Saturn is a very big planet.
土星是一颗特别大的行星。
But it is very light for its size.
可它个头大，身子却很轻。
It is even lighter than water.
它比水还要轻呢。
If we had a huge pool, Saturn could float.
要是有个超大的水池，土星能漂起来。
It would float like a ball on the water.
它会像个大球一样浮在水面上。
That is because it is made mostly of gas.
因为它大部分都是气体呀。
No other big planet can do that.
别的大行星，可做不到这一点。
