The interior of a parked car can become hot, even on a moderately warm day. This is a direct consequence of physics principles. Solar energy interacts with the car’s components, leading to a significant temperature increase inside the vehicle.
Sunlight’s Role
Sunlight, a form of electromagnetic radiation, is the initial energy source that heats a car’s interior. This radiation includes various wavelengths, with visible light being a prominent component. The car’s windows are largely transparent to these visible light waves, allowing them to pass through. This initial entry of solar energy sets the stage for the subsequent heating process.
Heat Absorption by Materials
Once inside the car, visible light energy strikes interior surfaces like the dashboard, seats, and steering wheel. These materials absorb the light energy and convert it into thermal energy. Darker materials are effective at absorbing light, causing them to heat up more quickly and to higher temperatures. Dashboards, for example, can reach temperatures as high as 157 degrees Fahrenheit.
Trapping the Heat
Heated interior materials re-radiate the absorbed energy as infrared radiation. Unlike visible light, infrared radiation does not easily pass through the car’s glass windows. The glass acts as a barrier, trapping this infrared heat within the vehicle. This trapping mechanism, similar to a greenhouse, prevents heat from escaping.
The car’s enclosed cabin further contributes to the temperature rise. With minimal air circulation, the heated air inside cannot mix with cooler outside air. This combination of trapped infrared radiation and limited convection causes the temperature within the car to steadily escalate.
Rapid Temperature Rise
The combined effects of continuous solar radiation, efficient heat absorption by interior materials, and infrared radiation trapping lead to rapid temperature escalation inside a parked car. Studies show that a car’s interior temperature can increase by 10 to 20 degrees Fahrenheit within 10 minutes. Within 60 minutes, the average car can be 43 degrees hotter than outside.
Even on moderate days, car interiors can reach dangerous levels quickly. For example, on an 80-degree Fahrenheit day, the car’s interior can soar to 109 degrees Fahrenheit in 20 minutes and 118 degrees Fahrenheit in 40 minutes. This rapid increase highlights the efficiency of the heat-trapping process.