Koyaanisqatsi

Ok, granted, not that much, compared to the mass of the Eartrh and the Moon (to achieve balance); the low amount of upper atmosphere traffice; etc., but a thought struck me that I figured only you guys/gals could address.

How much mass in geostationary orbit will result in competing tidal shifts (with the moon) and what other gravimetric influence can we expect from an extrapolation of current and projected norms (in regard to space "junk")?

Granted, we're nowhere near anything remotely "cause for concern," but at what point should there be "cause for concern" and what are the counter-measures envisioned, if any?

In other words, at what point (in relation to Earth's mass) would an accumulated amount of space "junk" effect the Earth in any adverse manner, if ever and will orbit breakdown take cae of it before it reaches a possible critical level, assuming this has been accounted for in NASA (and other like insitution's) projections?

Yggdrasill

The junk in orbit has limited effect upon tides, even if the mass in question had been anywhere close to something that would affect the tides. This is because the mass is not concentrated, it pulls the water in billions of different directions and counteracts itself. There could be cause for concern if we start building space-stations several kilometers across (think deathstar), or if some strange fenomenon deposited a large asteroid or moon in orbit around the earth. There are a lot of things that could solve the problem, we could nudge the object into the atmosphere using nukes, we could attach a cable that extends into the atmosphere (which would pull it down), we could assemble some engines on the object which would push it into the atmosphere. The cable system already exists for bringing down obsolete satellites, but I'm not sure how far-spread it is.

What is more important is the increased possibility of getting hit by something in space as a result of space junk, it is a lot more difficult to counter. If it is evenly distributed it would become a problem when the effective gravity on the surface has been significantly reduced. (That isn't going to happen.) If it isn't evenly distributed it could become a problem at a few percent of the moon's mass. <- (An educated guess...)

Volker.Doormann

You can calculate the zenit or nadir tidal force Fy of satellites using the formula

Fy = 2g * (Y/E) * (r/y)^3

While g = gravitation of earth, Y = mass of satellite, r = radius of earth , y = distance from center of earth to satellite, E = mass of earth.

You can compare the tidal forces of a satellite with the tidal force of Sun Fs resp. Moon Fm by computing

Fs = 2g * (S/E) * (r/s)^3 and Fm = 2g * (M/E) * (r/m)^3

while S = mass of Sun, s = distance to Sun, M = mass of Moon, m = distance to Moon.

Volker