Category Archives: Mac’s Notebook

The Mantle of the Earth Now Believed to be Hotter Than Before.

A visualization of the layers of the Earth

The mantle of the Earth. The 1800 mile thick section of the Earth’s interior between the crust, which we live on, and the core, the ball of molten metal at the center of the planet. Compared to the other two sections, its makeup is more variable, with sections closer to the core being made up of solid rock, and upper sections reaching their melting temperatures and becoming molten. The mantle is responsible for much of the interesting geological occurrences on the planet, the most impressive of which is likely volcanic eruptions, which occur when molten mantle rock is shoved upwards and reaches the crust.

Molten rock from the mantle causes volcanic eruptions

Of course, volcanoes are only possible if the rock of the mantle is molten, which requires very high temperatures. This makes the question of the temperature of the Earth’s mantle one that scientists are very interested in solving. Scientists already know certain things about the Earth’s mantle, most importantly that there’s a boundary a couple dozen miles below the surface of the Earth that marks the point above which the rock begins to melt. To find the temperature of mantle rock, scientists should just have to find what temperature its components melt at, and derive it from that.

A sample of peridotite

The main obstacle to this has been that the material most of the upper mantle is made of, peridotite, tends to have water within it, and it’s very difficult to control the amount of water to get it to match the Earth’s core. Previous attempts to account for this have found that the temperature of this boundary point is likely 1350° Celsius, or 2462° Fahrenheit. However, a new method to test the amount of moisture in a sample of peridotite found that previous samples weren’t dry at all, despite previous assumptions! As a result, they found that the temperature of the mantle is likely 60° above what had previously been estimated, or 1410° Celsius. While this number may seem relatively insignificant, previous changes to the temperature of the mantle had been around 10° or less, so this represents a substantial change to our understanding of what lies beneath our feet.

The Oldest Garment in the World

Archaeologists recently confirmed that the Tarkhan Dress (which has decayed to just being a shirt at this point) is between 5,100 and 5,500 years old. This dates it to near the beginning of Egyptian society. Of course, it was a shock to find a (mostly) intact garment of such an age, since normally linen is destroyed by the ravages of time fairly quickly. (Fun fact, one of the major forces contributing to clothing falling apart over long spans of time is the friction caused by particles of dust coming into contact with it.)

The Dress was originally found in an Egyptian cemetery in the early 1900’s. Its significance was largely overlooked by the academic community, until 1977, when it was sent to the Victoria and Albert Museum. The long sleeved garment was found inside-out, and had significant creasing, suggesting that it had been actually worn, likely by one of the tomb’s occupants. At the moment, the dress stops at the midriff, but evidence such as similar, slightly younger garments, and images on nearby tombstones indicate that it would originally have been floor-length.

Alice Stevenson, the author of a recent study about the dress’ age.

The Dress has long been suspected to date back to the time of Egypt’s First Dynasty, but this was recently confirmed by radiocarbon dating. Radiocarbon dating is a process that we’ve only known about for around a century. It uses the decay of a certain Carbon isotope (isotopes are a type of particle that share chemical properties with each other, but slightly differ in mass) to measure how much time has passed. Carbon-14 is the one carbon isotope that is radioactive — which doesn’t mean it’s dangerous, just that it emits energy — and by finding the amount of it in a substance, we can tell how old it is. Since we have lots of evidence from very old things, like trees, we can use those as reference points to get very accurate dates, to within a few centuries.


The Mysterious Band of Holes

The First Photograph of the Band of Holes
The First Photograph of the Band of Holes

What would the ancient Incans have needed with thousands of holes, all around three feet wide, and two to three feet deep?  This question has plagued archaeologists ever since an aerial photograph, pictured above, publicized the phenomenon in 1931. When archaeologists got there in person, they found that the holes had been constructed by people, either by creating a pile of soil and digging a hole in that, or by piling stones in a circle. While this dispelled the rumor that the holes had been created by ancient aliens, it provided absolutely no hint as to who did make them, and why.

Victor Wolfgang von Hagen, one of the archaeologists who visited the Band in person.
Victor Wolfgang von Hagen, one of the archaeologists who visited the Band in person.

One of the earliest theories was that they were in fact all empty graves, and that the bodies had been destroyed by various natural phenomena over hundreds of years, but another man named Charles Stanish, an archaeologist  working at the University of California, Los Angeles, wasn’t convinced by this explanation.

Charles Stanish
Charles Stanish

In 2015, Charles Stanish took a team down to the Band of Holes, where they created a more detailed map of the holes, numbering 6,000, and became increasingly convinced that the holes dated to the time when the Incans conquered the Chinchan people. Based off of that belief, he hypothesized that the holes were actually a way of measuring the tax a Chinchan family would have to pay to their new overlords. There is circumstantial evidence for this — Monte Sierpe, the location of the Band of Holes, lies close to an administrative center of the Incan Empire, the place where taxes would have been collected, and the Incans had used similar schemes in other locations. They have yet to find conclusive proof, but Stanish plans to return, and look for microscopic evidence that would have been left behind. For the time being, the Band of Holes remains mysterious.

What do Horseshoe Crabs have to do with the Doctor’s Office?

Horseshoe crabs. The living fossils who have barely evolved since before the age of the dinosaurs likely aren’t a constant presence in your mind, but they play an important role in the medicine that keeps you healthy.

Horseshoe Crab, Limulus polyphemus
A Horseshoe Crab

These crabs have lived on Earth in their present form for over 450 million years,  living long before the dinosaurs were born, and long after the last of them died. They’ve played a fairly substantial role in human life, as they make excellent bait, and have edible eggs.

Fred Bang

However, an alternate use for them was recently (by the crabs’ standards) discovered by Fred Bang in 1956, who found that a cell in the blood of horseshoe crabs would cause it to harden when exposed to bacteria. This cell is called an amebocyte, and serves a similar role as white blood cells do in humans. This reaction naturally serves to insulate the crabs from bacteria, but Bang realized that it could be used as an easy way to detect the presence of bacteria in medicine. This allows scientists to easily determine which batches of a product pose health risks to humans, replacing a much slower practice of experimenting on rabbits to achieve the same results.

Tom Bentz, preparing to extract blood.

This blood is extracted by scientists who trap crabs on the shore and extract some of their blood, before releasing them back into the waters they were taken from. Currently, there is some debate on whether this method is humane enough, as the species is considered at risk and this method unavoidably leads to death in a small number of the crabs.

What to Look Forwards to in Space Travel in the Near Future

Today NASA announced its plans to contract with SpaceX, a private company headed by Elon Musk, to transport astronauts to the International Space Station for the second time. This signals the beginning of a new age of space travel, as private companies begin to take on a role previously held exclusively by government agencies such as NASA, with SpaceX leading the pack.

Elon Musk, CEO of SpaceX

SpaceX made headlines in 2012 when it became the first private company to make a manned trip into space, two years after it became the first private company to successfully return a rocket from low-Earth orbit. Its CEO, Elon Musk, is famous for his goal of getting humans living on Mars sometime in the next two decades, a timetable far ahead of most other feasible projects.

Getting a human colony on Mars has been a tenet of science fiction ever since the genre began, but it’s finally starting to seem like it could become a reality in the future, as SpaceX recently announced plans to begin its program by landing its Dragon module on Mars by 2018. Its collaboration with NASA is also seen as a good sign, with scientists such as Philip Metzger saying that “I believe it is completely feasible. No miracle inventions are required. No new physics. Just straightforward engineering and a modest budget for the development cost.”

Philip Metzger, a physicist at NASA

As SpaceX continues to expand its manned missions, we should look forwards to beginning to see how feasible this quintessential human dream might become in the near future.