Observe. (If you don’t want to or can’t, it’s a video showing the compression wave that forms in traffic when a car brakes.)
I first saw that video a few years ago. I remembered it a few weeks ago when driving in traffic, and realizing that a particular traffic condition was caused by an event that had happened some time in the past, that had left an impression, a memory, in the patterns of traffic. The event, no longer present, was still recorded. The wave form in the traffic patterns was a record of an event—traffic can operate as a storage device.
Considering traffic as a memory storage device, it appears traffic reaches its capacity when it is no longer possible for traffic to move at all. In practice I think traffic would approach this limit asymptotically, as each additional event stored in its memory reduces the speed at which traffic moves, such that it takes additional time to store each event in proportion to the number of events already stored. That is, the memory storage of traffic is not infinite.
Notably, however, the memory storage of traffic can, at least in principle, be read. Traffic itself is an imperfect medium of storage—it depends on a constant flow of cars, or else the memory is erased, and also cars don’t behave uniformly, such that events aren’t stored perfectly. However, it isn’t perfectly lossy, either; I can know from an arbitrary slow-down that some event happened in traffic in the past.
You could probably program a really, really terrible computer on traffic.
But the more interesting thing, to me, is the idea that a wave in a moving medium can store information; this seems like the sort of “Aha” moment that, were I working on a problem that this could apply to, would solve that problem for me. I’m not working on such a problem, but maybe this will find its way to somebody who is.
Edit: It occurs to me this may look like a trivial observation; of course waves can store information, that’s what radio is. But that’s not what I mean; radio is information transmission, not information storage. It’s the persistence of the information that surprised me, and which I think might be useful, not the mere act of encoding information onto a wave.
Data storage and transmission are the same thing. Both are communication to the future, (though sometimes to the very very near future). Over long enough distances, radio and wires can be information storage. Like all storage media, they aren’t permanent, and need to be refreshed periodically. For waves, this period is short, microseconds to hours. For more traditional storage (clay tablets or engraved gold discs sent to space, for instance), it could be decades to millenea.
Traffic is quite lossy as an information medium—effects remain for hours, but there are MANY possible causes of the same effects, and hard-to-predict decay and reinforcement rates, so it only carries a small amount of information: something happened in the recent past. Generally, this is a good thing—most of us prefer that we’re not part of that somewhat costly information storage, and we pay traffic engineers and car designers a great deal of money to minimize information retention in our roads.
Acoustic memory in mercury tubes was indeed used by most of first-generation electronic computers (1948-60ish); I love the aesthetic but admit they’re terrible even compared to electromagnetic delay lines. An even better (British) aesthetic would be Turing’s suggestion of using Gin as the acoustic medium...
Observe. (If you don’t want to or can’t, it’s a video showing the compression wave that forms in traffic when a car brakes.)
I first saw that video a few years ago. I remembered it a few weeks ago when driving in traffic, and realizing that a particular traffic condition was caused by an event that had happened some time in the past, that had left an impression, a memory, in the patterns of traffic. The event, no longer present, was still recorded. The wave form in the traffic patterns was a record of an event—traffic can operate as a storage device.
Considering traffic as a memory storage device, it appears traffic reaches its capacity when it is no longer possible for traffic to move at all. In practice I think traffic would approach this limit asymptotically, as each additional event stored in its memory reduces the speed at which traffic moves, such that it takes additional time to store each event in proportion to the number of events already stored. That is, the memory storage of traffic is not infinite.
Notably, however, the memory storage of traffic can, at least in principle, be read. Traffic itself is an imperfect medium of storage—it depends on a constant flow of cars, or else the memory is erased, and also cars don’t behave uniformly, such that events aren’t stored perfectly. However, it isn’t perfectly lossy, either; I can know from an arbitrary slow-down that some event happened in traffic in the past.
You could probably program a really, really terrible computer on traffic.
But the more interesting thing, to me, is the idea that a wave in a moving medium can store information; this seems like the sort of “Aha” moment that, were I working on a problem that this could apply to, would solve that problem for me. I’m not working on such a problem, but maybe this will find its way to somebody who is.
Edit: It occurs to me this may look like a trivial observation; of course waves can store information, that’s what radio is. But that’s not what I mean; radio is information transmission, not information storage. It’s the persistence of the information that surprised me, and which I think might be useful, not the mere act of encoding information onto a wave.
Data storage and transmission are the same thing. Both are communication to the future, (though sometimes to the very very near future). Over long enough distances, radio and wires can be information storage. Like all storage media, they aren’t permanent, and need to be refreshed periodically. For waves, this period is short, microseconds to hours. For more traditional storage (clay tablets or engraved gold discs sent to space, for instance), it could be decades to millenea.
Traffic is quite lossy as an information medium—effects remain for hours, but there are MANY possible causes of the same effects, and hard-to-predict decay and reinforcement rates, so it only carries a small amount of information: something happened in the recent past. Generally, this is a good thing—most of us prefer that we’re not part of that somewhat costly information storage, and we pay traffic engineers and car designers a great deal of money to minimize information retention in our roads.
You have (re)invented delay-line memory!
Acoustic memory in mercury tubes was indeed used by most of first-generation electronic computers (1948-60ish); I love the aesthetic but admit they’re terrible even compared to electromagnetic delay lines. An even better (British) aesthetic would be Turing’s suggestion of using Gin as the acoustic medium...