Positron Cannon

Biodata

Appearance

The cannon is roughly the size of a microwave: a boxy machine with a solid cylindrical front section about the size of a volleyball. Its shape has been compared to an enlarged camera 8.

• Its construction incorporates a CRT picture tube; external components include power-supply modules and control circuits 6 50.
• After its first recorded activation, it smelled burnt and its original label had burned away 8.
• On a later worldline, it acquired a flattened dent on top while stored in the university warehouse 48 49.

History

Film Club member Yan Rui found the device in an old box and activated it at 6:05 p.m. on March 17 while it pointed toward the transformer distribution box outside the club window. It ran briefly, damaged the building's wiring, and caused a power outage. At that same moment, Jiang Ran sent a text that arrived three days in the past. The Student Union subsequently confiscated the cannon as a prohibited electrical appliance 6 7 15.

Jiang Ran, Qin Feng, and Cheng Mengxue kept the Film Club active so they could retrieve it. Qin Feng found that its power-supply module had burned out while its unfamiliar core components appeared intact. He repaired it, and the trio used it to reproduce the past-directed message on March 25, triggering a worldline shift 7 8 9.

Qin Feng later added external controls for selecting a message's destination by year, month, day, and hour. Following another worldline change, Jiang Ran found the cannon confiscated again. He retrieved it with Chi Xiaoguo, discovered the dent it had sustained in storage, and began studying how to repair it without damaging the CRT core 25 29 48 49 50.

Operation and Limits

• Message transmission: The cannon is aimed at the transformer distribution box while a phone sends a text nearby. The trio's account is that the resulting interaction creates a short-lived “Spacetime Black Hole” that carries the phone's radio signal into the past. Qin Feng disputes that the device actually fires a positron beam, despite its name 9 15 16.
• Transmission window: It runs for approximately 0.7 seconds before overloading. Sending must occur within that interval; the team's manual gives a maximum of 70 Chinese characters per message 9 29.
• Recovery: After overloading, it must remain powered off for 20 hours and receive a replacement capacitor before another use 9 15.
• Destination: Its initial setting sent messages three days into the past. Changing the focusing strength and beam density allowed the team to target other times; higher power also increased the risk of burning out the wiring or device 15 25 29.
• Core uncertainty: Qin Feng avoided dismantling the modified CRT tube because its workings were unknown and he could not be sure it could be reassembled. His improvements focused on external circuitry 9 15 30 50.
• Use restrictions: The trio later agreed to send messages no further than 30 days into the past, require unanimous approval and all three members' presence, and keep the device secret. These were their rules, not a stated technical limit of the cannon 29.

Notable Uses

• First controlled test: Sent “Test, test” three days into the past and changed the worldline 9.
• Xu Yan's rescue: Enabled a warning to the trio's past selves about her impending drowning 11 13 14.
• Change of sender: Cheng Mengxue sent a message using her own phone, showing that Jiang Ran did not have to be the sender 16.
• Cheng Mengxue's exam: A message sent nine days back helped her pass a calculus retake 25.