Environmental Engineering Reference
In-Depth Information
Table 2.2
Data for the Sun and the Earth
Sun
Earth
Ratio
Diameter (km)
1,392,520
12,756
1:109
Circumference (km)
4,373,097
40,075
1:109
Surface (km
2
)
6.0874
•
10
12
5.101
•
10
8
1:11,934
Volume (km
3
)
1.4123
•
10
18
1.0833
•
10
12
1:1,303,670
Mass (kg)
1.9891
•
10
30
5.9742
•
10
24
1:332,946
Average density (g/cm
3
)
1.409
5.516
1:0.26
Gravity (surface) (m/s
2
)
274.0
9.81
1:28
Surface temperature (K)
5777
288
1:367
Centre temperature (K)
15,000,000
6700
1:2200
years. The sun consists of about 80 per cent hydrogen, 20 per cent helium and
only 0.1 per cent other elements. Table 2.2 contains data about the sun in
comparison to the Earth.
Nuclear fusion processes
create the radiant power of the sun. During these
processes, four hydrogen nuclei (protons
1
p) fuse to form one helium nucleus
(alpha particle
). The alpha particle consists of two neutrons
1
n and two
positively charged protons
1
p. Furthermore, this reaction produces two
positrons e
+
and two neutrinos
4
e
and generates energy. The equation of the
gross reaction illustrated in Figure 2.1 is:
4
1
p
4
2
+ 2e
+
+ 2
v
e
+
α
∆
E
(2.1)
Comparing the masses of the atomic particles before and after the reaction
shows that the total mass is reduced by the reaction. Table 2.3 shows the
necessary particle masses for the calculation of the mass difference. The mass
of the neutrinos
ν
e
can be ignored in this calculation and the mass of a
positron e
+
is the same as that of an electron e
-
.
The mass difference
∆
m
will be calculated by:
∆
m
= 4
•
m
(
1
p) -
m
(
4
α
) - 2
•
m(e
+
)
(2.2)
Energy
lpha
particle
α
Proton
Neutron
Positron
Neutrino
Figure 2.1
Fusion of Four Hydrogen Nuclei to Form One Helium Nucleus
(Alpha Particle)
