Have you ever noticed how the full moon looks bigger when it's near the horizon than when it's high overhead? If so, you're not alone. People have wondered about this strange effect since ancient times, and surprisingly, we still don't have a great explanation, but that's not for lack of trying.
你是否曾经注意到，当满月接近地平线时，它看起来比高悬头顶时要大？如果是的话，你并不孤单。人们自古以来就对这种奇怪的效应感到好奇，令人惊讶的是，我们至今没有一个很好的解释，但这并非因为缺乏尝试。
Some of the greatest minds in history - Aristotle, Ptolemy, Da Vinci, Decartes - have all wrestled with this problem and failed to generate an adequate explanation. One of the first ideas suggested was that the image of the moon in the sky really is bigger near the horizon. Perhaps the Earth's atmosphere acts like a giant lens, magnifying the moon as it rises and sets. But this explanation doesn't cut it. If anything, the refraction of the atmosphere would make the moon look slightly smaller. Plus, if you actually measure the size of the visible moon at different positions, it doesn't change at all.
历史上一些最伟大的思想家 - 亚里士多德、托勒密、达·芬奇、笛卡尔 - 都曾经努力解决这个问题，但都未能提出一个充分的解释。最初的想法之一是天空中的月亮在地平线附近真的变大了。也许地球大气层就像一个巨大的透镜，当月亮升起和落下时放大了它。但这种解释并不成立。如果有什么的话，大气的折射会使月亮看起来稍微小一些。此外，如果你真的测量不同位置上可见月亮的大小，它根本没有变化。
But then, why does it still seem bigger when it's rising? This must be some kind of optical illusion. The question is, which one?
但那么，为什么当它升起时看起来还是更大呢？这肯定是某种视觉错觉。问题是，是哪一种？
One explanation is the Ebbinghaus Illusion, where two identical objects look different because of the relative size of the objects they're surrounded by. Here the two center circles are actually the same size. Maybe the moon looks bigger near the horizon because it's next to tiny trees, houses, and towers in the distance. But when the moon is higher up, it's surrounded by the vast darkness of the night sky and looks tiny by comparison.
一种解释是艾宾浩斯错觉，其中两个相同的物体因为它们周围物体的相对大小而看起来不同。这里两个中心的圆实际上是相同的大小。也许月亮在地平线附近看起来更大，是因为它旁边有远处的小树、房屋和塔楼。但当月亮更高时，它被夜空的浩瀚黑暗所包围，与之相比显得很小。
Another possibility is the famous Ponzo Illusion. If you've ever tried to draw in perspective, you know that the closer something is to the horizon, the smaller you should draw it. Our brain compensates automatically for this by perceiving objects near the horizon as larger than they actually appear. The two yellow lines in this drawing are the same size, but the upper one seems bigger because we interpret it as receding farther into the horizon.
另一种可能性是著名的庞佐错觉。如果你曾经尝试过透视画，你就会知道某物离地平线越近，你应该画得越小。我们的大脑会自动补偿这一点，将地平线附近的物体感知为比它们实
际上更大。这幅画中的两条黄线大小相同，但上面的一条看起来更大，因为我们将其解释为更远地退到地平线上。
So, between Ponzo and Ebbinghaus, it seems like we've solved the mystery of the moon illusion, but, unfortunately, there are a few details that complicate things. For one thing, if this was just the Ebbinghaus effect, then we would expect the moon illusion to disappear for pilots flying high above the clouds since there wouldn't be any other smaller objects near the horizon. But in fact, pilots and sailors out on the ocean still claim to see the moon illusion.
因此，在庞佐错觉和艾宾浩斯错觉之间，我们似乎解决了月亮错觉的谜团，但不幸的是，有一些细节使情况变得复杂。例如，如果这只是艾宾浩斯效应，那么我们会期望对于飞行在高云层以上的飞行员来说，月亮错觉会消失，因为地平线附近不会有其他较小的物体。但事实上，海上的飞行员和船员仍然声称看到了月亮错觉。
On the other hand, if it's just our brain's autocorrecting the size of objects near the horizon, then we'd expect the moon illusion to be visible inside a planetarium, where the whole sky, including the horizon, is displayed on a spherical dome overhead. Studies have shown, though, that this is not the case. To make matters worse, it seems the moon illusion disappears entirely if you just bend over and look at the moon between your legs. Now, this is just getting ridiculous!
另一方面，如果这只是我们大脑自动纠正地平线附近物体的大小，那么我们会期望在天文馆内可以看到月亮错觉，那里整个天空，包括地平线，都显示在头顶的球形穹顶上。然而，研究表明，情况并非如此。更糟糕的是，如果你只是弯腰并通过双腿之间看月亮，月亮错觉似乎完全消失了。现在，这简直太荒谬了！
One of the most promising explanations today is known as Convergence Micropsia. Our brains judge the distance to objects and their apparent size by the focus of our eyes. When looking at the horizon, your eyes focus far off into the distance so your brain knows you're looking far away. The moon appears a certain size. Your brain thinks it's far away, which it is, so you naturally conclude the moon must be big. But when looking up at the night sky, there's nothing for your eyes to focus on, so they default to their rest focus, which is a point just a few meters away. Now your brain thinks the moon is much closer than it really is, so you naturally conclude the moon's not as big as you thought it was.
如今最有前途的解释之一被称为聚焦性微视症。我们的大脑通过眼睛的焦点来判断物体的距离和它们的表观大小。当看向地平线时，你的眼睛聚焦在远处，所以你的大脑知道你在看远处。月亮呈现出一定的大小。你的大脑认为它很远，事实上也是如此，所以你自然会得出结论，月亮一定很大。但当仰望夜空时，你的眼睛没有东西可以聚焦，所以它们默认回到休息焦点，那是一个只有几米远的点。现在你的大脑认为月亮比实际上近得多，所以你自然会得出结论，月亮并没有你想象的那么大。
Rather than explain why the moon looks so big near the horizon, Convergence Microspia explains why the moon looks so small when overhead. Still not satisfied? Well, frankly, neither are many scientists, so the debate over the moon illusion still rages on and may continue as long as we still see it in the night sky.
与其解释为什么月亮在地平线附近看起来那么大，Convergence Microspia 更愿意解释为什么月亮在头顶上方时看起来这么小。仍然不满意吗？坦白说，许多科学家也是如此，因此关于月亮错觉的争论仍在继续，并可能会持续，只要我们在夜空中仍能看到它。