The game field is the consensus of BTC. So, what is a field? Newton brought us universal gravitation, but he left the source of force to the smart readers. Maxwell used the concept of a field to abstractly express the source of electromagnetic force. Then, what is the source of the field? This leads to the two greatest theories of the 20th century: relativity and quantum theory. The interactions between matter form the geometric spacetime of relativity. The interactions between particles form the quantum field. But all of this is still just theoretical descriptions of nature—we haven’t reached the stage of constructing tangible proof.