New Evidence Shows Heat Isn’t Necessary For Water To Evaporate

If you’ve done much daydreaming about how water evaporates (we won’t judge), you might have considered heat to be a bit part of the equation. But a new study reveals that the presence of light is enough to get the job done.

The photomolecular effect

As MIT researchers discovered, light is actually more efficient than heat at completing the evaporation process. But since sunlight is the key factor in most of the planet’s natural evaporation, there’s been a longstanding assumption that heat is a requirement.

That theory has been under scrutiny for years in light of multiple studies involving so-called hydrogels containing liquid water that evaporated much more rapidly than expected. This prompted an MIT team to take a closer look.

What the experts found was that light is capable of delivering the energy needed to allow molecules to escape as vapor into the atmosphere. This process became known as the “photomolecular effect.”

Why it happens and what it means

While all light seems to work, studies show that certain wavelengths — green light in particular — are more effective than others.

More research into the science behind this effect is underway, but scientists believe it is possible because photons essentially target molecules close to the surface of the water. Since water doesn’t absorb light, there isn’t much wasted energy.

And this could all be happening in clouds and elsewhere in nature, which has sparked some theories regarding how we could harness the effect to benefit humanity and the planet itself.

Some folks think it might provide a more effective method of desalinating ocean water to compensate for shortages caused by human use and droughts. It could theoretically also lead to the development of more efficient cooling systems that rely on the evaporation process.

Chris Agee November 2nd, 2023

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