2. Height is also a ruler. If the height is 150 cm, hold a big tree and put your hands together. The length of this tree is about 150 cm. Because everyone's arms are flat, the length and height between the fingertips of both hands are similar.
3. If you want to measure the height of the tree, shadows are also helpful. Just measure the length of the shadow of the tree and your own shadow. Because the height of the tree = shadow length × height ÷ graph length.
If you want to know how far the mountain ahead is from you, you can ask the sound to help you measure it. Sound can travel 33 1 meter per second, so you can hear the echo by shouting at the mountain and watching it for a few seconds. Multiply the time to hear the echo by 33 1 and divide it by 2.
5、? "Astronomical Recorder" Coral scientists found that corals record time on themselves: they "carve" an annual ring pattern on the body wall every day and "carve" 365 annual rings a year, no more or less. So, if you want to know their age, just count the annual rings on their body walls. Scientists also found that 350 million years ago, corals "carved" 400 rings instead of 365. The reason is that the earth's rotation was only 2 1.9 hours a day, not 365 days a year, but 400 days.