PRELIMS
CrSb: First Altermagnet Showing Direction-Dependent Conduction Polarity (DDCP)
Why in News: Researchers at S.N. Bose National Centre for Basic Sciences and Indian Association for the Cultivation of Science, Kolkata, discovered that the magnetic compound chromium antimony (CrSb) is the first altermagnet to exhibit direction-dependent conduction polarity (DDCP).
What is DDCP?
- Direction-dependent conduction polarity: A material conducts with electrons in one direction and holes in another.
What is CrSb?
- Chromium antimony — an inexpensive, stable magnetic compound exhibiting DDCP.
Significance of CrSb:
- First altermagnet to show DDCP.
- Easy synthesis and abundant composition.
- Acts as both n-type and p-type in a single crystal.
- Potential in thermoelectrics, electronics, and spintronics.
Spintronic Relevance:
- Altermagnets have zero net magnetism but spin-dependent electron behavior, useful in spintronics.
Vanadium Substitution Result:
- Replacing 2% of Cr with vanadium made the material fully p-type, matching theoretical predictions.
Android Phones Power Earthquake Early Warnings in 98 Countries
Why in News: A study published in Science reveals how Google’s Android Earthquake Alert (AEA) system has delivered successful quake warnings to users in 98 countries between 2021 and 2024.
Function: Uses accelerometers in Android smartphones to detect P-waves (fast seismic waves) and warn before destructive S-waves arrive.
How It Works:
- Crowdsources accelerometer data from stationary Android devices.
- Detects P-waves and triangulates with nearby phones.
- Algorithms estimate epicentre and magnitude.
- Alerts issued before S-waves arrive.
Earthquake Waves: Caused by sudden release of energy at the focus of an earthquake.
Types of Earthquake Waves:
1. Body Waves
- Travel through the interior (body) of the Earth.
- Originate from the focus.
Two types:
P-waves (Primary)
- First to arrive
- Move through solid, liquid & gas
- Vibrate parallel to direction → causes stretching & compression
S-waves (Secondary)
- Arrive later
- Travel only through solids
- Vibrate perpendicular → forms crests and troughs
- Crucial in understanding Earth’s internal structure
2. Surface Waves
- Generated when body waves interact with surface rocks
- Travel along Earth’s surface
- Slowest but most destructive
- Velocity & direction affected by material density and composition
AI Satellites – Dynamic Targeting by NASA
Why in News: NASA is testing a new AI-enabled satellite system called Dynamic Targeting, allowing satellites to make independent decisions in orbit without waiting for Earth-based commands.
What is Dynamic Targeting?
NASA initiative to equip satellites with onboard AI.
Enables satellites to:
- Scan terrain in real-time.
- Identify usable/cloud-free data.
- Decide autonomously whether to take an image.
- React without ground control inputs.
Significance / Benefits
- Reduces data waste by avoiding unusable (e.g. cloud-covered) images.
- Saves energy, bandwidth, and processing power.
- Reduces workload on human analysts.
- Enhances real-time decision-making in space.
AI Advantages in Space
- Intelligent data filtering onboard.
- Enables smart image capture.
- Facilitates autonomous response during critical events.
Strategic Applications
- Wildfire and volcanic activity detection.
- Monitoring storm systems and climate changes.
- Real-time response in disaster-prone zones.
- Enhances early warning systems for emergencies.
Ministry of I&B Orders Blocking of 25 Obscene Content Websites
Why in News: The Ministry of Information and Broadcasting has directed intermediaries to block 25 websites found hosting obscene and unlawful content, under relevant provisions of Indian law.
Legal Framework Invoked:
Information Technology Act, 2000
- Section 67: Punishment for publishing or transmitting obscene material.
- Section 67A: Punishment for sexually explicit content.
IT Rules, 2021: Intermediary Guidelines & Digital Media Ethics Code.
Bharatiya Nyaya Sanhita (BNS), 2023:
- Section 294: Punishment for obscene acts.
Indecent Representation of Women (Prohibition) Act, 1986:
- Section 4: Prohibition of indecent depiction of women.
Constitutional & Judicial Backing
- Article 19(2): Permits reasonable restrictions on free speech for decency and morality.
- Ranjit D. Udeshi v. State of Maharashtra (1965): SC held that obscene content is not protected under free speech (Article 19(1)(a)).
Philosophical Justification
- Mill’s Harm Principle (1859, On Liberty): Restrictions justified when liberty causes harm to others or society’s well-being.
Climate Tipping Point
Why in News: Researchers warn that the extreme marine heatwaves of 2023 may indicate the crossing of a climate tipping point—a potential irreversible shift in Earth’s systems.
What is a Climate Tipping Point?
- Critical threshold in Earth systems that, once crossed, leads to irreversible and self-perpetuating change.
- Defined by the Intergovernmental Panel on Climate Change (IPCC).
Examples Identified by IPCC:
- Amazon rainforest turning into dry savannah due to deforestation + warming.
- Atlantic Meridional Overturning Circulation (AMOC) slowdown.
- Melting of permafrost releasing methane, accelerating warming.
Why It Matters:
- Signals accelerated climate change and loss of system resilience.
- Threatens ecosystems, sea levels, monsoon patterns, and global climate stability.
