There are many mysteries in nature. Mysteries are things we don't understand, such as how the Egyptian pyramids were built. In fact, we are surrounded by mysteries. What we know about the world seems like very little.
自然界有许多神秘的事。神秘是指我们不理解的事物，比如埃及金字塔如何建造。事实上，神秘无处不在，我们对这个世界知之甚少。
Scientists tell us that what we see in the universe is only a small part of what is there. The rest is invisible, including dark matter and dark energy. These two unknowns make up around 95% of the universe. Evidence for their existence comes from their effects on what we can observe, such as the motion and positions of distant galaxies.
科学家告诉我们，我们在宇宙中看到的只是宇宙的一小部分，其余的不可见的，包括暗物质和暗能量，这两项未知物约占宇宙的95%。它们存在的证据来自于对我们所能观察到的物体的影响，比如遥远星系的运动和位置。
Yet, though we know very little, we are able to build airplanes and communicate with smartphones. In some ways we humans are very smart, or at least we think we are. We still need to face big issues, like climate change, and that is going to be a huge challenge. The challenge for humans will be our ability to adapt to our changing environment.
然而，尽管我们所知甚少，但我们能制造飞机，用手机通信。在某些方面，我们人类非常聪明，至少我们认为我们是聪明的。我们仍然需要面临重大问题，比如气候变化，这将是一个巨大的挑战。人类面临的挑战将是我们适应不断变化的环境的能力。
What about other forms of life? How do they adapt? Seasonal variations, for example, can be one of the greatest challenges for animals to overcome. Overcoming such challenges is a great achievement, but hardly easy. Some birds migrate thousands of kilometers each year to deal with seasonal changes. These migrations are amazing.
那么其他形式的生命呢？它们如何适应？例如，季节变化可能是动物要克服的最大挑战之一。克服这些挑战是一项伟大的成就，但绝非易事。有些鸟类每年迁徙数千公里以适应季节变化，这些迁徙让人吃惊。
Birds don't carry maps or compasses, yet they know where to go. They have developed the ability to see the Earth's magnetic field. This ability is a wonder of nature. It takes advantage of the fact that the earth is like a huge bar magnet. It has a north pole, which is positive, and a south pole, which is negative. Somehow the birds are able to see this magnetic field and use it to their advantage.
鸟类没有地图，也没有指南针，但它们知道要去哪里。它们已经发展出一种感知地球磁场的能力，这种能力是大自然的奇迹。它利用了地球是一个巨形磁铁的事实，北极为正，南极为负。鸟类以某种方式可以感知磁场并利用。
And even the way birds fly together is amazing. Many migrating birds fly in a V formation. They do this to conserve energy. In a V formation, birds can use the energy of the birds in front of them. This energy comes from the air currents generated by the wings. Conserving energy is necessary for the birds to survive the long journey. How do the birds know this? It's truly amazing how the birds know this.
甚至鸟类一起飞行的方式也很神奇，许多候鸟呈V字形飞行，这样是为了节约能量。在V形队列中，鸟类可以利用前面鸟类的能量，这种能量来自翅膀产生的气流。节约能量对于长途旅行的鸟类生存是有必要的。鸟类是怎么知道的？这一点真的很神奇。
