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Light can make water evaporate without heat

news.mit.edu

141–150 of 198 posts

Re: Light can make water evaporate without heat

#141

So can sound, almost as if anything with energy can move or excite particles. In other news scientist discovers water is wet.

Sound would literally mean waves of kinetic energy hitting both the surface of the water and traveling inside it. Does that really count as "without heat"?

Re: Light can make water evaporate without heat

#142
post #87

Earlier quoted context omitted.

You’re thinking about it right if you’re zoomed into the surface of the water plus a few millimeters above it. But the molecule clusters themselves evaporate after that, which pulls heat from the air.

Gotcha. That heat from the air is also energy input that has to be counted, so it still would equal out in the end, right?

Exactly

Re: Light can make water evaporate without heat

#144

Earlier quoted context omitted.

I imagine the leaves being green would encourage this evaporation. The upper layers of cells are probably effectively translucent and might be awash in green light, perhaps increasing the rate of evaporation and improving overall transpiration.

That’s my guess as well. The green chlorophyll is inside of the cell. It absorbs sunlight for food but reflects the green light back through the water-air boundary. Perhaps the effect on evaporation or water movement provides a better benefit for the plant than absorbing the energy of that spectra. For instance, by increasing the efficiency of respiration.

At its simplest, reflecting green light would send the light through the water twice instead of once. Neat trick, plants.

Re: Light can make water evaporate without heat

#145
post #71

> The researchers found that the effect varied with color and peaked at a particular wavelength of green light. I wonder if this affects photosynthesis in any way? IIRC plants are green because chlorophyll does not absorb that color. Maybe that’s partially because green light induces too much evaporation?

[dead]

Re: Light can make water evaporate without heat

#146
post #142

Earlier quoted context omitted.

Gotcha. That heat from the air is also energy input that has to be counted, so it still would equal out in the end, right?

Exactly

So a good analogy might be that it's like a tiny version of what happens in an atomizer. It takes more energy to evaporate water than to turn the same amount of water into a very fine mist. The droplets will then evaporate on their own, using an amount of energy equal to the difference between evaporation and misting.

Thank you, I've got a little clearer view of my world.

Re: Light can make water evaporate without heat

#148

So can sound, almost as if anything with energy can move or excite particles. In other news scientist discovers water is wet.

Sound would literally mean waves of kinetic energy hitting both the surface of the water and traveling inside it. Does that really count as "without heat"?

And what type of energy is light?

Re: Light can make water evaporate without heat

#149

I must be missing something. My ice cubes in my freezer evaporate with no light and no heat. My understanding of the situation was the surrounding air was pulling off moisture because of some sort of osmosis effect. So why is this news?

There is heat in your freezer, unless you cool it to 0 Kelvin.

Re: Light can make water evaporate without heat

#150

Earlier quoted context omitted.

Well, the chloroplast was evolved when all life forms were submerged in the sea

The sea is on the other side of a very carefully policed barrier.

Still, it's less of a challenge to pump water from your roots if you're in the sea. Did the earliest green plants even have roots?
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