Split Thread The validity of classical physics (split from: DWFTTW)

[humber]

OHGOD!!

(Hey! I'm channeling Janice from friends!!)

Do you all understand the impact of what he is saying?

He is saying that because the person jumping up and down in the caboose dissipates energy in a number of ways he will loose KE (Because, as we all know, in the Humberverse KE is STRICTLY relative to the earths surface) and start to move relative to the caboose.

And this is how we know the earth to be banana shaped.

Do you think that despite being part of the earth going around so fast and all that, the air in the caboose may be coupled to the gravitational field, in not quite the same way as the jumper? And that may change again when the friction to the floor is no longer there?
I wonder where the energy expended by the act of jumping goes, and there may be all sorts of moments and so forth. Then some friction perhaps, or even a pressure drop here or there. Stuff like that. And even more.

Sure the treadmill works!

Sir, I use windspeed and it's consequences on real world aircraft every day of my working life. You might be interested to know that, prior to the invention of navigation systems such as Omega and INS, there was NO WAY to measure the wind in an aircraft in flight. All you could do was infer it by seeing how it affected your track and groundspeed vs your true airspeed and magnetic heading.

Cause, you see, in the FRAME OF REFERENCE of the aircraft RELATIVE to the air around it, the ground plays no part and has no consequence. I can jump up and down in my aircraft all day, and never end up pinned to the rear bulkhead!!!!!

Now lets go on- What is the TAS of a Hot Air balloon in zero wind? (Hint, it's a ROUND number!!)

I wouldn't want to disturb your turbulence-free world.

 

[humber]

Dear god.

Where have you been for the last 500 years, humber?

That's irony, right?

 

[humber]

No you don't

You are a bright boy.

 

[humber]

Yeesh. Have you never been in a moving vehicle?

Have you ever thought that your human faculties may not be capable of measuring the difference?

 

[humber]

You're the one with the PhD in statistics. What do you suppose the chance is that ALL of us are wrong on everything we've said for the past few thousand posts - and that you alone are right?

Sir, your logic is impeccable.

 

[RossFW]

Has anybody else seen what's happened here?

From the start, it was quite clear that Humber didn't understand some very basic physics. He couldn't get the idea or relative movement. He thought KE was absolute and only mesurable WRT the earths surface. He thought different objects exclusivley in a free stream had different final velocities.

Some very able scribes (MUCH more able than me) eloquently pointed out his mistakes.

We thought he didn't get it.

I actually think he does.

Notice his jibe at me-

I wouldn't want to disturb your turbulence-free world.

In other words, he now sees that in a theoretical, ideal situation (you know, the ones used to illistrate laws of Physics) what I have said holds. His only recourse is that (and of course he's right) in the actual atmosphere there are variations which will change things (and those changes will be easily described by the laws of physics).

That being said, still, winter mornings can be turbulence free to any measurable degree.

Similarly with the caboose- he's (sort of) right. There WILL be (very minor) changes due to friction, currents or whatever. He HAS changed his tune and would (nice guy that he is ) admit that in an IDEALISED, THEORETICAL world where the air in the caboose is exactley still relative to the caboose, and our jumper jumped exactley vertical to the floor, he would return to exactley the same spot.

He knows his original contentions were wrong, he's trying to insert correct ones without us noticing.

Of course, if he's not saying that, he's just a dope.....

 

[Christian Klippel]

Hi RossFW,

He knows his original contentions were wrong, he's trying to insert correct ones without us noticing.

he does that all the time. I call that "moving the goalposts". In any case he will never ever admit that he is (or was) wrong.

Besides that, i am pretty sure that as long as the speed of the caboose is constant, the road is nicely flat and the person really jumps straight upwards, the effects of any possible air turbulences and stuff inside it will be negligible as to the overall outcome. The person will still land on the same mark, maybe some microns away, if at all. The mass of the body jumping is just too big to have any noticeable effect. Measurable, yes, but hardly noticeable by the bare eye.

Of course, if he's not saying that, he's just a dope.....

Fixed that for you.

Greetings,

Chris

 

[jjcote]

Are you suggesting that if this experiment were actually performed, that the person jumping could do so to the height of the caboose, (and even hit it) and then land exactly in the same spot on the floor?

Uh, yeah, that's exactly what we're saying. In fact:

A hobo wakes up in a boxcar. The door is shut. He can tell from the noise that the train is in motion (at a constant speed, on the level), but he doesn't remember where the train is going. There isn't any light leaking in from outdoors, but there's another hobo in the corner with a lantern. The boxcar is well sealed. Can you think of any way (without opening the door) that the hobo can figure out which way the train is moving? Like, by throwing things up in the air, bouncing them off the walls, stuff like that. In particular, if he tosses his hat, or some hay, straight up toward the ceiling and watches where it lands, will that give him a clue?

 

[humber]

Has anybody else seen what's happened here?

Transparently, so.

From the start, it was quite clear that Humber didn't understand some very basic physics. He couldn't get the idea or relative movement. He thought KE was absolute and only mesurable WRT the earths surface. He thought different objects exclusivley in a free stream had different final velocities.

I will let you know when I need you to tell me what I thought. Yes, my progress under your tutelage has been startling.

Some very able scribes (MUCH more able than me) eloquently pointed out his mistakes.

Now it's your turn. I even told you it was not well posed. Mach?

We thought he didn't get it.

I actually think he does.

Notice his jibe at me-

It was at you, not for you.

In other words, he now sees that in a theoretical, ideal situation (you know, the ones used to illistrate laws of Physics) what I have said holds. His only recourse is that (and of course he's right) in the actual atmosphere there are variations which will change things (and those changes will be easily described by the laws of physics).

No! You put up the challenge, and now you want you change the rules to cover up. You mentioned the Earth, that is a unique physical object, and I assume you agree it has gravity. Even under "ideal" conditions, there must be such a force in order for the observer to jump.

That being said, still, winter mornings can be turbulence free to any measurable degree.

Or even at 100mph.
Where "to any measurable degree" is whatever meets your approval or observation.

Similarly with the caboose- he's (sort of) right. There WILL be (very minor) changes due to friction, currents or whatever. He HAS changed his tune and would (nice guy that he is ) admit that in an IDEALISED, THEORETICAL world where the air in the caboose is exactley still relative to the caboose, and our jumper jumped exactley vertical to the floor, he would return to exactley the same spot.

That's right. He has never used the expression "Cartoon Physics", ever.
Yes, small effects can add up. There are more. No hysteresis in your world?
Perhaps he is trying to tell you that because you ignore reality so that it can be smugly replaced with an easily-digested idealised situation, is why you think the treadmill works? Do you think?

If glibly ignored, some of those ever-so-tiny-effects may become elephants? The elephant in the room of the friction to the belt, to but name one?

He knows his original contentions were wrong, he's trying to insert correct ones without us noticing.
Of course, if he's not saying that, he's just a dope.....

I don't see how he could have slipped anything by you.

 

[Dan O.]

Similarly with the caboose- he's (sort of) right.

No, he isn't right at all. In the caboose example, the measurement resolution was a chalk mark. None of the perturbations are significant on that scale. If humber could do the math he would know that.

 

[Modified]

Similarly with the caboose- he's (sort of) right. There WILL be (very minor) changes due to friction, currents or whatever.

True on the ground as well. I don't think that's what humber is saying. He actually thinks that if you throw a ball straight up in an enclosed vehicle traveling at constant speed, it will be flung to the rear of the compartment.

 

[Dan O.]

True on the ground as well. I don't think that's what humber is saying. He actually thinks that if you throw a ball straight up in an enclosed vehicle traveling at constant speed, it will be flung to the rear of the compartment.

That means that if someone "Jumped" up they would be thrown against the front of the compartment because the energy is coming from a different direction (in the humber universe only though).

 

[spacediver]

thing is, these minor fluctuations are simply noise from our point of analysis.

They won't cause currents in any one direction systemically, so the pertubations would be just as likely in one direction as another.

But this is again the new goalpost phenomenon...

Anyway, would very much like Humber to answer this excellent question:

Uh, yeah, that's exactly what we're saying. In fact:

A hobo wakes up in a boxcar. The door is shut. He can tell from the noise that the train is in motion (at a constant speed, on the level), but he doesn't remember where the train is going. There isn't any light leaking in from outdoors, but there's another hobo in the corner with a lantern. The boxcar is well sealed. Can you think of any way (without opening the door) that the hobo can figure out which way the train is moving? Like, by throwing things up in the air, bouncing them off the walls, stuff like that. In particular, if he tosses his hat, or some hay, straight up toward the ceiling and watches where it lands, will that give him a clue?

 

[spacediver]

True on the ground as well. I don't think that's what humber is saying. He actually thinks that if you throw a ball straight up in an enclosed vehicle traveling at constant speed, it will be flung to the rear of the compartment.

Nah, he's (at least currently) not denying that the ball is moving at the same speed as the vehicle, but he's failed to recognize that the air molecules inside the vehicle are also moving with the vehicle.

He thus mistakenly thinks that if you have a loose object in the vehicle, it will experience air resistance and slow down WRT the vehicle.

In humberverse, the ball would act normally in a moving car so long as there was a vacuum.

 

[RossFW]

Mach?

Totally irrelevant to True Air Speed. I spent around 600hrs in the last 12 months at M.85 or there abouts. If it was into 100mph headwind (which it frequently was) my groundspeed was 100mph less than my TAS. Period.

Of course, if he's not saying that, he's just a dope.....

Thanks, Chris. Apparently I needed that!!

 

[humber]

Uh, yeah, that's exactly what we're saying. In fact:

A hobo wakes up in a boxcar. The door is shut. He can tell from the noise that the train is in motion (at a constant speed, on the level), but he doesn't remember where the train is going. There isn't any light leaking in from outdoors, but there's another hobo in the corner with a lantern. The boxcar is well sealed. Can you think of any way (without opening the door) that the hobo can figure out which way the train is moving? Like, by throwing things up in the air, bouncing them off the walls, stuff like that. In particular, if he tosses his hat, or some hay, straight up toward the ceiling and watches where it lands, will that give him a clue?

I think my other post covers some of that, jjcote.

Do you not see that you are starving yourself of informationin order to make a completely anodyne world? Where there is no acceleration? No energy exchange? No dependency on anything?

Why? To convince yourself that "equivalence" works? Don't bother, it does. It's all taken care of because that is way the world is. "Equivalence" is a confirmation (a sigh of relief) that it isn't otherwise.
You might build mental models, leaving out the details so as to expose the important parameters, but you don't leave out the important parameters.

It is one thing to have idealized thoughts, but they don't actually work that way, because none of the real world components are "ideal".
You can't create a fully-functioning frame of reference, where the object is said to be traveling, from still air and a belt. As Dr Drela says, you can build a model to some arbitrary level of accuracy, but I doubt that he meant that you could build an arbitrary model.

 

[RossFW]

One more try-and I don't believe I'm doing this!!!

Humber, you seem to be down to saying that the treadmill is inaccurate because it's idealised and the world isn't.

Fine.

But how's this-

If the cart works on the treadmill is it a fair indication that it will work, with minor variations in performance for the differences between it and a "Real wind", in an actual experiment using actual, out side conditions.

If I take a while to read your reply, it's because I'm on the phone to Boeing explaining why they're wasting there time with that damned, idealised wind tunnel.

 

[humber]

Nah, he's (at least currently) not denying that the ball is moving at the same speed as the vehicle, but he's failed to recognize that the air molecules inside the vehicle are also moving with the vehicle.

Like ducks in a row...
What drives them forward? What makes air the pressure in the vehicle?

He thus mistakenly thinks that if you have a loose object in the vehicle, it will experience air resistance and slow down WRT the vehicle.

With all those molecules lined up, can anything move?

In humberverse, the ball would act normally in a moving car so long as there was a vacuum.

Oh, we wouldn't leave out the ducks!

Aah, a ballistics and turbulence free world.

Not the back of the car, no. Do you think you may have missed the point right there?
That the way the jumper is not coupled to gravity in the same way as the air, may make you think that a treadmill where the road is not only the road, but the power of the wind, might just be a little bit different from a balloon in a car?

So, you scoff at my "naivety", but you just demonstrated, that you do agree, that KE is important, and air is important, and acceleration is important and that air resistance does slow thing down?
You do agree, though you don't say it, that the Earth is the reference frame.

If you ignore enough differences, your "equivalent" model might not be so equivalent after all.

 

[spacediver]

don't wiggle out of this one humber. We posed a question to you to test your conceptual understanding of some basic physics, and you are harping on about treadmills and equivalence.

Answer the question, can the hobo gain any useful information about the direction the vehicle is traveling in without visual access to the outside world.

It's a simple YES or NO.

 

[RossFW]

that KE is important

KE is a relative value, it varies with the observer.

and air is important?

the air in the cabin is not moving

and acceleration is important

Nothing is accelerating in the direction of the cars motion

and air resistence is important

only if you are moving relative to the air which, in the dirrection of travel, no-one is.

but the power of the wind, might just be a little bit different from a balloon in a car?

Nope. If you are travelling at the same speed as the wind, it is EXACTLEY as if there is no wind at all.