A Contender for "Most Scientifically Irresponsible Passage":
In his post below, Jonathan asks, "What is the most scientifically irresponsible passage in the United States Reports?" There are lots of contenders, but one nominee might be another contribution by Justice Scalia, footnote 2 in Kyllo v. United States.
Kyllo considered whether pointing an infrared thermal imaging device at a home constitutes a "search" under the Fourth Amendment. Justice Scalia concluded that it did, it part because the device allowed the police to gather information about the interior of the home, namely, its temperature. In dissent, Justice Stevens argued that using the device was not a "search," in part because the device only revealed information about the exterior of the home. Justice Scalia responded to Stevens in footnote 2:
Of course, it is possible to draw reasonable inferences about the likely interior temperature of a home from the home's exterior temperature profile. Assuming a steady state system, we can make reasonable assumptions about how houses are usually built (for example, that there are no heat sources in the walls themselves) to find out information about the interior temperatures. But that information is only as good as the assumptions themselves. For example, if someone made a wall that had an good insulator and then a heat source on the exterior, the exterior would be hot even though that temperature would tell us nothing about the interior of the home.
None of this necessarily means that Scalia was wrong as matter of law, of course, but I believe he was wrong as a matter of physics. That's my best sense, at least; I hope readers will let me know if I'm the one who is wrong here. (Of course, if it turns out that Scalia was right, I suppose I'll have to designate this "the most scientifically irresponsible blog post at the Volokh Conspiracy"...)
Kyllo considered whether pointing an infrared thermal imaging device at a home constitutes a "search" under the Fourth Amendment. Justice Scalia concluded that it did, it part because the device allowed the police to gather information about the interior of the home, namely, its temperature. In dissent, Justice Stevens argued that using the device was not a "search," in part because the device only revealed information about the exterior of the home. Justice Scalia responded to Stevens in footnote 2:
The dissent’s repeated assertion that the thermal imaging did not obtain information regarding the interior of the home, post, at 3, 4 (opinion of Stevens, J.), is simply inaccurate. A thermal imager reveals the relative heat of various rooms in the home. The dissent may not find that information particularly private or important, see post, at 4, 5, 10, but there is no basis for saying it is not information regarding the interior of the home.Whether Scalia or Stevens had the better legal argument is debatable. But my understanding is that as a matter of physics, Scalia was wrong and Stevens was right. My research into this suggests that infrared radition is surface radiation: it emanates from surfaces, down to a depth of about 1/1,000 of an inch. See MIKE LLOYD, THERMAL IMAGING SYSTEMS 2-5 (1997). As a result, an infrared image only reveals the temperature of a surface, not the temperature of the space behind the surface. So the device really did reveal only the exterior temperature of the home, not the interior of the home.
Of course, it is possible to draw reasonable inferences about the likely interior temperature of a home from the home's exterior temperature profile. Assuming a steady state system, we can make reasonable assumptions about how houses are usually built (for example, that there are no heat sources in the walls themselves) to find out information about the interior temperatures. But that information is only as good as the assumptions themselves. For example, if someone made a wall that had an good insulator and then a heat source on the exterior, the exterior would be hot even though that temperature would tell us nothing about the interior of the home.
None of this necessarily means that Scalia was wrong as matter of law, of course, but I believe he was wrong as a matter of physics. That's my best sense, at least; I hope readers will let me know if I'm the one who is wrong here. (Of course, if it turns out that Scalia was right, I suppose I'll have to designate this "the most scientifically irresponsible blog post at the Volokh Conspiracy"...)
Related Posts (on one page):
- Chen's Genesis for the Rest of Us:
- More on Heat Transfer and Thermal Imagers:
- Most Scientifically Irresponsible Passage in U.S. Reports:
- A Contender for "Most Scientifically Irresponsible Passage":
- "The Most Scientifically Irresponsible Passage":
In other words so long as the interior of the home is giving off more infared radiation into the walls of the home than the walls of the home emit to the outside world the walls keep heating up. Eventually this process stabilizes letting one infer from the exterior radiation of the walls the amount of heat inside the walls.
Now sure their could be a heat source inside the walls as you say. However, this hardly proves anything. Scalia did not argue that the radiation directly eminates from the interior of the house.
Moreover, anytime we look at someone on the street the photons that hit our eyes have likely been absorbed and reemitted many times by air molecules in the interviening space. In fact I don't believe whether or not we are seeing the same photons as were initially emited from the person is even a sensical question to ask in QM.
Now of course whenever we see someone and infer they are wearing a green shirt this inference is only as good as our assumptions about the transmission of the light from them to us. In reality the image we see only reveals the photons incident on our detector from a certain direction not the photons that left their body. It is possible that someone has cleverly manipulated the air between them and us to create the illusion of someone with a green shirt.
However, if we want to retain any sense at all of the phrase 'reveals information' we say that looking at someone reveals information about what color clothes they are wearing regardless of the underlying physics of light propogation or remote possibility for being tricked. All that really matters is that this is a reliable way of determining the information at question not the means of physical transmission. That's just what the phrase means.
This debate reminds me of a chapter from Feynman where he complains about Orthodox Jews discussing the nature of electricity in order to settle some bizarre religious issue.
[OK Comments: LTEC, I believe Stevens agrees with your first point, which to him is why looking at something is not a Fourth Amendment search.]
So long as the interior of the home is giving off more infared radiation into the walls of the home than the walls of the home emit to the outside world the walls keep heating up.
I don't follow, LogicNazi. There are three kinds of heat transfer: conductive, convective, and radiative. Why would the infrared-length radiative heat transfer from the interior to the wall necessarily have to match the infrared-length heat transfer from the wall to the outside world? It's been 15 years since I studied these issues carefully, so maybe I'm just missing something, but I don't necessarily see that.
But assuming that the walls of my house are roughly equal in radiance and in insulation, the infrared output of each room would be proportionate to the image. To the extent that they are not, what is the probative value of the IR image? It's introduced to prove a "hot spot," supposedly an area where the grow lights for marihuana plants are generating a lot of heat. If an IR glow is not proof that a room is quite hot, then probative value is zero. (And yes, at dinner time your kitchen is a hot spot. My specialist friend used it also for commercial buildings, to spot gaps in roof insulation and water leaks into it (viewed from his airplane).
I was in contact with an IR specialist, now dead, who regularly analysed police use of these devices, and was annoyed at how often police would image a house, find nothing probative, and then turn up the gain (brightening the image) until it looked very hot. The less smart ones would do it while the video was running, enabling it the manipulation to be seen. He said in the old days they'd do things like compare the electrical usage of the house to comparable houses around it, but had gotten lazy... now they just ran the license plates of cars parked at head shops, then imaged their houses, and juggled the video until it fit and gave arguable probable cause.
Technically, the fancier detectors (rarely used due to cost of machine and of operation ... it has to be cooled by compressed rare gasses) are photo buckets that count photons. The cheaper ones have tiny elements that measure temperature at each element. Both require lenses made of special glasses, since ordinary glass blocks IR of these wavelengths.
True, but that is not what Scalia said. According to your quote:
In a, shall we say, standard house, in a cold November in Vermont, if one corner room is a kitchen with a big fat Thanksgiving dinner being cooked in it with ranges and ovens a blazing, and another corner room is unused with the hot air register closed, then thermal imaging of the outside wall will reveal the relative heat of the two rooms. It will tell the observer that for some reason the one room is hotter than the other - information about the interior, hey, a search.
Thermal imaging will not, it is true, tell the actual temperature of the two rooms, it will only tell the actual temperature of the exterior walls on the other side of the two rooms' interior walls.
When Stephens says:
He is wrong. The device does not reveal the actual temperature of anything other than the exterior walls, but it reveals information about the relative temperatures of the rooms behind those exterior walls.
Check out House Detective on hgtv, website www.hgtv.com. They use thermal imaging devices aimed at walls to get information telling them whether and where water leaks are inside the walls from relative temperature differences of the outside of the walls.
The legal questions are: 1. is using the device a search for which a warrant is necessary because information about the inside of the house is actually obtained, and, 2. of course, does the device give the authorities any useful or meaningful information, ie probable cause, about what is going on inside the house.
[OK Comments: Lev, can you back up your claims? I bought an infrared thermal imager -- actually, it's less of an imager than just a point thermometer, but it works in the same way -- and it gives me actual temperatures, not relative temperatures. And your point about even relative temperatures seems to be subject to a host of assumptions about what is in the wall, how it is insulated, and the like. And as for your point 2, is that your personal take on what the legal issues should be? I'm not familiar with that in the cases.]
My guess here is that the bright lights that marijuana plants adore irradiate the walls as well. The walls of that room heat, and most of it would be emitted from those walls in the IR rather than being transfered to other rooms (NB, this is just a guess). I'm surprised that some people would think that IR, visible, and gamma ray (valuable to trace radioactivity) photons should be treated differently solely because of the photon's wavelength. It doesn't pass the sniff test.
Seems self-evident that a picture like this is conveying "information regarding the interior of the home":
http://www.ir55.com/images/1PDS2394820938409238402new-2.jpg
[OK Comments: Why is that self-evident, Enoch?]
The point of my comment was that the physics distinction being discussed here is really theology, and not the right way to settle this issue. The issue should be settled by our legislators, based on a revised modern meaning of what "search" means, based at least in part on an understanding of why we are restricting searches in the first place.
And Scalia is technically correct that thermal imaging does obtain information regarding the interior of the home, by inference from the external information. A thermal imager does reveal the relative heat of various rooms in the home, as long as each of those rooms touches the outside wall.
[OK Comments: Andrew, you are of course free to adopt a "living Constitution" approach as a matter of law, but whast does it mean to say that as a "technical" matter you can make an inference that is often accurate? If you're making an inference that A suggests B, you're no longer technically getting B.]
In Kyllo itself the thermal imager revealed information from inside the house, namely, that marijuana was being grown inside. The police in Kyllo didn't recieve divine inspiration that they would find marijuana in the house. The thermal imager told them.
[OK Comments: Why is that relevant?]
Orin, physics (fortunately) has little to do with law. Scalia was correct in that the purpose and effect of the thermal imaging was to determine information about the interior of the home. You think the police were interested in the temperature of the exterior walls?
Why go to physics on this question? The Constitution isn't about photons.
{OK Comments: Randal, this post isn't about constitutional interpretation. It is about physics. Of course, you might think that the more interesting issues are constitutional ones, but that's just not the purpose of this particular post.]
Energy consumption is related to interior temperature by insulation. The more insulation, the higher the interior temperature for a given energy consumption. But in the case of the sought-after UV lights, it's not temperature that you want, but energy consumption, from which UV lights are inferred. Exterior temperature gives you this directly. Interior temperature is a red herring.
(If you have resistive electrical heating, you can leave on lights, TVs, computers for free in the heating season. A watt is a watt and it all winds up as heat. More TV just mean less furnace. Energy efficiency is pointless in the winter.
When we teach relativity, we also teach Newtonian mechanics, and we tell the students where Newton went wrong with absolute time. I realize the analogy is somewhat flawed because Newtonian mechanics is approximately correct and easily co-exists with relativity. Not so for evolution and intelligent design which stand in contrast to one another. Of course, in a sense, so do absolute and relative time. Now does time exist at all? In the 1940s Godel demonstrated “rotating universe” solutions to Einstein’s field equations, which seem to make time travel possible. But Godel says that if time travel is possible then time itself really doesn’t exist. Einstein was quite disturbed that his field equations permitted something so bizarre as a Godel Universe. The point being there is always room for doubt about scientific theories and this includes the theory of evolution too. However, thus far it’s holding up pretty well. So well, I use it as a guide on what to eat.
These equations come straight out of textbooks, and will be correct unless the person has heated walls/some other tricking device. Therefore, we probably know information about the inside of the house.
Stevens is right, we aren't measuring the inside of the house. Scalia isn't far off, we are calculating probable information about the inside of the house.
[OK Comments: Chris, your point about "probably knowing" is the key, and explains why Scalia is wrong, I think.]
Maybe when EVERYONE can see the thermal radiation of our home, we'll start taking steps to mask it. You know... to protect our privacy and all that. Then the cops can go ahead and use the information if we choose to broadcast it.
Does anyone REALLY think IR information is "public" at this point? Scalia didn't.
As I see it, this case is about the impact of new technology on expectations of privacy. The Mk I human nose has been around forever, and just about everyone has a working nose; thermal imaging devices have not been, and not that many people have routine access to the devices. Maybe expectations of privacy would, over time, shift if every digital camera on the market had a thermal imaging mode..
Chris Ball: well, it depends on how you define measurement. Most measurements are indirect, not direct -- with a spring scale, you aren't directly measuring mass, but instead the change in length of a spring, which is proportionate to the force exerted by the local gravity field on an object, which is proportionate to the mass of the object. With the thermal imager, you're seeing the amount of IR emitted by each point on the surface of the home, which is affected by the exterior temperature, the structure of the house, and the location of any heat sources within the house.
Orin: In response to your question to Lev asking him to back up his claims:
Like a thermal imager, your IR thermometer measures the *actual* outside temperature of a spot on a wall. But it also lets you gauge relative *inside* temperatures: If there are two rooms behind the wall at different temperatures, the wall will most likely be warmer outside the warmer room, and cooler outside the cooler room, and the imager will directly tell you which room is warmer (but not by how much).
Scalia's point is that the capture of information from the house is what's important. Where the photons come from is is not. This makes sense to me.
[OK Comments: John, you're making a point about constitutional theory, right? That is, you're making a claim about what the law *should* mean? Note that my post is about physics, not law.]
Is that OK, under current law? (It should be, by Stevens, and shouldn't, by Scalia. Of course, for Scalia needing the mike shoudl be irrelevant-- it's a matter of whether you are learning about the interior of the house while standing outside.)
Here's another Scalia-killer. What if the police in Apartment 12A touch the wall with their hands, feel infrared heat, and realize that Apartment 12B is hot? Are they allowed to use that information? They have discovered something about the temperature of the inside of one room of Apartment 12B by using infrared emissions from it.
As many have pointed out, the IR device doesn't measure the temperature of the inside of the house. And, as many have pointed out, it doesn't measure the temperature of the outside walls. It measures the photons that hit the surface of the IR device. Those photons are reacting to pressure from photons immediately behind them in the air, which are reacting to pressure from photons immediately behind them, which (if you repeat this a few million times) are reacting to pressure from photons on the surface of the house, which (if you repeat this a few million times) are reacting to pressure from photons emitting from a stove, or fire, or high intensity lightbulb in a room in the house. One could say, equally accurately, that an IR device is measuring the 'temperature' of a room in the house, of a wall in the house, of the insulation in the house, of the air in the yard, or of the glass on the lens of the IR device.
(Another analogy: imagine there is an explosion on a boat in the ocean. That explosion vibrates the boat enough to shake the water and create a wave. You are sitting on the beach and feel the wave with your hand. Did you feel the energy of the water at the beach, the energy of the water in the ocean between you and the boat, the energy of the vibration of the hull of the boat, or the energy of the explosion in the boiler room? The answer: Yes.)
Steve
Likewise, the information contained in the external IR readings comes from inside the house, even though the only physical molecules being measured are outside the house. Scalia does not say that the IR is measuring the molecules or photons inside the house, simply that it is revealing information about the interior of the house.
As for the bit about relative temperatures, it is quite correct that the IR is actually measuring the specific temperature of the top few molecules of the house. But the fact that the walls of one room are 95 degrees is meaningless. It conveys very little information of use to the police; perhaps all the walls of that house and all the houses are 95 degrees, because it's summer. But the fact that the walls of one room of the house are 95 degrees while the others are all 75 degrees, THAT is information, and that is what the police are measuring, by measuring the specific temperatures of the top few molecules of each part of the house.
Putting the data on relative surface temperatures together, reveals information about the interior of the house, "assuming a steady state system," as you say. That information depends on assumptions, is extraneous and an irrelevant point. You assume that I'm writing this all in English, and so it should make sense. But what if I was really writing in Spanish, and just talking gibberish (I may be as it is anyway). Sure the conveyance of information depends on assumptions. That they depend on assumptions that are reasonable is what makes it better as opposed to worse information. (Such as that, yes I really am writing in English, or that, yes the house was not built with an external heat source built into the walls, and that the insulation is fairly even throughout the house.)
The real point is the legal one: cops are basically just looking for an excuse to enter the house and search, and can not be trusted not to cheat.
I believe that it is time for the normally quite astute Mr. Kerr to redesignate this post...
[OK Comments: Pat, I believe you're confusing two different things. The distinction between "off the wall" and "through the wall" was not about surface radiation vs radiation from inside, but rather about active vs. passive measurement. Stevens was focused on the fact that infrared is passive measurement: it passively measures radiation that automatically emanates from surfaces. In contrast, other devices require active measurement, actually sending electromagnetic impulses to the place to be monitored and then making mresurements based on what happens to those impulses. Scalia rejects the passive/active distinction, but that doesn't address the exterior/interior distinction. That is, you can have passive measurement of the exterior or passive measurement of the interior.]
Agreed. When most people lament the lack of scientific understanding in American, they are usually talking about creationism/evolution. I'm more bothered by demonstrably intelligent, educated professionals who don't understand the most basic implications of the most basic rules of thermodynamics (in this case), or Newtonian physics, econ, or computer science (not this case).
2) If anything detectable outside the house is fair game, what about the devices that can detect and replicate the view on a CRT-type computer screen from across the street, or can even read the data the disc heads pass over whether the computer is accessing them or not. (Hard now that disk have gotten so much faster) I think that anything that uses special miltary or NSA-grade equipment to pull off has gone from "reasonable" to "unreasonable" search.
Obviously a thermal imager would not "reveal the heat of various rooms" to, say, a feral chimpanzee shivering outside the house against the winter cold and desparately seeking a warm place to stay. The chimp would not have benefit of intellectual training to make the inferences. But to a human with knowledge of what inferences are most probably correct (though not necessarily knowledge of why they are likely correct), and with absense of subterfuge or clever "rigging" of the house, the device would "reveal the heat of various rooms".
Scalia would have been more scientifically correct to say "To a properly trained observer, and in the absence of a clever subterfuge made by alterions on the house, a thermal imager reveals by straightforward inference the relative heat of various rooms in the home to a very high probability".
I think that even to those sensitive to misstatements about science, Scalia's actual assertion in this particular case is little more than a venial sin.
I think that many people would consider this invasive even though the microphone only records vibrations on the exterior of the glass.
And as some have noted, Scalia was taking a common-sense rather than strictly scientific view: regardless of how the image is picked up, what it reveals is information about what is inside the home, and that is information that we normally expect to remain private.
I'm going to take a liberty of suggesting an editorial revision:
In afternoons in late August, the brown colored siding the west facing wall of the first story of my tudor house is often hotter than the both interior of my house and the outside air. The siding remains warmer for several hours after sunset.
The white portion of the wall remains cool all day.
And yet the rooms upstairs -- behind the white paint -- are warmer than the rooms downstairs -- behind the brown siding. Who'd a thunk? :)
Unlike WM13's hypothetical aliens interfering with the spectral emmissions of stars, the heat from the sun is neither hypothetical nor negligible!
I think Scalia got it right as a matter of physics, as applied to law. It's true that the IR radiation the police sense originates on the exterior of the building. But, the temperature of the exterior of the building is driven mostly by what is happening in the interior of the building.
Perhaps a good way to understand it is by analogy to speech. When you and I are in a room and you talk, I "hear" you by sensing fluctuations in air pressure on my eardrum. Those fluctuations are caused by pressure waves which you generate, which we call "sound." The air acting on my eardrums is not the same air as the air into which you introduced the sound. The energy/information/sound traveled through the atmosphere without any substantial gross displacement of the conducting medium (air).
When you see something, photons (or radiation, if you prefer) come off the object you're looking at (usually reflected from some other source) and travel to your eye. In a perfect void, or over a short distance in a reasonably light-transmissible substance (like air) you can think of the photons going from the target to your eye relatively undisturbed. But, there is always some degree to which they are diffracted and/or absorbed and re-transmitted. You can still extract a pretty good amount of data even in the presence of a high degree of noise caused by this diffraction or diffusion. So, even when the photons hitting your eye are not the exact same photons which bounced off the target, (as would be the case in fog) you can still "see" to some degree.
The fact that the particular photon the cops detect "originated" on the surface of the wall does not mean take away from the fact that the signal which they are looking for came from within the house. The important thing for most purposes (including this one) is the signal, not the carrier medium. If the signal originated inside the house, then I think it is fair to say that the cops were "looking" inside.
Well, I don't have any idea of what you bought, but what they use on The House Detective sequences with Steve Ramos NoCal inspector fairly regularly, is a handheld video display thermal imager that when pointed at an interior wall that has been identified as possibly having a water leak, shows pretty pictures that show which areas are relatively cooler from water evaporation and relatively warmer from being dry. If there is no color variation and a "warm" temperature, the conclusion is no leak, yet. Maybe the colors represent actual temperatures, beats me, but the colors yield about the temperatures inside the wall by receiving emanations and penumbras transmitted through the ether from the exterior of the wall to the equipment.
And so what. Normally data are evaluated rather than accepted without question. That is my point number 2:
2. of course, does the device give the authorities any useful or meaningful information, ie probable cause, about what is going on inside the house.
I might ask, how does one get probable cause if one does not evaluate what data are available, if one accepts some one thing uncritically and by itself? And isn't that a, you know, legal issue - "based on the evidence available was there sufficient evidence to amount to probable cause such that a warrant, whether for search or arrest, should issue?" Isn't that what all that 4th amendment stuff about what is necessary to justify warrants is about?
Scalia said: "A thermal imager reveals the relative heat of various rooms in the home."
Orin said: "[..] as a matter of physics, Scalia was wrong and Stevens was right."
To back up his assertion, Orin said: "[..] an infrared image only reveals the temperature of a surface, not the temperature of the space behind the surface."
The temperature of a surface depends, in large part, on the temperature of the space behind the surface. Using a thermal imager to observe that the surface of the walls outside one room are hotter than the surface of the walls outside another room yields the inevitable conclusion that the first room is hotter than the second room, i.e. it "reveals the relative heat" between the two rooms, in the same way that noting that a spring stretches further when one object is placed on it than when another is placed on it yeilds the inevitable conclusion that the first object is heavier than the second object.
To dispute Scalia's claim that "A thermal imager reveals the relative heat of various rooms in the home" is not to dispute the science behind thermal imaging but rather the philosphy of what constitutes "measurement" and "observation" and the linguistics of what the word "reveals" means - and to take a rather dubious position on both counts, I might add. This makes Scalia's words here a very poor candidate for being "the most scientifically irresponsible passage" in anything.
As a matter of physics, Scalia was right. As a matter of what Scalia said about physics, Orin was wrong. I have no idea whether Stevens was right or wrong as a matter of physics, because Orin declined to quote Stevens and I am declining to go look it up.