iStock
iStock

Researchers Pore Over the Physics Behind the Layered Latte

iStock
iStock

The layered latte isn't the most widely known espresso drink on coffee-shop menus, but it is a scientific curiosity. Instead of a traditional latte, where steamed milk is poured into a shot (or several) of espresso, the layered latte is made by pouring the espresso into a glass of hot milk. The result is an Instagram-friendly drink that features a gradient of milky coffee colors from pure white on the bottom to dark brown on the top. The effect is odd enough that Princeton University researchers decided to explore the fluid dynamics that make it happen, as The New York Times reports.

In a new study in Nature Communications, Princeton engineering professor Howard Stone and his team explore just what creates the distinct horizontal layers pattern of layered latte. To find out, they injected warm, dyed water into a tank filled with warm salt water, mimicking the process of pouring low-density espresso into higher-density steamed milk.

Four different images of a latte forming layers over time
Xue et al., Nature Communications (2017)

According to the study, the layered look of the latte forms over the course of minutes, and can last for "tens of minutes, or even several hours" if the drink isn't stirred. When the espresso-like dyed water was injected into the salt brine, the downward jet of the dyed water floated up to the top of the tank, because the buoyant force of the low-density liquid encountering the higher-density brine forced it upward. The layers become more visible when the hot drink cools down.

The New York Times explains it succinctly:

When the liquids try to mix, layered patterns form as gradients in temperature cause a portion of the liquid to heat up, become lighter and rise, while another, denser portion sinks. This gives rise to convection cells that trap mixtures of similar densities within layers.

This structure can withstand gentle movement, such as a light stirring or sipping, and can stay stable for as long as a day or more. The layers don't disappear until the liquids cool down to room temperature.

But before you go trying to experiment with layering your own lattes, know that it can be trickier than the study—which refers to the process as "haphazardly pouring espresso into a glass of warm milk"—makes it sound. You may need to experiment several times with the speed and height of your pour and the ratio of espresso to milk before you get the look just right.

[h/t The New York Times]

nextArticle.image_alt|e
MARS Bioimaging
The World's First Full-Color 3D X-Rays Have Arrived
MARS Bioimaging
MARS Bioimaging

The days of drab black-and-white, 2D X-rays may finally be over. Now, if you want to see what your broken ankle looks like in all its full-color, 3D glory, you can do so thanks to new body-scanning technology. The machine, spotted by BGR, comes courtesy of New Zealand-based manufacturer MARS Bioimaging.

It’s called the MARS large bore spectral scanner, and it uses spectral molecular imaging (SMI) to produce images that are fully colorized and in 3D. While visually appealing, the technology isn’t just about aesthetics—it could help doctors identify issues more accurately and provide better care.

Its pixel detectors, called “Medipix” chips, allow the machine to identify colors and distinguish between materials that look the same on regular CT scans, like calcium, iodine, and gold, Buzzfeed reports. Bone, fat, and water are also differentiated by color, and it can detect details as small as a strand of hair.

“It gives you a lot more information, and that’s very useful for medical imaging. It enables you to do a lot of diagnosis you can’t do otherwise,” Phil Butler, the founder/CEO of MARS Bioimaging and a physicist at the University of Canterbury, says in a video. “When you [have] a black-and-white camera photographing a tree with its leaves, you can’t tell whether the leaves are healthy or not. But if you’ve got a color camera, you can see whether they’re healthy leaves or diseased.”

The images are even more impressive in motion. This rotating image of an ankle shows "lipid-like" materials (like cartilage and skin) in beige, and soft tissue and muscle in red.

The technology took roughly a decade to develop. However, MARS is still working on scaling up production, so it may be some time before the machine is available commercially.

[h/t BGR]

nextArticle.image_alt|e
ESA/Herschel/SPIRE; M. W. L. Smith et al 2017
Look Closely—Every Point of Light in This Image Is a Galaxy
ESA/Herschel/SPIRE; M. W. L. Smith et al 2017
ESA/Herschel/SPIRE; M. W. L. Smith et al 2017

Even if you stare closely at this seemingly grainy image, you might not be able to tell there’s anything to it besides visual noise. But it's not static—it's a sliver of the distant universe, and every little pinprick of light is a galaxy.

As Gizmodo reports, the image was produced by the European Space Agency’s Herschel Space Observatory, a space-based infrared telescope that was launched into orbit in 2009 and was decommissioned in 2013. Created by Herschel’s Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS), it looks out from our galaxy toward the North Galactic Pole, a point that lies perpendicular to the Milky Way's spiral near the constellation Coma Berenices.

A close-up of a view of distant galaxies taken by the Herschel Space Observatory
ESA/Herschel/SPIRE; M. W. L. Smith et al 2017

Each point of light comes from the heat of dust grains between different stars in a galaxy. These areas of dust gave off this radiation billions of years before reaching Herschel. Around 1000 of those pins of light belong to galaxies in the Coma Cluster (named for Coma Berenices), one of the densest clusters of galaxies in the known universe.

The longer you look at it, the smaller you’ll feel.

[h/t Gizmodo]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios