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How do we know the Universe
hasn’t always existed?
There’s a wealth of evidence that the Universe began in a Big
Bang around 14 billion years ago. We can see distant
galaxies racing away from each other, and the space around
them is filled with cosmic radiation whose intensity and
spread are consistent with that expected from the aftermath
of the Big Bang. But none of this rules out the possibility that
there was another universe before ours.
According to some theorists, when Einstein’s theor y of
gravity is combined with quantum theory, the Big Bang could
really be part of a Big Bounce, in which the collapse of a
previous – and perhaps very different – universe is followed
by the creation of our own. While speculative, these theories
do at least resolve the otherwise tricky question of what
existed before the Big Bang. RMIf you spend time in the
sunshine, your body must
expend energy to prevent you
from overheating. One way it
does this is to sweat, which
leads to lethargy and
dehydration if you don’t drink
enough. The more you exert
yourself, the more work your
body has to do to control your
temperature, which makes
everything feel like an effort. The
cold makes people feel tired for
the opposite reason, as the body
must consume energy to stay
warm, including through
shivering. Bear in mind, though,
the Sun doesn’t only make you
feel tired. By influencing your
circadian rhythm – the body’s
internal clock – it also helps you
get up in the morning. CJWhy does sunshine make me tired?
HEAVIEST LAND CARNIVORES
- Walrus
Weight: 1,200kg
Diet: shellfish, occasionally seals
Walruses spend a third of their lives on land or ice - Polar bear
Weight: 700kg
Diet: ringed and bearded seals - Brown bear
Weight: 680kg
Diet: salmon, berries, seaweed - Siberian tiger
Weight: 318kg
Diet: deer, pigs
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