&
The Earth’s atmosphere is in
constant motion, and the density of its
numerous layers can vary rapidly.
So the refraction (or bending) that a star’s
light experiences as it propagates
through the atmosphere is also
constantly changing. This means,
effectively, that the apparent position and
brightness of a star changes slightly from
moment to moment. This makes the star
appear to wobble or ‘twinkle’.
However, a star is so far away that it is
just a point of light whereas a planet,
being so much closer, is a tiny disc of
light. Although your eyes can’t resolve
the disc unaided, the extent of the planet
on the sky is generally much larger than
the size of the atmospheric variations
which cause twinkling. So, although
planets do actually twinkle to some
extent, it is much less noticeable than it
is for stars. AGWhy do planets not twinkle?
Can we prevent mental illness?
Not all conditions. Some may be
preventable with advances in therapy, drug
treatments and genetic analyses but many
are unavoidable. For example, about 1 in 3
people who face extreme trauma such as
military combat, sexual abuse, terrorist
attacks or earthquakes suffer from
post-traumatic stress disorder (PTSD), with
nightmares, anxiety, flashbacks and
insomnia. We can treat their symptoms and
help people become more resilient, but to
prevent PTSD completely we would have to
stop all wars, all natural disasters, and all
the ways people inflict misery on others.
Depression is common and deeply
distressing but it may be a natural
response to unbearable conditions.
Evolutionary theories liken it to physical
pain, in motivating us to escape or avoidThe Moon (middle) is the
brightest object, with Venus
below, followed by the red dot
of Mars and the star Spicathe circumstances that cause it.
The associated feeling of listlessness may
have evolved to save energy and withdraw
from activity when situations become too
bad or uncontrollable. SB- Skin
Average weight: 4,535g
Function: Protects against
pathogens; provides insulation;
synthesizes vitamin D; regulates
temperature; provides sensation - Liver
Average weight: 1,560g
Function: Breaks down toxins;
produces hormones, proteins
and digestive biochemicals;
regulates glycogen storage - Kidneys
Average weight: 260g (pair)
Function: Remove waste
products; regulate sodium and
water retention; filter blood;
produce urine and hormones - Spleen
Average weight: 175g
Function: Filters blood; holds a
reserve supply of blood; recycles
iron; synthesizes antibodies;
removes bacteria - Pancreas
Average weight: 70g
Function: Produces insulin and
glycogen; secretes enzymes that
assist in the absorption of
nutrients in the small intestine - Thyroid
Average weight: 20g
Function: Controls body’s
energy use; makes proteins;
controls hormone sensitivity - Prostate gland
Average weight: 11g
Function: Secretes an alkaline
fluid that constitutes 50-75 per
cent of the volume of semen - Brain
Average weight: 1,500g
Function: Drives executive
functions such as reasoning;
coordinates responses to
changes in environment - Lungs
Average weight: 1,300g
Function: Supplies oxygen to
be distributed around the body;
expels carbon dioxide that is
created around the body
TOP TEN
HEAVIEST ORGANS IN THE BODY- Heart
Average weight: 300g
Function: Pumps oxygenated
blood from lungs around the
body; pumps deoxygenated
blood to the lungs
PHOTO: GETTY X2, NASA, CERN, ALAMY
Depression may
play a role in
protecting us
from traumaEESST T OORRGG