. If the Earth was a sphere we should be able to look down at the Sun from mountains or planes."

38 Comments
2024/05/20
05:36 UTC

2

An odd question about categories for a physics based thing in a world building project im doing.

Heyall, strange question, like, real weird. I am making a world for some writing thing im trying to do and have based much on physics. My question is thus:

Is there anything that exists that would not fall into the categories of matter, energy, and the abstraction of the laws of reality (stuff like strong force, weak force, friction, etc)

2 Comments
2024/05/20
05:32 UTC

5

What we would see from cat's perspective in Schrodinger Cat experiment

we know it will exist in superposition from the outside but what would be happening from cat's perspective

6 Comments
2024/05/20
05:22 UTC

1

How to find relative velocity?

Question: If one spaceship is going .700 times the speed of light 180 degrees, and another ship is going .200 times the speed of light also 180 degrees, what is the relative speed between the ships?

Note: this was a canvas quiz and I put .500c as the answer because I thought the relative velocity would equal the difference in speeds between the ships but it was incorrect. Can anybody explain to me how to find relative velocity?

Btw the answer choices were

  1. 0.581c
  2. 0.613c
  3. 0.486c
  4. 0.500c (wrong)
  5. 0.546c
1 Comment
2024/05/20
04:50 UTC

0

How do Northan Lights work

7 Comments
2024/05/20
03:44 UTC

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