1

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.

2

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.

3

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.

4

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?

5

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

« on: 28/06/2024 18:38:20 »

On a different forum I had to put a poster on ignore after he repeatedly posted reams of rubbish from bOng co-pilot, despite my request for person to person discourse only.

A supposedly bannable offense on several sites, but it's not going to happen here since, well, the entire mod staff being made entities, and not famous ones either.

Side note: Ah... Bing. Had to look it up. Didn't know the MS product was called co-pilot.
What sort of topic was being discussed that this poster had to resort to using such a source?

6

Just Chat! / Re: What keeps a bicycle stable in the vertical orientation?

« on: 25/06/2024 13:16:13 »

The resulting centrifugal force on the rider opposes the lean

Rider not even needed. A bicycle, riderless, at sufficient speed (about a running pace) will stay up on its own.
Excellent answer BTW. Yes, it's all in the angle of the steering tube, coupled with the curve of the fork, putting the hub off center of the axis of the steering rotation.

7

Question of the Week / Re: QotW - 24.06.28 - Are there stars which aren't part of a galaxy?

« on: 23/06/2024 19:14:54 »

stars are formed from gas and soot, where does the soot come from? (intergalactic burning of fossil fuels no doubt, when will they ever learn)

The 'soot' is from burning of the hydrogen and helium, the virgin gasses. So these later stars are built from the expelled remnants of the earliest starts. Our entire solar system is built from such material.

A common on earlier info:

We can consider ever larger structures (regions of space) until we identify regions we call Clusters or Super-Clusters.   All the mater in these regions is gravitationally bound together, they do not tend to drift apart, but they appear much as many seperate galaxies orbiting around each other in some complicated way (literally "a cluster of  galaxies").

Our local group (Us, Andromeda, all the little guys hovering nearby) are gravitationally bound, and thus, given enough time, will merge into one object, minus the odd stars that get flung away at escape velocity by 3+ body encounters of really massive objects. Yes, as has been pointed out, many of those not-in-galaxy stars have been flung out of galaxies, but they can only last so long before burning out. There is gas out in deep space, and new stars, not part of any galaxy do form out there.

Back to the gravitational binding: Our local group is it. We are not gravitationally bound to anything else, not the Virgo supercluster, the Great Attractor, and other 'nearby' super-high mass areas. We (our local group) are moving at greater than escape velocity from any of them, so we'll never be part of them. Given enough time, they'll disappear over our event horizon and will cease to have further causal effect on us.

There's always the off chance that our solar system will be flung out of the local group not only in the direction of Virgo some day, but fast enough for our system to suddenly be gravitationally bound to it. Better do it quick if you want it to happen before Earth dies. Any mass large enough to do that (*cough* Andromeda *cough*) will likely be here after Earth is gone.

8

Physics, Astronomy & Cosmology / Re: Where did the big bang come from?

« on: 25/05/2024 05:28:44 »

You say time dilation is a coordinate effect and not a physical one. However if I start with two synchronised clocks, keep one in my house and send the other off on a zillion mph hi tech craft for lets say, one year, and then reunite them there will be a physical difference. What say you?

The dilation is due to the speed difference. In one frame, the zoomy clock is moving at a zillion mph and runs slower, but relative to a different inertial frame, the zoomy outgoing clock is stationary and it is your house clock that is moving, and is thus running slow. That's what I mean by it being a coordinate effect. Which clock runs faster during some duration depends on the choice of coordinate system.

The comparison when the two clocks are reunited is the example of differential aging, and that is objective, since the different readings of the two clocks at that event is the same regardless of choice of coordinate system. So differential aging is physical, objective, and frame invariant.

9

Physics, Astronomy & Cosmology / Re: What empirical evidence led to Einstein's choice of postulates for SR?

« on: 23/05/2024 14:10:44 »

Thanks Halc, you may rename it as you choose and move it

OK, this is the new topic, split off, leaving not much in chat. A post or two here could have been left with the old thread.


As for me bringing up LET, I did so as an example of absolutism (not relativity), and not because aether had anything to do with the points I was trying to make, which is that one can have an equivalent theory without the postulates of SR, which results in a valid interpretation of the same data, and oddly enough, without relativistic velocity addition.
The reason nobody seems to go with any form of absolutism is because it renders it impossible to measure any distance or duration. Lacking a test for the absolute frame, all empirical tools give wrong values.

10

Physics, Astronomy & Cosmology / Re: What empirical evidence led to Einstein's choice of postulates for SR?

« on: 23/05/2024 13:22:54 »

you did say "light does not radiate from a moving object at c" in reply #9. Am I missing something?

Semantics
I was perhaps ambiguous in my reply.
The separation between moving object and the light pulse increases at the rate of 1.5c in my example. The light pulse of course is moving at c, the rate of change in its separation from the point in space where it was emitted.

As for moving the topic, I can do that, but I would like to re-title it at the same time, and that means you have to select a title more appropriate for the main sections. I suggested one, but it wasn't clear if that conveyed your actual question.

11

Physics, Astronomy & Cosmology / Re: What empirical evidence led to Einstein's choice of postulates for SR?

« on: 23/05/2024 11:20:03 »

I certainly was not considering LET(aether! God forbid!).

I never tried to imply that you were. I just bring up LET because (never mind the aether part), it is an absolutist way of looking at things, a valid way of looking at things which denies all premises of special relativity. So Einstein making those premises was a choice, not something that was obvious from the evidence.

I am somewhat confused by your statement that light emitted by a moving body does not travel at c: suppose an observer measures a body passing by at 0.5c and then this body emits a pulse of light- surely in both the frame of the observer and the frame of the emitter the speed of said light pulse will be c?

According to Einstein's premises, yet, it will be c, and I didn't say otherwise. But I said that it would distance itself from said moving object at some rate other than c.

I had the object moving east and the light west, so after a second, the two are 1.5 light seconds apart. Sure, in the frame of the object, the pulse is 1 light second away after a second, but the object isn't a moving object in that frame.

One final request, Halc, refresh my ageing brain as to the conflict between Maxwell and Newtonian mechanics.

Maxwell's equations are frame invarint under Lornentz transformations. Newton's equations are not. That's the best I can do. I'm actually not familiar with Maxwell's equations, and I don't do electrical problems because I'd get things wrong.


and I've never detected signs of aging brain from you.

12

Physics, Astronomy & Cosmology / Re: What empirical evidence led to Einstein's choice of postulates for SR?

« on: 21/05/2024 14:31:57 »

What I want to know is, in the early developmental stages of relativity(ie the work of Lorentz), when and how it was determined that in the case of light hitting a moving object the speeds would no longer be additive/subtractive.

That was derived from the postulates. It is only true under Einstein's postulates, and not under say LET, a form of absolutism which does not accept either of Einstein's premises.

(1) does not, in my opinion, require any postulate from relativity: once emitted the speed of the radiation will be determined solely by μ and ε.

Einstein could have instead just accepted Maxwell's equations as a postulate instead (Maxwell's work conflicts with Newton's) of the frame invariance of light speed since the latter can be derived from the first, but the theory wasn't about electromagnetism, so it was simpler to cut to the chase.

On another note, I don't know how you are using the word 'impinge' in your posts above.

The speed of light,(1) radiating from a moving object

Light does not radiate away from a moving object at c.  If an object is moving at say 0.5c east, then light that is at the object (coming from it or not) moving west will be 1.5 light seconds away one second later.
The postulate says light moves at c relative to any inertial frame, and the object is said to be moving, meaning we're using a different inertial frame than the one in which the object would be stationary.

LET does not accept any of the above. It is an absolutist theory, so light moves at c period, relative to the one and only preferred frame, and not relative to any other non-preferred frame. Velocities are still additive under LET. This doesn't make LET wrong.

What experiments/theory led to the conclusion that light impinging on a moving object at any arbitrary speed( <c) would always arrive at c? I have struggled with the wording of this question and am still not satisfied with it. 

It's a postulate. If there was hard evidence behind it, it wouldn't need to be a postulate. So it is merely an assumption, and one that not all competing theories accept.
I'm pretty sure that Maxwell's work was a heavy influence on the choice, but it's frame invariance does not prove the absence of a preferred frame.

13

Physics, Astronomy & Cosmology / Re: Where did the big bang come from?

« on: 18/05/2024 06:10:31 »

Both clocks are at an airport. One remains at the airport (the one I said is stationary)

Earth is spinning, so relative to any inertial frame, that airport is accelerating. it isn't stationary at all.
So if your Blackbird flies west, it will meet the airport after 12 hours on the other side, and both Blackbird and airport got there in about the same time, same speed, different directions. I could not say which clock would read the greater elapsed time.

The exercise is to meditate going with the clock on the plane then repeating while staying on the ground in hopes to reconcile how the 2 clocks would not indicate the same time has passed.

A human keeping the clocks company would have no effect on the experiment.

My conclusion was that time contracts, that you call dilation.

The rest of the world calls it dilation, so best not to make up new words for established concepts.

But now, I can't understand what you are saying about it being relative to the observer.

It's relative to an inertial frame. The typical 'observer' is often just there to identify the frame: "The frame in which Bob is stationary". Bob could be a cardboard picture of a guy. His presence or absence does not affect the physics.

The basic gist under special relativity is that relative to any inertial frame, fast moving clocks tick slower than slower clocks. But this is relativity, so relative to that 'fast moving' clock, it is all the other clocks that tick slower. Any clock is stationary in its own frame by definition, so it runs at 'normal' speed in that frame.

The 2 clocks show a different time but relative to the observer. So how are the 2 clocks off?

The two clocks in say the airplane experiment show different times. This comparison is objective, not relative to anything.
How much apart? It depends on the situation. For your west-flying Blackbird, I could not say which clock would log more elapsed time. If the plane flew west, the Blackbird clock would show less elapsed time.
The famous HK experiment that first did this had slow airplanes that landed periodically, but eventually made it all the way around. The time difference was 59 nanoseconds less if eastbound, and 273 nanoseconds more if westbound.

Like if someone lives at the top of the Himalayas and another lives in an underground cave, time would not pass the same for the 2.

That's time dilation due to gravity, yes. The HK thing had to take that into account since the airplane was often at higher altitude than the clock on the ground.

How about a spaceship that goes far away at high speeds and comes back, wouldn't the time it was gone be different from the time that passed on earth by years?

Yes, it can be much less. If your ship is fast enough, you could age 1 year and you find that 200 years has passed on Earth when you get back.

14

Physics, Astronomy & Cosmology / Re: Where did the big bang come from?

« on: 17/05/2024 01:44:28 »

Good to see your return. Been a while it seems.

According to the theory of relativity, time isn't a constant

According to relativity, time isn't absolute. According to some alternate, but still valid, theories, time and space are both absolute. Nobody in the cosmology field ever seems to use these alternate theories, especially since they lagged relativity theory by almost a century.

when the jet lands at the airport and you compare the clock that traveled and the one that didn't they will show a different amount of time has passed.

Yes, this has been demonstrated, but it takes really accurate clocks to measure the difference. It's far more noticeable with say GPS satellites, all of which contain such accurate clocks.

Even though each second that passed was a full second relative to the person experiencing it, the actual time that passed isn't the same as the clock that remained stationary.

Time and space is not absolute, remember? So there is no 'clock that remained stationary'. Stationary relative to what?

So in essence, because time contracted for one clock, the other had less time pass.

No, the length (interval) of the spacetime path traversed by one clock is shorter than the other. This is a physical effect. Time isn't something that 'contracts'. There is time dilation, but that is a coordinate effect, not a physical one.

I couldn't figure out what it was growing into but had to accept it. My thoughts were always directed towards the end of infinite because well, it had a beginning, a fixed point attaching it to reality that was actually wrongfully ignored. My mind (would suspect most of us) is linear with space and time, everything has a beginning. I kept meditating on infinite in every form I could imagine. Still the question of what the universe is growing into remained

No valid model has the universe expanding into some otherwise unoccupied space. Instead, space itself is expanding. There can be no edge to the universe, be it finite or not. That just doesn't work.

The universe has a beginning so to speak, yes. It was never a point. The big bang happened everywhere, not at a point in space. Relativity theory has time as part of the universe rather than the universe occurring in time. That means it is meaningless to talk about 'before the universe', or it being created, or some such.
The alternate (absolute) models do support a universe contained by time, so such language is appropriate if you're using those models.

Hope some of this helps.

15

Plant Sciences, Zoology & Evolution / Re: What Organisms Have The Most Dissimilar DNA ?

« on: 14/05/2024 16:12:30 »

When I look at the picture of Ben and his banana together I am convinced. I find it difficult to tell the difference between the two

I see a difference. The bananas need two condoms, and Ben doesn't need any because, well just look....

So, can ewe think of a few organism's with such fundamentally  disparate and incongruous DNA

I came up short on this.  I looked at a biological tree.

The banana and Ben are both close together there on the upper right, neighbors except for that fungus amongus.

So what was furthest away?  All that bacteria it seems, but then it comes down to how the difference is measured.
I mean, we have different number of chromosomes than most things, and all those of different lengths. How do you line them up and decide this one is shared and that one is not?  You pick a method of doing that and get around 50% for the banana.

But there apparently is this concept of a 'particular gene', and regardless of the volume of genetic literary works you gots, a thing has that gene or it doesn't. I think that's where the numbers come from.  So it turns out we have a bunch of genes (not a lot) that is unique only to humans and bacteria.  It wasn't carried up that tree pictured, else everything on the path would have it. So we share some unique genes with bacteria precisely because bacteria probably transferred it to us at some point in history. It was advantageous, so it spread to most/all of the species. It shows that genetic variation isn't accomplished only by random alterations to genes from say cosmic rays or something. They can be gifted.

16

Physiology & Medicine / Re: How Do the Immune Cells Detect The Invading Infection ?

« on: 14/05/2024 15:56:29 »

See the picture below ? A genuine non-doctored bona-fide picture of a real cell defending the body.

I noticed that.  It needs to fight the baddies (green and yellow ones) and not the blue toast that you ate a while ago, nor the purple tooth that you should have put under your pillow, nor the bewildered pink video game controller that entertains the warrior once he's done.

How do the cells know where the infectious cells are

Well, they come across them by accident. They sort of get everywhere since they ride the pipes. They find something with DNA that doesn't match them, and they resist it. Cancer isn't fought because the DNA looks OK to them.  The little lambs in their ewey mommys are alien, and the ewe needs to put out little local anti-rejection drugs at the placenta barrier to prevent rejection of the DNA of the lamb, because otherwise it would very much be smote.

Apparently they're not quick on the draw. They have to learn that something is bad, so they don't recognize it right away. This is why vaccines help. It kind of sends them all to school where they show pictures of the baddies to them and then they recognize them quicker when the real ones show up.

I think a slight variation on the question is, how do they stick around (in the current and all) when they find bad stuff. You see pictures of the white cells gathering their forces to battle some baddy. That means they can resist the current, and locomote to the scene, or at least to stay at the scene.  I have no answer to that, so I pose the question to subsequent posters.

17

General Science / Re: How Do We Know The Temp Of Absolute Zero If We Can never Reach It ?

« on: 14/05/2024 11:12:27 »

How Is The Temperature of Absolute Zero Known If We can Never Achieve It ?

How was it known to today's precision?  I don't know the history of that. The law of gasses gives a good guess.
It says that "the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature" so you grab a bottle, fill it with some gas, seal it, put the bottle in a vacuum, and then measure the temp and pressure. Then do that at other temps. Graph what you get. It should give a pair of straight lines for pressure and temp. Extrapolate the lines down to where the pressure is zero and where the temp line is yields absolute zero, Kelvin.

I say I don't know how because that only gets you an approximation.  You cool a gas enough and it suddenly becomes liquid and that has to mess with the pressure curve since it is now (mostly) sitting at the bottom of your bottle and is not so busy pressuring it.

18

Physics, Astronomy & Cosmology / Re: Observing Quantum Entangled particles At the Same Time . What Happens ?

« on: 13/05/2024 19:24:33 »

Long time no bleat.  Glad to see ewe back.

Now, say we have a pair of entangled particles. Observing one immediately changes the other.

This is a misconception. Quantum theory does not say this. It simply says that if both are observed in the same way, the two measurements,  when compared, will be found to be correlated.

what happens if ewe observe both the particles at the exact same time ??

Simultaneity is relative, which means that in one frame, one measurement takes place first, and in another frame, the other does. In some frames the two will be simultaneous. Nothing special happens. Same as before is all. The two measurements,  when compared, will be found to be correlated.

Do all vending machines dispense goods for free ?

They've always been free. Ewe've just naively been stuffing money into the things, thinking it will help. It hastens the process maybe, but that's all.

19

New Theories / Re: How does light propagate? By what means does light get from Point A To Point B?

« on: 15/04/2024 20:41:25 »

and a meter is defined as the distance that light travels in one somethingth of a second

I think I can compress ES's post to a short line.
A meter is what light travels in one somethingth of a second relative to an inertial frame.

The original official definition might have omitted that presumption since one can get light to move pretty much any distance you want in a second if the right kind of non-inertial frame is chosen.

because only when light is right next to an observer can he measure its speed? which will then be c.

Technically, even then the speed cannot be measured, and is only presumed. A meter is best measured by light reflected from one end to the other and back, in two somethingths of a second. Since an inertial frame is required for this, obviously you can't have both ends of the meter stick be comoving at once.

Your quote refers to non-inertial frames as "more complicated frames", and any expanding frame would be one of those.

20

New Theories / Re: How does light propagate? By what means does light get from Point A To Point B?

« on: 15/04/2024 00:38:58 »

If we insist that speed of light in vacuum is constant while also accepting that space is stretching

Nobody insists any such thing. Per relativity theory, light moves at c only relative to a flat (Minkowskian) inertial frame, and an expanding metric is not an inertial one, and probably isn't Minkowskian either.
Since spacetime is locally flat anywhere, light moves locally at c.

Similar stories for other kinds of non-inertial metrics like a rotating frame or an accelerating one, either of which can also be mapped onto flat Minkowskian spacetime.

As such, it will take ever-so-slightly longer than one second for light to travel that distance because it can only travel 299,792,458 meters in one second.

A more pointed example illustrating the non-constant speed of non-local light in an expanding metric:

Light emitted from the creation of the hydrogen in your body was emitted near 'here' at the recombination event 13.8 billion years ago and is currently ~45 GLR away, meaning it has averaged a velocity of over 3c. Meanwhile, the CMB light that we detect here today was emitted 13.8 billion years ago from material that was at a proper distance that was much closer then than where Andromeda is now. which is an average velocity of around 0.0001c

An example closer to home which doesn't involve expanding space: If you put a reflector on the surface of Mars and Mercury, light shone to Mercury will make the round trip at a speed a bit less that c, and the round trip to Mars at a speed a bit above c.Both are as measured by an Earth observer, and both are examples of light speed being dependent on gravitational potential.