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In this newsletter

• Space debris from rockets is threatening airplanes

• Human crowds act just like liquids

• Fragments of plastic detected in human brains

• Single largest structure in the known universe

Space debris from rockets is threatening airplanes

Researchers warn that falling space debris is increasingly posing a threat to airplanes. These are the debris from spacecraft orbiting the Earth, and with the growth of aviation and spaceflight industries, the risk of collisions is on the rise.

A lot of material gets left behind after the rockets are used to insert satellites into orbits. Millions of pieces of space debris, ranging from softball-sized chunks to tiny fragments, orbit Earth. Upon re-entry, these objects mostly burn up in the atmosphere, a process called ablation, transforming into fine particles as they melt and vaporize.

The growing number of space launches leads to more debris in orbit, increasing the chance of re-entry overpopulated areas. These large, heat-resistant objects can survive re-entry and cause significant damage if they collide with an aircraft. 

By analyzing 2023 air traffic data, researchers mapped the areas with the highest risk of disruption from re-entering space debris. They found that regions like Vancouver, Seattle, and the Eastern seaboard each face approximately a 25 percent annual chance of airspace disruption due to falling space junk.

In 2022, Spain and France closed airspace due to a re-entering rocket body, causing significant flight delays. This was the first time airspace was shut down due to this risk. Without stricter regulations, the amount of space debris will continue to grow, posing a long-term threat to aviation. 

To resolve this, researchers suggest that rockets could be designed to re-enter the atmosphere in a controlled manner, directing them to land in the ocean. The insights were published in the journal Scientific Reports.

Human crowds act just like liquids

Human crowds can exhibit behaviors similar to liquids under certain conditions, according to a team that observed crowds at the opening ceremony of the San Fermín festival in Pamplona, Spain, for four years.

An estimated crowd of 5,000 festival goers was monitored by placing two cameras overlooking the 50m by 20m plaza chosen for the event. The team measured factors like how tightly packed the crowd was and how fast they were moving. By analyzing footage, the team concluded the crowd was so dense they could treat it like a fluid in their mathematical model.

During the festival's opening, the density of the crowd went from two people per square meter to six people per square meter. When an upper limit of nine people per square meter was reached, pockets of several hundred festival attendees began to move at regular intervals. 

The crowd's movement generated a wave-like effect, where individuals separated by considerable distances moved in near-perfect synchronization. Their movement created the effect of ripples moving through the crowd. The team found these regular waves of motion happened naturally, without any outside force, like pushing, causing them.

The research can help address safety concerns at large events like concerts and festivals where the risk of crushing or suffocation is high. 

The insights were published in the journal Nature. 

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Fragments of plastic detected in human brains

In a study of 52 donated human brains, researchers discovered that microplastics can penetrate the blood-brain barrier and build up deeper in brain structures.

The University of New Mexico-led research highlights global plastic production as a key driver. Traces of polyethylene and other polymers were found in every sample and newer specimens had higher concentrations than older ones. 

The amount of microplastics in the brain appears to be increasing over time. Findings indicate a 50% rise in concentration over just eight years.

While the exact mechanisms are still being investigated, microplastics may enter the brain through various pathways. When present in the air, they can be inhaled and potentially reach the brain via the olfactory bulb. They can also be ingested through contaminated food and water, potentially crossing the blood-brain barrier.

The potential health consequences of microplastics in the brain are largely unknown. They may trigger inflammatory responses and oxidative stress in brain tissue, potentially leading to cell damage. Studies have found higher concentrations of microplastics in the brains of individuals with dementia, raising questions about a possible link.

The findings were published in Nature Medicine.

Single largest structure in the known universe

Astronomers from Max Planck Institute in Germany along with those at the European Space Agency (ESA) have found the largest known structure in the universe. Dubbed ‘Quipu’, it is a collection of galaxy clusters, groups, and individual galaxies that are not gravitationally bound to each other.

Quipu is named after an Incan system of counting and storing numbers using knots on cords. It is estimated to be 1.3 billion light-years across, making it the largest known structure in the universe. It is so large that it is responsible for a large part of the gravitational pull that causes the peculiar motion of the Local Group with respect to the Cosmic Microwave Background (CMB) frame. 

Researchers also revealed four other massive structures: the Serpens-Corona Borealis superstructure, the Hercules supercluster, and the Sculptor-Pegasus superstructure. All the newly discovered structures are relatively close, between 425 million and 815 million light-years away, suggesting even larger structures may exist further out.

The discovery of Quipu is significant because it challenges our understanding of the universe. It is not yet clear how such a large structure could have formed. 

Quipu is also important because it can help us to understand how galaxies evolve. 

The insights were published in the pre-print server arXiV. 

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Thanks for reading.
Until next time,
Adya