Dear Jim,
Could I prevail upon you to check these astronomical estimations for me?
(Suggestion: you might like to get some students to help you!)
The circumference of the Earth is about 40 000 000�metres or 40 megametres,
so its diameter is about 12.7 megametres and its radius is about 6.4
megametres.
The average distance from the Earth to the Sun is about 150 000 000 000 m or
150 gigametres (150 Gm).
The average distance from the Earth to the Moon is about 380 000 000 m or
380 megametres (380 Mm).
In a year, the Earth intercepts about 1 yottajoule of energy (1 YJ) from the
Sun.
>From the Earth to the nearest star, Proxima Centauri, is about 40 terametres
(40 Tm).
>From the Earth to the nearest visible star, Alpha Centauri, is 41 terametres
(41 Tm)
>From the Earth to the nearest galaxy, M 31 in Andromeda, is about 20
exametres (20 Em)
>From the Earth to the furthest, normal, galaxies is about 40 zettametres
(40�Zm).
>From the Earth to the furthest quasars is about 110 yottametres (110 Ym).
As the distance from Earth to the furthest Quasars is about 110 yottametres,
this means that the diameter of the whole Universe is about twice this value
or 220 yottametres (220 Ym).
Comparing planets
You can use SI prefixes if you want to compare the size of various objects
where the numbers are either very small or very large.
As an example I will use the planets of the Solar System. When I looked up
their mass I obtained the following figures: Mercury 3.3022 X 10^23 kg,
Venus 4.8689 X 10^24 kg, Earth 5.9742 X 10^24 kg, Mars 6.4191 X 10^23 kg,
Jupiter 1.899 X 10^27 kg, Saturn 5.684 X 10^26 kg, Uranus 8.6978 X 10^25 kg,
Neptune 1.028 X 10^26 kg, and Pluto 1.6 X 10^22 kg. To complete the set the
mass of the Sun is 7.3483 X 10^22 kg and the Moon has a mass of 1.9891 X
10^30 kg.
None of these numbers are easy to compare - in their present form - but if
we use SI prefixes we can make them readily comparable. I�ll start with
Mercury.
Mercury has a mass of 3.3022 X 10^23 kg. We can think of this as:
3.3022 X 10^23 kg = 3.3022 X 10^20 megagram
3.3022 X 10^23 kg = 3.3022 X 10^17 gigagram
3.3022 X 10^23 kg == 3.3022 X 10^14 teragram
3.3022 X 10^23 kg == 3.3022 X 10^11 petagram
3.3022 X 10^23 kg == 3.3022 X 10^8 exagram
3.3022 X 10^23 kg == 3.3022 X 10^5 zettagram
3.3022 X 10^23 kg == 3.3022 X 10^2 yottagram and this can be read as
330.22 Yg since 10^2 = 100.
To further simplify the numbers I�ll round them to the nearest yottagram.
>From this the mass of Mercury is 330 Yg and I can draw a table to show the
comparable mass of all the planets and also the Sun and Moon. In the table I
have also given you comparable figures for the distances from the Sun and
the diameters and surface areas, so that you can see the ease of using SI to
make simple comparisons between complex numbers.
Planet mass distance diameter area
Mercury 330 Yg 60 Gm from Sun 4.878 Mm 75 Mm2
Venus 4 869 Yg 108 Gm from Sun 12.104 Mm 178 Mm2
Earth 5 974 Yg 150 Gm from Sun 12.756 Mm 510 Mm2
Mars 642 Yg 230 Gm from Sun 6.794 Mm 145 Mm2
Jupiter 1 899 000 Yg 780 Gm from Sun 142.800 Mm 64 020 Mm2
Saturn 568 400 Yg 1430 Gm from Sun 120.000 Mm 45 280 Mm2
Uranus 86 978 Yg 2870 Gm from Sun 51.800 Mm 8 440 Mm2
Neptune 102 800 Yg 4500 Gm from Sun 49.500 Mm 7 720 Mm2
Pluto 16 Yg 5900 Gm from Sun 2.500 Mm 111 Mm2
Moon 73 Yg 384 Mm from Earth 3.476 Mm 38 Mm2
Sun 1 989 100 000 Yg - 1 392.530 Mm 6 100 000 Mm2
As a final thought you might like to think about the area that the Solar
System uses for the revolutions of its planets. This is about 10^20 square
kilometres (km2), 10^14 square megametres (Mm2), 10^8 square gigametres
(Gm2), or 100 square terametres (Tm2).
Thanks,
Pat Naughtin
CAMS - Certified Advanced Metrication Specialist
- United States Metric Association
ASM - Accredited Speaking Member
- National Speakers Association of Australia
Member, International Federation for Professional Speakers
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