Does electricity travel at the speed of light?
There is a simple answer and a complicated answer.Simple - no. The electrons in a wire that form the electric current move very slowly. The second hand on a watch moves faster than the electrons. The actual speed of electrons is about 1.2 inches per minute in a typical, home lighting circuit.Complicated - The effect, or electromagnetic wave, of electric current moves at nearly, but not quite, the speed of light.Think of a tube full of balls. If you push one more ball into the tube, the ball at the other end comes out immediately. This is why turning on a light switch has an immediate effect. The electrons in the wire all push on each other and thus the light goes on instantly.In theory, electricity moves at the speed of light and in practical application, this is true.However, in practice it is slightly slower because the electron from atom #1 has to cross the space to atom #2 in order to bump its electron over to atom #3 in the wire. This tiny delay adds up over very long distances and the speed of electricity over millions of miles turns out to be very close, but not quite the speed of light.
What causes the 3 - 4 second audio delay between two separate newscasters communicating over great distances when radio waves travel near light speed?
There are several causes of latency in transmission beyond the simple case of latency due to the actual transmission itself. The fact is that it is not possible to just simply transmit the image through some kind of array of mirrors in it's original form without some significant distortion of the image.Rather the image is captured by a camera and then encoded in some form for transmission this by necessity requires some amount of processing time this is true even in the case where bandwidth is no object and the stream can be encoded directly in raw format, more often than not bandwidth is limited and comes at a cost as such the encoding will usually involve some degree of compression to optimize bandwidth use. Efficient encoding of video can't be done on individual frames in isolation as the encoder needs to examine a series of frames which requires some buffering of the data at the source before encoding.During transmission especially when transmitting over a wireless channel such as a satellite or microwave link but even when transmitting over fibre links some redundancy is added to the transmission encoding of data to allow for a certain amount of bit errors during transmission, this needs to be processed at the receiver and then the video stream needs to be buffered for several frames to enable the decoding process. Buffering is also performed to allow for transient interference or temporary reduction in bandwidth just like for any other video stream transmission.In general the problems would probably be more common where the remote broadcast sources is in a remote location away with poor infrastructure and using a satellite was the only option. If there were a suitably equipped terrestrial TV station on the ground within line of sight using a terrestrial microwave link and routing the stream to the remote station via high capacity fibre over the internet would have a far lower transmission latency, typically no more than 120 ms between sites connected by direct fibre connections like would be the norm for a well equipped TV station or other large business sites.Even if transmitting straight up and straight back down to the point of origin to a satellite in GEO on the other hand is a 72,000 km round trip requiring 250 ms in reality this would be longer as the path will not be vertical but at an angle meaning the distance from transmitter to receiver is further.