A major development to self-driving cars may change the way we will drive in the future. Google, the leading company in self-driving technology, has changed its development plan. It had driverless cars built by car factories, but now will start building its own cars.

Google has started to build some kinds of experimental electric self- driving cars that look like a Smart car or Fiat 500. There is no steering wheel (方向盘)，gas pedal (油门) or brake (刹车). The only thing a human passenger controls is a red "e-stop" button for fear stops and a start button. The car's only "friendly" face is designed to make it help people accept self-driving technology.

Google workers took part in a long experiment, in which they used self-driving cars for their usual travel to work. No accident happened, but Google's heads realized that depending on a human passenger to drive in an emergency wouldn't work because they may be reading, working, or sleeping. Now the self-driving car drives by itself if the driver takes his hands off the wheel for over ten seconds.

Google's self-driving cars are now limited to a speed of 25 miles per hour for safety reasons. The cars aren't allowed to drive on highways. However, a Google engineer said that once the cars are solved to run safely, we can drive at the speed of 50, even 80 miles an hour.

Google recently announced that its cars had covered 700,000 miles of public roads, and they were now running in busy city streets. People who love self-driving cars say this will improve transport by making roads safer, cutting down accident, and making less pollution.

Energy is something that makes things work or causes changes. Light, heat, sound and electricity are forms of energy. Here is an introduction to them. 

When you talk about, or even think about Iron Man, the first image that pops into your head is the red and gold suit worn by Tony Stark. It provides Stark strength, protection against most attacks (攻击) and the power of flight. Iron Man is just a story, but the suit is not. Engineers call it an exoskeleton (外骨骼). It is the protective or supporting structure covering the outside of the body. 

In fact, the exoskeletons were used in hospitals at first. They have changed the lives of many people with injuries (受伤) or illnesses that affect movement. A disease had paralyzed Stacey Kozel and she could not walk anymore. But in 2016, she went hiking with an exoskeleton. In recent years, more and more exoskeletons have been used in factories. It is easy for people to do the tiring or dangerous work with the exoskeletons. "We usually pay attention to efficiency (效率). Using the exoskeletons saves us much time and money. The workers can make more products at the same time. "One factory manager said. "Also, wearing the exoskeletons can reduce the risk of injury. "What's more, exoskeletons can be used in rescue (救援) operations, providing workers with a lot of strength to lift heavy objects while protecting them from being hurt by falling weights.

However, the global spread of exoskeletons remains difficult. For one thing today's exoskeletons are expensive because they need to be charged (充电) regularly. For another, most exoskeletons can help people do only one type of movement. A company called SuitX is developing new forms of exoskeletons now. The company hopes people of all ages can use their products in the future.

That would be really cool, but some people worry that the technology will divide humanity. People who can afford exoskeletons will become stronger and achieve more than those without suits. We may end up with two classes of humanity: the superhumans and everybody else. That wouldn't be fair. Also, researchers have found that when people work in exoskeletons, muscles (肌肉) compete with each other, causing the brain to work less efficiently. Over time, it can also cause harm to the body.

So will exoskeletons harm or benefit humanity? No one knows for sure. More research is needed.