STORY OF OUR UNIVERSE-BIG BANG
Theory rose
from a basic question, where did our universe start? Did it just sprung into existence
or is it a continuous timeline of existence without end or beginning?
Countless theories have been developed to explain this, big
bang is most profound and it’s hence stood out. It gives an idea about the
beginning of time.
Expanding Universe
Astronomer
Edwin Hubble had observed movement of galaxies closer to ours over years, in
1929 conclusions drawn from these observations presented astounding results. His
observations indicated red wavelength Doppler’s shift.
Doppler’s shift
Sound produced by vehicle coming towards
you is clearly heard, as it passes you and goes farther, and then the pitch
drops, this is an example of Doppler Effect. As the source (being vehicle here)
is moving and not stationary hence there is a change in transmitted and
received wavelength. Basically when something is approaching towards observer
its wavelength is shorter and has spectrum color of blue, when moves away from
observer reflected wavelength has spectrum color of red. So when Hubble saw red
Doppler shift it led to conclusion that galaxies are moving away from ours.
Back to expanding universe
Important thing to notice here is, galaxies on all sides of
earth are moving away. If galaxies that are forward or backward of Milky Way
alone are moving away, we can conclude that universe is moving in one
particular direction, but here galaxies in all directions(that is all sides of milky
way) are moving away from us at speed of light.
For a closer picture, consider this experiment
Take a deflated balloon; mark 5 dots on it using marker/pen.
Now, blow that balloon, you can notice that all dots are moving away from each other, no matter
which dot you take as reference and observe, you can see that other dots are
moving away from it. There by concluding that the balloon is expanding
uniformly in all directions. Apply same phenomena to expansion of our Universe,
dots here are galaxies and balloon is the universe. Similarly it’s established
that universe is expanding at the speed of light uniformly in all directions.
THE BIG BANG
Stephen Hawking thought what if we rewind this? Going back
in time same way (contracting universe), universe has been expanding and now we
go back in time to the point where it all existed in immensely hot (millions of
degrees), extremely dense point which is a singularity (yes, the one in black holes).
Predictions say it took millionth of a millionth of a second
for big bang to occur, this singularity’s density was too much to handle
anymore and too hot as well, it burst out with a big “bang”, bang is from the expression
used to describe sound produced in explosions, this is the biggest and most
violent explosion in the history of universe.
Few seconds after big bang:
Initially protons, electrons and
neutrons were moving at such great speeds (due to very high temperatures) that
they could overcome attractive forces, so no matter was formed. Within few
seconds it cools down enough for nuclear forces to take over and form atoms. On
cooling further over years, weak force such as gravity could also take over and
lead to formation of planets, stars and galaxies.
E=MC2 Energy mass conservation
It plays a vital role in explaining formation of matter from
big bang theory, this blast had unimaginable amount of energy, which was
converted into matter eventually as the temperature decreased.
Explosion of this magnitude sets of huge amount of
radiation, and this radiation exists till today. In 1964 Arno Penzias and
Robert Wilson accidentally picked unknown background radiation which is now
called cosmic microwave background radiation (they won Nobel Prize for it in
1978) and it is proof of a consequence expected from big bang. We are exposed
to this radiation everyday of our lives and it’s below harmful level and yet good
enough for detection. This is most widely accepted story of our universe.
