There is a question out there which begs a further string of thought: “If a ghost can walk through walls, why doesn’t it fall through the floor?” Well, a “ghost” has no body, therefore no weight, so it cannot be affected by gravity. So, to begin with, a "ghost" hovering outside a window is therefore unaffected by gravity - so it is not a moving (falling) object or body.
However, there is another moving body to consider, and that is the Earth itself. Think. A “ghost” is a concept of a human spirit with no physical existence. This means that gravity, traction, friction, atmospheric pressure, etc. would have no effect on them. They wouldn’t be able to interact with the terrestrial environment at all – no stomping, no throwing things, no ghostly sounds, no apparitions.
The earth moves at a phenomally fast rate of speed as it circles the Sun. A “ghost” would be left behind in space in a matter of minutes as the Earth passed through its noncorporeal form. How fast does the Earth move through space? The average distance from the Earth to the Sun is about 149,597,890 km. So in one year the Earth travels a distance of 2Pi(149,597,890) km. That makes the velocity about: velocity = 2Pi(149,597,890) km/1 year Divide that down by 365 days in a year, and 24 hours per day, you get: velocity = 107,300 km/h or 67,062 miles per hour. At 67,062 miles per hour a ghost would have little time to do anything except watch the earth moving away from it in space at a phenomenal rate of speed.
You wouldn’t be able to see, hear, or interact with any “ghost” because it would get left behind in space. If the “ghost” occupies a fixed point on a XYZ axis relative to a fixed point in space, then the Earth moves away from that point at almost 67,100 mph. Think about how fast a car racing past you at a hundred miles/hour is moving, and how it is near impossible to see anything of the car except a blur. At almost 67,100 mph the ghost couldn’t see or hear anything, nor could anyone see or hear it.
And it's even faster than that. The Solar system is moving away from the site of the Big Bang at well over a million miles an hour, so a ghost phasing into existence at the time of its death would be left behind in deep space, with no real clue on which way the Earth and its Sun had went. Also, our eyes work on the principle of generated or reflected light in order to see. A "ghost" has no physical body, therefore it could not be seen unless it could generate energy or light. If ghosts could do that they could appear routinely and talk to us directly. People who see "ghosts" are not seeing discorporated human spirits. Ghosts likewise could not see - light reflected off of physical objects would pass right through them, even if they could sustain a residual form. Every human eye works on the same principles of light reflection/refraction, therefore if you could see "ghosts" so could every other person in the world. We'd all see them, all the time.
Also consider how many human beings have existed on this planet over the last 100,000 years - the length of time that humans as a separate species have been estimated to have been in existence. That many people, that many souls, there'd be so many "ghosts" on the planet, from cavemen to ancient Babylonians to Romans to Normans to Mandarin Chinese to Napoleonics to Zulu warriors to Russian freedom fighters to German Nazis to modern day soldiers to the civilian populations of every culture on Earth that has ever existed. You wouldn't be able to sleep, drive, eat, go to the bathroom, etc. without ghosts watching you (assuming they could see).