1

Physics, Astronomy & Cosmology / Re: Is it Just Hadrons that The Large Hadron Collider...collides ?

« on: 29/10/2024 19:27:09 »

What is so special about Hadrons ?

They're made of smaller things.

Are there other particles on the menu to be collided too ?

For the most part, no. Electrons for instance are not thus accelerated, although it seems capable of it.

How do they store the particles ?....are they kept in a test tube or something ?

Everything is made of them, so it is simply a matter of isolating them (from Hydrogen say) and then sending em down the pipe.

How many particles are fired at one time ?

Hundreds of billions (of protons, which are hadrons) per beam, and multiple beams.  I've heard a thousand times that figure, so not sure if there are thousands of beams or they can make some beams more dense.

2

Physics, Astronomy & Cosmology / Re: Are Atoms Perpetual Motion Machines ?

« on: 29/10/2024 18:12:28 »

Where does the energy come from ?

It was always there since the atom was made.

2: Does this make atoms (et al) Perpetual Motion Machines ?

No. A PMM is something from which indefinite work can be extracted, at however small a rate. One cannot extract indefinite energy from the motion of an atom.

3

Physiology & Medicine / Re: What Happens To White Cells After They Have Dealt With An Infection ?

« on: 29/10/2024 17:15:32 »

Blood cells (of any type) are fairly short lived, so the white cell counts go down by attrition and lack of many more being produced after their need is gone.  The counts return to normal levels around 5-25 days after infection is cleared, depending on the sort of infection involved.

Red cells might live 4 months. White cells have a life expectancy of only a few days, so if you stop making them in abnormal quantities, their numbers quickly decrease to normal levels.

I have given a unit of red blood cells, and that has the longest wait time before I'm allowed to donate again. Giving whole blood, plasma, platelets, all have shorter wait times.
I've not heard of giving white cells, but I know that early in the covid days before the vaccines came out, whole blood from a person who had recently gotten over a covid infection was in serious demand to serve as a treatment for the more dire cases.

4

Just Chat! / Re: What is the purpose of the conductor in an orchestra?

« on: 28/10/2024 13:31:59 »

but the principal job of a non-playing conductor is to moderate the balance between sections more subtly than the dim and cresc markings on the score, and to add interest by varying the tempo and accent.

Not during performance I hope. This moderation (interpretation of the composer's dream) is done at rehearsal and hopefully not significantly changed in performance. There is also something to be said about changing it up when something is performed night after night, as opposed to school performances that tend to occur 1-3 times at best.


And Alan, love the anecdotes.

5

Just Chat! / Re: What is the purpose of the conductor in an orchestra?

« on: 28/10/2024 13:29:24 »

To be honest, if our conductor made an impromptu change in something just on the night when a piece was being performed, then a lot of us would have missed it and played the thing as we did in rehearsals anyway.

It would seem terrible if any alteration was made without rehearsal. Yes, it's during rehearsal that he's most needed, but also most ignored because until the music is more familiar, concentration is mostly on the paper and less on the peripherally visible conductor..

We had a school band piece where you play the first half, then the 2nd which starts with one of those attacks after a long pause between the halves, then the first again exactly the same. In concert (a competition), our conductor was quite nervous and got to the end of the first half and mistaken thought he had finished, putting the baton down. We're all waiting for the attack signal. Of maybe 80 of us, I think I heard two small toots. The rest of us were watching and very confused. The band leader picked up on our distress immediately and resumed, but it wasn't supposed to go that way.

6

Just Chat! / Re: What is the purpose of the conductor in an orchestra?

« on: 28/10/2024 13:21:50 »

Halc, I am going to dispute, most likely out of ignorance!, something you said. You suggested that after a long pause or a sustained note it is entirely not clear when the attack of the next note is supposed to be. Surely if one has a good sense of time(something I lack) coupled with the sheet music, one has a pretty good idea?

They've practiced, so yes, but a pretty good idea doesn't get everyone on the attack simultaneously, and there's no beat to follow through say a fermata.

In a choir, our was small enough to lack a conductor, so heads turned to the organist and head nods. You get this piece with a loud long final note that needs an abrupt cutoff. All of us are looking at the organist (well to the side, hard to see from the rear, or down in a pit, invisible to the audience) for the head nod. It sounds terrible if the voices don't cut off as one.

7

Just Chat! / Re: What is the purpose of the conductor in an orchestra?

« on: 27/10/2024 17:53:22 »

It's to keep everybody in sync. If you're in one corner of the band/orchestra, you might not be able to hear all the others, and one group can get devastatingly out of sync with others. We ran into this marching in Mexico city, 6 wide down a 2 lane road. A car was parked, blocking one lane, forcing 3 columns to go and the other three to follow. This spit the drums and made it so those in the rear could not see the conductor (the drum major up front with the super tall stick).  We got measures out of sync and it was a disaster. Those who heard both sides just stopped playing.

Anyway, imagine a classical piece with a dramatic pause or long held note. It is entirely not clear when the attack of the next note is supposed to be. The conductor makes this explicit, and everybody should be watching for it.

Small groups (jazz ensembles, barbershop quartet, etc) don't need one, but usually one of the players visible to all uses head/instrument motion to fill the role.

8

Physics, Astronomy & Cosmology / Re: What is the exact cause of the time dilation of the twin?

« on: 17/10/2024 17:00:23 »

I had been told years ago by a theoretical physicist(who now holds a distinguished position at an American university but who will remain nameless) that GR was needed for accelerated frames of reference.

That's actually pretty sad for somebody claiming those credentials.  I googled "is GR needed for accelerated reference frames" and got correct replies from several sources with poorer credentials, but one from a university site.

AI overview: "No, general relativity (GR) is not required for accelerated reference frames:

    Special relativity (SR) is sufficient
    SR can handle accelerated frames and objects, and is sufficient to explain the Twin Paradox. SR is valid in the presence of accelerations because it describes flat Minkowski spacetime"

That is a very poor reference (as is any LLM), but it's correct.  The twin paradox bit is barely relevant since discussion of it is rarely described via changing accelerated reference frames.  That quote seems to answer more "Is GR needed to describe acceleration" rather than to describe accelerated frames, but accelerating objects are perfectly well described in inertial, accelerating, expanding, rotating, and other kinds of frames.

The next hit is better, from University of California, Riverside
"It's a common misconception that special relativity cannot handle accelerating objects or accelerating reference frames. Sometimes it's claimed that general relativity is required for these situations, the reason being given that special relativity only applies to inertial frames. This is not true."

I got no immediate hits that said that GR was required, but I'm sure they're out there. Bottom line is, GR is needed for curved spacetime, which only comes into play with gravity and dark energy, and none of the discussion here has been about those things.  I do not know my GR well enough to say do the tensor calculus required to generate numeric answers. Tensor mathematics is not required for anything in SR, including Rindler frames.

"What is the exact cause of the time dilation of the twin?"
The same thing that causes time.
And I'm not sure we actually know what that is.

I don't think time is something that is caused.  It is exactly like asking what causes distance, which seems to be an ill-posed question.  I do agree that most of the recent discussion has digressed from the immediate topic title, but since it is mostly framed as questions about relativity and not assertions of speculations, I've not moved any of it to the lighter side.

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Physics, Astronomy & Cosmology / Re: What is the exact cause of the time dilation of the twin?

« on: 17/10/2024 14:10:29 »

Is the bold statement backed up by experimental evidence?

I don't think they've ever made a set of gears with a 1000-1 size ratio, let alone turn any reasonably rigid object at significant relativistic speeds.  The bolded statement  is backed by the very simple mathematics of γ=1/√(1-v²) which is identical on both sides since the sole variable v is identical on both sides.

If an identical measuring tape is glued to the ship, will the earth observer see two of those tick marks go by every second?

The situation is not symmetrical since the ship is accelerating and the Earth is not.  Earth can have a tape measure of indefinite length attached to it, one that the ship can read forever.  The ship (at proper acceleration of 1G) can trail not even a light year of tape behind it.  The tape cannot extend beyond the ship's event horizon without breaking.

How many ticks per second the Earth observer sees depends on when he looks.  At some point, the ticks go by infinitely fast just before the tape ends, and then they see no more.
There was that ship event where the ship guy sees 2 ticks/sec go by.  In Earth frame, the event there that is simultaneous with that ship event, the tape will already have been exhausted.

I made the mistake of trying to apply SR to a scenario where some of the frames of reference were not inertial and were thus in need of GR for solution.

GR is only needed for situations involving gravity (which I suppose my black hole mention does).  But the accelerating frame of the ship is a straight SR exercise.  You might want to look up Rindler frame or Rindler coordinates for info on how SR treats an accelerating frame like this.

SR handles accelerating frames just fine, as it does rotating frames. It handles normal expanding frames as well, but not accelerating expansion frames which involves dark energy and puts things into GR territory.

10

Physics, Astronomy & Cosmology / Re: What is the optimum speed to make a point in space disappear?

« on: 16/10/2024 16:48:22 »

I read-read that and I did come across kind of snarky. Apologies for that.

In the example in the other thread where the spacecraft was travelling at 2c relative to the tape measure you said the earth would be hardly receding at all and that it would not reach 1 light year with unlimited time of travel of the craft.

Right, but it has nothing to do with speed, but rather continuous proper acceleration.  The greater the proper acceleration, the closer the event horizon is to the ship, and Earth will never fall through the event horizon, but will instead remain close (in the accelerating frame of the ship) and forever visible, just like a lantern dropped into a black hole.
Of course quantum mechanics says that at some point the last photon to reach you will leave Earth, so looking at it from a quantum viewpoint, Earth will remain visible only until that last photon reaches you, but the 'never disappear' statement presumes continuous light, not quantum.

So there must be a speed at which the earth appears to recede the fastest

No, there's no such speed, especially since ship speed reaches any arbitrary value regardless of rate of acceleration. First of all, the appearance of velocity is dependent on one's choice of frame type.  Secondly, for all constant levels of acceleration and relative to said accelerating frame, Earth will 'appear' to drop away slowly at first, pick up speed as the ship velocity relative to Earth grows, and then slow as Earth approaches the ship's event horizon.  It will never appear to cross that horizon.

For linear non-accelerating travel, that is limited to c, and in flat spacetime, Earth will always be visible.  In real spacetime, at any ship speed, the ship will eventually cross Earth's event horizon, but both Earth and ship will always be able to see each other.  There is no way to exit the visible universe.  Despite recession velocities > 3c relative to the cosmic frame, new stars become visible (enter the visible universe) every day, and none of the ones visible ever vanish from sight (unless they cease emitting light).

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Physics, Astronomy & Cosmology / Re: What is the exact cause of the time dilation of the twin?

« on: 15/10/2024 22:26:22 »

ISS is orbiting the earth, thus it's accelerating. But your accelerometer won't show the correct value of acceleration there. It will show something close to zero g.

Read my post.  Any accelerometer shows proper acceleration and an orbiting satellite will undergo no proper acceleration. The acceleration you speak of is coordinate acceleration, and even that might be zero. I mean, in the coordinate frame of my house, my orbiting sat-TV satellite is stationary (no coordinate acceleration) which is why I can point my dish at it and not have to move the dish.

Does it mean I will see the earth recedes with speed 2c? What happens to the cosmic speed limit?

With respect to #70: yes the earth will appear to recede at 2c because your rapidity will be 2c. From the earth you will be seen to be travelling at <c.

There's no direct appearance to a recession speed.  It is very frame dependent.
Relative to the inertial frame in which the ship is momentarily stationary, the Earth will be receding at around 0.964c.  Nothing can exceed c relative to an inertial frame. But if there was a tape measure glued to Earth that goes all the way along your journey, with a tick mark every light second, you'd see two of those tick marks go by your ship every second. That's what it means to be moving at a proper velocity of 2c relative to Earth.

Relative to the ship's accelerating frame, Earth will be seen receding almost not at all, and will never reach a light year away even after indefinite ship time, all very much like dropping a clock into a black hole.

Celerity (and not rapidity) is another word for proper velocity, at least they're the same in Minkowskian spaceitme.  One must be careful to use the correct term in other contexts.  And yes, the >c recession of galaxies relative to the expanding cosmic frame (not an inertial frame) is like a celerity of sorts. The proper distance between us and the distant thing (measured along a line of constant cosmologtical time) grows at a rate of >c.  Inertial frames are not even relevant at such distances, but if you remove all energy, the distant galaxy would not be moving faster than c relative to any inertial frame since the distance would not be along a line of constant cosmological time. It would be far closer, and its velocity in that frame would be sub-luminal.  It would still be moving at well over c in the non-inertial expanding frame, but that's a coordinate difference, not a physical one.

Accelerating a clock alters its tick rate

Not true.  I gave examples early in this topic that demonstrates otherwise, bottom of post 20.

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Physics, Astronomy & Cosmology / Re: What is the exact cause of the time dilation of the twin?

« on: 02/10/2024 16:50:54 »

Oh dear, here we go, again. Word salad.

Indeed.  The prior posts have been removed for several reasons.

1) Nonsense in the main sections of the forum
2) Contained personal information
3) Had nothing to do with the topic title, hence is a hijack of a topic
4) Contained a bibliography which was nowhere referenced
5) Contained no content from any of said bibliography
6) Word salad as Paul points out
7) Duplicate posts

At least the first three of those violate forum rules.

13

New Theories / Re: Gravity In Relative Motion - is there any solution?

« on: 28/09/2024 02:51:02 »

So does it mean that kinetic energy starts to be added to the inertial mass/energy of a body only when a certain velocity is reached?

No.  It would violate energy conservation if I did work on an object and no energy was transferred to it because it wasn't yet moving fast enough. This again is not unique to relativity theory.

If total relative velocity of our (me and the object in question) motion is equal to 0,99c - how can we know how our velocities are distributed in other frames?

The relative velocity addition formula can do the frame transforms for velocity.  Lorentz transforms are for coordinate transformations between frames.

Is there any difference between me incoming towards the object at 0,99c and object incoming towards me at 0,99c?

Yes.  The vector of one velocity is the opposite of the other.  Different objects are stationary in the two respective frames.

And what if in some other frame we (me and object) are incoming at each other with equal speed? Where the additional mass/energy will be added?

Each object contributes its own kinetic energy in that frame.

[/quote]And coming back to ISS and your answer - can you help me finding the fragment of text telling that relativistic mass becomes a 'thing' only at extremely high velocities and that it's effect is completely non existent below some specific velocity?[/quote]It doesn't have a minimum speed. It's a thing at any speed (even zero), but not very significant at low speeds where classical approximations are sufficient to express the KE of the object (E=mv?).

And if not that - should I understand that classical mechanics might lead to effects that are contradictory to effects of SR?

Classical mechanics is a good approximation at low speeds. Neither classical nor relativistic mechanics says that objects gain no kinetic energy until some minimum speed is reached.

So until some particular value adding velocity allows escaping gravity but then and then just like that - "Flop!" - and now adding velocity will start increasing gravitational pull?

Yet again, this is totally wrong. Stop asserting this.

Nope. [Einstein is] completely and utterly wrong about it. There's only 'as much' energy, that 'fits' into a given amount of mass (matter).

Only so much in stationary matter. There's no limit to KE, else again, energy conservation would be violated.

You simply can't get more energy from a given amount of matter than energy released due to annihilation - in which mass is literally turned into photons and stops existing as matter.

A fast moving small thing emits more energy (higher energy radiation) in such an annihilation. There's no limit to it. You seem to be in continuous denial of a simple theory, rather than taking the position of trying to learn about what you don't want to accept. You cannot falsify a theory that you refuse to attempt to understand.  I see little point in responding to somebody so closed to learning.

Your chosen quotes from wiki do not contradict this, except in their using the word mass to mean relativistic mass, which is an unconventional usage of the term.

14

New Theories / Re: Gravity In Relative Motion - is there any solution?

« on: 27/09/2024 23:38:45 »

I can defend relativty

1. there's a definitive & limited amount of energy in matter (according to Einstein it's unlimited) - equal to (half of) energy released to matter-antimatter annihilation.

Einstein is right. There is no limit to how much say kinetic energy one can give to a given object.  One can always apply a force on it to make it go faster, assuming one can find an energy source to do so.  So in the frame say some neutrino, the small bunny in my front yard perhaps has more energy than one stationary anti-bunny.

2. Body moving at 100% c

A 'body' has mass and cannot move at c, as Paul has pointed out. This is really basic stuff that shows you apparently know nothing about relativity theory.

gravitational attraction decreases gradually as source-object accelerates from 0 to 100%c

Gravitational attraction isn't a function of acceleration. Not one bit.

Because I really despise making theoretical calculations with real-life units like (kilo)grams, meters or seconds, I made myself a simplified system of units based on constant c (moving 1 space unit in 1 time unit).

They're called natural units, and in such a system, c=1 and can be treated as such in all equations.  But you assign c=10, which isn't a natural unit.

let me show you an example:
https://en.wikipedia.org/wiki/Mass_in_special_relativity#Relativistic_vs._rest_mass

Relativistic mass has been depricated since about 70 years ago.  By definition, mass is proper mass, and is frame invariant.  What varies from one frame to the next is momentum.  This is not a change in theory (The original SR paper did not treat mass as proper mass), but rather a standardization of convention.  Nevertheless, the idea of relativistic mass has an incredible presence on the internet, which is why chat bots use it so much.

Gravity is not a function of mass in relativity theory. It is a function of stress energy, which is frame invariant.

Basically according to Einstein there's no limit to the energy for any amount of mass (matter) - you can pack infinite amount of Giga-Joules into a single proton (or electron).

Or negative even. Potential energy is negative and there's no limit to the depth of a hole you can drop a proton into.

Well, sorry but in  my uneducated opinion, matter/antimatter annihilation turns WHOLE mass into energy and there's ALWAYS a finite & measurable amount of it released

Because you started with finite energy. Einstein doesn't say you can get more energy from a stationary thing. It has to be moving fast to have more energy than the stationary one.  If it's fast enough, you can do more work with it than the anti-matter thing, and it doesn't even have to disappear to do it.

and it's theoretically IMPOSSIBLE to get any more energy from matter.

So this assertion is clearly wrong.

Thing is, that for some reason physicists keep thinking that mass has a definitive amount energy at rest (inertial frame) but then you can 'pack it' with potential and kinetic energy to infinity.

If it has KE, it isn't at rest is it?  If it has PE, that is negative.  There's a limit to how close to zero PE can get, but it isn't really defined where zero is. I.E. there's not a place you can be that is free from gravitational potential.

Let's take a theoretical comet/asteroid entering edge of Earth's atmosphere at a relatively small (flat) angle - question: Will making the asteroid/comet faster increase or decrease the chance of it hitting Earth?

Bunch of problems with the pic:  The comet cannot be a comet since it is moving too slow. It is clearly in eccentric orbit about Earth, while comets orbit the sun and move much faster relative to Earth when in its proximity.
The tail of the comet points the wrong way. It should extend to the right, not down where you drew it. A comet tail is not a wake, despite all the popular images depicting it that way.

That aside, if the comet takes the same initial trajectory but is moving only a tad faster, it will have less time to accelerate to the right as you depict. It will miss. This is basic Newtonian mechanics and all of this has squat to do with relativity theory.

In Einstein's model increasing speed = increasing energy = increasing mass what should lead to stronger gravitational attraction

This is completely wrong. Relativity theory says no such thing. Mass is not a function of speed. Gravity is not a function of mass, at least not directly.
Please do not say what Einstein's model predicts if you don't know how (and when) to apply the model. It is a straw man fallacy.

My model predicts something directly opposite - the faster the comet moves, the less it is attracted to Earth

This is also wrong. Yes, it will miss, but because of what Newton says, not because the attraction is less.

What Einstein's model is suggesting is that the faster the interplanetary bearing ball will be moving in relation to Earth (stripped out of the atmosphere), the stronger it will be attracted to the surface - and that a slower cosmic bearing ball has bigger chance of escaping Earth gravity.

Totally wrong. Relativity theory says no such thing.

Ok, here's question to those willing to stand in defense of Einstein's model - let's have 2 bodies of equal mass accelerated simultaneously at the same rate to relativistic velocities - so that both are moving at the same speed next to each other (appear stationary to each other)

Gravity isn't a function of acceleration.  So you're saying that you still have two objects that remain relatively stationary.  Gravity between them (in their own frame) will be unaffected per the first postulate of SR.

- will the increased velocity of those objects (observed in some other frame) have any effect on gravitational interactions between those accelerated bodies or they won't observe any difference?

In a frame in which the two objects are moving fast, the two objects will accelerate towards each other more slowly.  Less acceleration, not more like you describe.  It will take more time for them to collide than they would in a frame where their mutual center of mass was stationary.  In a frame where they're moving at 0.866c, they'll take twice as long to collide with each other.

I'm pretty sure (like 85-90%) that not even the most loyal supporters of Einstein's model  can tell with >50% certainty what the model actually predicts - and if some actually can make such prediction, it will most likely go against predictions of some other Einstein supporters...

The validity of a model has nothing to do with a vote of support. Plenty of people support relativity without understanding it. Some support alternative theories, and a small fraction of those understand both Einstein's theory and their own choice.  Supports relativity does not imply that one can make correct predictions.

As for myself - I literally have no idea what Einstein's Relativity tells us about such/similar scenario

You're sure making an awful lot of incorrect assertions about it for somebody who admits a lack of understanding.

So ok, one more 'scenario' - what would happen with ISS if SuperMan or some other OmniMan would simply stop it's motion around Earth?

Hope they take their time about it.  The ISS is delicate and does not take kindly to large forces being applied to a small area.  Irrelevant, I know.  We assume it is sturdy for this exercise.  We assume Superman can exert reactionless force, but only because it doesn't change the answer.

Let's say it would stop moving right above my house and then would be left 'hanging there' not moving in relation to surface (at least horizontally) - what would happen then with it?

Nothing to do with Einstein.  It would fall somewhat to the east of your house after around 5 minutes.  East is due to Coriolis force.
If the object has sufficient altitude, it won't hit Earth at all. If it has even more altitude, it won't even lose altitude, which is how geosync satellites manage to stay put despite not moving in relation to surface.

Now, in this case I can at least try figuring out what Einstein's model predict in similar situation..I'd say that according to Einstein, ISS would simply keep 'hovering' there endlessly or maybe even it would slowly 'drift away' from Earth.

Seriously, you thing Einstein would suggest that??  This is pretty hard evidence of crackpottery.

Why I'd say so? Well, since it stopped moving in relation to Earth's surface, it's energy decreased and so did the gravitational pull towards Earth - that's how I'd see Einstein's model..

A stopped thing still has mass, which is non-zero energy. Surely you don't think otherwise. OK, it seems you do...
If you want us to take your posts seriously, take seriously the thing with which you disagree.

What my model predicts however, is that I'd have at best 10 minutes to move most important stuff from my house before couple hundreds (thousands?) tons of 'space junk' would turn it into a landing pod (although 'falling pod' seems to fit better) - it would simply start falling down from it's orbit like 2 seconds after it's motion would stop...

1) half that time  2) it will miss  3) it starts falling right away (just as it is doing now), not after 2 seconds.


I cannot quote the copilot answer since it isn't text, but almost everything in it is completely wrong, and is a fine example of why it is terrible to ask any chatbot questions on theories about which it has no actual understanding.

15

Question of the Week / Re: QotW - 24.10.04 - Do snails get dizzy?

« on: 27/09/2024 12:56:21 »

do snails get dizzy?'

No. Getting dizzy is a byproduct of a vestibular system, a feature of vertebrates.  This system detects angular acceleration, and it is the detection of the angular acceleration of the cessation of spinning that makes one dizzy.

Snails instead have statocysts which detect linear acceleration, which gives them a sense of orientation, but not of spinning.  A snail in a car wheel would feel heavy linear acceleration, but essentially constant orientation (radially outward).

16

Physics, Astronomy & Cosmology / Re: what organic substance/biofilm could stay on the skin for 9 years

« on: 17/09/2024 19:59:47 »

Long time no see, Harry!

You already know a forum is not a substitute for professional help, but it sounds like you're not exactly getting any workable results from the professionals.

You can try some better clues.  I suppose the jar is gone, else the substance could be identified.  Do you remember the consistency (slimy, but thick paste, a lotion, or more of a runny liquid)?  How long was it on you before first trying to remove it?  How long before you noticed an undesirable reaction?

What was the shape of the container?  Even that can give a decent clue.  Was it stored with medical jar, food, or with automotive chemicals, or what?  What possessed you to apply it to you skin without knowing what it was?  I presume that wasn't intentional, but hard to avoid given the actual intended purpose of the stuff.  (Instructions: Use gloves when applying this to your bricks).

17

New Theories / Re: What's the unit of Torque?

« on: 13/08/2024 02:54:21 »

This thread is so full of erroneous comments and outright speculation that I'm moving it to the lighter side.  I mean, 50 posts, and what has been answered?

An error laden quote from Gemini in the OP mentions the Newton-meter, but post 10 (a wiki quote) identifies the Newton-meter (with force being a vector) as the unit of torque.
End of story.  The rest seems to be yet another blog seeking to get off track in as many ways as possible, which is not the intent of the main sections of the forum.

The units of both are mass length squared per time squared.

This is so wrong.  It seems to presume that energy and torque are the same thing, and then applying a relativistic notion of mass-energy equivalence to torque.

Once you have started a circularly symmetric body rolling on a horizontal frictionless surface,

If the surface is frictionless, the wheel will probably just slide and not roll at all. Which way the body rotates (if at all) depends on where relative to the CoM the impulse is applies.

18

General Science / Re: what is Nothing or ?energy landscape.? or waves

« on: 04/07/2024 21:45:20 »

Do particles pop in and out of existence? Virtual particles aren't actually particles, apparently.

Good question. Much depends on the view one takes. Current theories depend on the existence of virtual particles, so one can perhaps wave away (declare to be just a mathematical tool) all theories and presume some alternative which doesn't predict them.

They cannot be detected by experiments, right?

This depends on your interpretation of experimental results. For instance, anomalies in the measurements of magnetic moment of muons can perhaps best be explained away as virtual particle detection.

Any detection of Hawking radiation or Unruh radiation would be a direct measurement, but neither can be observed in a lab, and such radiation is currently significantly colder than the background radiation. Observation of a very tiny end-of-life black hole would be solid confirmation.

Technically, every measurement of quarks and gluons in a bit particle smasher experiment constitutes such a detection.

So, how do we know that it's correct?

One can never be sure that an interpretation of experimental results is the correct interpretation. But our best theories, the ones that make the best predictions, also predict the existence of virtual particles, parallel universes, and other things that cannot be directly measured.

If partials do appear and vanish back to wherever, what replaces the void they occupied?

Not always. They need positive energy from somewhere, else yes, they're just transient.

If the universe is just made up of waves

Over simplification, and no, I don't think I can explain all of quantum theory in a forum post, or at all for that matter.

19

Just Chat! / Re: Fed up with the lack of reasoned discourse

« on: 29/06/2024 21:11:25 »

I usually stay away from electrical topics since I'd probably get the magnetism parts wrong. I am not, for instance, qualified to critique the post done by E-S above.  But this situation is pretty basic.

Em fields have finite speed and this means there is a time lag between action and reaction although in almost all cases this will not be detectable.

Fields are by definition everywhere and don't 'go' anywhere. Changes to the field do travel, and yes, at c.  All this is true to everything from gravity to the strong force.

So there is no action/reacton going on here. There is say two similarly charged objects moving towards each other. There is always a force between them, so at no point does an 'action' by one of them commence. But the force grows as they approach, and maybe, due to the speed of the field change, the force between them may be less when they're X-distance apart than the force that would be between them at the same distance, but they're relatively stationary. This is due to the change of the field not getting to either of them yet. So still balanced forces, but not the same force if they were not approaching.

There is no cause/effect distinction. The situation is symmetrical so the ball acts on the bat as much as the bat on the ball.


Now let's change frames and see what relativity of simultaneity says.
In one frame, the two objects (synced clocks actually) are identical and moving toward each other at the same speed. The symmetry means they must always be moving at the same speed. The net momentum is always zero in this frame. The acceleration of each is continuously going up until the point of closest approach.  So lets consider this approach from a different frame.

From some different frame, the left object is say momentarily stationary, and accelerating to the left.  The right object, in that frame, is simultaneously accelerating less since from its perspective, the separation of the objects is greater. The time on the right clock is less than the time on the left one.  Is this a problem?  If it's accelerating less, it first appears that momentum of the system is not conserved, but momentum under relativity is γmv, and since the right mass is moving, momentum is exactly conserved in this case as well.

he says that if the field is changing during such an interaction the action and reaction will not be equal and hence the conservation of momentum will be violated.

That statement is wrong just for calling out a nonexistent action-reaction relationship.  The field change is entirely symmetrical in the frame where the interacting identical charges (almost 'touching' electrons say) have a net momentum of zero.

My counter argument is that em fields carry momentum

Here's where I get shaky since it gets into quantum mechanics and force carrier particles and charges that don't have measured locations. I'm not sufficiently knowledgeable to comment about such things. The post by ES does very much imply that say spinning magnets (even orbiting masses) radiate away energy and angular momentum, but I'm not sure if any of that is applicable to a standard bat/ball collision. My reasoning above is classical, not quantum.

If this thread needs to be split now, i'm fine with that.

I can do that, or re-title the thing (and perhaps move it) to reflect its changed purpose. Let me know what you'd like.

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Just Chat! / Re: Fed up with the lack of reasoned discourse

« on: 28/06/2024 23:23:01 »

The discussion was about possible exemptions to the conservation of momentum because of the finite speed of em propogation

That can be an interesting discussion. Don't know the scenario specifics, but my gut feel is that no exception can be identified, leaving one to explain different times of accelerations of separated objects from one frame to the next.

I here got into a pretty heated investigation into angular momentum conservation due to acceleration of spinning things, which have frame dependent centers of gravity. Ouch. I think bOng would have a low probability of producing a good answer to that one.


In the end, AI (real AI) is going to outdo us, and your best conversations (such as the one you want with Einstein or somebody) will be with the artificial thing. I don't think the chatbots can do that since they don't surpass anything, just sort of average it all out, which only works well if the consensus matches what the bulk of the training material says. How does a chat bot weed out the true crap when it finds so much of it in its training material?