In a room in a residential building in the center of City, Krystal, who was sleeping, was awakened by a rapid phone ringing. Krystal opened her sleepy eyes, took out the phone from under her pillow, pressed the button, and a video call message that had been recorded a long time ago appeared in front of her eyes.
Because the distance between Mars and the earth is too far - the closest distance between the two planets is more than 50 million kilometers, it takes more than three minutes for electromagnetic waves to complete a one-way journey - which means that the distance between the two places is more than 50 million kilometers. The minimum communication delay is more than six minutes, so it is impossible to communicate in real time between the two places, so if people have communication needs, they usually record the information and send it. Now the information Krystal received is such a video message that was recorded in advance and then sent.
