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I frequently observe people arguing (on this very web site) about the question if falling is a mode of flying or not. It appears to me that the majority of people have a strong opinion that it is not.

Surely it is a matter of definition. I made the effort to look it up in a number of online dictionaries. Most sources provide many possible options to define flight, like Merriam-Webster:

1a : an act or instance of passing through the air by the use of wings

but it continues with

2a : a passing through the air or through space outside the earth's atmosphere

Wikipedia tried to put everything into one paragraph:

 Flight is the process by which an object moves through an atmosphere (or beyond it, as in the case of spaceflight) without contact with the surface. This can be achieved by generating aerodynamic lift associated with propulsive thrust, aerostatically using buoyancy, or by ballistic movement.

Flight may be aerodynamic, propulsive, aerostatic, or ballistic.

When one throws a ball, the ball is flying. It flies until it hits anything else than air. Why would it be different if the ball is thrown upwards, or pushed downwards, or just dropped?

In my understanding, falling is just a very special case of flying. Is this correct?

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  • $\begingroup$ By this definition, so is hovering? $\endgroup$ – user3528438 Nov 10 '19 at 20:46
  • $\begingroup$ @user3528438 I would say so. It would be strange if a helicopter stopped flying while it is hovering. $\endgroup$ – bogl Nov 10 '19 at 20:50
  • $\begingroup$ Can you link to one of the specific discussions you mentioned on this site? As you said, this comes down to what definitions you use and I'm not sure what the context is. As written, I don't see a lot of point in defining the terms formally but for all I know it is important for some people. $\endgroup$ – Pondlife Nov 10 '19 at 21:08
  • $\begingroup$ @Pondlife I'm afraid not. These discussions happen in the comments which are not persistent. The context is the usage in this site, and clarifying terminology should be in everybody's interest. $\endgroup$ – bogl Nov 10 '19 at 22:06
  • $\begingroup$ There's a reason we use the term "sustained flight" to get rid of all the ambiguity. $\endgroup$ – Sanchises Nov 10 '19 at 22:40
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Since falling is just the final result of a ballistic arc if you let it go long enough, and ballistic arcs are considered "flight" per the Oxford Dictionary (as in the ballistic arcs of balls, spacecraft, arrows, etc being considered "flights"), then technically, a falling object is in flight.

You could give it just the tiniest lateral push when you drop it so it goes down with a slight ballistic curve; in the end, no different from driving it laterally so it has horizontal energy/inertia with a high velocity that exactly counteracts gravitational pull, and give it a vacuum so it can do that indefinitely - a satellite - , the only difference being that and the ball being the location in or out of the atmosphere and energy put into it.

In other words, orbital vehicles, baseballs, bullets, are all "falling" and are technically in flight, and so is a ball you drop straight down... if the Oxford Dictionary definition is what you want to use.

In my own airplane, if I push over with just the right elevator input, and go zero G, my plane is now in a ballistic arc. The wings are superfluous, for a few seconds anyway, and my plane is "falling", just not straight down. So if you accept that in that condition it is still "flying", the falling is flight.

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No, falling is not flying.

Sources:

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    $\begingroup$ When I read your answer I thought it was a Douglas Adams reference :-) $\endgroup$ – Pondlife Nov 10 '19 at 23:01
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    $\begingroup$ I was expecting the video from Toy Story, Falling with Style. $\endgroup$ – Ralph J Nov 11 '19 at 6:20
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    $\begingroup$ @Pondlife Even better! I made my post into a community wiki and hope that everybody will add their favourite "falling vs flying" reference from popular culture. $\endgroup$ – DeltaLima Nov 11 '19 at 9:01
  • $\begingroup$ I pleases me that this answer has more upvotes than the obtuse rationalizations offered on both sides of the argument. Sometimes we forget common sense definitions. Flying is the exact opposite of falling: It is the ability to overcome gravity to travel through the air. Webster and others back this up... $\endgroup$ – Michael Hall Nov 11 '19 at 20:06
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A fall is the collective sequence of deterministic states describing the instants between an initial condition (any initial condition, i.e. either releasing an object from a height into the air, releasing an upwards-thrown ball, etc.) and a final condition/state, which are predictable in their entirety, based on Physics. If you take everything into account (air composition, density, object mass distribution, center of gravity, gravitational acceleration and its variation with height, air resistance, centrifugal force, Coriolis force, Euler force, everything), then you can calculate the final conditions from the initial conditions with very high fidelity. It doesn't matter that the mechanics are spectacularly complex and the necessary information is huge, in volume. In Physics, you can usually work your way out of complexity by simulating, which still provides an adequate degree of accuracy when adequately modelling the states. The difference lies, therefore, in the inertness of the falling object!

In contrast, when in flight, no amount of intermediate instance state information (even given the initial conditions) can allow an external observer to predict a state that could be rendered as final. In fact, only short-lived predictions can be made for a flying object by anyone not actively influencing the object.

In short, when you see something falling, you always know what happens next (or soon after). Ball lands, projectile drops, plane crashes, etc. According to this, a flying squirrel flies because you cannot predict the landing point at any point after its jump and while airborne. Only the animal knows what it's trying to achieve and it's actively exploiting Physics to make it happen (after much training, of course!).

So, falling is flying only... in the face of science!

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  • $\begingroup$ The final state of a glide (flight) can be predicted by holding conditions constant, simply ask the squirrel to do its best to hold them throughout its flight. $\endgroup$ – Robert DiGiovanni Nov 11 '19 at 5:38
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    $\begingroup$ Well, this is "bending the rules" a bit. But technically, holding conditions constant is not flight, it is falling... with style! $\endgroup$ – Vector Zita Nov 11 '19 at 18:09
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What is the definition of falling? Downward component to trajectory? Ballistic trajectory? Zero motion in horizontally forward direction? Zero aerodynamic force acting perpendicular to flight path, i.e. zero lift? Vertical speed component negative and increasing rather than steady-state? A non-zero acceleration component acting perpendicular to the flight path and also acting at least partially earthward, not skyward? (I.e. semi-ballistic trajectory due to insufficient lift.) Or something else? We can't answer without knowing which we mean. Some have suggested that if an aircraft is sinking at a constant rate but the nose is pointed above the horizon, then that is in some sense a "fall". Many would not agree.

Is an orbiting spacecraft "falling", according to common sense? And how about according to your chosen definition of "falling" from the list above? It's not so simple to define "falling", is it. Is the earth "falling"? Is the earth "flying"?

Implicit in this answer, is a hint that the question may not be a very useful one, because it is insufficiently constrained. But this may shed some light on possible answers nonetheless.

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  • $\begingroup$ You don't need my definition of falling to answer this question, because I mean any of them. From the ones you have listed, is there one that is not a particular case of flying? $\endgroup$ – bogl Nov 11 '19 at 7:53

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