15 January 2022 | New Scientist | 55Answers
Quick quiz #134
Answers1 Uranium-238
2 Prospero
3 Blood
4 Walter Brattain
5 The secretary bird
(Sagittarius serpentarius)Cryptic
crossword #74
AnswersACROSS 1 Bilayer,
5 Blush, 8 Litterbug,
9/21 Dry Ice, 10 Weird,
11 Scalene, 12 Rheumy,
14 Pathos, 17 Flounce,
19 Pares, 22 Cochineal,
23 Gland, 24 OsmosisDOWN 1 Below, 2 Lattice,
3 Yield, 4 Robust, 5 Big data,
6 Undue, 7 Huygens, 12 Rafting,
13 Menaced, 15 Harness,
16 Velcro, 18 Omega,
19 Prism, 20 Salts#149 All in a spin
SolutionAs the circumference of the plate
cog is five times that of the teacup
cog, most people’s first answer is
that the cup will rotate five times.
This isn’t correct.The centre of each teacup rotates
at a distance of 3 metres from
the centre of the plate. A circle’s
circumference is π x 2r. The
centre of each teacup – and also
its circumference – must therefore
travel π x 6 metres to return to its
starting position.As its circumference has length
π x 1 metres, the number of
teacup rotations is therefore
6π ÷ π = 6.Tom Gauld
for New Scientist
We three-dimensional creatures
see all the distances between
galaxies expanding, indicating
an inflation of space, but we can’t
perceive extra space dimensions
beyond our three, into which the
expansion is taking place.
Roger Leitch
Bath, UK
There are two parts to the
answer to this question.
First, when mathematicians
and physicists want to describe
space – any space – the
mathematical tools and
techniques they use don’t
depend in any way on the
space being part of a higher
dimensional space. So they can,
for example, do geometry on
the surface of a sphere without
considering that the sphere
is embedded in our everyday
three-dimensional space.
Four-dimensional space-time
is more complicated than the
surface of a sphere, but the idea
is the same. It is possible to
calculate the shortest distance
between two points, for example.
Second, if space is expanding
into some higher dimensional
space, we can’t, with our current
knowledge of physics, know
anything about it. And it may even
be beyond our comprehension.Mike Follows
Sutton Coldfield, West Midlands, UK
This isn’t a question that physics
can answer with our present
knowledge or without some
form of qualification.
The trite answer is that both
space and time were created at
the big bang about 14 billion
years ago, so there is nothing
beyond the universe. However,
much of the universe exists
beyond the observable universe,
which is maybe about 90 billion
light years across.
Because the universe ishomogenous on this scale, we
imagine that what is beyond
our observation looks much
the same as what we can see.
If the universe is infinite, there
is nothing beyond it, by definition.
A finite expanding universe
conjures up the idea that it
would have a boundary or edge,
separating it from something
beyond. Of course, the universe
has at least four dimensions
(three for space and one for time)
which is nigh on impossible for
us to visualise.
However, space could be
represented as two dimensions,
confined to the gossamer-thin
surface of a sphere. You could
travel in any direction on the
surface without encountering an
edge. If the radius were to increase,
the “universe” would expand
as ours does, but it wouldn’t
be expanding into anything.
Finally, we could speculate
that our universe is part of a
multiverse with many other
universes beyond our own,
but it is unlikely that we are
expanding into them. ❚“ A finite expanding
universe conjures up
the idea that it would
have a boundary,
separating it from
something beyond”