An asteroid ended the age of the dinosaurs 66 million years ago. Could something as catastrophic as that happen again?6600 万年前，一颗小行星结束了恐龙时代。 如此灾难性的事情还会发生吗？

Asteroids are something astronomers closely track. Recently, the asteroid named 2024 YR4 made headlines for its tiny, but real, chance of colliding with Earth in 2032. In February 2025, NASA increased the impact probability of this asteroid hitting us to 2.3%. Scientists have calculated that YR4 is between 40m and 90m in diameter. It would have the power of a nuclear bomb if it was to hit Earth, causing severe damage if the impact was in a populated area. However, Dr Robert Massey of the Royal Astronomical Society urges calm. He said he is not "losing sleep over" the asteroid, but stresses that funding planetary defence and spotting potential threats is essential.小行星是天文学家密切追踪的对象。 最近，一颗名为 2024 YR4 的小行星因其在 2032 年与地球相撞的微小但真实的机会而成为头条新闻。2025 年 2 月，美国宇航局将这颗小行星撞击我们的可能性提高到 2.3%。 科学家计算出YR4的直径在40m到90m之间。 如果它击中地球，其威力将相当于核弹，如果撞击在人口稠密地区，则会造成严重破坏。 然而，英国皇家天文学会的罗伯特·梅西博士敦促大家保持冷静。 他表示，他并没有因为这颗小行星“失眠”，但强调为行星防御提供资金和发现潜在威胁至关重要。

So what are asteroids? They are fragments of rock left over from the creation of the solar system 4.6 billion years ago. They frequently orbit close to Earth pushed by the gravity of other planets, though it was only in the late 1900s that scientists were able to systematically track near-Earth objects and learn this. They found that asteroids of more than 40m across, that's large enough to destroy a city, cross the Earth's path within lunar distance several times a year.那么什么是小行星？ 它们是 46 亿年前太阳系形成时留下的岩石碎片。 它们经常在其他行星的引力推动下在靠近地球的轨道上运行，尽管直到 1900 年代末科学家才能够系统地跟踪近地天体并了解这一点。 他们发现，直径超过 40m 的小行星（大到足以摧毁一座城市）每年都会在月球距离内多次穿过地球轨道。

The chance of an asteroid being large enough to penetrate our atmosphere intact and destroy a city is likely to happen once in every hundred years. In 1908, an asteroid exploded over Siberia, injuring people and buildings across more than 500 square kilometres. However, actual impacts aren't as common as near-misses. For example, the asteroid Apophis raised alarms after it was discovered in 2004 because it was estimated to be around the size of a cruise ship. Even scarier, in 1994, the comet named Shoemaker-Levy 9 crashed into Jupiter, and, if it had hit Earth, all life would have been wiped out, just like the dinosaurs were.小行星足够大，可以完整地穿透我们的大气层并摧毁一座城市，这种情况可能每百年就会发生一次。 1908 年，一颗小行星在西伯利亚上空爆炸，造成 500 多平方公里的人员和建筑物受伤。 然而，实际影响并不像未遂事件那样常见。 例如，小行星阿波菲斯在 2004 年被发现后就引发了警报，因为据估计它的大小与一艘游轮差不多。 更可怕的是，1994年，名为舒梅克-利维9号的彗星撞上了木星，如果它撞上了地球，所有生命都会被消灭，就像恐龙一样。

So, it's safe to enjoy admiring the night sky because the chances of you being hit by an asteroid are very, very small, even if they're not zero.所以，欣赏夜空是安全的，因为你被小行星撞击的可能性非常非常小，即使它们不为零。