Brian Aldiss likes to illustrate scientific principles in his science fiction, but it is always in the background: his books are not science texts. Here are some physical phenomena in Hothouse:

The Earth does not turn on its axis any more.

In fact, while we will not live to see it, this is the ultimate destiny of the Earth. The problem is that tides cause friction, which convert energy into heat, and the sun and the moon cause tides. This slows down the rotation of the earth.

The moon is fixed relative to Earth

Again, this is due to slowing down of the orbit because of tidal forces. However,  to compensate for the slowing, the moon will be much farther away– something Aldiss does not account for.

The sun is going nova

Sadly, stars, like living things, have a life cycle and must eventually burn out. In the final stages of their life cycle they become a red giant, in a final display of energy. Eventually the sun will engulf all of the inner planets as it bloats during its dying millennia. This process takes several billion years, by which time, humans will probably not be around. Or, as in Hothouse, will have evolved into a different species altogether.

Giant spiders have spun a huge web between the Earth and the moon.

As beautiful as this image is, it is quite impossible.

The physics of Helliconia