Asteroids were created when our solar
小行星是在
system formed 4.6 billion years ago
4.6亿年前太阳系形成时产生的
Today there are around 800,000 orbiting the Sun,
现今有大约80万颗绕太阳运行
and a few are potentially hazardous to Earth
其中一小部分对地球有潜在危险
Just how difficult is it to predict their movements?
预测它们的运行该有多难?
Just like the Earth, asteroids rotate as they orbit the Sun.
就像地球一样 小行星围绕太阳旋转
When one side is facing the Sun,
当其一边面向太阳时
the surface heats up and absorbs that heat.
表面受热升温并吸收热量
As it rotates away from the Sun,
当它远离太阳旋转时
the surface cools and radiates that heat outwards.
其表面冷却并将热量向外辐射
This gives the asteroid a small kick in the opposite direction.
这为小行星提供了反方向的微弱推进力
This is known as the Yarkovsky effect.
这被称为雅科夫斯基效应
The effect is tiny, but because asteroids have spent
这种影响是极小的 但因为小行星已经
billions of years in the solar system,
在太阳系里度过了数亿年
it can add up to notable changes.
它也能累积带来显著变化
Although we can’t perfectly predict the orbits of asteroids
尽管我们不能完美预测小行星运行轨迹
and whether one will impact the Earth
以及是否其中一颗会撞击地球
at some point in the future,
但在未来某个时间点上
it’s incredibly unlikely, and not worth losing sleep over just yet.
某颗小行星撞击地球是非常不太可能的 目前我们也不值得为此担心失眠