2026年真题28

Listen to a talk on a physics podcast (man) Have you ever wondered why ice floats on water? It’s a curious phenomenon that has puzzled scientists for centuries. Normally, solids are denser than liquids because their molecules are packed more closely together. But water has a unique molecular structure, and it behaves differently. As water molecules cool and form ice, they arrange themselves in a crystalline structure that occupies more space than when they are in liquid form. This arrangement causes ice to be less dense than liquid water, enabling it to float. But why is this important beyond just curiosity? Well, Imagine a world where ice sank. Lakes and ponds would freeze from the bottom up, and this could have a huge impact on aquatic ecosystem. Aquatic life relies on ice forming at the surface, which creates an insulating layer that prevents the entire body of water from freezing. This insulation is vital for the survival of fish and other animals during harsh winters. Even if the top layer is frozen, they can survive in the water underneath. Floating ice, especially in polar regions, also reflects a significant amount of sunlight back into space. This helps regulate global temperatures. If ice sank, it wouldn’t remain on the surface to reflect sunlight. It’d disappear beneath the water, allowing more solar energy to be absorbed by the darker ocean or lake surfaces. This would lead to warmer water temperatures, accelerating global warming and disrupting climate patterns worldwide.

Listen to a talk on a physics podcast (man) Welcome to Science in Motion, where we explore the hidden physics behind everyday experiences. Today, we’re investigating why ice skating feels so smooth and fluid. The answer lies in a fascinating physical phenomenon that’s happening right beneath your feet. When a skate blade moves across the ice, it’s not just slicing through a frozen surface, it’s actually causing a tiny bit of it to melt. The pressure from the blade creates a thin layer of water between the skate and the ice. This slippery film is what allows skaters to move so gracefully. It’s called the pressure melting point, it means ice can melt at temperatures below freezing simply because of the force being applied. As the skater moves, the blade keeps applying pressure, maintaining this delicate balance between solid and liquid. However, friction between the blade and the ice can also generate heat. Too much heat and the ice melts more than it should, slowing skaters down or even causing them to lose control. That’s why elite skaters develop techniques to minimize friction. In addition, researchers are studying these dynamics to design skate blades that reduce friction and boost performance, but the story doesn’t end at the rink. Similar principles are at play in nature, specifically in glaciers. Pressure and melting help these massive ice sheets move across landscape. As scientists dig deeper into how these mechanisms work, they are learning how glaciers might respond to cimate change, offering clues about our planet's future.

Listen to a talk in a physics class. Imagine a time when the only lights available were flickering candles or oil lamps. Now Fast forward to today, where life is illuminated by the glow of energy efficient LED lights. So what makes these tiny light emitting diodes so revolutionary? Well, the first practical visible spectrum LED was developed in 1962. It was a breakthrough that altered the landscape of lighting technology and set us on a path toward reduced energy consumption. LEDs, that's short for light emitting diodes, are a type of solid-state lighting. They use a semiconductor to convert electricity directly into light. Compared to incandescent bulbs, which waste a lot of energy as heat. LEDs are incredibly efficient. That's their biggest benefit. They use about 75% less energy than incandescent bulbs and last 25 times longer. So that lowers electricity bills and also significantly reduces the carbon footprint. But the impact of LEDs goes beyond energy savings. They've enabled new lighting designs that were previously unimaginable. That's because of their small size, which allows LEDS to be integrated into flexible strips, smart bulbs, and even clothing. So virtually endless possibilities in architecture, art and everyday consumer products. And they're still developing. With ongoing research, we could see such intriguing possibilities as LEDS that can purify the air, improve your mood through human centric lighting, or even transmit data in a system known as Li-Fi, a kind of wireless communication using light from LEDs.

Listen to a talk on a history podcast (woman) The Western Roman Empire, which flourished for about the first five centuries of the first millennium, is often celebrated for its engineering marvels, but one of its lesser-known achievements is its contribution to urban planning. Roman towns were laid out with remarkable precision, often following a grid system which was quite advanced for its time. Streets intersected at right angles, dividing the city into organized blocks that made navigation easier and promoted efficient trade, communication and administration. At the heart of every Roman city was the forum, a multi-functional space that served as the civic, commercial and social hub. It was the heart of public life where citizens gathered for various activities ranging from political discussion to socializing. Surrounding it were carefully zoned areas, residential quarters, marketplaces, temples, and public buildings, each with a designated place in the urban fabric. This early form of zoning helped maintain order and efficiency. Romans also prioritized infrastructure. Roads were paved and well-drained, and public amenities like baths, latrines, and fountains were strategically placed to serve dense populations. Their cities were designed not just for grandeur but for functionality, though that balance wasn’t always perfect. In poorer districts, overcrowded hosing led to sanitation problems and fire hazards, revealing the limits of even the most advanced planning. Still, Roman urban design laid the groundwork for modern city planning. Concepts like grid layouts, centralized public spaces, and functional zoning trace their roots to these ancient innovations. The legacy of Roman urbanism lives on in many cities today.