What comes to mind when you think of space? Imagine a friend boasting about a spacious building, stadium or museum they recently visited. Do you envision the building as vast and expansive? Is it simply very large, or does it seem empty?

当你想到太空时，你会想到什么？想象一下，一个朋友在炫耀他们最近参观过的一座宏伟的建筑、体育场或博物馆。你是否将这座建筑想象得既宏伟又宽敞？它只是很宏伟，还是看起来很空？



The word spacious does not necessarily mean empty. It simply indicates that there is enough room to move around the objects inside it. Similarly, outer space is not completely empty. It is vast and forever expanding, but there's a lot of stuff in it.广阔的这个词并不一定意味着空。它只是表明里面的空间足够让物体自由移动。同样，外太空也不完全是空的。它广阔无垠且不断扩张，但里面有很多东西。

As a kid, I used to wonder about questions like how far away the clouds are, what lies beyond Earth and how vast space is. This curiosity led me to pursue master's and Ph.D. degrees in astronomy. I have been teaching about these very concepts for two decades as a physics instructional professor at the University of Texas, Arlington.小时候，我常常想知道云有多远、地球之外有什么以及太空有多大等问题。这份好奇心驱使我攻读天文学领域的硕士和博士学位。作为德克萨斯大学阿灵顿分校的物理教学教授，这些概念我已经讲了二十年了。

Where does space begin?太空起自何处？

Earth is surrounded by different layers of various gases. At sea level, Earth's atmosphere contains about 100 billion molecules per cubic centimeter. As we ascend, the atmosphere becomes thinner and thinner.地球被各种不同的气体层包围着。在海平面，地球大气层中每立方厘米包含约1000亿个分子。随着我们不断发展，大气层变得越来越稀薄。

At an altitude of about 50 to 62 miles (80 to 100 km), there isn't enough air for airplanes to fly. This boundary, which separates the Earth's atmosphere from outer space, is called the Kármán line, named after the Hungarian-American engineer and physicist Theodore von Kármán. Everything above the Kármán line is called space.在大约50至62英里（80至100公里）的高度，那里的空气不足以供飞机飞行。将地球大气层与外太空分开的边界线被称为卡门线， 以匈牙利裔美国工程师和物理学家西奥多·冯·卡门的名字命名。卡门线以上都被称为太空。The density of space can vary, but, on average, it is around only 1 atom per cubic centimeter. Just imagine – a dice-sized cube of Earth's atmosphere contains billions of air particles. But in space, the same-sized cube contains only one or two particles.空间密度可能会有所不同，但平均而言，每立方厘米大约只有1个原子。想象一下——一个骰子大小的地球大气层立方体包含了数十亿个空气粒子。但在太空中，同样大小的立方体只包含一两个粒子。

The interstellar medium and radiation星际介质和辐射Space, or outer space, is a vast, near-perfect vacuum largely devoid of matter. This vacuum contains very few particles compared with Earth's atmosphere. However, it's not entirely empty.太空，或外太空，是一个广阔、近乎完美的真空，几乎没有任何物质。与地球大气相比，真空中包含的颗粒物很少。然而，它并不完全是空的。

Space is dotted with scattered matter called the interstellar medium, which includes hydrogen and helium atoms. These are the most common elements in space, and they exist in both charged and neutral forms. The interstellar medium also contains cosmic dust – tiny particles of various elements, including carbon and silicon, scattered throughout space.太空散布着被称为星际介质的分散的物质，其中包括氢原子和氦原子。这些是太空中最常见的元素，它们以带电形式和中性形式存在。星际介质中也包含宇宙尘埃——即由碳、硅等各种元素组成的微小粒子，它们遍布整个太空。

High-energy particles called cosmic rays – which are primarily protons and the nuclei of atoms – travel through space at nearly the speed of light. Cosmic rays come from various stars including our Sun, as well as from supernovae, the material falling into black holes, colliding galaxies and more.被称为宇宙射线的高能粒子——主要由质子和原子核组成——以接近光速的速度在太空中穿行。宇宙射线来自各种恒星，包括我们的太阳，以及超新星、落入黑洞的物质、相互碰撞的星系等。

Space is filled with various forms of radiation, including cosmic microwave background radiation. This is remnant heat from the origin of the universe. High-energy cosmic events like supernovae and black holes also emit X-rays and gamma rays.太空充满了各种形式的辐射，包括宇宙微波背景辐射。这是宇宙起源时残余的热量。超新星和黑洞等高能宇宙事件也会发射X射线和伽玛射线。

Magnetic fields generated by stars, planets and many other celestial bodies also permeate space. These fields influence the motion of charged particles by attracting or repelling them like magnets.恒星、行星和许多其他天体产生的磁场也渗透到太空中。这些场像磁铁一样吸引或排斥带电粒子来影响带电粒子的运动。

Dark matter and dark energy暗物质和暗能量Scientists predict that an as-yet unseen form of matter that does not emit light or energy, called dark matter, makes up a significant portion of the universe's mass. Researchers guess that it exists because they can see its gravitational pull on other visible matter.科学家预测，存在一种尚未被发现的物质形式，它不发光也不释放能量，被称为暗物质， 构成了宇宙质量的重要部分。研究人员猜测它的存在，是因为他们能看到它对其他可见物质的引力作用。

Similarly, scientists predict a mysterious form of energy called dark energy is driving the accelerated expansion of the universe. Unlike dark matter, dark energy is not related to matter or gravitational forces, but it's a property of space itself.同样，科学家预测一种名为暗能量的神秘能量形式正在推动宇宙的加速膨胀。与暗物质不同，暗能量与物质或引力无关，而是空间本身的属性。

Imagine the universe as a balloon. Dark matter is like the balloon's material, affecting its shape, while dark energy is like the air being pumped into it. It doesn't change the balloon's material, but it influences how quickly the balloon expands.将宇宙想象成一个气球。暗物质就像气球的材料，影响其形状，而暗能量就像注入气球的空气。它不会改变气球的材料，但会影响气球膨胀的速度。

Does space warp? Can gravity bend space?太空会扭曲吗？重力会扭曲空间吗？Space can also warp. Imagine that space is like a big, stretchy trampoline. If you put a heavy ball, like a bowling ball, in the middle of the trampoline, it makes a big dip downward. This dip is similar to how space warps around something big, like a planet or a star. The bigger the ball, the stronger the gravity and the deeper the dip.空间也会扭曲。想象一下空间就像一个又大又有弹性的蹦床。如果你把一个重的球，比如保龄球，放在蹦床中间，它会使蹦床向下形成一个大的凹陷。这种下降类似于太空围绕行星或恒星等大物体扭曲的方式。球越大，重力越强，凹陷就越深。

If you roll a smaller marble across the trampoline with the bowling ball in the center of it, marbles might start going around the dip made by the bowling ball's gravity. The marble follows the curve of the dip, just like how planets follow the curve of space around the Sun.如果你把一个小弹珠在蹦床上滚动，而保龄球在蹦床中心， 那么弹珠可能会开始在保龄球产生的重力凹陷处周围运动。小弹珠沿着凹陷的曲线滚动，就像行星沿着太阳周围的空间曲线运行一样。

Imagine that you shine a flashlight across the trampoline. If the light goes near the dip made by the bowling ball, it might bend a little bit as it travels. This is like how light bends when it passes near a very big object in space, such as a galaxy.想象一下你用手电筒照射蹦床。如果光线接近由保龄球重力形成的凹陷区域，它可能会在传播过程中发生轻微的弯曲。这就像光在穿过太空中一个非常大的物体（如星系）附近时会发生弯曲一样。

Think of a black hole, which has huge gravity, as an even bigger, deeper dip in the trampoline. If you rolled a marble too close to this super-deep dip, it would fall in and disappear, just like how things can get pulled into a black hole in space and can't escape.将一个具有巨大引力的黑洞想象为蹦床上更大、更深的凹陷。如果你滚动一个小弹珠靠近这个极深的凹陷，它可能会掉进去并消失， 就像太空中的物体被黑洞吸引进去而无法逃脱一样。

So, space can warp or bend around big things that have lots of gravity, just like a trampoline bends when you put a heavy ball on it.所以，空间可以围绕具有强大引力的巨大物体发生扭曲或弯曲，这就像你在蹦床上放一个重球时，蹦床会发生弯曲一样。

Space is more than just emptiness. It contains a mix of particles, radiation, magnetic fields and mysterious forms of matter and energy. Imagine space as a 3D playground, inside which objects like stars, planets, nebulas and galaxies exist and together make up our fascinating and complex universe.空间不仅仅是空无一物。它包含粒子、辐射、磁场以及以神秘形式存在的物质和能量的混合物。将太空想象成一个3D游乐场，里面有恒星、行星等物体， 有星云和星系，共同构成了我们迷人而复杂的宇宙。