Which type of electromagnetic waves is least suitable for long-distance communication because of the risk it poses human

What is the earliest point in the universe that we can observe? why can’t we see back further than this?

What is the name for the remnant of an asymptotic giant that has lost its shells? black dwarf white dwarf yellow giant black hole

An electromagnet is a device in which moving electric chargers in a coil of wire create a magnet.whats one advantage of using electromagnetic in devices