Wondering About Wetness

dropletsIn a discussion a while back I mentioned in passing that humans sense wetness and time. That was challenged on the basis that we don’t sense time at all and — when it comes to wetness — sense only pressure and temperature. There is some truth to that. We don’t have an actual time sensor, nor do we have specific “wetness” sensors.

I’ve been thinking about this ever since (not constantly; you know, on and off). A key question is whether wetness can be reduced to pressure and temperature and remain wetness. And time is a topic all on its own!

For the record: Here is my final answer…

The first thing is that the property of wetness is itself an emergent property of liquid water. Steam and ice are not wet.[1] An H2o molecule has no “wetness” property. It does have some electrical properties that cause groups of H2o molecules to behave in a way known as wetting.

We experience many emergent phenomenon:

  • A movie (or a video) is a series of still pictures(frames) seen fast enough to appear to us as motion (hence the term, motion pictures).
  • A musical chord emerges from simultaneous notes; a melody emerges from notes played successively in time.
  • The pixels that make up the image on any monitor or display screen are little dots of red, green and blue. White, yellow, cyan, and magenta, are emergent colors.[2]

If we separate the colors or the notes or the pictures, we no longer perceive the emergent phenomenon. They are irreducible. They exist only in the sum of the parts.

air pressureA characteristic of these emergent phenomenon is that what emerges does so only in our minds. There do exist emergent phenomenon where the emergent property is physically measurable. Air pressure is an emergent property of the motion of air molecules. It can be measured with a gauge.

But the motion of a movie, or harmony of a chord[3], or the perception of white from red + green + blue, cannot be measured with any gauge. They are integrated and perceived within the human mind. Even a shift of mental focus, such as with some optical illusions, can change our perception.

Is wetness also a set of sensory inputs integrated and perceived only in the human mind? As with musical chords, wetness has physical properties that can be measured. Wetting is a specific and quantifiable process we can characterize objectively. But the sensation of wetness, as with the sensation of a chord, may be a type of qualia — something experienced only by minds.

water tower hot cold

The wetness of water seems more than just a temperature and a pressure. Water has a vast range of temperatures, and many not-wet things have temperatures in that range. Given the range water does have, temperature doesn’t describe wetness very well.

Water does have some unique temperature characteristics. It’s a huge heat sink — it can absorb and hold heat like crazy. Your hand in any decent amount of water doesn’t affect the water temperature, so you feel constant temperature.[4] Water cools what it evaporates from. If your arm is wet, a good breeze chills it.

That heavy close feeling of high humidity comes from water vapor in the air blocking evaporation from your skin. You sense water’s heat behaviors on that subtle of a level!

These unique temperature characteristics may be a big part of the integrated sensation of water. (For that matter, even the electrostatic properties involves in wetting may be sensed by your nerves in ways below your perceptual horizon.)

wet skinPressure is more specific. One characteristic of water is that it touches your skin smoothly everywhere. In fact, specifically, it wets your skin. That’s a fairly unique sensation. Many dry things have a surface texture water lacks. (The viscosity of water may also play a role in the sensation of wetness.)

Slick rubber, leather, or metal, can sometimes briefly fool us by feeling wet. A common response having touched such an object is to rub thumb and finger to see if a surface of water is present. Another characteristic of wetness is that it transfers to what touches it.[5]

My bottom line, though, is this: Is it possible to describe “wetness” in terms of temperature and pressure in a way that is both descriptive and unique? Can it be reduced to a description of temperature and pressure or does that leave something out?

The wide range of water temperatures is so generic. Pressure and texture might describe more, but I think that — as with the canonical seeing red — wetness is an irreducible sensation (a qualia) you have to experience to know.


time slowsWhat about time?

Maybe that’s something to do in more detail another time. For now just consider what it means to have a thought. That is, for your mind to process a serial set of symbols.

In order to have the thought, “I think, therefore I am!” there must be time in which to have the thought.

Your sense of balance is based on “sand” in little hollow donuts inside your head. You don’t sense the sand moving around inside the donuts. You do sense your balance. (There are more than the five physical senses.)

There may be no physical time sensor in the human body, but the biological processes of our bodies occurs in time, and our mind occurs in time, so it seems to me we have a very definite (if non-physical) sense of time.


So it’s been interesting to chew on, but I think I’m going to go with my original answer: Humans sense wetness and time. The former is an irreducible qualia perceived in the mind (yet also having distinct and complex physical properties; see tree, forest, sound). The latter is a non-physical sense that also occurs in the mind.

I do think it is very interesting to pay attention to qualia, to tease them into what parts we can discern, but I’m not sure reducing them to those parts keeps the whole. It’s like focusing on the pixels.

water pixels


[1] Anyone who’s lived in really cold country — with temps down to -20 (F) for days in a row — knows that ice is rock-hard and dry as a bone at those temps.

For example, the water ice on Pluto isn’t just rock hard, it is rock! And it’s no more “wet” than a rock you’d pick up off an Earth mountain would be. (Assuming it wasn’t raining or something.)

Steam isn’t wet, either, but when it hits something that cools it down, condenses to liquid water, which makes the surface wet.

[2] For that matter, seeing an image at all from a set of dots is an emergent thing.

[3] This one is, perhaps, debatable. The beat notes and harmonics created by a chord are physically present. It’s really a version of the “tree falls in the forest” question. It depends on how you define sound: pressure waves or what is heard.

But ask yourself why different musical intervals (e.g. a fifth versus a seventh) please the ear differently or why different chords (e.g. C versus Cm7) sound different. That reaction is human.

[4] Being in colder water always sucks heat from your body. Being in hotter water always heats you up. The water always wins. This is why falling into icy water is a killer.

[5] The “offset” (lithographic) printing industry depends on this not being true in all cases. Specifically, water and oil don’t mix.

About Wyrd Smythe

The canonical fool on the hill watching the sunset and the rotation of the planet and thinking what he imagines are large thoughts. View all posts by Wyrd Smythe

14 responses to “Wondering About Wetness

  • Steve Morris

    I think you nailed wetness. Time is a more difficult topic. Time is not a qualia, although our experience of it may be. Time is a physical thing that is reducible, but to what? It’s a fundamental physical phenomenon that physicists struggle to define.

    • Wyrd Smythe

      “Time is not a qualia, although our experience of it may be.”

      Yeah, it really is its own topic. If we experience it in some fashion, then it’s at least something like qualia. What is the “something it is like” to experience time? I’d argue it’s not a physical thing if physical means matter. It’s physical in the sense that gravity and energy are, though. It certainly seems a real aspect of existence.

      On the other hand, so is wetness, so maybe it’s all in how you look at it.

      As you indicate, we don’t understand time yet, and it’s pretty mysterious in all sorts of interesting ways. There’s a great xckd cartoon about how, as dimensions go, if you have to be constantly pushed though one, time isn’t as bad a choice as the others. XD

      Can you imagine being forced through a spatial one? o_O

      FWIW: The jury is still out, so I’m maintaining a (perhaps futile) hope that Einstein turns out to have nailed it. I’m fine with matter and energy being quantized. They obviously are (or seem to be). But I want space and time to be smooth and continuous (just like Al intended). Maybe it’s part of the basic wave-particle duality we already know exists.

      But that’s just something I fancy. (For a while it looked like the BICEP2 results put a pin in that balloon, but their results turned out flawed.)

      • Steve Morris

        And yet if you force yourself through a spatial dimension, time eases off and slows down 😦 So you do have a choice.

      • Wyrd Smythe

        😀 And Minkowski space in SR is where the whole idea of time as the “fourth dimension” comes from in the first place!

        The thing is, time doesn’t slow down for you, just for people watching you. You’re kind of stuck with your proper time.

    • rung2diotimasladder

      @ Steve: “Time is a physical thing that is reducible…”

      Unless you’re a Kantian. For him, time was a necessary form of inner experience (in other words, without it, we wouldn’t have experience at all). I think he’d say we can experience an “objective” time (which is what I think you’re talking about), but time itself is subjective.

      • Steve Morris

        Our perception of time may be an intrinsic part of human experience, but it also has an objective reality. The universe existed for 13 billion years before any humans existed to experience it. Would Kant have disputed that?

      • rung2diotimasladder

        I doubt he’d dispute: “The universe existed for 13 billion years before any humans existed to experience it” in so far as this is recognized as a scientific claim derived from phenomena and reason.

        Kant rescued science from Hume’s skepticism on causality and tried to give scientific laws universality. Hume restricts knowledge to sense data and then shows how we can’t derive causality from this mere data. All we can have are beliefs, Hume claims. Kant agrees that causality can’t be derived from mere sense data, but tries to show that we can have more than beliefs…we can have laws.

        That said, the mind does not draw the laws of nature from the physical world in-itself (what he’d call “nouemena”). Science is not strict empiricism or strict rationalism, but a combination of the two. He would be at odds with “scientific realists,” or those who hold that science tells us the world as it is in itself. The world as it is in itself is unknowable for Kant. But knowledge of the world of appearances IS possible.

        The problem for Kant would be calling time a thing itself. I’m not sure that’s what you meant by calling time a “physical thing”…I could have been misinterpreting you.

      • Steve Morris

        I would agree that you can never be 100% certain of anything (including your own beliefs), and I am not a strict scientific realist in the sense you describe. But to say that the world is unknowable strikes me as a dogmatic position itself. I think that at this point, science is a work in progress, so we can’t be certain that time is a thing, but neither can we simply say that it isn’t. There is certainly something that looks like time that’s out there somewhere 🙂

      • Wyrd Smythe

        @Tina: “For him, time was a necessary form of inner experience (in other words, without it, we wouldn’t have experience at all).”

        This is what I was getting at in the post in that short bit about time.

        (FWIW, I have a follow-up post I’ve been lazy about finishing and posting, but I couldn’t resist the title: Thinking about Time. It’s possible some of that post might inform this discussion. Or vice-versa, actually.)

        @Steve: “Our perception of time may be an intrinsic part of human experience, but it also has an objective reality.”

        I think anything we experience as qualia has to have objective reality, and I think we all — including Kant — agree on time’s objective reality. (We have no clue what that actually is, which has led to some creative ideas about the nature of its reality.)

        (FWIW: At issue in this post is whether humans sense time. I’m taking its objective reality in some form as given.)

        @Steve: “But to say that the world is unknowable strikes me as a dogmatic position itself.”

        I got the impression you and Tina might mean different things? Kant is referring to the (I believe true) fact that everything our minds can know about the world outside our minds comes to us through our five senses. Which are interpreters of that external reality. All we can know is what they tell us.

        Taking the dual step of accepting the external reality and the legitimacy of others (in particular their testamony about their perceptions of that same reality) allows us to zero in on a description of that reality. It thus validates our senses to some extent and allows us to trust in that reality. But we can never know for sure some form of solipsism isn’t true.

        The idea that science will answer most questions presented by that reality is a separate (and interesting) question. I know there are many who believe we will eventually know all there is to be known about the physical universe, that science will answer all questions (for a reasonable value of “all”).

        (FWIW: I am not among them. 🙂 For my money, Gödel, Turing, and Heisenberg, seem to show we can’t know everything, even in principle. Those three all refer to specific situations, but I can’t help but wonder to what extent three separate and fundamental limits apply to the universe in general.)

      • rung2diotimasladder

        “There is certainly something that looks like time that’s out there somewhere”

        It’s on your face in the form of glasses. 🙂

        All kidding aside, I’m not really a Kantian in the strict sense. I just wanted to put that out there.

        His work on time does strike me as revealing. I think it is one of those fundamental attributes of experience, probably a key to many mysteries, but who knows where it comes from. I tend to think it’s both “subjective” and “objective” (those are not words I’d like to use, but they’ll do for now), both of which are different kinds of phenomena. Where I depart from Kant is in assuming there’s something behind the phenomena that can’t be reached. There may be, there may not be. Who knows.

  • SelfAwarePatterns

    Interesting post Wyrd!

    On wetness, it might be worth noting that not all chemicals have a liquid phase. Carbon, for instance, is a solid until it sublimates into a gas at 3915 K. Although I suppose someone could argue that carbon’s liquid phase temperature range is just too narrow for us to observe, some fraction of a degree between 3914 K and 3915 K.

    You could also argue that “solid” is just liquid that takes a very long time to flow (possibly millions or billions of years). If so, then it really is just a distinction that exists in minds.

    • Wyrd Smythe

      Thanks! I was surprised about carbon not really having a liquid state, so I poked around a bit. Turns out carbon is like CO2. At normal pressures the solid sublimates, but at high pressures you do get a liquid.

      There’s a science teacher experiment involving a small chunk of frozen CO2 in a capped bottle. The CO2 melts and becomes a liquid due to the pressure. When upcapped, the liquid instantly vaporizes. (There’s another version involving enough CO2 to explode the bottle. 😀 ) There’s some controversy regarding the triple-point of carbon, but it does seem to have a known liquid stage (although maybe not well known — some serious pressures involved!).

      Carbon Phase Diagram

      Phases usually involve distinct arrangements of the atoms or molecules, so there are objective criteria for “solid” and “liquid” but it would be interesting to know to what extent solids “flow” given enough time. Warm them up enough, and they certainly do. Even rocks. OTOH, lava (I assume) and molten steel would be considered liquids.

      Good thing I was just talking about the “wetness” of water. Phases of materials is a different worm can. Philosophy is much easier. It’s harder for people to prove you’re wrong! XD

  • reocochran

    Okay, I would never try to convince you of something such as sensing time. I would immediately agree with water and wetness. In the middle of the night, I have awakened to being covered with sweat. So my subconscious mind during my REM sleep pattern sensed this uncomfortable state I was in and woke up.

    I love your sense of logic and how you explain things. I may seem like an “arguer” but you would “win” or I would “concede” most of our friendly debates if we were every close enough to do so, in person. 🙂

    • Wyrd Smythe

      I know what you mean about dreams. Perceptions of what’s going on around us filter into them all the time!

      The thing about debate is that the points should matter, not the debating skill. But there is a lot to be said for being able to speak your piece clearly. Some of that is practice. Some of that is thinking about your thoughts — self-checking your own thinking. (I sometimes have a debate in my head, and my opponent never lets me get away with anything! That guy challenges everything I say! 😡 ) Some of it, admittedly, is love of words and debate. Someone who loves the game always does better, I think.

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