For a show that looks deep into space, tonight’s edition takes a different turn, trying to look for things we cannot see.
The team here look into the attempts to find the hypothetical materials known as dark matter and dark energy. The former is a material that fills all universal space but we have yet to detect it. The latter is a force supposedly accelerating the expansion of the universe. Given that 95% of the universe is invisible, there should be a lot of this stuff about, even if we are not sure it exists.
The Sky at Night is on BBC Four at 22.00.