by Timothy Duignan
Salt water is fun to swim in - but it also
the electrical signals vital for life.
Nogueira/Unsplash, CC BY
Your tongue is a salt detector - it dissolves the solid salt
crystals sprinkled on your chips to create an intense flavor
But salt is way more important than just being a food additive. Salt
water is literally
the most common substance on the surface of Earth, and it's
really important - for life and for the planet.
Here are five things that will surprise you about plain old salt
1. Salt water carries
the electrical signals that make life possible
Salt water is made when a solid salt, such as table salt (sodium
chloride), is added to water and breaks apart into individual freely
moving particles called ions.
There are many kinds of
salt water, depending on which ions are present.
These ions act just like a balloon that's been rubbed against your
hair. They carry an electrical charge, and allow salt water to
Your body uses salt water to send the electrical signals that cause
your heart to beat and your brain to think.
To do this, the body has
special molecules called
ion pumps that move these ions around.
Many diseases are caused when these
ion pumps malfunction.
It also matters which ions carry these signals.
For example, replacing
sodium with its closest elemental relatives on the periodic table
gives either a
treatment for bipolar disease in
the case of lithium, or a
lethal injection ingredient in the
case of potassium.
2. Salt water acts as
a conveyor belt to carry heat around the planet
As made famous by the movie
The Day After Tomorrow, Europe
and North America are kept warm by
the Gulf Stream, a massive current
of warm water flowing north from the tropics.
The Gulf Stream is a huge flow of water north from the tropics.
This current is driven by changes in the saltiness of ocean water.
As the polar ice caps freeze in winter, the surrounding ocean water
becomes saltier. Saltier water is heavier and so it sinks to the sea
floor, stirring the ocean and driving these currents.
climate change melts the ice caps, these currents may be
upset the flow of heat and
nutrients around the world in complex ways.
3. Salt water can be
used to suck carbon dioxide out of the air
To prevent the worst effects of climate change we need to extract
carbon dioxide (CO2) from the air and store it on a huge
scale. The ocean currently already does this,
removing more than a quarter of all
the CO2 that humans put into the air.
CO2 reacts with water to form ions that increase the
ocean's acidity - which is a major problem for animals that live in
it. But we could use this effect for our benefit.
large volumes of air to water
containing potassium ions (similar
to salt water) can effectively capture CO2
This could be done
wherever power is cheap and there is somewhere to store
4. Building batteries
that use salt water could solve energy storage problems
Wind farms and solar panels are very effective at capturing energy -
but to address climate change
we need new and cheaper ways to
Lithium ion batteries, the most commonly used technology, use
lithium ions dissolved in a liquid to carry electricity back and
forth between the positive and negative terminals of a battery.
The liquid currently used
is expensive, slows the charging of the battery, and
can catch fire.
Replacing this liquid with salt water is a key goal of
battery research - with expected
benefits in cost and safety. These types of batteries are also
easier to manufacture, important for meeting increasing battery
5. But we still can't
predict even the simplest properties of salt water
Over the past century the importance of understanding salt water has
been recognized - some of science's greatest Nobel prizewinning
worked on this problem.
We're still making exciting progress on this question today, in part
by using powerful supercomputers and quantum mechanics to simulate
how salt water behaves.
Unfortunately, our ability to predict the properties of salt water
still has a long way to go.
For example, extremely
salty water can make a supersaturated solution which can be used to
make hand warmers (below video).
Heart-shaped hand warmers!
If this type of solution is left for long enough it will
spontaneously form a solid salt, but our theoretical predictions for
how long this will take are literally more than a quadrillion times
The magnitude of this
miscalculation tells us we're missing something vital!
The study of simple salt water is a hard sell compared with more
exciting science about
black holes or
curing cancer. But this
doesn't mean that it is any less important.
In fact, understanding salt water is vital for understanding our own
bodies and our own planet.
It may even be the key to saving them...