Since I was born and brought up in a rural town, I have a great interest in nature. Having the chance of studying abroad in my second year at college, I decided to go to Canada just because I wanted to see the beautiful phenomena there. So after I finished the study, I went to Yellowknife in the Northwest. I clearly remember the sixth night in Yellowknife. Suddenly my host mother came to my room around 8 p. m. and told me to change clothes and go outside quickly carrying her camera.

The northern lights were flickering (闪烁) in the sky! I was amazed and just stood there with my mouth open. I forgot to take pictures of the mysterious lights.

Since that night, whenever it was sunny, I went outside at night and looked at the sky. It was so cold that my hands and feet were numb (失去知觉的) with cold. Actually, the time of my being able to be out was limited. I had to bring her camera back to the house in one hour at most, for the camera was going to be broken because of the cold temperature.

As I took pictures of the northern lights, I came to find a characteristic movement of the lights. They first appear in the north part of the sky and then they come down to the south. After that, suddenly, they come in the middle of the north and south only for a while, which is the time when the best northern lights can be seen. Since it is only a few seconds for the northern lights to come down to the middle of the sky, it is very hard to get good pictures.

The stronger the sun acts, the better and stronger northern lights flicker in the sky. That’s because they occur from the collision (碰撞) between atmospheric gases and solar wind. Much more solar wind comes to the earth when the sun is active, leading to the best northern lights.

Genetic modification (基因改良) dates back to ancient times, when humans influenced genetics by selectively breeding organisms (培育生物) according to an article by Gabriel Rangel, a public health scientist at Harvard University. When repeated over several generations, this process leads to great changes in the organisms.

Dogs were likely the first animals to be purposefully genetically modified, with the beginnings of that effort dating back about 32,000 years, according to Rangel. Wild wolves joined our hunter-gatherer ancestors in East Asia, where the aggressive canines were kept in the household and bred to become docile and easier to get along with. Over thousands of years, people bred dogs with different desired character and physical characteristics, eventually leading to the wide variety of dogs we see today.

The earliest known genetically modified plant is wheat. This valuable crop is thought to have originated in the Middle East and northern Africa in the area known as the Fertile Crescent, according to a 2015 article published in the Journal of Traditional and Complementary Medicine. Ancient farmers selectively bred wheat grasses beginning around 9000 B. C. to create improved varieties with larger grains and hardier seeds. By 800 B.C., the cultivation (培养) of improved wheat had spread across Europe and Asia. The continued selective cultivation of wheat resulted in the thousands of varieties that are grown today.

Corn has also experienced some of greatest genetic changes over the past few thousand years. The main crop was changed from a plant known as teosinte, a wild grass with tiny ears and only a few seeds. Over time, farmers selectively bred the teosinte grasses to create corn with large ears bursting with seeds.

Beyond those crops, many of the fruit and vegetables we eat today, including bananas, apples and tomatoes, have experienced several generations of selective raising, according to Rangel.

In 1973, researchers also modified bacteria to be used as drugs. In 1982, human insulin (胰岛素) made from genetically engineered bacteria, became the first genetically engineered human drugs approved by the FDA.