Water, water, everywhere. We live on a blue planet the surface of the earth is more water than anything else. Our bodies are more water than anything else. You can survive a good deal longer without food than you can without water. Water is essential to life. This much, most people know. I suspect it’s also the only widely known chemical compound. I’m not sure how many others I can name but I do know that water is H2O.

I recently read something that started me thinking about water and how amazing this most fundamental compound is. It really is far more remarkable than I ever realised.

We have several fundamental laws of physics to thank for the nature of both hydrogen and oxygen. Change the nuclear or electromagnetic forces, and water might not form. Change the atomic structure of hydrogen and water might not form. Change the electronegativity of oxygen (it pulls electrons strongly) and it might not bond with hydrogen and so no water.

It is also highly ‘fortunate’ that water exists in all three states (liquid, gas, ice) and yet it is what happens to water when it freezes that is also so common we rarely notice it and yet so critical that if it didn’t, we would all die. One of the fun things about winter in Sweden is going for a walk on a frozen lake. The first time this happened we were incredibly anxious, until we noticed the snowplough making a skating track on the lake. We were less worried about falling in after that. And right there is the thing: ice is on the top and there is water underneath. And that is a bigger deal than I realised.

Water when it freezes it expands and crystallizes giving it a structure that is less dense than as a liquid water, meaning ice floats. Not all liquids do that when frozen. Most of them contract become dense and sink. If water did that instead of being on the surface and insulating and protecting the life below it would sink to the bottom and freeze from the bottom up massively disrupting the balance of the ecosystems or perhaps more likely, preventing them from forming in the first place. Nutrients could no longer cycle through water, ecosystems would be disrupted and the entire balance of the planet would inexorably shift.

We need water to drink, but we also need it to be the way it is when it freezes. Water not only regulates your temperature but the temperature of the planet, we know this and it is why so many people are worried about melting ice caps, rising sea levels, and global warming. More ice reflecting, rather than absorbing the sun’s heat, would be better for all of us.

If water contracted when it froze, the loss of floating ice would disrupt ecosystems, climate stability, and fundamental processes that sustain life on Earth. Life as we know it might not have evolved under such conditions, and if it had, it would look drastically different from what we see today.

Astrophysicists love to imagine different physics or different process that might give rise to other forms of life but the only form of life that we know is dependent on something that did not evolve, it just was. We are indeed highly fortunate that oxygen atoms and hydrogen atoms form in such a way to give water the unique properties it has.

And there is more to water than all of the above features. Water can absorb large amounts of heat without significant temperature change, but also water droplets stick to things. You see how water runs down a window pane but one of the incredible things about water is that it can also go up. Plants can develop capillary actions and bring water upwards because water is adhesive.

The shape of water is also necessary because water has polarity giving it a bent shape and is a product of fundamental laws of physics and chemistry. If life evolved it could only do so because water is the way that it is and there is no evolution in that – it is a product of the constants of physics. Change water’s shape and you’re into the realm of quantum mechanics and I’m very much out of my depth (pun intended) there.

Water makes ice which floats, it dissolves liquids, it absorbs heat, it is essential to metabolic processes, photosynthesis, it is transparent allowing light to penetrate it, it is bent, it has polarity and it has adhesion, and there isn’t another liquid on the planet that doesn’t rely on water that you could drink or even wash with.

According to DeepSeek, “Water’s existence hinges on the precise values of the fundamental constants in our universe. These constants govern everything from atomic bonding to stellar processes, making water—and life as we know it—a direct consequence of our universe’s unique physical laws. Alter the constants, and water disappears from the cosmic menu.”

There are plenty of reasons the next time you have a drink of water to wonder at the amazing abundant gift it is.