If a phone call were to be made between two planets that are affected by time dilation, excluding any dilation signal between the phones, several things would happen due to the time difference between the planets:
Time Difference: The planets experiencing different levels of time dilation would have their clocks running at different rates. For example, if one planet is closer to a massive object and experiencing stronger gravitational effects, time would pass more slowly there compared to the other planet. As a result, a minute on one planet may be equivalent to several minutes or even hours on the other planet.
Communication Delay: The time dilation would introduce a significant communication delay between the two planets. When someone speaks on one planet, their voice or signal would need to travel to the other planet, which could take a longer time due to the time dilation effects. This delay would increase as the time dilation factor between the planets becomes larger.
Time Desynchronization: Due to the time dilation, clocks on the two planets would gradually drift apart, leading to time desynchronization. Suppose there was an initial time synchronization between the two planets at the start of the phone call. In that case, over time, the clocks would diverge, and the time on one planet would become significantly different from the other. This would create challenges in coordinating activities, scheduling events, or even maintaining accurate timekeeping records between the two planets.
Relativity of Simultaneity: Another effect of time dilation is the relativity of simultaneity. Events that are perceived as simultaneous on one planet may not be perceived as simultaneous on the other planet due to the time difference. This could lead to confusion or miscommunication when referring to specific moments or events.
In summary, a phone call between two planets affected by time dilation would encounter significant time differences, communication delays, time desynchronization, and potential confusion regarding the simultaneity of events. These effects arise from the fundamental principles of relativity and the different rates at which time passes in regions with varying gravitational fields.