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Natural sciences

Grade 9

The earth, galaxies ans space programmes

Module 14

The sun

For us the earth is the centre of our existence and for many years people believed that the earth was also physically the centre of everything. It was Copernicus (1473-1543) who moved away from this geocentric view and formulated his heliocentric theory. This caused a sensation and forced science in another direction. Johannes Kepler (1571-1630) expanded on this theory and maintained that planets in our solar system revolved in orbits around the sun. He formulated three laws of planetary movement that scientists use today.

The Sun – Our Star

  • The sun is a spinning ball of fire (burning hydrogen and helium gasses). Its volume is 1.3 million times that of the earth and it weighs 333 420 times more.
  • The pressure in its core is extremely high and converts the sun into a giant nuclear power plant. It splits hydrogen atoms and in this way creates temperatures of up to 15 million o C. This causes the surface of the sun (photosphere) to be turned into an inferno that glows at about 5 500 o C.
  • The sun has spots that shoot out solar flames of up to approximately 100 000 km. These solar flames can disturb radio waves and therefore interferes with broadcasts.
  • We call the atmosphere of the sun the chromosphere. It is surrounded by the corona.
  • The SOHO (Solar and Heliospheric Observatory) was launched by NASA in 1995 and now orbits the sun to transmit information about the sun to the earth.

solar eclipses

  • SOLAR ECLIPSES occur when the moon comes between the earth and the sun. The eclipse is often only partial and then it is like dusk, as it was on 21 June 2001. During a total eclipse of the sun it becomes completely dark. Such an eclipse occurred in the northern part of our country on 4 December 2002, when it became completely dark.
  • Any given town or place on earth will experience about 40 lunar eclipses and 20 partial solar eclipses in any 50-year period. A total eclipse of the sun such as the one in December 2002 occurs only once every 400 years in a particular place.
  • The next total solar eclipse in South Africa will only occur in November 2030.
  • The dark part of the eclipse is called the umbra ( U ) – or area of total shadow.
  • The outer parts are only partly shaded and are called the penumbra (P).
  • A total eclipse lasts 7,5 minutes, as the earth rotates and the observer moves out of shadow.
  • Only people in the path of the shadow of the eclipse will be able to observe the eclipse.
  • When observing a solar eclipse one has to protect ones eyes. Permanent damage to eyes can be caused if the right precautions are not taken.
  • Special spectacles can be made or bought. A simple method is to take a piece of cardboard that will fit over your eyes and cut out a small ‘window’. The window should be covered with a double layer of the foil in which teabags are packaged.

Research assignment 2:

Visit the following websites to learn more about solar eclipses:

Also find out more about various beliefs regarding solar eclipses in ancient times.

What did the Chinese believe? And the Tahitians?

Pythagoras, the Greek, was the first to explain eclipses. Why do you think this was?

Assessment of Research Assignment:

Did you a) plan how you would obtain the information, b) collect information and

c) communicate information and findings?

[LO 1.1; LO 1.2; LO 1.3]


LO 1: Scientific investigations:

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

This is evident when the learner:

  • plans investigations;
  • conducts investigations and collects data;
  • evaluates data and communicates findings.



Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11069/1.1
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