I don’t know about you, but I always used to believe that we had most of nature figured out. We have general relativity to do things with space, energy time and mass, we understand nuclear physics well enough to do fusion, we can make photographs of the universe and model black holes, we have Navier stokes for describing the movement of fluids, we have laws for electricity, laws for growth and populations and so on…
However, I’d like to give you a glimpse of how little we might actually know despite all of our massive advances in science and engineering. Introducing… 🥁🥁🥁 the photomolecular effect!
The photomolecular effect
Think we understood water? Think again. Do you know when water evaporates? The most well known way to make liquid water evaporate is to heat it up to its boiling point. There’s also a lesser known effect where a water molecule can randomly escape the liquid when it happens to randomly gain enough kinetic energy to escape the surface tension.
So that’s it right? We understand how water evaporates? Nope! Turns out there’s a third way for water to evaporate! In 2023, MIT scientists published a paper describing how water evaporates when hit by light, which they dubbed “the photomolecular effect”.
The effect is at its strongest when polarised green light hits the surface of a body of water at an angle of 45 degrees. What is most notable about this effect is that it is much more effective than using heat to make water evaporate. When 100% of light is used to heat up water to help it evaporate, the theoretical limit is , whereas the photomolecular effect has been observed to reach evaporation rates of and even . This is 3-5x more efficient than the previously known effect.
What is particularly notable to me is how this effect has been occurring wherever water is found for billions of years. It affects how clouds form and evaporate, how pools evaporate, how leaves hold water, how your glass of water in a home can evaporate spontaneously and much, much more.
And yet, we didn’t know about it. It has been happening to the most important and bountiful molecule known to us, and we simply didn’t know about it.
What can you do with this?
Most of the time when I see an article describing a newfound discovery such as the photomolecular effect, it’s standard to talk about how scientists, engineers and businesses can use this newfound effect to improve our models, make new and improved devices and machinery and equipment and much more.
This makes the discovery seem distant and intangible. Even though the paper’s right here!
Riiiighhhttt… here
There are also some newer papers published by the same authors going deeper into (i) modelling the effect using equations and (ii) coming up with a more comprehensive theoretical understanding of how this is possible, but… that’s it! There’s not much else publicly available on this topic, meaning this is completely new ground!
If you want to do interesting science, math or engineering maybe you can tinker with the equations, or get a few green LEDs and some hydrogel and maybe a fan or some tubes and you can get started tinkering with this stuff!
- The paper mentions cooling effects, can this be used in an interesting new way in an evaporative cooling setup?
- What does this effect mean for fog or clouds?
- I noticed that in poorly ventilated cellars, pools of water can remain for weeks. Could we perhaps speed this up somehow know that we know about this effect?
- Could this be meaningful in situations where we grow plants? Might it be useful or meaningful to increase or reduce evaporation rates now that we know where we might’ve been inadvertently causing evaporation with (green) light?
- Can you think of other situations where this might be relevant or interesting?
The world is your oyster! Knowledge is power!
Get tinkering! Do stuff!
You are allowed to make things!