Action and reaction forces that are equal and opposite arise when one structure engages with another. I could see how that was so in most scenarios but puzzled over how it delivered jet engine thrusts in thin air and rocket thrusts in a space vacuum. We will return to action and reaction later in this blog.
I remember at school drawing force diagrams. Even in dynamic situations they had forces that balanced and enabled my doing the required calculations. A typical scenario was as per the diagram of a cyclist following a curved path. On it centrifugal force equaled centripetal force and weight was balanced by the opposing normal thrust up from the ground.
A few years later at college our mechanics lecturer asked us to draw just such a diagram and showing only the forces that acted on cycle and rider. Without exception everyone drew a diagram like that shown. We had come together from various parts of the country but all of us had learnt of centrifugal force and not one of us had questioned its reality.
The lecturer explained that there was no centrifugal force. Centrifugal force was a fictitious force created to establish a mathematical force balance. Centripetal force was the only horizontal force between road and tyre and it was what enabled the rider and cycle to accelerate away from their would be straight line velocity.
I tell the above tale because mathematics can be a wonderful tool but it sometimes doesn’t truly represent reality. On the above diagram we also show the weight of bike and rider acting toward the earth and most described as a force of gravity. Newton saw gravity as a force that pulled objects down whereas Einstein saw no such force. He said if you step off a building you are removing the force that held you up and went on to explain gravity in his general theory of relativity. It was about massive bodies warping the energies of space time
Einstein was right in saying there is no external downward force acting on a body stepping off a building. However he failed to realise that a desire for the earth and its energies existed within the particles of the body stepping off the building. Whilst on the building its particles exchanged energies with the body and held it up. Once off the building the body particles were free to seek earth energies.
The attraction toward the earth is on a per particle basis and so in the relatively steady earth energy environment results in an accelerating motion independent of particle numbers (mass). Attractions between particle structures are not limited to massive bodies. See how raindrops cling to window panes. The smoothness of the pane enables many raindrop particles to energy engage with the pane particles. Raindrop particles can energy benefit from staying together but can also energy benefit moving toward earth energies and or by interacting with window pane energies. Such conflicts will often break them apart but in a beneficial way.
The earth in space is a particle structure travelling at speed and in a direction that would take it away from the sun, but its particles desire photon energies and the sun as a particle structure is releasing photon energies. Consequently many earth particles are attracted toward the sun, drawing the other energy linked particles of the earth with them. Energies collected and distributed by the earth are soon in excess of particle needs and many of earth particles now want away from those photon excesses. Particle energy desires are at the heart of the orbital motion of earth about the sun.
We humans are energy structures just as the chair we sit on is an energy structure. When we sit on it, its energy structure reacts to our energy structure and we feel its pushing up on our bottoms. Neither the chair nor our particles want the higher photon energy levels associated with their getting too close and so the closer particles get the more highly they energy resist the approach. The difference between us and the chair is that our brains receive from body sensors information related to those energy interactions.
We feel how powerfully particles can energy resist their contacting one another when we fall or jump from a height. contacts. The desire for particles to remain apart is what damages a car’s structure.
The same sort of photon energy exchanges that stopped our particles from further engaging with the chair hold particles apart within structures whilst their linked energy desires hold them strongly together. When you try to break or bend a structure you are opposing particle energy desires.
Energy interactions that bind or draw particles together or which are intent on parting them are strong and related to just how unwanted or how much better the energy environment can be.
In the case of our jet and rocket engine’s mentioned earlier the particle photon energy releases caused by the burning of fuel has particles seriously wanting to be away from one another. Exhaust particles close to the engine structure are thrusting away the engine particles just as much as the engine particles are thrusting them away and all of the other particles. Action and reaction are happening more so in the engine itself than between the engine exhaust and the air.