Name: 【TED-Ed】月球錯覺 (The moon illusion - Andrew Vanden Heuvel)
Uploaded: 2015-11-09T23:00:00.000Z
Duration: 4 min 9 s

Have you ever noticed how the full moon looks bigger when it's near the horizon than when it's high over head?

你有沒有注意過，滿月在接近地平線時看起來比較大，升上天頂的時候卻比較小？

情態副詞

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.

自古以來大家一直對這個奇怪的現象感到好奇，而且驚人的是，我們還未找到一個極佳的解釋，但這不是因為沒有試著找答案。

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.

許多歷史上數一數二的思想家：亞里斯多德、托勒密、達文西、笛卡爾，都苦思過這個問題，卻無法得出合宜的解釋。

One of the first ideas suggested was that the image of the moon in the sky really is bigger near the horizon.

其中第一個想法認為，天空中月亮的影像在靠近地平線的時候的確比較大。

Perhaps the Earth's atmosphere acts like a giant lens, magnifying the moon as it rises and sets.

或許地球的大氣層就像一面巨大的透鏡，能在月亮起落時將它放大。

If anything, the refraction of the atmosphere would make the moon look slightly smaller.

如果真是如此，大氣層的折射會使月亮看起來稍微小一點。

Plus, if you actually measure the size of the visible moon at different positions, it doesn't change at all.

再者，如果你實際測量月亮在不同位置的大小，你會發現它根本沒有改變。

But then, why does it still seem bigger when it's rising?

那麼為什麼當月亮升起時看起來比較大呢？

This must be some kind of optical illusion.

One explanation is the Ebbinghaus Illusion, where two identical objects look different because of the relative size of the objects they're surrounded by.

一種解釋是艾賓浩斯錯覺：兩件一樣的物體因周圍物體的相對大小而看起來不同。

Here, the two center circles are actually the same size.

這兩個位在中心的圓其實是一樣大的。

Maybe the moon looks bigger near the horizon because it's next to tiny trees, houses, and towers in the distance.

或許月亮接近地平線時，看起來比較大是因為它的旁邊有小樹、房子，以及遠方的塔樓。

But when the moon is higher up, it's surrounded by the vast darkness of the night sky and looks tiny by comparison.

但當月亮升至高空時被夜空中廣大的黑暗包圍，在相互比較下，看起來較小。

Another possibility is the famous Ponzo Illusion.

另一個可能的解釋是有名的龐佐錯覺。

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.

如果你曾嘗試以透視法作畫過，你就知道你應該將愈靠近地平線的東西，畫得愈小。

Our brain compensates automatically for this by perceiving objects near the horizon as larger than they actually appear.

藉由將接近地平線的物體看成比實際上來得大，我們的腦袋自動補償了這個現象。

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.

圖畫中的兩條黃大小一樣，但上面的線段看起來比較大，因為我們將它解釋為退向遠方的地平線。

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.

那麼，透過龐佐還有艾賓浩斯，我們似乎已經解決了月亮錯覺的謎團，但不幸的是有一些細節使得月亮錯覺更加令人費解。

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.

一方面，如果這只是艾賓浩斯錯覺的話，我們會預期月亮錯覺在飛航員於雲端飛行時會消失，因為那裡並沒有其他靠近地平線的較小物體。

But in fact, pilots and sailors out on the ocean still claim to see the moon illusion.

但實際上，飛行員和海上的航海員都宣稱看過月亮錯覺。

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.

另一方面，若這只是我們腦內自動在校正靠近地平線物體的大小，那麼我們會期待月亮錯覺在天文館也看得到，那裡的整個天空包含地平線在內，都展現在球形圓頂的上頭

Studies have shown, though, that this is not the case.

然而，研究顯示情況不是如此。

To make matters worse, it seems the moon illusion disappears entirely if you just bend over and look at the moon between your legs.

更麻煩的是，月亮錯覺似乎會在你彎下腰來從雙腿間看月亮時完全消失

One of the most promising explanations today is known as Convergence Micropsia.

今日，其中一項最具前瞻性的解釋叫做視物顯小理論。

Our brains judge the distance to objects and their apparent size by the focus of our eyes.

我們的大腦藉由將雙眼聚焦來判斷物體的距離，以及它們外觀的大小。

When looking at the horizon, your eyes focus far off into the distance so your brain knows you're looking far away.

看向地平線時，眼睛聚焦在遙遠的遠方，所以你的大腦知道你在看遠方。

Your brain thinks it's far away, which it is, so you naturally conclude the moon must be big.

你的大腦認為它非常遠，所以你自然而然認為月亮一定很大

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.

但當你抬頭看向夜空，那裡沒有東西可以讓眼睛聚焦，所以雙眼默認了其餘的焦距，也就是幾公尺之外的一點。

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.

如此一來，你的大腦認為月亮比實際上距離你更近，所以你自然而然地認為月亮並沒有你原先想的那麼大。

Rather than explain why the moon looks so big near the horizon, Convergence Microspia explains why the moon looks so small when overhead.

視物顯小理論沒有解釋為什麼月亮靠近，地平線時看起來較大，而對為何月亮在頭頂上方時看起來較小做了解釋。

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.

好吧，坦白說，很多科學家也不甚滿意，所以月亮錯覺的爭論還在持續著，而且只要夜裡還看得到月亮，爭論就會一直持續下去。