&
PHOTOS: NASA, ISTOCK X2, DAVID BARTON, SCIENCE PHOTO LIBRARYWHAT CONNECTS......The Space Shuttle with
a horse’s bottom?1.
e Space Shuttle’s
so d rocket boosters
e e manufactured in
P y, Utah. To get to
ch site in Florida,
3 km (2,400 miles)
each one had to
m a seven-day train
journey.2.
In order to fit through
the railway
tunnels along
the route,
the design of
each booster
segment was
limited to a
maximum diameter
of just 3.66m (12ft).3.
The width
of railway
tunnels is
determined
by the gauge
of the railway
track. The US uses
the standard track gauge
of 1.44m (4ft 8.5in).4.
Early trains were drawn by
horses. The track gauge was
chosen to allow two horses
side-by-side to pull a cart.
This standard was kept for
steam railways, to allow the
wagons to be reused.a horse’s bottThe
solid
were
Promontory
the launc
3 ,862
away,
make aIs new hydrogen being created in the Universe?
How hard is tooth
enamel compared
to other materials?
Tooth enamel is mostly hydroxyapatite,
which is a mineral form of calcium
phosphate. The apatite group of
minerals scores a five on the Mohs
hardness scale; which makes enamel
the hardest biological material. Tooth
enamel is harder than steel, but a lot
more brittle. So you can’t scratch your
enamel on metal cutlery but you can
chip it by trying to open a beer bottle
with your teeth. LV
EnamelThere are very few hydrogen atoms
being created afresh in the Universe.
But there are some. Occasionally, a type
of radioactivity called ‘proton emission’
can produce a ‘new’ proton and this
can form ‘new’ hydrogen by capturing
an electron. Hawking radiation can also
produce ‘new’ protons and hence ‘new’hydrogen. Yet both of these processes
are extremely rare and inefficient, so the
amount of new hydrogen being created
is insignificant compared to the amount
created in the Big Bang. Since stars are
destroying hydrogen in their interiors,
the overall amount of hydrogen in the
Universe is decreasing over time. AG