Physics Newsletter August #2
- Bhavya Goel
- Sep 1, 2024
- 3 min read
Physics Pulse: Physics Newsletter
By: Bhavya Goel - Researcher
INTRODUCTION
Welcome to Physics Pulse, a non-profit physics organisation run by high school students. In our newsletter, our goal is to share the latest breakthroughs in physics and rephrase the concepts in the simplest way possible. Be sure to follow us on Instagram @physicspulse_ to stay up-to-date on new releases and connect with our community of physics lovers. We hope you enjoy our effort and get ready to dive into the wonders of the physics world!
Can we Predict Crashes , Blackouts and Climate Tipping Points?
There is a famous anecdote about lemmings that they run off cliffs to their collective doom. The scientists call the edge of the cliff a ‘critical point’ , the spot where the behaviour of a system (like the lemmings) suddenly goes from one state(happy) to another(plummeting). Extending this argument into our world , there are systems that experience critical points and abrupt disasters such as Stock Market Crashes , power grid failures , and tipping points in climate systems and ecosystems.
Critical points aren't literal points always but they can be values of some system- such as investor confidence, environmental temperature , or power demand. So , can we calculate these critical points ? Well , studies have shown that systems tend to ‘slow down’ and become more variable near critical points. For a share market this would mean heavy fluctuations in the prices of the stocks. But these indicators don’t work in real world systems very well. But there is one method that seems to work well even in real world systems which is called : RAD (Rescaled AutoDensity).
This method is verified on incredibly intricate recordings of brain recordings from mice. To be specific , we looked at activity in areas of the mouse brain responsible for interpreting what the mouse sees.
When a neuron fires, neighbouring neurons might pick up its signal and pass it on, or they might let it die away. When a signal is amplified by neighbours it has more impact, but too much amplification and it can cross the critical point into runaway feedback—which may cause a seizure.
It was noticed that parts of the brain which perform simpler tasks are much away from the critical point and the parts performing more complex functions are closer to the critical point , which makes sense.
It makes sense that being very far from a critical point (think of safe lemmings, far from the cliff face) would make neural activity very stable. Stability would support efficient, reliable processing of basic visual features.
But results also suggest there's an advantage to sitting right up close to the cliff face—on the precipice of a critical point. Brain regions in this state may have a longer "memory" to support more complex computations, like those required to understand the overall meaning of an image.
Physics in Cricket?
If you have ever watched Cricket , there is no way you haven’t come across the legend of Sri Lanka Lasith Maliinga and his unorthodox bowling position.
Researchers have started to unravel why it is so hard for the batters to hit Lasith Malinga using a wind tunnel. Aafrein Begum Faazil and colleagues describe the changes in pressure fields surrounding a ball due to the spinning brought on by bowling with a near-horizontal arm.
The amount and way that a cricket ball jukes along its trajectory heavily relies on the interplay between the spin of the ball and operational Reynold's number, a dimensionless quantity that relates fluid density, ball dimension, air speed, and fluid viscosity.
To get to the heart of their question, the team employed a wake survey rake device made of multiple tubes designed to capture the pressure downstream of the ball. This was complemented by an imaging system capable of detecting pressure variations sensed in the connected manometers. The study examined the flow dynamics of cricket balls rotating up to 2,500 revolutions per minute in a wind tunnel.
"The simultaneous traversal-imaging technique combined with the traditional manometers utilised in this study yielded remarkable precision, exceeding all expectations," Siddharth said. "This demonstrated to be an outstanding approach for replicating the intricate and dynamic situations experienced in sports contexts within a wind tunnel setting."
The group found that low-pressure zones expanded and intensified near the ball when spinning, while these zones shifted and diminished downstream. At higher spin rates, the low-pressure zone begins to change to a persistent bilobed shape.
The results lend support to the theory that these newer bowling techniques tap into the Magnus effect, in which high-speed spinning creates effects that shift the ball mid-flight.
References:
Crashes , BlackOuts , and Climate Tipping Points : How can we tell when a system is close to the edge ? - https://phys.org/news/2024-08-blackouts-climate-edge.html
Cricket Physics - Wind Tunnel Experiments reveal why bowling with a near horizontal arm makes for tough batting. – https://phys.org/news/2024-08-cricket-physics-tunnel-reveal-bowling.html
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