Many astronomers think the Universe started in a Big Bang
about 14 billion years back. During those times, the whole Universe was inside
a bubble that was 1000s of times smaller compared to a pinhead. It was denser
and hotter than anything we can imagine.
Then it suddenly exploded. The Universe that we all know was
born. Time, space and matter all started with the Big Bang. In a fraction of a
second, the Universe grew from smaller than an individual atom to larger than a
galaxy. And it continued growing at a great rate. It is still growing today.
As the Universe expanded and cooled, energy transformed into
particles of antimatter and matter. These two opposite kinds of particles
largely destroyed one another. But some matter made it. More stable particles
known as neutrons and protons began to form when the Universe was one second
Over the next three minutes, the temperature decreased below
1 billion degrees Celsius. It was now cool sufficient for the neutrons and
protons to come together, building hydrogen and helium nuclei.
Following 300 000 years, the Universe had cooled to about
3000 degrees. Atomic nuclei could finally capture electrons to make atoms. The
Universe full of clouds of hydrogen and helium gas.
The Mystery of the Dark Universe
Normal matter comprises everything we can notice, smell or
touch. This matter, which is produced from atoms also comprises stars and
All objects made from atoms pull on one another based on how
much matter they contain. This is why a tiny, low mass object including an
apple drops towards a lot more massive object, the Earth.
Astronomers think that there must be also another type of
invisible 'dark matter' that is spread through the entire Universe. By learning
the Milky Way and numerous distant galaxies, they have discovered that visible
matter on its own cannot account for their rotation, size and shape. Alone,
normal matter would not be able to produce enough gravity to maintain the
Scientists also can tell that there is some unfamiliar
material in the space between the stars, due to its gravitational pull
influences the path of starlight travelling towards Earth. Dark matter can even
behave like a magnifying glass, bending and distorting light from galaxies and
clusters behind it. Astronomers can use this effect, referred to as
gravitational lensing, to map the distribution of dark matter.
No more than 15% of the matter within the Universe is made
from atoms. The rest is dark matter. However, Nobody knows what dark matter
consists of. We do know that it does not soak up, emit or reflect light,
because not one of our scientific instruments can directly detect it.
Numerous scientists think that most dark matter
is some unfamiliar subatomic (smaller than an atom) particle which interacts
only very weakly with normal matter. If this is correct, billions of these
particles will have passed via your body by the time you finish reading this
article. Experiments buried deep underground may one day capture a number of
these particles, finally solving the secret of what dark matter actually is.