TT e r m s page 2
Mass
Mass is not the same thing as weight.
Weight has meaning only when an object having a specific mass is placed in an acceleration field, such as the gravitational field of the earth.
At the earth's surface, a kilogram mass weighs about 2.2 pounds, for example.
But on Mars, the same kilogram mass would weigh only about 0.8 pounds, and on Jupiter it would weigh roughly 5.5 pounds.
Mass (symbolized m) is a dimensionless quantity representing the amount of matter
in a particle or object. The standard unit of mass in the International System is the
kilogram .... .
Mass is measured by determining the extent to
which a particle or object resists a change in its
direction or speed when a force is applied.
If you'd like to see an explanation video combining
mass and matter find
" See a physics video comparing mass to weight:"
here.
Matter
has many definitions, but the most common is that it is any substance which has mass and occupies space.
All physical objects are composed of matter, in the form of atoms, ...
Light an extension of 3 - Light here
- Light travels as waves .... like the ripples in a tank of water. The direction of vibration in the waves is at 90° to the direction that the light travels.
- Light travels in straight lines*, so if you have to represent a ray of light in a drawing, always use a ruler.
- *Not so. It could pass near to a star and its line is curved by gravity.
- Unlike sound waves, light waves can travel through a vacuum (empty space). They do not need a substance to travel through, ...
- Light travels extremely quickly. Its maximum speed is approximately 300,000,000 miles/second, when it travels through a vacuum.
- The very large difference between the speed of light in air (almost 300,000,000 m/s) and the speed of sound in air (343 m/s) explains why you:
- see lightning before you hear it - see a firework explode before you hear it - see a distant door slam before you hear it - source
- Imagine you’re in a park, looking at a leaf on the branch of a tree. We know light bounces off the leaf to your eye to tell you it’s green – but what is light, exactly?
- We can trace the first steps towards understanding light’s makeup to a benchtop in Copenhagen in 1820, where Danish scientist Hans Christian Ørsted was giving a lecture on electricity.
- A compass happened to be sitting near the battery he was using in his demonstration and he noticed the compass needle suddenly jerking when he switched the battery on or off.
- This meant electricity and magnetism were related – or, as it was more formally described later, a changing electric field creates a magnetic field.
- Then 11 years later, English scientist Michael Faraday discovered the opposite rang true: that a changing magnetic field also creates an electric field.
- It was the Scottish physicist James Clerk Maxwell who collected these ideas about electricity and magnetism (plus a few others) and pulled them together into one coherent theory of “electromagnetism”.
- But Maxwell’s most celebrated insight was when he combined the work of Ørsted and Faraday to explain the essence of light.
- He realised that a changing electric field could create a changing magnetic field, which would then create another electric field and so on. The result would be a self-sustaining electromagnetic field, endlessly repeating, travelling incredibly fast.
- How fast? Maxwell was able to calculate this too, at about 300,000,000 metres each second – pretty close to what had recently been measured for the speed of light.
- And so this is what light is: an electric field tied up with a magnetic field, flying through space.
- You can think of the two fields as dance partners, wrapped up in an eternal embrace. To keep self-generating, both electric and magnetic components need to stay in step. It takes two to tango.
Planck constant
is a physical constant that .. relates the energy carried by a photon [unit of light]... and is the basis for the definition of the kilogram.
In physics, a quantum (plural: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction.
Quantum mechanics
is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.
Quantum theory
is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. ...
Planck wrote a mathematical equation involving a figure to represent these individual units of energy, which he called quanta. See his Constant on this page.
Radiation in physics
The emission and propagation of energy in the form of rays or waves.
The energy is radiated or transmitted in the form of rays, waves, or particles.
A stream of particles or electromagnetic waves that is emitted by the atoms and molecules of a radioactive substance as a result of nuclear decay.
Space
Space is the boundless three-dimensional extent in which objects and events have relative position and direction.
Not so. See Spacetime.
Common intuition previously supposed no connection between space and time. Physical space was held to be a flat, three-dimensional continuum..... source
Spacetime
The four-dimensional continuum of one temporal and three spatial coordinates in which any event or physical object is located. source
The normal coordinates are Height, Width and Depth. Add time.
Space-time is a mathematical model that joins space and time into a single idea called a continuum. ...
Combining these two ideas helped cosmology to understand how the universe works on the big level (e.g. galaxies) and small level (e.g. atoms). source