During this year's Spring Festival, China experienced widespread rain, snow, strong winds, and cooling weather, with significant cooling in many areas. Recently, the saying 'wearing short sleeves underneath a down jacket is warmer' has been circulating online. Some netizens have suggested that they have worn it this way before and indeed feel warm; But some people also believe that this violates common sense. So, is this statement scientific? How to dress warmly and conveniently? Regarding the above issues, reporters from Science and Technology Daily interviewed relevant experts. It's almost impossible for a down jacket to be warmer with short sleeves underneath Professor Lu Yehu from the School of Textile and Clothing Engineering at Soochow University said in an interview with reporters that the human body is a continuous source of heat, with a normal body temperature between 36 and 37 degrees Celsius. If only short sleeves are worn inside the down jacket, in cold environments, the temperature difference between the skin and the outside cold air is large, and the driving force for heat transfer is stronger. Due to the inability of short sleeves to provide sufficient insulation protection, heat will be conducted from the skin surface to the outside world faster, resulting in faster heat loss from the body and a feeling of cooler. The insulation principle of down jackets is similar to that of insulated cups. Insulated cups rely on a vacuum insulation layer to reduce heat loss, while down jackets achieve insulation through a static air layer between the fibers. Wearing short sleeves under a down jacket results in a lack of insulation layer in the middle. Common clothes that serve as intermediate insulation layers include thermal underwear. They can form an additional thermal barrier between human skin and down jackets, reducing heat loss. And short sleeves cannot provide such insulation Lu Yehu said. In addition, short sleeved clothing cannot fit tightly to the wrist like long sleeved clothing, and the sealing effect is poor. During the activity, cold air from the outside is more likely to enter the interior of the down jacket through the cuffs and other parts, exchanging with the warm air around the body and taking away heat. However, the more clothes worn in down jackets, the better. If too much thick clothing is worn inside a down jacket, the heat generated by human activity cannot be dissipated in a timely manner, leading to sweating. Sweat evaporation will take away a lot of heat, which may actually make people feel colder, "said Lu Yehu. It is best to use the" onion dressing method ", which involves layering clothes like onions. For example, when going out on a cold morning, you can wear two layers of clothing inside a down jacket. As the temperature rises or activity increases at noon, the body heats up. You can take off the outer down jacket or middle warm jacket according to the actual situation. And when the temperature drops in the evening, putting on the clothes that have been taken off can keep the body comfortable and warm at all times. Although it is not recommended for the general public to wear lightweight and cold resistant clothes inside down jackets, there is a group of people who are suitable for this way of wearing to warm up, and they are swimmers. During the 2024 Paris Olympics, many netizens expressed confusion about swimmers wearing down jackets over their swimsuits in the summer. The main reason for wearing this is to keep warm Lu Yehu said that athletes should fully warm up before the competition to prevent their muscles from becoming stiff. Experts believe that muscle tension can be a big problem for athletes on the Olympic stage, where victory or defeat is determined in just a few seconds. Wearing down jackets can help athletes maintain their body temperature before the competition, keep their muscles, joints, etc. in a good state of preparation, and help them perform at their best level during the competition. (New Society)