Dark mass and Dark energy
Scientists have made huge discoveries about the universe, like the Big Bang, red-shift, and how galaxies move.
But—there’s still a lot we don’t know.
Two big mysteries are:
1. Dark Matter (sometimes called “dark mass”)
What is it?
It’s a type of matter that doesn’t give off any light or radiation, so we can’t see it with telescopes.
Why do scientists think it exists?
Because when we look at how galaxies spin, the stars on the outer edges move faster than they should, based on visible mass.
This suggests there must be “invisible” mass holding them together — this is dark matter.
How much is there?
Scientists think dark matter makes up about 27% of the universe.
2. Dark Energy
What is it?
A mysterious energy that seems to be causing the expansion of the universe to speed up.
Why do scientists think it exists?
Observations (like of distant supernovae) show that the universe is expanding faster and faster, not slowing down.
Something must be causing this accelerating expansion — we call that dark energy.
How much is there?
It could make up around 68% of the universe.
Summary:
Visible matter (stuff we can see like stars, planets, gas) = only about 5% of the universe.
The rest is dark matter and dark energy, which we can’t see but know exist from the way the universe behaves.
Scientists still don’t fully understand what dark matter and dark energy actually are — they are big unsolved mysteries in physics.
Practice Questions
1.What is dark matter?
2. Explain why scientists think dark matter exists.
3.What is dark energy?
4.Describe one piece of evidence for the existence of dark energy.
5.Scientists believe that the matter we can see only makes up about 5% of the universe.
What makes up the rest of the universe, and how do we know?
6. Explain the difference between dark matter and dark energy, and describe how each affects the universe.
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Drawing ray diagrams for a concave lens
Drawing Ray Diagram to produce a virtual image for a convex lens
Drawing ray diagram to produce a real image for a convex lens.
Specular and Diffuse Reflection
Seeing Coloured Objects Part 2
Viewing objects through coloured filters
Transparent, Translucent and Opaque