studiot

Start at the beginning and try to see where all these websites you refer to have hidden the analysis. You have a complete rocket standing there on the ground ready for launch. What do you know and what do you want to calculate ? In other words what are you variables ?

So what's your response to what I actually said please ? The calculus of variations is totally unnecessary for this. It barely reaches into ordinary differential equations and can even be done without them.

I'm sorry but this glib oversimplification of several important points in Physics gives entirely the wrong impression. You have made several outrageous statements, with not a shred of support. Do you understand, for instance the difference between the angular momentum and spin quantum numbers ?

Er...? Variational calculus ? That's second year university stuff. I said simultaneous equations. In the UK you start learning about these around 12 or 13, actually before you learn any mechanics. But it isn't one simple equation. You can't calculate anything with one simple equation as you have more an one variable involved. How many equations do you require to solve for 3 variables ?

I am trying to help you, not criticise so try not to react in haste. I didn't say you didn't study Mechanics. Quite the opposite in fact. I said you missed something important, when you did study Mechanics. No, I agree a rocket is not static, but it can be quasi static otherwise known as steady state. But that was not the point. Static systems are in general simpler than dynamic ones, indeed one way to solve synamic ones is to reduce them to static or quasi staic ones. Please read carefully my point about simultaneous equations before you reply. Even the simpler static systems may need simultaneous equations for solution.

The problem with this is that it is in opposition to one expression of a fundamental point of relativity. Notably that the is no preferred point of view. Discussing only from the POV of the own frame of a subject, is a preferred point of view.

Then consider the possibility that you have a fundamental misunderstanding of Mechanics, that goes back nearly to your first studies of the subject. Your basic misunderstanding is this: A rocket is a mechanical system. There is no 'the equation' for this system ie one single solitary equation. A very common situation in Mechanics is that you need to consider more than one equation to solve a system. You need a set of simultaneous equations. This is the case with the rocket system (rocket for short). All that is happening is that you have an equation for the whole system and another one for part of the system. When studying Mechanics you learn this very early on when calculating loads on a static system and reactions via forces and moments.

OOps! I inadvertently gave g the wrong units. It should of course be, m/s2 - not m/s Many thanks to @Sensei for pointing this out.

You are correct. It is a coincidence. But Genady is also correct that the units don't match. The numbers match in the case of Earth, but not in the case of say, Jupiter. Let us look at some figures. For Earth Dearth = 1.47 x 1011 metres - distance to sun For Jupiter Djupiter = 7.41 x 1011 metres - distance to sun For Earth gearth = 9.81 m/s For Jupiter gjupiter = 24.79 m/s For both G = 6.7 x 10-11 N-metre2/ kg2 So for Earth gearth / G = 9.41/ 6.7 x 10-11 = 1.47 x 1011 kg/metre2 which is the same number of kg/metre2 as the Earth is metres away from the sin. BUT For Jupiter gjupiter / G = 24.79 / 6.7 x 10-11 = 3.7 x 1011 kg/metre2 which is quite different numerically than 7.41 x 1011

I'm not interested to your (other) argument. But I would ask if this is not because of the sentiments put so fully in the words of the Hymn "Immortal, Invisible, God only wise" Definitely implying that God is central to that religion.

Very clever, John, +1 I would like to point out that not only is Nature v Nurture not balck and white, but the issue of belief or disbelief is also non binary. I didn't catch on to Joh's argument until he potently either. For myself as a youg child I just accepted the idea more or less as I was taught. About 12 I worked out for myself the logical inconsistency of an omnipotent being and for a few years I followed the debate. In doing so I never came across any conclusive pros, but the cons began to build up. Then I decided on my third way. I just don't care. I don't need a man in a long black or white garment and a pointy hat to tell me what's what. I can work that out for myself. So I asked myself "would it make any difference to how I go about thing ?". Since my self answer was no I came to the conclusion that the isue was irrelevant to me.

Thanks for a more detailed explanation. +1

What do you mean gas, minerals ? You can put solids or liquids into an 'ignition tube' and heat in a bunsen burner flame. Or you can put some on a carbon block or in a crucible and heat with a blowpipe. As others have said to heat gas you normally pass an electric discharge through to make it glow. Using an ignition tube is a chemical test or tests. Does it give off a gas?, does it burn? does it decompose totally? If so what colour changes are there and so on. Glow discharge methods require some sort of spectroscopic analysis of the light of the glow (which may only be visual).

All electric charges possess an electric field around them. When they move their charge interacts with both their own electric field and the electric fields due to any other charges. Moving electric charges induce a magnetic field. We call this effect electromagnetism. This field changes according to the movement of the charges concerned. This distinguishes it from 'permanent magenetic' fields which do not change with movement (apart from moving bodily themselves with the magnet) But as Genady says the term is also used in a more general manner to cover all matter electrical and magnetic.

cuts off the electricity of the brain and then turns it on? That is an exaggeration, if you read the article carefully. Our whole bodies, run on electricity. And the squirrels have an unusually low residual state in hibernation. Electricity is not turned on and off like a light switch, it is an integral part of body processes.

I have another comment that I doubt you will like. I have a soft spot for analogue systems. Discussion so far, as so often these days, has concentrated on discrete systems. Nature has no such requirements and uses both analogue and discrete systems as she feels appropriate. The large majority of Man's early constructs have been inherently analagoue. It is only comparatively recently that we have tried to fit everything into the discrete mould, often developed from analogue beginnings. Both analogue and discrete approaches have pros and cons, but discrete ones have an inherent limitation not suffered, in principle, by analogue ones. So it would not suprise me if one day artifical consciousness was generated from an analogue system.

The equipartition theorem no less. +1

Well microwave radiation is certainly a large, wide ranging subject in its own right. So I was going to ask you "In what context are you interested in microwave emitters and their construction ?". But clearly microwave emission is happening all the time around us or there would be no microwaves! If the EmDrive works at all, which I doubt, it is all in the tranmission aspect (ie waveguides). So pony up and focus your question please. I take it you are not interested in the biological aspects I mentioned. Note the heating effect of microwaves depends on indirect heating of water or sugar molecules which in turn heat the whole material in you microwave, but as Seth noted these are not the sort of microwaves you generate from pea sized emitters. Here are some real figures and a calculator. https://www.everythingrf.com/rf-calculators/cavity-resonance-frequencies

I was answering your question how EM (no particular frequency) radiation could impart translational energy to molecules. Changing the state from solid to liquid or liquid to gas seems to me to be adding KE to the molecules by the bucketful, since they are then rushing about in a way they did not before the irradiation. Perhaps I misunderstood you.

Laser vapourisation ? https://www.mayoclinic.org/tests-procedures/prostate-laser-surgery/about/pac-20384874 Laser welding and other uses of lasers as heat sources to melt materials ?

Heaven help us if some fools combines this self awareness with that shape shifting robot that melts itself to get outof jail. https://www.bbc.com/news/av/world-us-canada-64668021 Oh sorry they already did that in Holywood - Terminator II.

The idea of unchemists doing unwork fantastic. Reminds me of that great letter about setaside that was doing the rounds about 10 years ago.

Yes, why not ? The smallest microwave wavelenght is 1mm so a quarter wave antenna is only 0.25mm. Many insects have antenna that are in the 0.25 to 5mm length range and some are known to respond strongly to microwave radiation. Equally artificial antenna of this size can easily be constructed.

I wish I could give plus one for each line of this. Just so funny.

OK Both, I believe. Misner, Thorne and Wheeler include description and references in their chapter on gravity waves. But I would say my most important point concerned was the sheer size of objects involved, seeing as you seem to be interested in what possibilities there are for manipulating gravity. You also need to be careful to distinguish between working in space and time separately v spacetime. A wave equation is an eqaution connecting space and time. The ordinary (linear) wave eqaution allows separation of these two variables, by virtues of the linearity. Gravity waves occur in spacetime, but as I said before linear ( ie linearised versions), so the model is essentially non linear. This arises because the solutions to the wave equation, being a partial differential equation, contain arbitrary functions, and it is usual to choose the simplest. But a gravity wave equation will have additional complicated (even complex) relativistic conditions that must also be met. Considering your antenna: Antennas are passive devices (and only thre dimensional at that), which means that they do not generate the required wave, that has to be done by somethng else, as does any modulating signal. So you would still need all the paraphanalia already under discussion. Also since the waves are actually 4D, what do the 'lobes' of such an antenna look like in 4D ? Directional antennas are not impossible in theory because there is already a phenomenon called gravitational lensing (which again involves the big guns) under observation.