The Sun's spots, which they had known about for years,seemed to have unexpectedly vanished.人们知道太阳黑子已有多年，但它们出人意料地消失了

know about知道； 了解； 听说过有关 ... 的情况

I'd love to know about the plan.

我想知道这个计划。

This is all I know about it; for the rest, you may ask others.

对这件事我就知道这些，至于其他情况，你可以问别人。

There were people who carried on looking for sun spots for 50 years,有人继续寻找太阳黑子观测了五十年

carry on继续进行；从事，经营

We'll carry on our conversation tomorrow.

我们明天将继续进行会谈。

look for寻找；寻求

He turned on the torch to look for his keys.

他打开了手电筒，寻找钥匙。

As the tide receded we were able to look for shells.

潮水退去，我们就能寻找贝壳了。