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THE BIG BANG
Although people often believe that a
god created the world, current
scientific experts have come up with
a theory for creation called the big
bang which has scientific proof!
This theory involves a great
explosion where everything in the
known universe was formed. All the
energy and matter found today in the
universe expanded from tiny point and formed the galaxies, stars,
planets, asteroids, gases, dust and energy. Even today the universe is
still expanding. In fact one example of how we can prove this is by
looking at a phenomenon called red shift.
It was discovered by accident that light emitted from stars in other
galaxies seemed to be shifted more towards the red end of the
spectrum than expected. i.e. when we expected violet light we actually
got blue!
We know by analysis that certain gases when stimulated give off
certain colours. These light spectra can be used to identify stars.
This is an example of a spectrum – VIBGYOR (ROYGBIV backwards)
Red Shift
The reason for this is because it is moving away from us as the
universe is expanding! This is a scientific proof.
Mr Powell
Wavelength
The reason this shift occurs is
because the wavelength of the
light gets a little longer because of
this movement. The reverse effect
happens when ambulances sirens
sound higher pitch when it is
coming towards you. The sound
waves are compressed by the
motion, and the wavelength
decreases. Remember that red
light has a longer wavelength than
blue.
More On Spectra
When light passes through a prism, it separates into the colours that
make it up. White light changes to a swath of colours. This rainbow is
called a spectrum. You can make spectra (the plural of spectrum) in
many ways: with a prism, with drops of water (as in a real rainbow), or
with gratings (like in the glasses you can get). Scientists build special
instruments to separate light, usually with gratings. These instruments
are called spectrographs.
When astronomers pass the light of a star through a spectrograph,
they get a spectrum of the star. The spectrum looks like a regular
rainbow of colours—except that there are dark lines in it. Here is a
spectrum of our sun:
Mr Powell
What's going on?
It turns out that each element absorbs light of a particular frequency or
a particular colour. If that element is in the cool atmosphere of the star,
those atoms will absorb the light at that colour and produce the line.
Each element has a specific "signature" or a specific set of lines.
Here are spectra for some elements common in the atmospheres of
stars:
In a star, these elements absorb light at their special frequencies. On
the following image you will see a star's spectrum. Your job is to
identify all the elements you can detect in the star's atmosphere.
Which elements are present?
Answer - Hydrogen & Magnesium
Mr Powell