ever watch the blue angels jeannie. cool huh, how they hold formation right close to each other. you know what blue angel two, three and four are looking at in that four ship diamond? think they're watching their altimeters? airspeed indicators? vertical speed indicators? uh uh. their eyes are glued on the leader. only one relative speed matters to each one. and though the formation may be traveling at five hundred knots, the relative speed of the four blues is ZERO knots. the sun moves at the same speed as the galaxy but relative to the stars that make up the galaxy much, much slower.



no it isn't but the entire system consists of it's own gravitational force. those three tricky swabbie fly guys in blue could begin to barrel roll around their commander and the commander could fly to paris or fly to rome and his three minions would arrive with him. a little dizzy perhaps on arrival but they'd be there. did they follow the leader? not really. no moreso than one molecule of h20 follows another in a bucket being carried from the well to the kitchen. one molecule adheres to another and that one to another and so on as a system of molecules we refer to as water. the blue angels are a system made up of jet fighters. the solar system.............well, you get the idea.

If only the sun's gravity is all that is at work, then the planets would just crash into the sun. In space, there is only movement. There is no "up" or "down" so the the term "falling" is meaningless.

If something in orbit is simply falling towards the mass it orbits, then why hasn't the moon fallen and crashed on the earth?

And also if this is the case, then all the near miss asteroids that have passed between the earth and the moon would have started orbiting or would have crashed on the earth.

not meaningless in the least. falling does not necessarily relate to up and down and it is a term used by physicists to illustrate in simple terms what happens in orbit. no, the sun's gravity is not all that is at work. never suggested such.



simply because the moon orbits at a speed that keeps it in it's orbit.



not so. asteroids that pass between earth and moon are moving at a speed in excess of escape velocity. those that do impact earth are on a trajectory that puts them in contact with earth's atmosphere which slows them to less than orbital speed. then the earth's gravity rules and CRASH. like these easy ones.

jr is right, you have to consider the weight of the asteroid, the speed, and the gravitational pull of the earth or larger body. it is the same reason a bullet will travel in a straight line until it slows down enough for gravity to pull it down.

good annalogy with the bullet, moe. a bullet fired fast enough at the right trajectory would escape the atmosphere and enter an orbit about the earth too. the appollo space craft had to accelerate from launch to just over seventeen thousand mph in order to enter low earth orbit. that's why it had such big, honkin' motors. lol. then after retrieving and docking with the lunar lander it would accelerate further to about twenty three thousand mph which was escape velocity. from there it would continue to accelerate as the moon's gravity began to overcome earth's and finally the astronauts would slow the aircraft down so as not to fly right on by the moon and enter orbit. reversing the process would get them back home.

here's a question; we hear often about astronauts living in 'zero gravity'. but is there really such a thing as ZERO gravity?

Actually the bullet is falling towards the center of the Earth at 32 ft/sec squared the instant it leaves the barrel of the gun. Speed has nothing to do with it. The bullet never travels in a straight line, it travels in a ballistic curve.

dead wrong. if a bullet is fired from a height of four feet and doesn't hit the ground for four seconds how does that equate to falling at thrty two feet/second/second? it fell at an average rate of one foot per second and it hardly feel thirty two feet in the first second as you suggested. it requires drag to slow it down enough to fall to earth. that is the reason for the balistic curve. but suppose you fired the bullet on the moon? would it travel in the same balistic curve and impact the moon's surface in the same distance? if i drop a feather in earths atmospere will it accelerate to thirty two feet per second in the first second? of course not. drag comes into play no?

You couldn't be more wrong. This is simple high school physics. Look it up.

If a bullet is fired from four feet and is not pointed UP, but horizontal, it will take EXACTLY the same time to hit the ground as one dropped from four feet. The only exception to this is the curvature of the Earth must be taken into account for complete accuracy.

Why does it orbit at the same speed all the time, and why do we only see one side of the moon? That seems unrealistic.

What keeps it moving? What keeps it from hitting the earth or flying off into space?

A bullet eventually slows down and falls. Why not the moon?

not so. what you describe is the force of gravity on the bullet but not the vertical velocity of the bullet. are you really saying that a sniper's bullet fired from two thousand yards will take no longer to impact the ground than the same bullet dropped from shoulder height? what you have not considered is the speed of the bullet and how the atmosphere affects it. fire a bullet straight out in front of you at a height of four feet and at the same time drop a bullet from four feet and tell me that they will both hit the ground at the same time. or make it easier on yourself. throw a baseball or a rock and drop another. then ask pudge rodriguez to throw a baseball as hard as he can as though he's gunning down a-rod attempting to steal second and you throw a ball at the same time and tell me that pudge's cannon shot wasn't still sailing into center field when yours hit before clearing the infield dirt.

an airplane in straight and level unaccelerated flight has the same force of gravity acting upon it as does the bullet or the feather along with the force of drag, lift and thrust. so why does the airplane not fall to the ground accelerating downward at 32'/sec2? the reason is lift counters gravity equally the force of lift being exerted on the wing through the fluid dynamics created by the air flowing over and under it. reduce thrust without changing pitch angle of attack and you lessen the force of fluid dynamics over the wing and the force of gravity exceeds lift and the aircraft decends. but the descent is readily controlled and the airplane will not accelerate downward at 32'/sec2.

a sky diver will accelerate at 32'/sec2 only until he reaches terminal velocity which is dictated by the density of the atmosphere and his body position. the same forces act on a bullet as acto on the airplane or the skydiver although the initial thrust is momentary where the thrust of an aircraft is available as long as their is fuel to burn to maintain thrust.

why does a glider stay aloft for much longer when released from a tow plane than a brick dropped at the exact moment from the same tow plane. the reason is that the glider has much better aerodynamic characteristcs than does the brick just as a speeding bullet has better aerodynamic characteristics than a bullet with zero horizontal speed. you're simply still dead wrong. and the curvature of the earth has no more effect on the bullet than it does on an aircraft flying from san francisco to paris as far as the effects of gravity are concerned.

newtons law is why the moon orbits at the same speed all the time jeannie. quite simply, there is nothing to slow it down. an object in motion will remain in motion.

we only see one side of the moon because the moon rotates on it's axis at a speed that keeps the near side twoards us as it orbits the earth. a bullet slows down because of the earth's atmosphere and unlike a rocket a bullet has no continuous thrust to overcome drag. see my aerodynamics 101 lecture above. lol. no atmosphere affects the moon.

Yes I have heard that explanation about why we can only see one side of the moon. --That it rotates on its axis at a speed that keeps the near side towards us.... BUT I have not heard any explanation on HOW it does that. How and why does it rotate at that exact speed and how and why does it rotate just so perfect that we can only see one side of it? It seems unlikely that its just coincidence.

so it's an unlikely coincidence. you asked, i answered. doesn't change what is because it's an unlikely coincidence. how it rotates on it's axis at the given speed is also newton. doesn't matter if motion is straight line, rotational, whatever. once put in motion it maintains that motion.

You don't even understand high school physics! Here is a link to Newton's Cannon which explains it.

http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html

Gravity acts on the object all the time at the same rate no matter what the objects speed.

Your explanation of ballistics is so bad, I don't even know where to start. To hit anything with a gun you have to aim UP to allow for how far DOWN the bullet will FALL due to the force of gravity. It doesn't fall from drag, it falls due to gravity ... and only gravity ... 100% of the time. Drag only slows the velocity of the bullet.

so why did tha cassini space craft not fall to earth due to gravity if speed has nothing to do with it? did you try throwing that rock and timing it's flight compared to one you dropped? will a 22 cal. bullet strike the ground at the same time as a nato round fired along the same trajectory? will your toss to second base hit the ground at the same time pudge's does. will a feather fall to the ground in the same time a coke bottle does in anything other than a vaccume? if you think so then let's leave it that you and i understand physics in an entirely different manner. gravity does have an equal and constant affect on everything. that is why the moon stays in orbit. but the moon is not subjected to earth's atmospere, it moves in a vaccume.

But if what is put in motion maintains that motion why do our satellites eventually fall out of orbit?

Stating an observation is not the answer to the question why or how.

That is what I would like to know. Why and how.

But of course you believe that life in the universe was just an accident.

they don't all eventually fall out of orbit. orbits decay because some outside force acts upon the object in orbit. space lab was subjected to several hits from meteorites so it's speed was altered. we have communication satalites in geodesic orbit that are obsolete and unused which will be in orbit forever.



well we simply don't know the why and how of everything concerning the universe. but i'm not an astronomer or a physicist. i simply have an amature's understanding of those questions you asked. if you don't like or agree with what i understand, fine. but you asked and i answered to the best of my understanding on the topic.



i'd bet that i could say a believe nothing whatsoever several thousand times and people will still say i believe this or that. i don't recall ever using the word 'accident' in my replies here much less do i recall ever speaking my thinking on how life began. and yet you BELIEVE otherwise. so much for belief, huh?

You don't understand physics in a different manner. You don't understand it all. The items being discussed are at the high school level and I have an advanced degree. There is only one "physics" and the math is not that difficult.

The action of gravity is the same all the time (please review the website I just posted). The way any spacecraft deorbits is to slow down. This act doesn't affect the force of gravity, it just lets the trajectory hit the Earth like Newton's cannonball.

so what you are saying, MW, is the the velocity and wieght are meaning less? if you fired 2 guns set up exactly the same at the same time, 1 with a high power charge load, and one with a lower power charge load, they would both hit the ground at the same time and distance?

that's what he's saying. and he's said that if you were to drop a bullet from the same height as the guns were fired that too would hit the ground at the same time as the two fired bullets to boot.