12. Fiber & Satellite Latency

When calculating how long it will take for light or any electromagnetic wave to travel a certain distance, we generally use the speed of light, which is approximately 299,792 kilometers per second in vacuum. However, the speed of light slows down when passing through different media such as glass or fiber optic cables. In fiber optic cables, the speed of light is about two-thirds of its speed in a vacuum, or about 200,000 kilometers per second.

For the purpose of this response, let's look at the following distances:

The average distance from London to New York is approximately 5,585 kilometers.

The average altitude of a geostationary satellite is about 35,786 kilometers above the Earth's equator.

If we are calculating for fiber optic cables:

London to New York: 5585 km / 200,000 km/sec ≈ 0.028 seconds or 28 milliseconds.

For a geostationary satellite, we need to account for the signal going up to the satellite and back down again, thus:

London to satellite and back: (35,786 km * 2) / 299,792 km/sec ≈ 0.238 seconds or 238 milliseconds.

These are very rough estimates and only cover the travel time of light or an electromagnetic wave. They do not account for any additional delays that might occur due to the processing and retransmission of signals at each end, or routing delays as signals pass through various network devices. For instance, it takes more than just the propagation delay for a signal to travel through a fiber optic cable - there are also delays associated with processing and routing the data.

Lastly, it's also important to note that the routing of data over the Internet often doesn't follow the most direct geographical path. For instance, data traveling from London to New York might not take a direct path, but instead might be routed through various Internet backbone networks, potentially increasing the travel distance and time. Similarly, signals to geostationary satellites aren't sent straight up, but rather must be sent at an angle, further increasing the travel distance.

TLDR; because of the distance and speed of light and other electromagnetic it will in theory take 28ms from just the distance and because satellites are at geostationary orbit just from the distance you get 238ms.