Editing 2321: Low-Background Metal
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==Explanation== | ==Explanation== | ||
+ | {{incomplete|Created by a TIME TRAVELER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}} | ||
In this comic, a team including [[Megan]] and [[Black Hat]] who have invented a {{w|time travel}} machine presents it and their problems to [[Cueball]]. Time travel is a common trope in science fiction, and specifically [[:Category:Time travel|here on xkcd]], and such a discovery would be likely to change the world as we know it. However, Megan and Black Hat's machine requires the use of "low-background" metal, which is in short supply. | In this comic, a team including [[Megan]] and [[Black Hat]] who have invented a {{w|time travel}} machine presents it and their problems to [[Cueball]]. Time travel is a common trope in science fiction, and specifically [[:Category:Time travel|here on xkcd]], and such a discovery would be likely to change the world as we know it. However, Megan and Black Hat's machine requires the use of "low-background" metal, which is in short supply. | ||
− | Megan explains that, while delicate equipment is often shielded from radiation by lead, metal produced in modern times is contaminated by {{w|nuclear fallout}} in the atmosphere, which means that the shielding itself has enough radioactivity to interfere with highly delicate equipment. In order to shield this equipment, "low-background metal" is salvaged from sunken ships. | + | Megan explains that, while delicate equipment is often shielded from radiation by lead, metal produced in modern times is contaminated by {{w|nuclear fallout}} in the atmosphere, which means that the shielding itself has enough radioactivity to interfere with highly delicate equipment. In order to shield this equipment, "low-background metal" is salvaged from sunken Roman ships. This metal, primarily lead, was used as ballast in the ships. The Roman lead was produced before atmospheric nuclear tests occurred and therefore did not have {{w|radionuclides}} in the air used in its manufacture. Because it has spent many centuries continually underwater, it is both shielded from radioactive particles, and has had time for natural radioactivity to fade. |
− | The number of shipwrecks of that age that can be found and successfully salvaged for metal is quite small, which puts this material in short supply. Megan mentions that they have only enough for a single trip. The team realizes (apparently at [[Black Hat]]'s suggestion), that a solution is to use their single trip to take modern military hardware back to the era of the {{w|Roman Empire}} and use it to sink multiple ships. This would both provide for many more shipwrecks to salvage, and give the team a good idea of where those wrecks were, when they returned to modern times. They could also specifically target ships that were in waters that are well-suited for salvage operations. | + | The number of shipwrecks of that age that can be found and successfully salvaged for metal is quite small, which puts this material in short supply. Megan mentions that they have only enough for a single trip. The team realizes (apparently at [[Black Hat]]'s suggestion), that a solution is to use their single trip to take modern military hardware back to the era of the {{w|Roman Empire}} and use it to sink multiple ships. This would both provide for many more shipwrecks to salvage, and give the team a good idea of where those wrecks were, when they returned to modern times. They could also specifically target ships that were in waters that are well-suited for salvage operations. (A less destructive approach would be to simply drop metal into the water, without sinking any ships, eliminating the need to bring back modern military hardware.) |
− | + | Megan is most likely referring to {{w|low-background steel}}, used in real life as shielding for highly sensitive particle detectors in physics and medicine. Low-background steel is in actuality salvaged from ships sunk before 1945 (the {{w|Trinity (nuclear test)|Trinity nuclear test}}), however, the ships used typically date back to World War I or World War II, and not the Roman Empire. | |
− | + | The title text refers to {{w|Greek fire}}, which was an incendiary weapon invented and employed by the Byzantine empire. It was a flammable liquid, famously said to burn on water, that was used in naval combat to set fire to enemy ships. As it was a closely-guarded military secret, many of the details have been lost to time, and modern chemists have only been able to develop educated guesses of what it ''probably'' was. Randall proposes a rather outlandish alternative hypothesis: that all records of Greek fire were actually in reference to the modern weapons used by the time travelers. | |
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− | The title text refers to {{w|Greek fire}}, which was an incendiary weapon invented and employed by the Byzantine empire. It was a flammable liquid, famously said to burn on water, that was used in naval combat to set fire to enemy ships. As it was a closely-guarded military secret, many of the details have been lost to time, and modern chemists have only been able to develop educated guesses of what it ''probably'' was. Randall proposes a rather outlandish alternative hypothesis: that all records of Greek fire were actually in reference to the modern weapons used by the time travelers | ||
In [[1063: Kill Hitler]] a single-use time machine is available. It is also used by Black Hat. However, due to the way the time machine in this comic is used, it must be assumed that they can use it again after the salvage of lead from the sunken ships. | In [[1063: Kill Hitler]] a single-use time machine is available. It is also used by Black Hat. However, due to the way the time machine in this comic is used, it must be assumed that they can use it again after the salvage of lead from the sunken ships. | ||
==Transcript== | ==Transcript== | ||
− | :[Black Hat stands behind Megan who addresses Cueball who stands on the other side of a table with a machine | + | :[Black Hat stands behind Megan who addresses Cueball who stands on the other side of a table with a machine The machine is a rectangular box with a small dome with one large and two small antennas on top. It seems to point in Cueball's direction as it has a broad protrusion at the back and protrusion at the front that gets smaller towards the tip. A large word is written on the side, and below that is possibly more illegible text.] |
:Megan: Our time machine works. | :Megan: Our time machine works. | ||
:Megan: But we're almost out of low-background metal. | :Megan: But we're almost out of low-background metal. | ||
:Cueball: What's that? | :Cueball: What's that? | ||
+ | :Machine: Time | ||
:[Close-up on Megan who lifts her hand palm up.] | :[Close-up on Megan who lifts her hand palm up.] | ||
Line 40: | Line 38: | ||
:Black Hat: ''Hmmm...'' | :Black Hat: ''Hmmm...'' | ||
− | :[The three are now in a helicopter, with Megan piloting, Cueball as a passenger in the back, and Black Hat firing a flamethrower at a Roman ship beneath them through the window behind the cockpit. Two sailors with Roman type helmets are looking on as the stern of their ship catches fire. One of them throwing his arms out to the side. The intact sail is still up behind them and behind that another sailor jumps into the water, down to a fourth sailor already in the water. Two already-burning ships can also be seen to the left of the ship under attack. One is burning | + | :[The three are now in a helicopter, with Megan piloting, Cueball as a passenger in the back, and Black Hat firing a flamethrower at a Roman ship beneath them through the window behind the cockpit. Two sailors with Roman type helmets are looking on as the stern of their ship catches fire. One of them throwing his arms out to the side. The intact sail is still up behind them and behind that another sailor jumps into the water, down to a fourth sailor already in the water. Two already-burning ships can also be seen to the left of the ship under attack. One is burning al over, with the mast still up but the sail long gone, and the third ship is almost completely sunk, but the part above the water is aflame. Seven small clouds are aroudn the helicopter in the sky.] |
:Flamethrower: ''Fwooosh'' | :Flamethrower: ''Fwooosh'' | ||