摘要：All the stuff that gets sucked into a black hole is compressed into a tiny dot in the middle. That dot is smaller than a grape. It

Black holes are small but dense

黑洞很小，但密度很大

All the stuff that gets sucked into a black hole is compressed into a tiny dot in the middle. That dot is smaller than a grape. It's smaller than a grain of sand. In fact, it's so small it takes up no space at all! 所有被吸进黑洞的东西都被压缩成中间的一个小点。那个点比葡萄还小。它比一粒沙子还小。事实上，它非常小，根本不占任何空间！

If you could hold a black hole in your hand, it would be invisible, yet heavier than the Sun. The Sun weighs about 2,000,000,000,000,000,000,000,000,000,000 kilograms. That's 300,000 times more than Earth and 30 billion times more than you!

如果你能把黑洞拿在手里，它是看不见的，但却比太阳重。太阳的重量约为200,000,000,000,000,000,000,000,000千克。它比地球大30万倍，比你大300亿倍！

So how can something so small have such strong gravity? Black holes have strong gravity because they're very dense. Density means how heavy something is for its size. A piece of packaging foam is very light. But a piece of gold exactly the same size is very heavy. This is because gold is denser than foam. It has more stuff packed into the same amount of space.

那么这么小的物体怎么会有这么强的引力呢？黑洞的引力很强，因为它们的密度很大。密度是指某物相对于其大小的重量。一块包装泡沫很轻。但是一块同样大小的金子却很重。这是因为黄金比泡沫密度大。它在同样的空间里装了更多的东西。

Earth is quite dense. It's mostly made of rock and metal, which is very heavy for its size. But black holes are even denser. They are much smaller than Earth, but they are much heavier. In fact, they are the densest objects in the universe.

地球的密度很大。它主要是由岩石和金属构成的，相对于它的大小来说，金属很重。但黑洞的密度更大。它们比地球小得多，却重得多。事实上，它们是宇宙中密度最大的物体。

来源：英语·点