1. 只见天上横着一条巨大的光束
There is a light beam across the sky.
2. Something keep as horizontal, it means 横,something keep as vertical, it means 竖。
3.一个飞碟快速地快速地自传着,好像悬在了空中。
With the quickly spinning , a UFO looks as if hanging in the sky.
4. As a light, hung by a rope, it means 悬。
5. I think you know how to translate it into English, but you can't understand why there are 两条明显的白色涡流, I'll explain this.
It depends on UFO's jet, You know there is a kind of fireworks, it can't explode, but brings out a lot of smoke, you take two, one with your left-hand, another with your right-hand, and you try to rotate yourself, every firework will create a vortex likes what you ask. That's it.