1. Topic 1 Physics and Physical Measurement
1.1 The Realm of Physics -
Range of magnitudes of quantities in our universe.

2. 1.1.1 State (express) quantities to the nearest order of magnitude.
When dealing with very large or very small numbers we are often only interested in an approximate figure.
For example, the remotest object we can detect is the quasar RDJ located at a distance of 2.8X1022 km away.
It is just as meaningful to say it is 1022 km from Earth.
This is said to be its order of magnitude.

3. Order of magnitude
The order of magnitude is the power of 10 closest to the number.
However, when converting a number a number to its nearest base 10, the rule is:
Numerals greater than 3.16 become 10 and those below 3.16 become zero.
The reason for this is that = 3.16

4. Try this quick quiz Measurement Dimension OM 1.9 x 1022 m 4.0 x 1016 m
Distance to the Andromeda Galaxy
1.9 x 1022 m
Distance to nearest star
4.0 x 1016 m
Diameter of the Earth
1.3 x 107 m
Thickness of a credit card
5.0 x 10-4 m
Thickness of hair
2.8 x 10-5 m
Mass of Hydrogen
1.67 x 10-5 kg

5. Calculations in OM’s
When estimating the order of magnitude of a mathematical calculation, it is convenient to convert each number to its order of magnitude first.
Example: Determine the order of magnitude of this calculation (3.0 x 1010)(8.4 x 106)
Solution 3.0 x 1010 has an OM of 1010; 8.4 x 106 has an OM of 107
1010 x 107 = 1017
Note the full answer is 2.52 x 1017, which does have an OM of 1017.

6. 1.1.2 State the ranges of magnitude of sizes, masses and times that occur in the universe, from smallest to greatest.
Sizes—from m to m (subnuclear particles to extent of the visible universe).
Masses—from kg to kg (electron to mass of the universe).
Times—from s to s (passage of light across a nucleus to the age of the universe).

7. 1.1.3 State and compare the order of magnitude of selected (significant) systems in the universe.
Rounding the height of an ant, which is about 8 x 10-4 meters, to the nearest power of ten results in 10-3 meters.
Another way of saying this is that the order of magnitude of the height of an ant is 10-3 meters.
Now, if we compare the height of a human being (100 meters) with the height of an ant (10-3 meters), we come up with the ratio human height/ant height = 100/10-3 = (-3) = 103 = 1000.
A human being is roughly 1000 times (or 103 times) taller than an ant.
In other words, a human being is 3 orders of magnitude (3 powers of 10) taller than an ant.

8. Order of Magnitude of some Masses
 Order of Magnitude of some Lengths
 MASS
 grams
 LENGTH
 meters
 electron
10-27
 radius of proton
 10-15
 proton
10-24
 radius of atom
 10-10
 virus
10-16
 radius of virus
 10-7
 amoeba
10-5
 radius of amoeba
 10-4
 raindrop
10-3
 height of human being
 100
 ant
100
 radius of earth
 107
 human being
105
 radius of sun
 109
 pyramid
1013
 earth-sun distance
 1011
 earth
1027
 radius of solar system
 1013
 sun
1033
 distance of sun to nearest star
 1016
 milky way galaxy
1044 
 radius of milky way galaxy
 1021
 the Universe
1055 
 radius of visible Universe
 1026

9. Great Web Sites Measurement (timeline form)
View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons.