Day 3 and there’s no let up in the number of chats and questions – 4,400 students registered and nearly 2,500 answered questions, not to mention loads more chats!

Today’s highlights in the Extreme Speed Zone:

• The Universe is expanding very slowly:

daisybamber : How fast does the universe grow and if there is nothing beyond the universe then what does it grow into?

samgeen : The universe travels at the speed of the Hubble constant – which is 21 km/s for something 1 million light years away. So it expands very slowly

• We can’t count the number of particles inside a black hole:

What thing has the most atoms in it and particles?

• And Matt gets weekly email updates on the latest volcanic eruptions…

When did the last volcano erupt?