For example, what is the spread of WeChat qq SMS? Why do people get curious and ask for an explanation as soon as they send it out?

It is propagated by electromagnetic waves from 800mhz to 2.4ghz, and the propagation speed of electromagnetic waves is the speed of light, plus conversion and enhancement in the repeater tower. The current form is also the speed of light. It is all done in an instant, and the main delay is the relay station, not the broadcast process. Current and electromagnetic waves travel at the speed of light, and light can run around the earth seven and a half times a second, so the propagation delay can be completely ignored. The common general delay is 1 sec to several seconds, which is mainly the second-order delay caused by processing filtering and enhanced distribution when the signal passes through the signal tower and the operator server.