7 hours ago, qqwertzde said:

for this experiment.

Do you happen to know if that experiment was ever conducted with a completely non conductive object such as a plastic cube or maybe a rubber stopper or something like that?  I've seen levitation of conductive objects but was unaware of the frog et al levitation.  I wonder why this hasnt been done on larger scales.  I guess we're still searching for the room temp superconductor.

but also - I agree with Chock.  We dont really know how gravity works.  I would say both gravity and time are mysteries.  We see the effects but not not the source/science.

5 hours ago, sightseer said:

 

but also - I agree with Chock.  We dont really know how gravity works.  I would say both gravity and time are mysteries.  We see the effects but not not the source/science.

 

 

Einstein gave us a pretty impressive explanation for gravity in terms of massive bodies warping the geometry of space-time, for which there is very impressive evidence.

 What we don't have is a quantum gravity theory, which we need to understand the centre of black holes and the hot dense state at the "hot big bang". 

The "fundamental" aspect of gravity that Mr Chock points to is, I would say, the quantum description of gravity which is currently lacking.

Mass is concentrated energy. Thus its energy that is impacting the geometry of space-time around a massive body.  How energy warps space-time is perhaps the mystery, and perhaps we can explain that when we have a quantum theory of gravity. 

 

 

 

Edited February 4, 20224 yr by martin-w

4 hours ago, sightseer said:

but was unaware of the frog et al levitation

 

All materials are diamagnetic. Everything, all living things and all objects have molecular magnetism. Am atom in a magnetic field creates its own magnetism.

Your rubber or plastic cube would still be levitated in a powerful enough magnetic field. 

Edited February 4, 20224 yr by martin-w

6 hours ago, Chock said:

That's what I'm referring to, i.e. we understand what gravity does, but you'll note that NASA use the same words as I did in writing 'we don't know what it is in any fundamental way' when discussing what gravity is.

 

4 hours ago, sightseer said:

Do you happen to know if that experiment was ever conducted with a completely non conductive object such as a plastic cube or maybe a rubber stopper or something like that?  I've seen levitation of conductive objects but was unaware of the frog et al levitation.  I wonder why this hasnt been done on larger scales.  I guess we're still searching for the room temp superconductor.

but also - I agree with Chock.  We dont really know how gravity works.  I would say both gravity and time are mysteries.  We see the effects but not not the source/science.

First to the simple question, the experiment with the frog. The frog is actually not a conductive object, and it is obviously not a metal such as iron that is "ferromagnetic". Speaking in a very simplified manner, ferromagnets react strongly to a magnetic field and can be turned into magnets themselves. There is a whole bunch of other forms of magnetism (it is a very complex subject), but most normal materials are "diamagnetic". They can't form magnets and react very weakly to a magnetic field. But still, they do react, and if you apply a strong enough magnetic field, a sizeable force will develop. The frog is a diamagnetic object. 25 years ago, when Andrei Geim performed this experiment, high-temperature superconductors were still pretty young and they can create very large magnetic field (around 10 Tesla). That is strong enough to make a small object like a grasshopper or a tiny frog float. However, the fields we can produce are nowhere near powerful enough to let larger objects float in the air. 

If you are interested in levitation, you might enjoy the Levitron. You can either buy one or build one yourself:

 

Now to the difficult part: what does it mean to "know" or "understand"? My question to Chock was actually aimed at this point. When I asked what he means with "understanding on a fundamental level", he did not really answer the question but referred to NASA. Now, NASA is certainly an authority, and the text Chock quoted isn't really wrong, but it also does not "define" what it means to know.

And that's for a good reason: this question is an extremely difficult one to answer and philosophers have spend the last couple of millennia coming up with a variety of answers to it ( https://en.wikipedia.org/wiki/Epistemology ). In fact, it is easy to reject any form of knowledge (my favorite joke: http://consc.net/misc/univ-joke.html ). Plato already came up with the allegory of the cave, according to which nothing we see is actually real, only a reflection of what goes on behind us. Bishop Berkeley formulated the idea that the world isn't real at all, it all just happens in our minds (a precursor to The Matrix). Yes, you can consistently make such a claim, it is just not particularly useful. That's where science excels: coming up with an explanation for a large number of experimentally observed phenomena based on a minimal set of assumptions (axioms). These theories are thoroughly tested in experiments and very useful for developing new technology.

When it comes to scientific theories ( https://en.wikipedia.org/wiki/Scientific_theory ), our knowledge is always preliminary. Everybody knew the Earth was flat until Pythagoras, and much later Copernicus. Everybody knew that Newton's theory described everything until the 20th century, when Relativity and quantum mechanics took over. Newton's theory is still useful for engineering and much more, but it has a limited range of validity and fails to describe very small and very fast objects. Likewise, no gravity researcher really expects that Einstein's Relativity will remain unchanged forever, and the graviton is only one hypothesis how it could be modified.

 I stand by my assessment that there is probably no other theory in history that provided us with so much "understanding" as Relativity. It only needs two fundamental axioms:

- the speed of light is the same in any inertial reference frame (i.e., for any observer who is not accelerating)

- heavy mass (the one appearing in Newton's law of gravity) and inertial mass (the one appearing in Newtons' second law) are the same. This is a simplified form of the equivalence principle.

These two ideas, plus a number of technical assumptions that are heavily based on math, are sufficient to explain the formation of the solar system, galaxies, and cosmology. They explain time dilation and length contraction of fast objects, and why clocks are moving at different speed when they are closer to a massive object. They explain black holes, gravitational lensing, and gravitational waves. It just doesn't get much better than this🙂

Peter

Nobody disputes that we understand the effects of gravity (well, perhaps apart from flat earthers) but this is entirely different to knowing and being able to explain the physics behind what causes these effects. This is not a philosophical point, it's a scientific gap in our knowledge.

A caveman could understand the effect of an aeroplane starting to fly when it reaches a certain speed by simply observing that it lifts off at that speed, but this does not mean he could explain why it was happening from a physics standpoint. For that he would need to know and understand that it's a pressure differential caused by the fluid dynamics of molecules spreading out further above the wing as they speed up and spread out, so reducing in pressure causing the higher pressure air under the wing to push the wing up.

This is analogous to what I'm talking about with gravity; even though we can observe and predict the behaviour of gravity, we don't know what is going on that causes these effects.

Edited February 4, 20224 yr by Chock

1 hour ago, Chock said:

A caveman could understand the effect of an aeroplane starting to fly when it reaches a certain speed by simply observing that it lifts off at that speed, but this does not mean he could explain why it was happening from a physics standpoint. For that he would need to know and understand that it's a pressure differential caused by the fluid dynamics of molecules spreading out further above the wing as they speed up and spread out, so reducing in pressure causing the higher pressure air under the wing to push the wing up.

This is analogous to what I'm talking about with gravity; even though we can observe and predict the behaviour of gravity, we don't know what is going on that causes these effects.

I think gravity is much better understood than aerodynamics. Your example is excellent: Does an airplane fly because of Bernoulli's principle? That's what we have been taught when we were young, but it actually falls far short of explaining it. Bernoulli's principle employs energy conservation, and as any pilot knows when anxiously looking at the fuel gauge, energy is not really conserved in an airplane. A more complete understanding of aerodynamics rests on Newton's second law and particle dynamics, which also explains the role of vortices at the end of wings and why winglets are useful.

However, turning your argument around: that would still not explain why an airplane flies since it requires you to understand the concept of a "force". What is a force? Something that causes an acceleration? Then, what is acceleration? The answer to that question is still not fully understood, but let me stop there.

A force is actually a rather abstract notion and really only defined through its action on a moving body (through its "effect"). We may have an intuition now what a force is, but the ancient Greeks did not ( https://en.wikipedia.org/wiki/Zeno's_paradoxes#Arrow_paradox ). Relativity is actually much more elegant than Newton's theory, it almost entirely relies on geometry alone. A lot of its effects can be explained in a very intuitive way. But if you dig deeper (like with aerodynamics), you're opening a can of worms (in the form of differential geometry).

2 hours ago, qqwertzde said:

I think gravity is much better understood than aerodynamics. Your example is excellent: Does an airplane fly because of Bernoulli's principle? That's what we have been taught when we were young, but it actually falls far short of explaining it. Bernoulli's principle employs energy conservation, and as any pilot knows when anxiously looking at the fuel gauge, energy is not really conserved in an airplane. A more complete understanding of aerodynamics rests on Newton's second law and particle dynamics, which also explains the role of vortices at the end of wings and why winglets are useful.

However, turning your argument around: that would still not explain why an airplane flies since it requires you to understand the concept of a "force". What is a force? Something that causes an acceleration? Then, what is acceleration? The answer to that question is still not fully understood, but let me stop there.

A force is actually a rather abstract notion and really only defined through its action on a moving body (through its "effect"). We may have an intuition now what a force is, but the ancient Greeks did not ( https://en.wikipedia.org/wiki/Zeno's_paradoxes#Arrow_paradox ). Relativity is actually much more elegant than Newton's theory, it almost entirely relies on geometry alone. A lot of its effects can be explained in a very intuitive way. But if you dig deeper (like with aerodynamics), you're opening a can of worms (in the form of differential geometry).

If you want to freak someone out on that subject, who knows about aeroplanes and understands about pressure differentials on a curved wing, ask them to explain how the split flap on the DC-3 increases lift. 🤣

5 hours ago, Chock said:

This is analogous to what I'm talking about with gravity; even though we can observe and predict the behaviour of gravity, we don't know what is going on that causes these effects.

I'm not sure how much more of a fundamental understanding of gravity we can have than the fact that spacial distortions cause it.  It is no longer a mysterious attractive "force".  Space itself is changed by masses, and those changes in turn affect other masses.  Pretty fundamental.

Before Einstein, many physicists believed in the ether. which was an invisible medium of transmission for electromagnetic and gravitational forces.  Well, according to Relativity, space itself is the ether where gravity is concerned.

Now, a good example of what you are talking about is the electric force which causes "action at a distance".  Why do like charges repel and opposite charges attract?  I haven't come across a good explanation of this.

One last point.  We actually already have anti-gravity propulsion.  It is based on Newton's third law of motion - every action produces an equal and opposite reaction.  So if I expel compressed gas with enough force, the container holding the gas will move in the opposite direction.  If I rotate a propeller and push enough air molecules downward, I can cause a craft to hover in the air and literally defy gravity.  Now, here's the real question - why does a reaction produce an equal and opposite reaction in the first place?  What is the mechanism behind this effect?  Why would accelerating particles in one direction cause propulsion in the opposite direction?  Personally, I believe that , like gravity, it is related to spatial distortion, but I haven't come across any proof of this.  Too much math involved! 

Dave

Edited February 4, 20224 yr by dave2013

16 minutes ago, dave2013 said:

I'm not sure how much more of a fundamental understanding of gravity we can have than the fact that spacial distortions cause it.  It is no longer a mysterious attractive "force".  Space itself is changed by masses, and those changes in turn affect other masses.  Pretty fundamental.

 

Its not as fundamental as it could be though Dave. Mass is energy and in the case of gravity its really energy that is distorting spacetime. But why does energy distort space time? That's the question. There's clearly an interaction between the energy that represents the mass of the attracting body and spacetime itself. 

I mean its not as simple as Einstein's famous rubber sheet analogy, where a weight is placed in the middle to represent a planetary body (or any mass) and the rubber sheet represents spacetime. If it were that simple you wouldn't get attractive gravity. The rubber sheet analogy is a two dimensional representation of four dimensional space time, which is hardly a good analogy. If it were that simple you would get displacement and a repulsive force, not an attractive force. Clearly its not that simple and the rubber sheet analogy doesn't describe what really going on.

 

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Why do like charges repel and opposite charges attract?  I haven't come across a good explanation of this.

 

Magnetic fields are made of photons. Its the constant exchange of photons from a charged object to another object.

 

 

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Now, here's the real question - why does a reaction produce an equal and opposite reaction in the first place?

 

I think that's a question for the quantum mechanics experts. 

Edited February 4, 20224 yr by martin-w

22 hours ago, Chock said:

Those 'tic tac' UFOs, which a US Navy F/A-18 filmed, may possibly be using such stuff to propel them but again this is just something we either don't know, or if we do know, then is massively top secret stuff. If the classic 'flying saucers' which people report do indeed make massive changes in trajectory pretty much instantaneously, as is often claimed, this does sort of point toward the notion of them being able to use gravitational control of the space they are occupying to 'move around' without incurring massive acceleration and deceleration stresses, but again, we just don't actually know.

 

Yep, as you say "as is claimed". That's all we have, what people say, no real evidence, no proof. But if the phenomenon is as described, it would point to some sort of gravity manipulation and Star trek style inertial dampeners. 

8 minutes ago, martin-w said:

I mean its not as simple as Einstein's famous rubber sheet analogy

I'm not a physicist, so I don't wish to belabor this discussion too much. 

Mass is not literally condensed energy.  There is the concept of mass-energy equivalence, but this is not the same thing.  As a mass accelerates its momentum, a form of energy, increases.  Stated another way, its inertial mass increases, but it doesn't actually get bigger.   

Anyway, how a mass actually changes the space around and within it is, I agree, not fully understood.  Certainly, the rubber-sheet analogy is an extreme simplification of what's actually going on.  Yet the fact remains that the space is indeed distorted, bent, curved, etc. in some way which affects other masses, and the closer they get the greater the effect.  The spatial distortion even affects photons, which are practically massless, but they are a form of energy, so it follows that gravity, or spatial distortion, also affects energy.  

Anyway, I don't think there is any other better explanation for what causes the gravitational effect than Einstein's theory, but it is, after all, still a theory, so who knows if a better explanation will someday be proposed and proven to the point that we have a new theory?

Dave

May be I'm just being pig-headed.  That in combination with lack of (generally accepted) knowledge like magnetic fields consisting of photons.

So...I find it fascinating that nothing we know of is actually solid until we get down to the point where we can't prove they are not -- the sub atomic level.  The entire known universe is varying densities of varying particles.  Atoms are not solid - most of their occupied 'space' is 'free space' (nothing? something? energy waiting to be something?).  No thing we encounter is solid -- its all atoms held together by forces.  All substances are varying collections (different atoms) in different patterns (molecules) in varying densities (gas, liquid , solid, plasma I guess)... and this amazing varied collection of stuff doesnt even stop where we think there used to be nothing -- deep space...now we have dark matter -  which may be the same stuff deep inside an atom for all I know... or maybe its a totally undiscovered set of elements that we can't see because in our so called reality, Hydrogen is the first element... I really don't know.

But I have been told that Newtonian physics cannot explain the workings of an atom and Ive also been led to believe that we have never actually seen the workings of an atom - its all just probability tables and mathematical models that appear correct --- to us.

So, it may be pig headed of me but I just get the feeling that there is some major piece missing that when or if we ever do see it we will look back and say "Oh yeah, we used to think that"

a question:  At what percent of the speed of light does radioactivity cease? 

  I think it must.  If atomic clocks which are based on the half life of a Cesium atom run differently when in different situations, half life must change.  

Also - To me a frog is somewhat conductive just as any living thing which contains water would be.  But I had forgotten that all atoms can act like mini magnets so I can see where a rubber or plastic cube would also levitate.  Its just that , since we do not really know the inner workings of the atom even yet,  I don't feel that we can say we have a great understanding or knowledge of gravity or time.

I'd still love to hear a science/physics based explanation for ghosts and esp or premonitions.

1 hour ago, dave2013 said:

Mass is not literally condensed energy.

 

E = MC^2

Yes it is. Unless someone more knowledgeable tells me different. 

 

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Stated another way, its inertial mass increases, but it doesn't actually get bigger.

 

Think you might be confusing mass and matter. Not the same thing. 

 

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 Yet the fact remains that the space is indeed distorted, bent, curved, etc. in some way which affects other masses, and the closer they get the greater the effect.

 

Yes! But why? Why does mass/energy warp spacetime? 

 

35 minutes ago, sightseer said:

The entire known universe is varying densities of varying particles.

 

Reality is actually about fields. Multiple interacting fields. The electromagnetic field is associated with photons, the electric field is associated with electrons, the quark field is associated with quarks, the Higgs field is associated with the Higgs Boson. Particles are merely excitations in the field.

 

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Atoms are not solid - most of their occupied 'space' is 'free space'

A fallacy. Atoms are not mostly empty space. The electron can't be said to be in one place, its more like a cloud within the nucleus. If electrons were little tiny billiard balls they would spiral in to the nucleus. 

 

Quote

 

 

The view that an atom mostly consist of empty space stems from the old times when Bohr's atomic model (as a miniature planetary system in which electrons surround the nucleus) was the best picture of what an atom is like.
But there are no electron particles moving around an atom. One cannot view the electrons as little balls moving inside a molecule and somehow avoiding falling into a nucleus. Such a configuration would be unstable. The nuclei would attract little charged balls until they fall into them.
But it is very well understood why atoms are stable - the ground state is a delocalized stationary state of the electrons in an atom, a state living indefinitely (unless the nucleus decays). In terms of quantum field theory, the space is filled by the electron field. The resulting electron density can be calculated by quantum mechanics. Indeed, this is one of the outputs chemists are interested in when they use quantum chemistry packages like GAMESS.

 

https://www.mat.univie.ac.at/~neum/physfaq/topics/touch.html

 

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I'd still love to hear a science/physics based explanation for ghosts and esp or premonitions.

 

Most scientists would say that there is no decent evidence for either. 

53 minutes ago, martin-w said:

Particles are merely excitations in the field.

Can you elaborate and still keep it at or near laymen's terms?  What is meant by 'excitations'?  Excited by what? Are particles a tangible thing to any degree?  

53 minutes ago, martin-w said:

its more like a cloud within the nucleus.

a cloud of what?

53 minutes ago, martin-w said:

Most scientists would say that there is no decent evidence for either.

They never look.  They spend great deals of time and money searching for what they assert are new and different particles.

I've never seen a quark but I have firsthand experience with ghosts, esp and premonitions.  I think the golden rule for any scientist is to keep an open mind. 

Edited February 4, 20224 yr by sightseer