And unless you're watching this far in the future after we've had some sort of apocalypse, there are screens all around us.

除非，我們經歷某種世界末日後，你在很久以後的未來看這部影片，我們周遭都有螢幕。

So of course, a lot of people are worried that exposure to all this unnatural light is harmful.

當然，很多人擔心暴露在這些不自然的光線下是有害的。

But can digital screens really hurt you?

但數位螢幕真的會傷害到你嗎？

Well, at the very least, they can can cause temporary annoyances like headaches.

它們確實會引起短暫的麻煩，如頭痛。

But the research is still out on permanent damage.

但永久性的傷害仍在研究中。

If you stared at a screen for too long, you may find yourself feeling what's known as digital eye strain, or computer vision syndrome.

如果你盯著螢幕太久，你會覺得自己感覺有了數位視覺疲勞，或是電腦視覺症候群。

The most common symptoms are blurred vision, headache, and pain in the neck and shoulders.

最常見的症狀為視力模糊、頭痛、脖子痛、肩膀痛。

Unfortunately, even though we know it's connected to spending a bunch of time looking at a screen, there are a bunch of potential causes —

不幸的是，就算我們知道它與花大量時間在螢幕上有關，

from screen viewing making you blink less often and squint more, to it affecting your pupil response time, to it exposing you to more blue light.

但也存在許多潛在原因，因為螢幕的關係導致你眨眼次數變少，斜視次數變多，從而影響你的瞳孔反應時間，也讓你暴露在更多藍光下。

Or people could be suffering from digital eye strain because they don't have the right lens prescription, or one that doesn't take into account astigmatism.

或是有人困擾於數位視覺疲勞，因為他們沒有正確的眼鏡度數，或是沒有考慮到散光的因素。

Basically, there's no one cause.

基本上，這些都不是原因。

Luckily, the symptoms of digital eye strain go away when you give your eyes a proper rest, and studies haven't shown any long-term effects even if you suffer from it regularly.

幸運的是，只要讓眼睛適度休息，數位視覺疲勞的症狀就會消失，就算你經常受到該症狀困擾，也沒有研究表示會有長期影響。

And if you want to avoid that pain in the first place, doctors recommend you take a 20 second break from your screen every 20 minutes, staring off at an object 20 feet away.

如果你一開始想避免這種痛苦，醫生建議你每看 20 分鐘的螢幕就要休息 20 秒，而且要離螢幕 20 英尺遠。

Still, there might be another way screens could harm you, and that's through exposure to blue light that can kill cells in your eyes.

一樣，螢幕可能會用其他方式傷害你，也就是因為暴露在藍光下，進而殺死眼睛的細胞。

The color of blue light comes from its short wavelength, which also means it has high energy — enough that blue light can damage and eventually kill the cells in your eye's retina.

藍光的顏色來自其短波長，也代表它具有高能量足以讓藍光傷害並最終殺死眼睛視網膜中的細胞。

The light reacts with certain molecules, knocking off bits of them and creating reactive oxygen species, or ROSes, which will bond with almost anything.

光會與某些分子發生反應，並將其中一些分子除去，創造出活性氧分子或叫 ROSes，它們幾乎會與所有物質結合。

They can cause so much damage that cells eventually destroy themselves in a process called apoptosis.

它們會造成巨大傷害，導致細胞最後自我毀滅，這過程叫做細胞凋亡。

We know this happens because researchers have done a lot of experiments —

我們之所以知道這種情況，是因為研究人員進行了很多實驗，

not directly on human eyes, of course, but on animal models like rats or human retinal cells grown in petri dishes.

當然不是直接在人類的眼睛上，而是在老鼠的動物模型，或是生長在培養皿的人類視網膜。

The thing is, most of those studies focus on high-intensity light from LED lamps, and sometimes expose the subjects to that light for day-long lengths of time.

問題是，這些研究大多集中在 LED 燈發出的高強度光上，有時會將物體暴露在該光下一整天。

So even though we know that high intensity blue light definitely causes retinal cell death, it doesn't tell us much about the real-life dangers of screens.

因此，就算我們知道高強度的藍光絕對會造成視網膜細胞死亡，也未必能告訴我們關於螢幕對現實生活的危害。

There was one 2017 study that looked at the effects of low intensity blue light at three different wavelengths emitted from common types of screens.

2017 年的一份研究，研究三種不同波長的低強度藍光的影響，是從一般螢幕所發出的藍光。

Specifically, they found that blue light at 449 nanometers caused the largest increase in those harmful ROSes.

具體來說，他們發現 449 奈米的藍光，是有害的 ROS 造成最大傷害的時候。

But light with a slightly longer wavelength of 470 nanometers didn't do much damage.

但是波長稍長的 470 奈米的光卻沒有太大傷害。

That 21-nanometer change in wavelength might not seem like a lot, but the difference means the two colors of light have different amounts of energy.

21 奈米的波長變化似乎不多，但其中的差別是兩種顏色的光有不同能量。

The 470 nanometer light, which was a sort of turquoise, just didn't have enough energy to effectively break apart molecules.

470 奈米的光有點像藍綠色，它沒有足夠的能量來有效分解分子。

This suggests we'd do well to decrease the amount of shorter wavelength blue light from our screens if we want to save our eyeballs.

這代表如果我們要保護眼球的話，最好減少低波長的螢幕藍光。

Don't shut your eyes just yet, because it ignores one major comparison: daylight.

但先別急著閉上眼，因為該研究忽略了一個重要的對比：日光。

Look anywhere on a clear day and you'll see a lot of blue.

仔細看看晴朗的天空，就會看到很多藍色。

And that blue light is way more intense than what you get from staring at a computer screen.

而藍光比你盯著電腦螢幕的光還要強烈。

A paper published in 2016 looked at the amount of light — both in general and in the blue part of the spectrum — from a range of electronic screens and compared it against the amount of blue light you'd be exposed to from simple daylight.

2016 年有一份論文，針對一系列電腦螢幕的光進行研究，包括一般螢幕和光譜的藍色部分，並與一般日光下 可能會遇到的藍光數量進行比較。

Its conclusion?

結論是？

The blue light from devices like laptops and smartphones, quote, "does not represent a biohazard, even for long-term viewing."

筆電和智慧型手機發出的藍光，不會「造成生物危害，即使是長期觀看」。

So you go ahead and watch as many more SciShow videos as you want.

所以盡量看你想看的 SciShow 影片。

We're officially non-hazardous!

正式宣布我們無害！

And in the meantime, thanks for watching this episode of SciShow, and thanks especially to our community on Patreon for making this show possible.

同時，感謝觀看這集的 SciShow，特別感謝Patreon 的社群幫忙促成 SciShow。

We have a whole team of people working to bring you amazing facts and answer fascinating questions every day of the week.

我們有一個完整團隊，每天努力告訴你驚人的事實，並回答有趣的問題。

And we wouldn't be able to do any of this without your support.

如果沒有你們的支持，我們什麼都做不了。

And if you're not yet a patron and interested in becoming one, just check out patreon.com/scishow to learn more.

最後，如果你不是贊助人但有興趣的話，就到 patreon.com/scishow 了解更多資訊。