New Scientist - USA (2021-10-30)

30 October 2021 | New Scientist | 55

Answers

Quick quiz #125

Answers

1 Osteoclasts

2 31 – Belphegor’s prime is

10000000000000666000

00000000001

3 The Rosetta Stone

4 Magellan

5 The blue-footed booby,

Sula nebouxii

Quick crossword

#94 Answers

ACROSS 1 Pasteurisation,

9  Ozone, 10 Deoxidise,

11  Operation, 12 House,

13  Yttrium, 15 Inertia,

17  Titanic,  19 Laptops, 21 Evert,

23  Eye doctor, 25 Immunised,

26  Biome, 27 A Scanner Darkly

DOWN 1 Photosynthesis,

2  Slowest, 3 Elevation, 4 Radii,

5  Spoonbill, 6 Thigh, 7 Oviduct,

8  General surgery, 14 Michelson,

16 Euphorbia, 18 Thermos,

20  Outlook, 22 Tonka, 24 Elder

#136 Narrowing

the spectrum

Solution

The seven colours are red, orange,

yellow, green, blue, indigo and

violet. Of these, only red, green

and indigo can be made from

letters that occur in the names

of the other colours. Of these

three, red and green can be made

from letters in the other two, so

indigo must be Lise’s favourite.

Tom Gauld

for New Scientist

A low bow

I saw a strange rainbow, at the
wrong height compared with other
ones I’ve observed from the same
location with the sun close to the
horizon. Under these conditions,
it is supposedly impossible to see
a rainbow at any other angle than
around 42 degrees, but the arc of my
“low bow” looked like 21 degrees.
Can anyone explain? (continued)

Mike Follows
Sutton Coldfield,
West Midlands, UK
This low rainbow could be due to
a temperature inversion. This is
where warmer air sits on top of
colder air at the surface, whereas
air temperature normally falls
as you ascend through the
atmosphere. Light travels faster
through warmer air, so instead
of travelling in a straight line to
the raindrops responsible for the
rainbow, the light travels from a
low sun on a curved trajectory,
like an arrow. Sunlight enters the
raindrops as if from a sun that is
higher in the sky, resulting in a

rainbow appearing lower than

under normal conditions.

Ben MacGregor

Thurso, Highland, UK

I have seen an inverted rainbow

produced by the reflection of the

sun in a calm sea, even though

I couldn’t see the reflected sun.

The low bow will have been

produced by an image of the sun

that was much higher in the sky

than the actual sun. This could

have been produced by multiple

reflections from surfaces such as

open windows or solar panels.

Angus McKee

Glasgow, UK

Was this picture taken from a

location with a significant patch

of water? [Ed: Yes, it was taken at

Sydney’s Northern Beaches, Australia]

This can reflect the sun, causing

another rainbow that looks like

a mirror image of the part of the

rainbow otherwise below the

horizon. If the sun was low down,

the normal rainbow would be

high, whereas the rainbow from

the reflected sun would be low.

Bill Tango

Manly, New South Wales, Australia

I recently saw a photo of a triple

rainbow. The main rainbow was

at the usual angle of 42°, and there

was a fainter secondary bow at a

somewhat larger angle. However,

the third rainbow wasn’t centred

on the antisolar point (located

opposite the sun from the

observer’s perspective) like the

others and appeared below them.

The explanation was that the

rainbows were seen over a body

of water, and the third rainbow

was caused by sunlight reflected

off the surface of the water.

Obviously, it requires a very

special set of circumstances,

including very calm conditions,

to see such reflected rainbows.  ❚