Rockets Need to Push Against Something

No. Rockets don't need to push against anything to propel themselves.

Don't feel bad if you got this wrong. We heard one of the stars of "Mythbusters" flub this concept. He calls himself an expert, but this makes us wonder -- an expert at what? He was trying to propel a boat with jets of compressed air. It wasn't working too well so he said he was going to point the jet's blasts toward the water so they would have something to push against.
This seems to make sense. But for 500 years we have known it's wrong, thanks to Isaac Newton's discovery of a principle of nature called Third Law of Motion. This describes the fact of nature that for every action there is an equal and opposite reaction. You've experienced this if you have every fired a gun and felt a recoil. The bullet is the action and the push against your shoulder, actually the gun trying to go the opposite direction, is the reaction.

But it doesnt' have anything to do with guns. Exert a force in one direction and there's an opposite force in the other direction. In the case of the rocket, the gas exploding out the back is the action, like the bullet, and the movement of the rocket in the opposite direction is the reaction.

Its a good thing rockets don't need to push against somthin' because space is basically filled with nothin' and space exploration would be impossible. Then we'd have to recall all those satellites and spacecraft we've sent up for having succeeded under false pretenses.



GreenSmile said…
maybe that is why they call it rocket science if some people just can't get it. action/reaction is pretty basic.
Tim Parz said…
This is wrong. I experimented with rockets to see if this was true or not. I put an air sheild on rockets so that they Can't push against air and they do Not propell. I open the air sheild and the rocket take off. This proves Rockets do indeed need to push against air to propell.
Tom said…
Good for you! An experiment is the way to find out things. But you have to compare your experimental results against other people's. When they don't match maybe the experiment was flawed? Also, if rockets have to push on air how canthey work in space where there is nothing to push against?
Tim Parz said…
They do not work in space further than 400 miles above the Earth. And i don't believe in NAZI NASA's claim of walking on the Moon.
Tom said…
The Russians, Chinese, ESA...they're all lying? Why?
C. Luther said…
Because Tim is just smarter and wiser and less sheep-like than everyone else in the world, Tom. Obviously.

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