Paper lanterns with candles in them. How can this lantern float in the air?

That's Kongming Lantern. Brief introduction to the origin and structure of Kongming Lantern

Kongming Lantern, also called Sky Lantern, is said to have been invented by Zhu Gekongming during the Three Kingdoms period. At that time, Zhu Gekongming was besieged by Sima Yi in Pingyang, unable to send troops out of the city for help. Kong Ming calculated the wind direction, made a floating paper lantern, tied with the message for help, and then escaped as expected, so later generations called this lantern Kong Ming Lantern. Another way of saying this is that this lantern looks like a hat worn by Zhu Gekongming, hence its name.

Modern people put lanterns on Kongming lanterns as a blessing. The wishes of men, women and children to write blessings by hand symbolize the bumper harvest and happiness every year.

The structure of Kongming Lantern can be divided into two parts: the main body is mostly bamboo grates, followed by cotton paper or paper paste, and the underframe is bamboo grates. Kongming lanterns can be large or small, round or rectangular. Generally speaking, Kongming lanterns are barrel-shaped made of bamboo pieces, surrounded by thin white paper, and their openings are downward.

When taking off with a light, tie a piece of coarse cloth or gold paper stained with kerosene or peanut oil in the middle of the bracket at the bottom, and light the fuel before flying. After the fire in the lamp burns for a while, it will produce hot air and the lanterns will expand. After flying, the whole lantern will soar in Ran Ran. If the weather is clear and the kerosene at the bottom burns out, the Kongming Lantern will automatically descend.