Energy & Green Tech

Harvesting big energy from small movement

Since the ancient Greeks, humankind has known that if you bring two things into contact, a small amount of electricity is created. One example is that we can rub a balloon with our hair and generate enough electricity to ...

Energy & Green Tech

Improving perovskite solar cell resistance to degradation

Perovskite solar cells (PSCs) can be made with low-cost materials, are highly efficient, can surpass traditional silicon solar cells, and have the potential to revolutionize renewable energy. However, one of the current drawbacks ...

Energy & Green Tech

A step toward producing solar fuels out of thin air

A device that can harvest water from the air and provide hydrogen fuel—entirely powered by solar energy—has been a dream for researchers for decades. Now, EPFL chemical engineer Kevin Sivula and his team have made a significant ...


Penguin feathers help inspire new de-icing techniques

Walking down a road during a white winter comes with its own set of challenges: the frigid cold, stepping around slippery ice on roads and the need to switch sidewalks to avoid dagger-sharp icicles that could potentially ...

Energy & Green Tech

Cleaning contaminated water with flax shives

Using the Canadian Light Source (CLS), a team of researchers from the University of Saskatchewan (USask) has found that a common agriculture byproduct can treat waste water contaminated by antibiotics and other pharmaceutical ...

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Water is a ubiquitous chemical substance, composed of hydrogen and oxygen, that is essential for the survival of many known forms of life. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products. Other water is trapped in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land.

Water moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea. Over land, evaporation and transpiration contribute to the precipitation over land.

Clean, fresh drinking water is essential to human and other lifeforms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. There is a clear correlation between access to safe water and GDP per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70 percent of freshwater is consumed by agriculture.

This text uses material from Wikipedia, licensed under CC BY-SA