https://www.youtube.com/watch?v=D-v_K1k8Se0&feature=share
I had a looooooooong discussion with one of my friends today... for some reason he could not grasp this concept... maybe I explained it to him wrong... be that as it may... I don't think I can do it any better... Hope the remarks help someone, along with the clip...
Everything is ACTION-REACTION.... there is no ACTION WITHOUT AN EQUAL AND OPPOSITE REACTION.
A boat/submarine/fish/man can swim in water because of the resistance the water(fluid-liquid medium) gives him(buoyancy/density are intrinsic)...
A bird/bee can fly because of the resistance the fluid(a gas in this example) know as air offers to the bird's beating wing... On the same principle the planes(jet or blades) and helicopters can fly, or the rockets... the air(fluid) around them offer enough resistance that the objects can propel themselves on the resisting fluid in which they are immersed and surpass the density deficit and 'fly' trough the fluid...
Now... what do you think will happen with the bird if you put it in a PERPETUAL (next to) ZERO pressure chamber - a VOID chamber a.k.a. a VACUUM chamber? Can the bird still fly? How about the plane? how about the jet plane? How about the helicopter? Can any of those still fly without a fluid environment and a fluid's resistance? What will happen to the buoyancy? Will it rise or will it drop to zero? And now the BIG question... WHAT WILL ROCKETS DO? Will they still be able to move? Are they gonna break the ACTION-REACTION laws of physics? How will they be able to move in a perpetual Void of interplanetary space? WHAT WILL OPPOSE THEIR ACTION so that they can move??? WHAT?!?!?!?!?!
Clarification:
Negative Pressure - a fancy word for the difference between two environments with different pressures, in which, the environment with lower pressure is considered 'negative pressure'.
VOID - is the TRUE ZERO PRESSURE SYSTEM ENVIRONMENT - there can be nothing lower than ZERO... just like ZERO DEGREES KELVIN... be mindful of that. (ZERO atoms and molecules of fluid)
VACUUM - the Vacuum is, ACTUALLY, THE EFFECT of the VOID... the ZERO PRESSURE ENVIRONMENT(theoretical or practical)
A technical detail - the pressure Travels from Higher to Lower pressure environments in an attempt to equalize and balance the difference of pressure. So, in essence, it is not that the VOID, actively, sucks the pressure out of any system in open contact, but the higher pressure system(gaseous fluids in this example) will rush to fill the whole VOID space(infinite space), giving the appearance of a VACUUM EFFECT. The VOID stays unchanged. And if the SPACE is INFINITE so must be the nature and potential of the Void(with it's Vacuum like effect) - to remain infinitely VOID regardless of any quantity of fluids anyone would put into it.
'Space may be the final frontier but it's made in a Hollywood basement' - Red Hot Chilli Peppers
Very good question. It's simple answer, but we were brainwashed.
When the gas comes out the tail if the rocket it does not need to push against anything. It's not like a bird or jet that is moving air to push itself forward. A rocket is a chemical reaction that creates it's own gas. The gas moving in one direction pushes the rocket in the other. Equal and opposite.
gas coming out the tail of a rocket is the same effect as a bullet coming out the barrel of a gun.
recoil.
A rocket would work if it fired bullets and yes guns do work in space even. The gas escaping pushes against the rocket. Gas goes in direction A Rocket goes in opposite direction B. Equal and opposite reaction. The mass of the rocket (and remaining fuel) is what the gas produced by the fuel pushes against not the vacuum of space. You have to think of every part of the rocket as separate not one object pushing against space.
get your friend to pick up something heavy. hopefully not breakable and in an open space. have him throw the heavy thing away from him very hard and have him notice which way he is pushed. action, reaction. i also like the answer that everittmickey gave with the recoil. it is a very good illustration.
the "pushing against" occurs when the rocket's explosive exhaust pushes against the tail of the rocket. the exhaust is the reaction mass. the matter that makes up the exhaust is the reaction mass. the exhaust is a gas and can not act as a compressor against the spacecraft. jumping off the earth is equivalent to you and your feet being the exhaust and the spot on the earth where your feet touches it being the nozzle on the spacecraft. you don't need to push against the air to push against the earth and the earth doesn't need to push against the air to push against you. it's inertia does that. in the nozzle example the gas released pushes against the nozzle. in the the ion thruster example the ions are pushing against the mass driver on the spacecraft. the force is not pushing against the external environment. it is the mass of the particles pushing against the mass driver. the mass driver does not rely on pressure. it relies on a powerful electromagnetic field pushing ions away from the mass of the craft. the fire hose example is even easier. perhaps you have heard the phrase pushing rope. the water coming out of the hose, once it leaves the hose no longer has any ability to push against the hose because it is liquid and can not act as a compression against the hose. it is in the act of leaving the hose that it pushes against the nozzle creating the reaction force.
so, in space, ACTION-REACTION laws are suspended? is that what it is proposed?
nope, not sure i can explain it any more clearly. rockets never did work by pushing against air. the mass of the exhaust pushes against the mass of the rocket. this balls out physics guy is misleading you. try finding every other video you can on 3rd law stuff and watch them. you'll get it. it is nothing to do with pushing against the atmosphere. in space or not in space.
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