to open under backward pressure from the stomach. TEENS  Yawning keeps us coolYawning keeps us...QIANTUQIANTUUnable to throw upUnable to throw up马不会呕吐。马不会呕吐。Not every animal can vomit (呕吐). Horses ……

the Arctic, flowing from west to east all the way around the Earth. It normally keeps extremely cold air bottled up toward the North Pole. Occasionally, though, the vortex weakens, allowing the cold air ……

This globe keeps itself up in the airGONE are the chunky, spinning globes of old ? this version has the globe floating in air, just like the earth in space. It's held up entirely by a magnetic force ……

jackets blow up while washing?The material (材料) of down jackets doesn’t let air pass through well..., so the jacket keeps getting bigger.The waterproof (防水的) coating stops air from getting out, so ……

at National Oceanic and Atmospheric Administration in the US. “This keeps the cold air locked up... at National Oceanic and Atmospheric Administration in the US. “This keeps the cold air locked up over ……

of pine wood (松木). They easily change shape in the air. The mud (泥巴) at the bottom of the rivers keeps... (泥巴) at the bottom of the rivers keeps the air away and protects the boats. Before the festival ……

the moon has little air around it. The Earth has a lot of air around it. This keeps the Earth neither too...The rocks on the moon tell us it is about 4.6 billion years old, or about the same age as the Earth ……

jump up to 60 cm in the air! We do so to let the females (雌性) see us or to protect our territory (领地).We can jump up to 60 cm in the air! We do so to let the females (雌性) see us or to protect our ……

为什么会起鸡皮疙瘩？Our body is like a machine. It works hard for us every day. Our body is amazing. How much do you know about it? Let’s take a look.Our skin covers2 and protects our body. It also keeps us ……

do you know about it? Let’s take a look. Our skin covers and protects our body. It also keeps us....Goose bumps help your skin keep warm. Your hair stands up to protect your skin from cold air. Each ……

out every winter. Why does it happen?The material of down jackets doesn’t let air pass through well.The material of down jackets doesn’t let air pass through well.When they are put ……

by a wall of invisible air. The air shield will protect the statue from dust and the over 1 million tourists who come to Italy to see it every year, an Italian museum official has said."This wall of air ……

of the bottle and keeps the bottle from squeezing (挤压) the straw closedTry to keep air from getting...Here's an experiment to see how much air your lungs can hold:You'll need Large pan 2-liter (升 ……

of the bottle and keeps the bottle from squeezing (挤压) the straw closedTry to keep air from getting...Here's an experiment to see how much air your lungs can hold:You'll need Large pan 2-liter (升 ……

吉尼斯世界记录
Mike and Steve (US) fly up to 5,545 meters (米) in the air. 他们搭乘的飞行器是1400个气球。They pop1 balloons one by one to get down. ……