Short on time before UPSC Prelims and struggling with tricky concepts? The exam increasingly tests your conceptual clarity and ability to apply core ideas, especially in the most dynamic subjects: Science, Economy, and Environment (SEE).UPSC Essentials’ new initiative, UPSC Prelims ‘SEE’ Snapshot, brings you, every Wednesday, a quick, exam-focused revision of key concepts. In each article, we pick three important current themes from Science, Economy, and Environment and decode them strictly through the Prelims lens—focusing on concepts and clarity.SCIENCEGPS interference Core Concept: — Both ships and aircraft depend on global navigation satellite systems (GNSS) for position, navigation, and timing (PNT) information. Of these, the American Global Positioning System (GPS) is the most popular GNSS, with the terms often used interchangeably. But there are other GNSSs as well, like Europe’s Galileo, Russia’s GLONASS, China’s BeiDou and India’s NavIC — GPS interference refers to spoofing or jamming, two types of deliberate cyber-attacks on Global Positioning System (GPS) signals, which disrupt or deceive vehicles’ navigation systems. While both are often used synonymously with each other, spoofing and jamming refer to slightly different kinds of interference. — GPS jamming involves a device (jammer) emitting strong radio signals on GPS frequencies in order to overpower weaker signals. This disrupts the functioning of GPS systems by rendering receivers unable to determine location or time. Story continues below this ad— GPS spoofing involves a device transmitting signals on the same frequencies used by GPS satellites, overwhelming or blocking the GPS receivers from acquiring or maintaining the right satellite signals. Unlike jamming, which disrupts signals entirely, spoofing deceives the receiver into trusting false data. (Image: Created by Google NotebookLM)— Of the two, spoofing is the more serious offence, disrupting signals and forcing pilots, for instance, to incorrectly account for factors such as altitude or terrain. Spoofing may tell an aircraft it is in a location it isn’t supposed to be in, and create confusion in the cockpit. UPSC Twist Points– GPS interference vs Trojan horse and Phishing— Trojan horse is a destructive program that looks like a genuine application. Unlike viruses, Trojan horses do not replicate themselves but they can be just as destructive. Trojans open a backdoor entry to your computer which gives malicious users/programs access to your system, allowing confidential and personal information to be theft. Story continues below this ad— Phishing: It is a common type of cyber-attack that targets individuals through email, text messages, phone calls, and other forms of communication. A phishing attack aims to trick the recipient into falling for the attacker’s desired action, such as revealing financial information, system login credentials, or other sensitive information. Fundamentally, these threats exploit human psychology rather than technical vulnerabilities. ECONOMYMonetary PolicyCore Concept: — Monetary policy refers to the use of monetary instruments under the control of the central bank to influence variables, such as interest rates, money supply and the availability of credit, with a view to achieving the objectives of the policy. The monetary policy is used by the RBI to maintain price stability while keeping in mind the objective of growth. — Notably, in May 2016, the RBI Act was amended to provide a legislative mandate to the central bank to operate the country’s monetary policy framework. The framework, according to the RBI website, “aims at setting the policy (repo) rate based on an assessment of the current and evolving macroeconomic situation and modulation of liquidity conditions to anchor money market rates at or around the repo rate.”Story continues below this ad— Various direct and indirect instruments are used by the RBI for implementing monetary policy, including Repo Rate, Reverse Repo Rate, Marginal Standing Facility (MSF), Liquidity Adjustment Facility (LAF), Bank Rate, Cash Reserve Ratio (CRR), Open Market Operations (OMOs) and Market Stabilisation Scheme (MSS). UPSC Twist Points– Monetary Policy vs Fiscal Policy— Both monetary policy and fiscal policy serve as critical tools for managing the economy of our country. One key distinction between monetary and fiscal policy lies in their implementation authorities and tools. Monetary policy is formulated and implemented by the RBI, which primarily focuses on regulating the money supply, interest rates, and inflation levels. — On the other hand, the government makes decisions pertaining to fiscal policy, and the Ministry of Finance plays a central role in formulating budgets, tax policies, and expenditure plans. The government employs fiscal policy to manage aggregate demand, promote growth, and address socioeconomic challenges.Story continues below this ad— Additionally, monetary policy tends to affect borrowing costs and financial markets more immediately, which affects investment and consumption patterns. Fiscal policy measures, on the other hand, such as tax reforms or infrastructure spending, may have longer-term and more extensive effects on economic development and growth.ENVIRONMENTHeatwavesCore Concept: — According to the Indian Meteorological Department (IMD), a heatwave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India. Heatwaves typically occur between March and June, and in some rare cases even extend till July. — The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, sometimes resulting in death.Story continues below this ad— A heatwave is declared when the maximum temperature of a station reaches at least 40°C or more for plains, 37°C or more for coastal stations, and at least 30°C or more for hilly regions. Based on departure from normal temperatures, the following criteria are used to declare a heatwave:(i) Heatwave: Departure from normal is 4.5°C to 6.4°C.(ii) Severe Heatwave: Departure from normal is 6.4°C.— Based on the actual maximum temperature in plains, the following criteria is considered:(i) Heatwave: When the actual maximum temperature ≥ 45°C(ii) Severe Heatwave: When actual maximum temperature ≥47°C— If the above criteria met at least in 2 stations in a Meteorological sub-division for at least two consecutive days and it was declared on the second day.— Heatwaves are especially fatal when high temperatures coincide with high humidity, a condition known as a wet bulb. UPSC Twist Points– Heatwave vs Heat domeStory continues below this ad— A heat dome occurs when an area of high-pressure stays over a region for days and weeks. It traps warm air, just like a lid on a pot, for an extended period. The longer that air remains trapped, the more the sun works to heat the air, producing warmer conditions with every passing day. — Heat domes, if they last for a long period, may cause deadly heatwaves. ALSO READ | Knowledge Nugget | From burials to upside down pots: What Virli Khandar excavation revealsPrelims Practice MCQLet’s see how much can you recallConsider the following statements:1. GPS spoofing disrupts navigation systems by completely blocking signals, making receivers unable to determine location or time.Story continues below this ad2. Monetary policy in India is implemented by the central government.3. A heatwave is declared when the maximum temperature of a station reaches at least 40°C or more for plainsWhich of the statements given above is/are correct?(a) 2 and 3 only(b) 1 and 2 only(c) 1 and 3 only(d) 3 onlyAnswer(d)UPSC Prelims ‘SEE’ Snapshot: Talking cars, GDP rebasing and Nor’westers — quick look Gear up for UPSC Prelims 2026—Practice smarter, revise faster, and succeed with our Special Quiz Magazine. Click Here Click Here to read the UPSC Essentials magazine for April 2026. Share your views and suggestions in the comment box or at manas.srivastava@indianexpress.comSubscribe to our UPSC newsletter. Stay updated with the latest UPSC articles by joining our Telegram channel – Indian Express UPSC Hub, and follow us on Instagram and X.