Time travel：a trip without hesitation

By Grace

科技是第一生产力，是社会进步的推动力，也是人类文明的标志。科技的创新和发展关乎人类的命运共同体。

科技又是一把双刃剑。科学技术的不断发展，带来的不仅仅是生活水平的提高，还有对环境、生命的多种危害。因此，我们要理性地看待现代技术，合理发展和应用现代技术，趋利避害，造福人类。

科普文章的阅读同样是近三年来新课标全国卷的考查重点和趋势。爱科学，懂科学，用科学是每一位高中生的基本素养和要求。

Time travel is a familiar subject of science fiction and fantasy stories,from H.G.Wells to Rod Serling to Hot Tub Time Machine.But could time travel ever be possible in real life?And,if so,how would humans even handle so advanced a technology?

Some scientists say time travel is theoretically possible,at least if you want to jump ahead to the future,but don’t start saving up for a time machine just yet.As physicist Paul Davies explained for CNN in 2013,“Over a century ago,Albert Einstein showed that time is actually flexible.That is,it can be either stretched（延伸）or shrunk by motion.”

In general,the closer you’re going to the speed of light,the slower time moves.“Fly to the star Vega,25 light years away,and back again at 99%of the speed of light,and when you return to Earth in 2062,you will have experienced only seven years’travel time in the spacecraft.In fact,you will have jumped 42 years into Earth’s future,”Paul Davies wrote.

So if you were to,theoretically,take a trip in a super-fast spaceship,you might feel as though only a few years had passed,but when you arrived back on Earth,decades would have passed and all your friends and family would be dead and gone.Time travel!

But what about going backwards?Could it ever be possible to pop back in time and stop bad things from happening and good people from dying?Theoretically,if you were to travel faster than the speed of light,you would be moving backwards in time.

But most scientists believe that nothing can actually travel faster than light,and,if you could go back in time,messing with the past would create all kinds of unsolvable problems,like what if you went back in time and killed your grandpa!

Although some theories have attempted to find solutions to these inconvenient time-travel problems,it remains a pretty widely held belief that traveling backwards in time isn’t possible for us humans.After all,as physicist Stephen Hawking said in his book A Brief History of Time,“If time travel is possible,where are the tourists from the future?”