The message arrived at dawn. When the notification lit up in her inbox, Eunsu was asleep. The blue glow of the terminal beside her bed drew a small circle on the ceiling. Eunsu opened her eyes. The room was dark. A thin thread of streetlight leaked in between the curtains. The blue light on the terminal was blinking. Origin: Proxima. Transmission delay: 4.24 years. Eunsu's heart quickened. She reached out and took the terminal. The screen brightened. Sender: Hyunwoo. Eunsu's finger froze above the screen. Hyunwoo. A message he'd sent 4 years ago had arrived now.
Eunsu got up from the bed and went to the kitchen. She drank a glass of water. Her hands were shaking. She set the glass down in the sink and looked at the back of her hand. The trembling wouldn't stop. She placed the terminal on the kitchen table. The glow of the screen reflected off the table's surface. Eunsu sat down in a chair and opened the message.
'Eunsu. It's 11 at night here. For you it'll arrive some morning in 2059, I suppose. In Proxima time, I'm writing this on March 14, 2055. I got the last letter you sent. You sent it so long ago that the you of now is probably very different from the you back then. I've changed a lot too. The gravity here is 1.1 times Earth's, so at first my knees ached, but now I'm used to it. The photo you sent me — I still have it. Only. '
The message broke off there. After 'Only' there was nothing. Eunsu scrolled the screen down. There was no further data. She couldn't tell whether it had been cut off by a transmission size limit, or whether Hyunwoo had stopped there. Eunsu looked at that single word, 'Only.' The word sat in the middle of the screen. The strokes of the letters were sharp. Four years ago, in some room on Proxima, Hyunwoo's fingers would have pressed out this word. And whatever he had meant to write after it, he had stopped.
Eunsu set the terminal down and looked out the window. The sky at 4 in the morning was a dark blue-black. Stars were visible. Proxima Centauri was not visible to the naked eye. It was too faint a star. 4.24 light-years. Hyunwoo was at a distance that took light more than 4 years to cross. Eunsu had last seen Hyunwoo in 2051. 8 years ago. In front of the boarding gate of the emigration ship, she had held Hyunwoo's hand. Hyunwoo's hand was warm. Eunsu's hand was cold. Hyunwoo said,
“Wait for me.”
Eunsu nodded. Hyunwoo walked into the passageway. After three steps he looked back. He looked at Eunsu. He opened his mouth, then closed it. He turned again and walked on. Eunsu stood there until the passageway sealed shut. The metal door of the gate closed. The airtight seal sounded. The emigration ship's engines began to hum at a low pitch. The air grew hot. The floor trembled. The vibration rose up through the soles of Eunsu's feet. Eunsu's hand remained in the empty air. Cold air passed between her fingers.
For the 8 years that followed, the two of them exchanged letters at the speed of light. The interstellar communication infrastructure had been built in the 2040s. Three relay satellites were positioned in Proxima's orbit. Only text and low-resolution images could be transmitted. Voice and video were impossible, limited by bandwidth. Even the hours in which one could write were constrained by the angle of the relay satellites. By Earth time, from the 1st to the 5th of each month, 2 hours a day. Transmission and reception happened within the windows when the communication channel opened. On the dawn of the 1st of each month, Eunsu turned on the terminal and checked her inbox. In most months the inbox was empty. There was no predicting which month a letter would arrive. Depending on the orbital position of the relay satellites, the transmission delay varied by weeks. A dawn when a letter might come, or might not. Eunsu had to grow used to that uncertainty. Whether 'letter' was even the right word, Eunsu wasn't sure. 4 years to send, 4 years to receive. A single round trip took 8 years. The first letter Eunsu sent Hyunwoo, she wrote the night the emigration ship departed.
“Go safely. Contact me when you arrive.”
Hyunwoo's reply arrived 4 years later.
“I've arrived. The sky is red. The stars are big and close.”
By the time Eunsu read that reply, 4 years had already passed since Hyunwoo reached Proxima. If Eunsu sent a reply, Hyunwoo would read it another 4 years on. By the time Eunsu wrote her reply, the question Hyunwoo had asked in his original letter was already a 4-year-old question. And by the time her answer arrived, the question would have become one from 8 years ago.
Eunsu picked the terminal up off the table again. She read Hyunwoo's message from the beginning. 'I got the last letter you sent. You sent it so long ago that the you of now is probably very different from the you back then. ' The last time Eunsu had sent Hyunwoo a letter was in 2053. 6 years ago. What had she written in that letter? Eunsu opened her sent folder. July 3, 2053. 'Hyunwoo. It's been raining a lot lately. There are many nights I stay up in the lab. Sometimes your absence doesn't feel real. I'll send a photo. A sunset taken from the lab window. It's the color you used to love. '
Eunsu lowered the screen and stared at the ceiling. A letter sent by the self she had been 6 years ago. When she wrote it, Eunsu was 28. Now she was 34. In those 6 years she had changed labs, cut her hair, spent 2 years with someone who wasn't Hyunwoo, broken up with that someone, and become alone again. Was the Eunsu of 6 years ago the same person as the Eunsu of now? What Hyunwoo had read was a letter sent by the Eunsu of 6 years ago. Hyunwoo had written his reply 4 years ago. It had taken another 4 years for his reply to reach her. What Eunsu was reading now was a reply the Hyunwoo of 4 years ago had sent to the Eunsu of 6 years ago.
Eunsu turned on the kitchen light. The fluorescent tube flickered and came on. On the table sat the cup-noodle container from what she hadn't finished the night before. The broth had gone cold, a film of oil floating on top. She cleared it away and wiped the table down. The dishcloth was damp. She could feel the wetness between her fingers. She set the terminal in the middle of the table and opened a screen for a new message. The cursor was blinking.
What was she going to write? Every single character she typed onto this screen would fly 4.24 light-years. It would become light, cross the universe, reach Proxima's relay satellite, drop from the satellite down to the ground module, and arrive at Hyunwoo's terminal. Arriving 4 years later. 2063. How old would Hyunwoo be by then? How would the years on Proxima have changed him? What was the word he had meant to write after 'except'? Eunsu laid her hands on the keyboard. Her fingers wouldn't move.
Eunsu carried the terminal to the living room. She sat on the sofa. The cushions were old and badly flattened. A spring pushed against her back. The television screen was off. Her face was reflected in the black glass. The skin under her eyes was dark. Eunsu opened the sent folder again. She read from the first letter in order. 2051. 2052. 2053. Three letters, that was all. The letters from Hyunwoo were three as well. Six letters in 8 years. 4 years to each one. Eunsu opened Hyunwoo's first reply again.
"The sky is red. The stars are big and close."
Back then, receiving this line had made her cry. That Hyunwoo was alive, that he had reached Proxima, that he was looking at a sky. All of it was already 4 years old, but for Eunsu it became real for the first time in that moment. The night she got that letter, Eunsu lay in bed staring at the ceiling, trying to summon Hyunwoo's voice. The voice in her memory was blurring. She remembered the tone, but the inflection was faint. 4 years had been enough time to erase a voice.
The second letter arrived in 2053. 'The institute is finding its feet. I've been struggling because the plant cultures won't take. The mineral composition of the soil here isn't what we expected. At night Proxima hangs large above the horizon. A red light. It makes me think of sunsets on Earth. I still haven't gotten the sunset photo you sent. It'll probably arrive a year from now.' When Hyunwoo wrote this letter, the sunset photo Eunsu had sent was still flying somewhere across the universe. Reading it, Eunsu imagined Hyunwoo's daily life. The residential module of the Proxima settlement. The red sky beyond the window. Hyunwoo seated in front of soil-analysis equipment. Would he be wearing glasses? Before he left he'd said his eyesight was going. He had a habit of cleaning his lenses. The way he'd wipe them on the hem of his shirt, tilting his head slightly. Eunsu had loved that motion. What effect had Proxima's weak light had on his eyes? Eunsu set the terminal down and looked at the window. Light is fast, but 4.24 light-years was a long distance even for light. By the time the sunset Eunsu had photographed reached Hyunwoo, that Earthly sunset was already light 5 years old.
Eunsu got up from the sofa and went to the window. Dawn was breaking. The dark blue-black of the sky was shifting to a deep navy. Orange began to spread above the horizon. Eunsu lifted the terminal and photographed the view outside. Not a sunset but a sunrise. She saved the photo and went back to the message screen. The cursor was still blinking. Eunsu rested her forehead against the window frame. The glass was cold. When she closed her eyes, the feeling of holding Hyunwoo's hand at the boarding gate of the emigrant ship came back to her. The warmth between his fingers. The pressure of his palm. 8 years had passed, and yet that one sensation stayed vivid. Eunsu opened her eyes.
Eunsu began to write. 'Hyunwoo. I got your letter. What were you going to write after "except"?' Eunsu stopped and deleted the sentence. She wrote again. 'Hyunwoo. I don't know whether I'm writing to the you of 4 years ago or the you of now.' She deleted it. She wrote again. 'Hyunwoo.' There she stopped. Eunsu lowered her hands to her knees. Outside a bird called. Just one. A short cry. Eunsu placed her hands on the keyboard again. There was so much she wanted to say. She also knew that by the time those words reached Hyunwoo they would already be useless. Still, she had to write. If she didn't, only silence would be left. And silence, too, traveled at the speed of light. Eunsu's 6 years of silence had reached Hyunwoo 2 years ago. How might Hyunwoo have interpreted that silence?
Eunsu set the terminal down on her lap. Outside the window, the light was growing brighter. Eunsu met someone else in 2055. His name was Jiho. Jiho worked at the same research institute. It began with sharing lunch. Jiho's laugh was loud, and his hands were large and warm. When she first held Jiho's hand, Eunsu tried not to compare it to Hyunwoo's. The harder she tried not to compare, the more she did. Jiho's fingers were thicker than Hyunwoo's, his palm broader. It was a different hand. A different person. Eunsu leaned on that difference. When she was with Jiho, she didn't think of Hyunwoo. That was a comfort. It was a comfort to be with someone close enough to touch by reaching out an arm, rather than waiting for someone 4.24 light-years away. She spent 2 years with Jiho. They parted in 2057. Jiho said,
“You're here, but you're not here.”
Eunsu asked,
“What did I do wrong?”
Jiho looked into Eunsu's eyes.
“You didn't do anything wrong. Sometimes you look out the window. Not like you're watching the stars—like you're measuring a distance.”
Eunsu didn't answer. Jiho got up and put on his coat. The sound of the front door closing rang out. Eunsu sat at the table for a long while. She didn't deny it. She couldn't.
In all that time, she didn't write to Hyunwoo. For 6 years, ever since 2053. A few times she opened the terminal. She pulled up the message screen. She got as far as 'Hyunwoo' and deleted it. While she lived with Jiho, she kept the terminal shut in a drawer. Each time she opened the drawer, she checked that the blue light wasn't blinking. It meant there was no new letter from Hyunwoo. She hated herself for the relief. On nights when Jiho slept beside her, thinking about the terminal in the drawer felt like a betrayal. Checking the terminal was a betrayal, and not checking it was a betrayal too. During the 6 years of Eunsu's silence, Hyunwoo had received the letter the Eunsu of 2053 had sent and written back. That reply was what had arrived today. Hyunwoo still didn't know about her silence. Eunsu's last letter had reached Hyunwoo in 2057. If it was now 2059 by Proxima time, then Hyunwoo had become aware of her silence a mere 2 years ago. Perhaps Hyunwoo was waiting for her reply even now. Perhaps he switched on the terminal on the 1st of every month and checked the inbox. Perhaps he saw the empty inbox and switched the terminal off. Or perhaps he was no longer waiting. You could meet people on Proxima too. The settlement's population was 2,400. There were plenty of people around Hyunwoo's age. Eunsu could not deny the possibility that Hyunwoo was watching the red star in the night sky with someone.
Eunsu closed the sent folder and opened the inbox. Hyunwoo's third letter. The one that had arrived today. 'But.' Eunsu looked at that single word for a long time. But. But what? But I met someone too? But waiting for you is hard? But this is the last letter? Eunsu couldn't know. Only the Hyunwoo of 4 years ago knew. The Hyunwoo of now was another person entirely. Just as the Eunsu of now was different from the Eunsu of 4 years ago. Eunsu set the terminal down and looked at the back of her hand. The veins stood out more than they had 6 years ago. The hand Hyunwoo had last held and the hand of now were not the same hand. The moment Eunsu's letter arrived, the very same thing would happen.
Eunsu returned to the message screen. 'Hyunwoo.' The cursor blinked behind it. Eunsu wrote on. 'I got your letter. Let me be honest with you. By the time you receive this letter, I'll be 38. It's been 12 years since I last held your hand. In that time, I met someone else, and then we parted. The stretch without you was so long that I grew afraid of getting used to your absence.' Eunsu wrote on without stopping. 'I want to know what you were going to write after “But.” When this letter reaches you, tell me. If you still remember it then. It's all right if you don't. I don't remember exactly who I was 4 years ago either.'
'But this morning at dawn, your letter woke me from sleep. My heart raced. It was the same as when I held your hand 8 years ago. I've changed, and you must have changed too. Yet the moment your name appeared on the screen, I knew there was one thing that hadn't changed. To explain what it is, the 4 years this letter will take to reach you aren't enough.'
Eunsu attached the sunrise photo. Attachment size: 2.3 megabytes. Accounting for the per-light-year attenuation rate in transmission, the photo's resolution would drop 30 percent by the time it reached Proxima. The orange would grow faint and the outlines of the clouds would smear. The sunrise Hyunwoo saw would not be the same as the sunrise Eunsu had photographed. But he would still be able to tell that there was light. Eunsu decided to send it anyway.
Eunsu's finger hovered over the send button. This letter would reach Hyunwoo in 2063. What kind of person would he be by then? Would he be waiting for a letter from Eunsu? Would he already be beside someone else? Eunsu pressed send. 'Sending' appeared on the screen. The progress climbed. 12 percent. The data was rising to the transmission satellite in Earth orbit. 34 percent. From the satellite, a beam would fire off toward deep space. 67 percent. 4.24 years at the speed of light. 100 percent. 'Transmission complete. Estimated arrival: around May 2063.' Eunsu set the terminal down on the table.
The sky outside the window was growing lighter. The orange deepened. Eunsu stood at the window and watched. Even at this very moment, the light of Proxima Centauri was racing toward Earth. Light that had set out 4.24 years ago. The light reflected off the red star Hyunwoo looked up at was probably passing somewhere in the solar system right now. Eunsu couldn't see that light. It was a star invisible to the naked eye. But the light was coming.
Eunsu went back to the kitchen and started making coffee. Ground the beans. The whir of the grinder's motor filled the kitchen. A bitter smell rose from the ground beans. Eunsu spooned them into the filter and poured hot water. The water soaked the grounds and swelled them up. The coffee dripped one drop at a time. At even intervals. Eunsu took out a cup and set it on the table. Beside the terminal. The screen was dark. Pouring the coffee, Eunsu checked the clock. 5:12 in the morning. Three hours until work. Eunsu took a sip and picked up the terminal again. Opened Hyunwoo's message one more time. 'Only—' Eunsu propped it upright on the table without turning the screen off. Steam rose from the coffee. It curled up thinly under the fluorescent light. The fluorescent glow reflected off the terminal's screen.
Eunsu went back to the window. The sky had brightened completely. The sun was still behind the building, but the light had arrived ahead of it. Eunsu suddenly thought of the sunrise Hyunwoo saw on Proxima. Proxima Centauri was a red dwarf. Hyunwoo's morning would be red. Earth's morning was orange. Under lights of different colors, standing on different times, there was no such thing as the same moment. When Eunsu drank the morning coffee, Hyunwoo might be asleep. When Eunsu fell asleep, Hyunwoo might be analyzing soil samples. There was no hour where the two of them overlapped. Days that never overlapped had piled up into 8 years. 2,920 days out of sync. Between the moment Eunsu sent a letter and the moment Hyunwoo read it lay 4.24 years. In that time the two of them lived their own days on their own planets. Eunsu lifted the cup. The coffee had gone cold.
Eunsu's phone rang. The morning call from the institute. Eunsu answered.
“Yes, I'll be there at 8.”
Eunsu hung up, packed the terminal into the bag. Put on shoes at the entrance. Stopped before opening the door. Hyunwoo's letter was inside the terminal in the bag. A reply the Hyunwoo of 4 years ago had sent to the Eunsu of 6 years ago. Eunsu gripped the door handle. The metal was cold.
In 4 years, Hyunwoo would open Eunsu's letter. Under the red light of Proxima, in a small room of the habitat module, watching the blue glow of a terminal. Who would be beside Hyunwoo then, what expression Hyunwoo would wear—Eunsu couldn't know. Eunsu opened the door. The air in the corridor was cold. While waiting for the elevator, the phone rang again. An unknown number. Eunsu answered. A stranger's voice, a woman's, came through the speaker.
“Is this Eunsu? This is the Proxima Settlement Communications Authority. There's an additional message in the transmission queue. The recipient address is identical to yours, so we're calling to confirm.”
Eunsu's hand froze over the phone.
“Who's the sender?”
“It's Hyunwoo. Sent in 2057. It was held in the queue for 2 years after a relay satellite drifted out of orbit. It will be delivered to your inbox sometime today.”
Eunsu couldn't hang up. 2057. Right after Hyunwoo had registered Eunsu's silence. Eunsu's mouth went dry. The elevator arrived. The doors opened. Eunsu didn't step in. Pulled the terminal from the bag. Opened the inbox. Still empty. Eunsu leaned back against the corridor wall, terminal in hand. The elevator doors closed. The corridor went quiet. Eunsu looked at the terminal's screen. The cursor was blinking.
