There are many deserts (沙漠) on the earth. And the following are some facts you may find interesting.

What are deserts like?

Deserts can be hot and dry places. Rain may not fall there for months or years. Some deserts are sandy and stony (多石的). Deserts can also be very windy places. The wind can change the shape of the deserts. It moves sand around from place to place.

Temperatures in the desert can vary enormously(非常). During the daytime, the temperature may reach 40℃ even in the shade (阴凉处). At night, deserts can become very cold. In winter there may even be a frost (霜冻) in the early morning.

Living in the desert

The camel is sometimes called "the ship of the desert". It stores food in its hump (驼峰) and can go for days without water. It has large feet which help it not to fall into the soft sand. Its long eyelashes (睫毛) keep out the sand during sandstorms.

An oasis is an area of the desert where water may be found. The water may be in pools or under the ground. People and animals visit an oasis for water and food. Plants grow at an oasis. Some farmers are able to grow crops here.

The Arabian Desert

The Arabian Desert lies between the Red Sea and the Arabian Gulf. In some parts of the desert, it is too hot for people to live. Oil was discovered under parts of the desert and in the Arabian Gulf. This oil has made some countries in the area very rich. Much of the money has been spent building fine cities with lovely parks and lakes, and people live a comfortable life there.

Every year, millions of birds are killed or hurt when they fly into buildings. Why does this happen?  Birds are flying into windows and tall buildings that are all covered by glass.

Many birds fly from one place to another. Most of the time, they live in the wild, such as forests and wetlands.  They might see small trees and flowers inside a window and want to rest on these plants. The birds do not know there is glass between them and the plants.  

Some birds fly at night. They use the moon and stars to help guide them in the right direction. Tall buildings with lights on at night can confuse（迷惑）the birds.  The birds see the light, but they cannot tell that the light is coming from inside a building. They fly toward the light and crash into a building. On many mornings, there might be several dead birds lying on the ground.

  Many office buildings now turn off their lights at night. This helps reduce the number of birds that fly into buildings and it also helps save energy.

If you look around the room you are in right now, you'll probably notice a number of electronics. But can you imagine if they all had to be joined together by wires (电线)? Picture the wire snaking along the floor, for example, from your smartphone to your speaker, or connecting your game controller to the computer screen, meaning you could never sit more than a couple of meters away from it. A world of electronics connected by wires wouldn't just be untidy, but a possible danger, too. That's where Bluetooth comes in. We've all heard of it — but what exactly is it?

Bluetooth is a method of short-distance (短距离) wireless communication between electronics that makes use of the power of radio waves. The idea was first thought of by Dr. Janp Haartsen at Swedish mobile company Ericsson in 1994. Things really stepped up in September 1998 when the Bluetooth Special Interest Group (SIG) was set up to develop and spread the technology. Bluetooth 1. 0 came out in 1999, and a year later it began to be used in mobile phones and desktop computers. Now Bluetooth has become an increasingly popular way of solving the problem of more and more electronics needing to be connected, without having to connect everything together with wires.

But if you look at the remote control (温控器) you use to choose the program on TV, you might rightly ask yourself why Bluetooth was such a big deal. After all, connecting objects with infrared signals (红外信号) which can't be seen had been done before. The problem with remote controls is that they need to keep what is called "line of sight". If something is standing between the remote control and receiver, it won't work. Because Bluetooth uses radio waves, the things standing in the way are no longer a problem.

Since its creation in the late 1990s, the technology has become more and more improved and widely used, with the 4 billionth Bluetooth objects shipped in 2020.