The why type question on your science (part 2)


Can stars collide?


In general, distances between stars are
so vast that it is unlikely that any
two will ever meet and collide. But, in
some places, notably in globular clusters,
stars can be crowded together much more
tightly and, indeed,
may well collide with each other.
Many clusters contain very large,
hot stars known as‘blue stragglers’,
which should have detonated as
supernovae billions of years ago. It’s
believed these stars formed more
recently as the result of collisions and
mergers of normal stars. It’s also
probable that stars collide in other
star-rich places,such as the central
regions of galaxies.Binary stars can
coalesce as one
star reaches the end
of its life, expands
and consumes
its partner.


What causes a halo around the Sun?


The appearance of a huge, perfectly circular
halo round the Sun in Mexico in 2015
sparked rumours of the impending end of
the world. In reality, it was the product of
sunlight being refracted through hexagonal
ice crystals high in the atmosphere. Water
droplets can do the same, producing a
smaller, more colourful halo.

CAN LIGHTNING OCCUR IN SPACE?


Lightning is a sudden
electrostatic discharge between
regions of differing electric
potential. It has been observed
on Venus, Jupiter and Saturn,
as well as Earth. In space, there
is little material to act as a
conductor of charge, so
traditional lightning is
probably rare. Processes
similar to lightning have been
observed in electro-magnetic
fields around black holes, as
well as in highly ionised clouds
of gas and dust called nebulae.


How fast is the Universe
expanding?

The expansion of the Universe is
unusual in that the further we look,
the faster galaxies appear to be
racing away from us. This is
captured in Hubble’s Constant, the
standard way of measuring the
cosmic expansion.
Analysis of the light from distant
stars and galaxies reveals both their
speed and distance, and these imply
that the cosmic expansion rate is
surprisingly sluggish: the speed of
recession increases by just 1km/h
for every 13 light-years of distance.
As such, we can all but forget about
the cosmic expansion on the scale of
our galaxy, where it’s overwhelmed
by gravity in any case.
Only on the largest scales does the
expansion of the Universe start to
really get up steam, with the most
distant visible galaxies, which lie
many billions of light-years away,
receding from us at sizeable
fractions of the speed of light.

WHY DO SHIPS SINK IN THE BERMUDA
TRIANGLE?


Ships sink in all parts of the ocean
and there’s nothing particularly
dangerous about the seas around
Bermuda. In fact, a 2013 study
found that the most dangerous
waters were the South China Sea,
the Mediterranean and the North
Sea. The Bermuda Triangle doesn’t
even make the top 10, despite being
one of the world’s busiest shipping
lanes. There have actually been
no sinkings in the Bermuda
Triangle since 1967. Various
theories, such as magnetic compass
anomalies, have no evidence to
support them.

Are there any games at which people can still
beat computers?


Humans still have the edge in the
game of Go. Like chess, it’s played
on a chequered board, but the
board has more squares (19x19) and
each piece can perform many more
potential moves. While chess
becomes more computationally
straightforward as the game
progresses and pieces are removed,
Go requires more judgment and
intuition. These attributes are more
suitable to human intelligence than
machine algorithms.