_For one-way signals such as television, a transmission delay of about one second obviously makes little or no difference. But for two-way conversations on the telephone, where there is rapid back-and-forth talking, even this tiny amount of time delay may be a problem. And then again, it may not be. There have been a lot of experiments to find out something about this delay problem, and these have given us a lot of different answers. Work is still going on, and there is still much to find out. In this chapter, we tell you about one small, early experiment. Its results were not conclusive, but they should give you one example of how to set up and carry out a typical experimental study on human behavior._ [Illustration: _Typical circular satellite orbit: r is distance from center of earth to satellite; R is radius of earth._] How a Synchronous Satellite Would Work For our purposes, we will not be concerned with all the problems of launching a synchronous satellite into its proper orbit. But you may be curious why we know that this orbit must be 22,300 miles high. It can be calculated by using two basic formulas from elementary physics. From Newton’s Law of Gravitation we know that the velocity, _v_, of a satellite moving in a circular orbit[5] will be _v_ = √((_gR_²)/(_r_)), where _R_ is the radius of the earth, _r_ is the distance from the center of the earth to the satellite, and _g_ is the acceleration due to gravity (_see diagram above_). We also know that this velocity must be _v_ = (2π_r_)/(_T_), since the distance the satellite travels to complete an orbit is 2π_r_, and _T_ is the time of one complete revolution. Thus we have the equality √((_gR_²)/(_r_)) = (2π_r_)/(_T_), and, solving for _r_, we get _r_ = (_gR_²_T_²)/(4π²)(^⅓) Since we are interested in a synchronous satellite, _T_ in this case will be 24 hours. We can now find _r_ (using _g_ = 32 feet per second per second and _R_ = 3960 miles), and then obtain the distance _r_ - _R_, which will be 22,300 miles. By using our previous formulas, we also can find the velocity of a satellite moving in this orbit, which will turn out to be _v_ = 6870 miles per hour. [Illustration: _One possible method of using synchronous satellites. Signals from New York (N) to Paris (P) would go via satellite S₁; signals from New York to Calcutta (C) would go via satellites S₁ and S₂._]