“Adelle”, Deborah raised her voice.
“Yes?”, The computer answered
“Have you completed all preparation for our return to 2456? You have the chronobeacon coded ‘Deborah_return_2456’?
“I have the chronobeacon. Time travel system passes all self-tests”
“Execute”
“We are now in circular equatorial orbit about the Earth, altitude 756 kilometers”
“Good. Contact orbital control and report our arrival”
“Orbital control is not responding”
“Why?”
“Unknown. There is no carrier on any frequency”
“Are we at the correct time?”
“Examination of stellar locations and automated time services verifies that we are at the correct time.”
“Transmissions on other frequency bands?”
“I am reading some automated transmitters - navigation beacons, time services, telemetry, but no voices and no video”
“I want to see the planet”
A window opened on Deborah’s monitor.
“Where are we?”
“We are at 130 degrees west longitude, 0 degrees latitude, altitude 756 kilometers”
“So, somewhere over the Pacific Ocean?”
“Yes”
“Show me Los Angeles, California”
The window panned upwards and to the right.
“Zoom in, please. Give me control of the camera using my joystick”
“You have control”
Deborah scanned around the Los Angeles area. I don’t see any movement
“Adelle?”
“Yes”
“Please point all sensors at the Los Angeles area. Is there any evidence of human activity there?”
“There is no sign of human activity there”
“What was the population of Los Angeles at the last census?”
“In the census of 2450, the population of Los Angeles, California was 8,143,232 people.”
8 million people!
“Use all sensors. Locate any survivors.
Also, prepare ten vehicles to descend to the surface and conduct an analysis of the atmosphere, ground, and water conditions”
“Understood”
About 10 seconds passed.
“Ready”
“What is in range now?”
“Europe, Africa, and the Middle East”
“Can you target an undeveloped area near Tel Aviv?”
“Yes, how about Ramat Gan national park”
“Show me a map”
“I don’t see it”
“It’s labeled Safari”
“I see it. That will be fine”
“The optimal launch time is in 4 minutes 35 seconds”
“Launch at the optimal time”
”Understood”
“Deborah, look at this”, Walter pointed to his monitor.
“What is it?”
“I have a camera pointed at Manhattan Island, in New York city. There are no buildings standing. There is lots of haze. And it’s not white, it’s gray, so I think there is a lot of soot and amorphous carbon in the air. I can’t see Boston or Washington. D.C., due to clouds”.
“Can we see Spain or Portugal yet?”
“They’re coming over the horizon in a moment. However, we can see West Africa and the Azores now”
“The probe is launched”, Adelle announced.
“Thank you, Adelle”. Deborah, after all these years, sometimes forgot that she didn’t need to be civil to the computers.
“There are clear skies over West Africa, so I can really see what is happening there. This is Dakar, in Senegal.”
“The buildings look like they’re standing, but I don’t see anything moving in the streets, no cars, no animals, no people. What is the resolution at this distance?”
“20 centimeters”
“Wait a second - capture a frame and display it over here?”
“What do you see?”
“Doesn’t that look like a body laying in the street?”
“There’s another one”
“Adelle”
“Yes”
“Look at Dakar, Senegal, and estimate the number of bodies laying in the streets”
“Understood”
“Let’s go back and look at Lisbon, Portugal”
Walter furiously typed away at his keyboard.
“That’s Lisbon. It’s a little farther away from us, and the air is hazy, so I can’t give you much better than 1 meter resolution.”
“I don’t see any movement. That must be a truck. Is that a body?”
“Hard to be sure. Could be”
“I estimate that there are eleven thousand bodies in Dakar”, Adelle announced.
“What is the latest estimate of the population of Dakar?”
“According to the 2450 census, the population of Dakar was 2,651,284 people.”
“Eleven thousand people doesn’t seem like that many out of 2-1/2 million people”
“Maybe most of them died inside. What we see are dying people who went outside”
Adelle announced: “The parachute has deployed. Touch down in 10 minutes. Correcting for local winds as predicted. Probe is on course for Ramat Gan”
“Begin analysis of the atmosphere. Look for toxins, radioactivity, abnormal concentrations of gases, anything which could explain the lack of human activity”
“Scintillation counter reports 3500 counts per minute” http://en.wikipedia.org/wiki/Scintillation_counter
Walter said, “Shouldn’t the radiation count be on the order of 10 counts/minute?”
“That’s what I remember”
“Adelle, what is the concentration of Carbon Dioxide?”
“The carbon dioxide concentration is 845 parts per million”
“I thought in your time you’d have done something about rising carbon dioxide levels to prevent global warming.”
“We did. We made massive investments in wind power, solar energy, tidal power, hydropower, and nuclear fusion. That solved a lot of environmental problems. If you have enough energy, you can drive chemical reactions from high entropy to low entropy.”
“Turning plastic waste into graphite and hydrogen”?
“Something like that”
“When the probe touches down, we can fire up more instruments”
“Adelle, can you point the camera on the probe at the ground, and display the images here, please?”
“Understood”
A moment later, a picture of almost solid blue appeared”
“The probe is still over the Mediterranean Sea.
“Adelle, can you point the camera on the probe towards Tel Aviv?”
“Understood”
They could clearly see the remnants of buildings, some them still several stories tall, but obviously damaged.
“Adelle, please point the camera at Tunis in Tunisia”
“Tunis is out of range of the probe”
“I mean the camera on the timeship”
“Understood”
Tunis came into view. They could clearly see the town and the Gulf of Tunis.
“Magnify”
The view zoomed in.
“I see more bodies”
“There must have been a horrific war.”
“Yes, but I am curious what kinds of weapons they used. Did they use a lot of chemical explosives? Nuclear bombs? Thermonuclear bombs? Chemical weapons or Biological weapons? Lasers or other directed energy weapons? Have they left or are they still present? Are there any survivors? Are there any captives? We need more intelligence”
“The probe has landed on target”, Adelle announced.
“Activate all instruments. Find out what happened”.
http://en.wikipedia.org/wiki/Nuclear_fission_product
“There are high concentrations of radioisotopes. I have a display on monitor 2”
Isotope | Concentration (parts/billion) |
Argon-37 | 895 |
Cesium-133 | 45 |
Cesium-134 | 0 |
Cesium-136 | 0 |
Xenon-135 | 3 |
“From the soup of radioisotopes, it looks like they used fission nuclear bombs”, Walter mussed.
“Why didn’t they use fusion bombs or matter-anti-matter bombs?”, Deborah asked.
“That’s a good question. If they used fusion bombs, there would be a lot less radioactive fallout for the same destructive force. On the other hand, if they had really good targeting systems, then they wouldn’t need such a large explosion to destroy a given target.”
“I don’t understand”
“In the old days, guidance systems were crude, based on mechanical gyroscopes and accelerometers. There was no terminal aerodynamic guidance system. So the rocket would tend to be fairly inaccurate. You needed a bigger explosion to compensate for that. If you could target accurately, then you needed a smaller explosion to accomplish your goal. Your war with Iran demonstrated that cruise missiles with terrain recognition radar and satellite navigation systems could be effective with chemical explosives”.
“Okay, so assuming that they used highly accurate fission bombs, why are there so many dead people in Dakar? It’s not a strategic target.”
“It depends on how long ago the war occurred and how widespread it was. It may be that the entire planet is poisoned with radiation”
“We have to find out how long ago this happened, and then go back in time to stop it”
“Before we go off half-cocked, it would be nice to gather some more information. We’re in a good position to gather scientific information on the consequences of a global nuclear war.”
“That’s a funny thing for a war criminal to say”
“Not at all. First of all, I no longer consider myself a war criminal. I have seen the error of my ways and now I am an advocate for peace.”
“I’m sorry, I meant no offense”
“None taken. If we can better understand the consequences of a global war, then that puts us in a better position to talk to policy makers about the need to avoid war.”
“That makes sense”
“Okay, then I’d like to change our orbit to a higher inclination so we can get full planet coverage”
“How about a sun-synchronous orbit?” http://en.wikipedia.org/wiki/Sun-synchronous_orbit
“What’s that?”
“That’s an orbit which is always aligned with sun as the Earth travels around the sun”
“That’s a wonderful idea. Do you know how to do that?”
“Adelle does. Adelle.”
“yes”
“Please change our orbit to sun-synchronous, inclination 98 degrees. Be as efficient as possible with reaction mass”
“Understood”
“I don’t understand the part about the reaction mass. We have whole oceans down there that we can beam up”
“Ocean water is corrosive, and I’d rather avoid that if I can. And I don’t want to beam up a bunch of radioactive water, because the water tanks are inside the iron shot shielding.”
“Oh”
“Relax - we can time travel to Europa, beam up some water, and then time travel back to Earth”
“Incoming transmission on chronochannel 13957.”, Adelle announced.
“Do we have an activated chronobeacon? How did they find us?”
“Unknown”
“Open a channel”
A younger version of Deborah appeared on the screen.
“You are in grave danger. I am sending you plans for a new weapon, a beam that suppresses the strong force. Build it and deploy it immediately. Unfortunately, I am not allowed to give you any further details”
The channel closed.
Adelle announced “I have received a large file. It contains the plans, suitable for the replicator, for a new weapon which suppresses the strong force”
“What’s the strong force?”, Walter asked.
“The strong force is the force that binds together the protons in the nucleus of an atom. The protons are very small and very close together, and they are positively charged. Were it not for the strong force, the nuclei of the atoms would fly apart, thereby destroying whatever substance it touched. I wonder about the physics of something like that?”
“Where did the file come from?”, Walter asked.
“Unknown”, Adelle replied.
“This could be a booby trap”, Walter warned.
“She said, or I said, that she was not allowed to give me additional details. I wonder if she, or I, was captured by the chronopolice, and convinced them to throw me a bone”
“Throw me a bone?”
“An expression. If you have a dog that is sitting under your dinner table, the dog is going to want the meat on the table. However, if, after you ate the meat, you gave your dog the bone, then the dog would still be happy. Dogs can gnaw on a bone for hours”
“I’ve never owned a dog”
“Me neither, I’m a cat kind of person”
“Adelle?”
“Yes”
“Can you analyze the plans to figure out what this weapon does?”
“No, I don’t understand the physics”
“How long would it take to build the weapon and test it?”
“5 minutes”
“Could we transport it outside the timeship, instrument it to detect dangers, and test it there?”
“Yes”
“What are you thinking?”, Walter asked.
“We put it in an orbit far away from us, track down a non-operational satellite, and shoot it while we watched. That way, we can tell if it is a booby trap or not.
“I’ll look for a non-operational satellite, you build the weapon.”, Walter suggested.
“Fine”
Walter’s task was actually quite simple. It turned out that all he really needed to do was find some space debris http://en.wikipedia.org/wiki/Space_debris. There was a lot of space debris, so he had lots of targets to choose from.
Deborah’s task was also remarkably simple. Adelle loaded the plans into the replicator, which then replicated the weapon at a point that Walter designated - a thousand kilometers from a defunct weather satellite, and ten thousand kilometers from the time ship.
“Adelle”
“Yes”
“Are you receiving the telemetry from the instrumentation on The Weapon.”
“Yes”
“Target the satellite”
“The satellite is targeted”
“Range to the satellite?”
“998 kilometers and closing at 1 kilometer/minute”
“Arm The Weapon”
“The Weapon is Armed”
“Fire”
The satellite vanished. There was no debris.
“How is The Weapon?”
“No abnormal radiation. No acceleration. Temperatures on the surface of the weapon remain unchanged”
“Well, Walter, do you still think it is a booby trap?”
“Maybe it is designed to blow up on the second shot”
“Have you ever heard of the Grue-Bleen paradox?
“No”
“What color is my jumpsuit?”
“Blue”
“No it isn’t, it’s Bleen”
“What’s Bleen?”
“Something is Bleen if it is Blue before some time t and Green after that time t. The paradox has to do with how we make inferences about the future from our observations about the past. Every time you’ve seen this jumpsuit, it’s been blue. So you make the inference that the next time you see this jumpsuit, it will be blue. However, that’s not necessarily so after some arbitrary time t, say, January 1st 2500.”
“That’s very interesting, but how does it apply to the problem of what to do with The Weapon?”
“It might be a booby trap. We might get 100 shots out of it, and it might blow up on the 101st shot. So, we go through the same procedure we just went through the fire the 101st shot, and it works fine. So we remount The Weapon and it blows up on the 102nd shot.”
“How do you get out of bed in the morning?”
“Well, I am 87 years old, and I have to make a decision every morning: to die in bed or to die somewhere else. I know I am going to die, so I might as well die doing something useful. Look, I am in command of this mission, and I am ordering that The Weapon be installed according to the plans that were sent us. Adelle”
“yes”
“Prepare a mounting for The Weapon as described in the plans that were sent us, and then recover The Weapon from orbit and install it there. Integrate The Weapon controls and power into ships systems”
“Understood”