91av

ACROSS

1 Er (6)

4 Form of surface mining (8)

9 Thomas H ___, “Darwin’s Bulldog” (6)

10 Margaret ___, astrophysicist, former director of the Royal Greenwich Observatory (8)

12 Medicine in the benzodiazepine family, prescribed for anxiety (8)

13 Unit equal to 1,000,000 (6)

15 x and y, typically (4)

16 One of five long bones in the human foot (10)

19 Cu, Au or Fe, for example (5,5)

20 Colour between the wavelengths of green and blue (4)

23 Umbra (6)

25 Variable visualised by an oscilloscope (8)

27 Of a crystal, having triangular faces (8)

28 Electroplated metal layer (6)

29 Charles ___, inventor of vulcanised rubber (8)

30 1980 science documentary presented by Carl Sagan (6)

DOWN

1 Ant-eating monotreme (7)

2 Simple photographic device (3,6)

3 Early internet discussion system (6)

5 Electrical connector; bung (4)

6 Ne, Xe or Rn, for example (5,3)

7 Prefix indicating a relation to sound or hearing (5)

8 Column of rising warm air (7)

11 Influential 1962 sci-fi film by Chris Marker (2,5)

14 Michael ___, pioneer in electromagnetism (7)

17 Type of polystyrene (9)

18 The study of the function and structure of cells (8)

19 # (7)

21 “I have often admired … the secret magic of ___” – Sir Thomas Browne, 1643 (7)

22 Form of machine-driven electronic dance music (6)

24 ___ acid, organic compound containing -NH2 and -COOH (5)

26 Molten rock (4)