Top Science News

Why Do We Salt Our Roads?

We’ve probably all noticed that it’s a little cold at the moment – in fact, Scotland, England, Wales and Northern Ireland have all experienced their coldest temperatures of this winter so far, dropping as low as -13°C in some places.

However, have we ever stopped to think why we use salt to grit our roads and pavements?

A common misconception of the reason we use salt in cold weather is that it causes the ice to melt. This is in fact not the case! When water and salt are mixed together, the freezing point of the water/salt solution is lowered to well below 0°C. Although how much the freezing point is lowered depends on how much salt is used, the salt solution used in most cities will lower the freezing point to about -9°C.

It is important to note that for the salt to effectively lower the freezing point of water it must be mixed in with liquid water. This is why many cities spray a salt solution on roads and pavements before any ice forms. If salt is put on top of ice, it will rely on the sun or friction from cars driving on the surface to melt the ice to a slush before mixing with the water thus lowering the freezing point.

Boldly Going Where No 3D Printer has Gone Before

3D printers typically build objects by depositing or solidifying material, usually plastic, layer by layer. However, researchers at the University of California, Berkeley have developed a new printer that creates structures by projecting light into a resin that then solidifies as a whole. The 3D printer has been nicknamed the “replicator” as a tribute to the machines in Star Trek that can materialise any inanimate object.

The researchers were inspired by CT scanners. These work by taking x-ray images of patients from many different angles which are then reconstructed to build a 3D model. The researches have applied the same process but in reverse. By using a computer program to produce 2D images at many different angles of a 3D model, they then compiled all the images into a video sequence. Using a resin that solidifies when in contact with specific intensities of light, they projected this video onto the resin while rotating the resin vat to create the object, in this case Rodin’s “The Thinker”.

Although further work is needed to increase the scale of the objects made and improve the finish of the objects, it took the researcher only a couple of minutes to materialise The Thinker using this method, while using traditional 3D printers would typically take a few hours.

The miniature copy of The Thinker created by the “Replicator” (Credit: Stephen McNally, UC Berkeley)

Alligator Have a Strange Taste for Rocks

The typical alligator’s diet is varied, including many types of mammals, birds and other reptiles, but scientists have long known that alligators also swallow rocks. The likely reasoning behind this was thought to be an aid in digesting their tough-to-process meals, much like birds have been found to do, or just an accident when digging into a live and thrashing dinner.

However, a new study points to a different reason: alligators could be consuming stones on purpose as a way of increasing the time they spend under water on dives.

Researchers looked at seven young American alligators in their lab and measured how long they stayed submerged before and after voluntarily swallowing small (<10mm in diameter) granite stones equivalent to 2.5% of the alligator’s body weight. The scientists found that the average duration of dives increased by 88% and the maximum duration increased by 117%. When swallowing the stones to increase their specific gravity, the alligators compensated by increasing lung volume and therefore dived with larger stores of oxygen.

Photo by Lance Anderson on Unsplash

Written by Jeanne Kroeger

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