Tree rings may hold clues to impacts of distant supernovas on Earth

Massive explosions of energy happening thousands of light-years from Earth may have left traces in our planet’s biology and geology, according to new research by University of Colorado Boulder geoscientist Robert Brakenridge. The study, published this month in the International Journal of Astrobiology, probes the impacts of supernovas, some of the most violent events in the known universe. In the span of just a few months, a single one of these eruptions can release as much energy as the sun will during its entire lifetime. They’re also bright — really bright.

Tree trunk, cross section showing annual growth rings, full frame

To study those possible impacts, Brakenridge searched through the planet’s tree ring records for the fingerprints of these distant, cosmic explosions. His findings suggest that relatively close supernovas could theoretically have triggered at least four disruptions to Earth’s climate over the last 40,000 years. Scientists have recorded supernovas in other galaxies that have produced a stupendous amount of gamma radiation — the same kind of radiation that can trigger the formation of radiocarbon atoms on Earth. While these isotopes aren’t dangerous on their own, a spike in their levels could indicate that energy from a distant supernova has traveled hundreds to thousands of light-years to our planet.

To test the hypothesis, Brakenridge turned to the past. He assembled a list of supernovas that occurred relatively close to Earth over the last 40,000 years. Scientists can study these events by observing the nebulas they left behind. He then compared the estimated ages of those galactic fireworks to the tree ring record on the ground. He found that of the eight closest supernovas studied, all seemed to be associated with unexplained spikes in the radiocarbon record on Earth. He considers four of these to be especially promising candidates. Take the case of a former star in the Vela constellation. This celestial body, which once sat about 815 lightyears from Earth, went supernova roughly 13,000 years ago. Not long after that, radiocarbon levels jumped up by nearly 3% on Earth — a staggering increase.

You can read more in the original paper (this version is adapted and abridged from Source).

Brakenridge, G.R., Solar system exposure to supernova γ radiation. International Journal of Astrobiology, pp.1-14.

Understanding climate change through forest simulators

The effects of climate change are sometimes difficult to grasp, but now a virtual reality forest, created by geographers, can let people walk through a simulated forest of today and see what various futures may hold for the trees. The researchers combined information on forest composition with information on forest ecology to create a forest similar to those found in Wisconsin. “As part of an NSF-funded CNH program grant with Erica Smithwick (E. Willard and Ruby S. Miller Professor of Geography at Penn State) we are working with the Menominee Indian Tribe of Wisconsin,” said Klippel, who also is director of Penn State’s Center for Immersive Experience. “Inspired by the Menominee’s deeper connection to the environment we believe that experiencing the future is essential for all environmental decision making.”

The first step, of course, was to create a forest of today. Using data on a typical Wisconsin forest, the researchers could have used strict or deterministic rules and placed trees in the forest. However, they chose to use a procedural method that would populate the forest using a set of ecological rules, creating a more organic, natural feel. “Orientation and small details of the trees are also randomized in the approach so that the trees don’t look exactly the same,” said Jiawei Huang, graduate student in geography, Penn State.

A virtual walk through this Wisconsin forest shows tall trees and understory. Strollers, using VR headsets and controllers, can reveal the types of trees in the forest, change elevations from forest floor to birds-eye view and in-between, and more closely examine the forest composition. The researchers chose two future scenarios, a base scenario and a hot and dry scenario. Using VR, visitors to the forest can see the changes in tree types and abundance and compare the base scenario to the hot and dry scenario.

The simulator scored high on heuristic evaluation criteria like natural engagement, compatibility with the user’s task and domain, natural expression of action, coordination and realistic feedback, navigation and orientation support, and sense of presence. The virtual environment is composed of realistic aesthetics, color schemes, illumination conditions, 3D models, and textures. The interactions with the menu, the environment, and the virtual objects are intuitive and compatible with user’s expectations.

You can read more in the original paper (this version is adapted and abridged from Source).

Huang, J., Lucash, M.S., Scheller, R.M. and Klippel, A., 2020. Walking through the forests of the future: using data-driven virtual reality to visualize forests under climate change. International Journal of Geographical Information Science, pp.1-24.

Landing a job isn’t always the right goal

Algorithms that assess the risk of citizens becoming unemployed are currently being tested in a number of Danish municipalities. But according to a new study, gaining employment is not the only relevant goal for those out of work — nor should it be for an algorithm.

Fieldwork and workshop progression in the study Source

Together with two colleagues from the Computer Science department at the University of Copenhagen, Professor Thomas Hildebrandt and Professor Irina Shklovski, Naja Holten Møller has explored possible alternatives to using algorithms that predict job readiness for unemployed individuals as well as the ethical aspects that may arise.

An employment framework is able to output assessments made by an algorithm that, via data on the citizen’s gender, age, residence, education, income, ethnicity, history of illness, etc., spits out an estimate of how long the person — compared to other people from similar backgrounds — is expected to remain in the system and receive benefits. The researchers aim to challenge the misconceptions related to unemployment that raise ethical concerns.

One important finding from the paper tells us that “not all struggles come from personal failings and that the structures within which we operate are often just as implicated. Caseworkers clearly recognized their own limitations and that they sometimes might act from a place of bias or carelessness in their work, but there was no clear route for an algorithmic system to mitigate these issues. Instead, caseworkers pointed to the unnecessary problems that the institution of job placement itself created.”

You can read more in the original paper (this version is adapted and abridged from Source).

Holten Møller, N., Shklovski, I. and Hildebrandt, T.T., 2020, October. Shifting concepts of value: Designing algorithmic decision-support systems for public services. In Proceedings of the 11th Nordic Conference on Human-Computer Interaction: Shaping Experiences, Shaping Society (pp. 1-12).