| Applying the Thales’ theorem:
The distance where the moon has to be from the Earth at the moment
the total eclipse is produced can be calculated .
|dl = 373.570 km
If the moon is situated near the apogee (405.500 km), the eclipse will
3. How can the distance to the Moon from the Earth be experimentally
determined -from the observation of the annular eclipse of Sun on 3rd
- To determine experimentally the distance to the Moon
from the Earth the eclipse’s day, we will base upon the shot taken by Josep Masalles Roman
at Villagordo del
Cabriel (39º33'10" N -
1º28'26" W - 699 m)
(fig.8). This photograph was taken by fitting together one Reflex camera
to a telescope Meade ( D:125 mm, F:1250 mm).
|Figure 8. Annular eclipse
|Figure 9. Meade
- Doing a picture treatment with the Paint Sho Pro program we can obtain
the percentage of the Sun’s diameter eclipsed by the moon.
|Figure 10. Image treachment
with Paint Shop Pro program
- Now we’re going to measure the apparent diameters of the Sun and the Moon
from the differences of the axis (x, y) of the extreme points.
- The obtained results are:
|Apparent radius (length’s units)
|Figure 11. Moon’s position in
a total Sun’s eclipse
|Figure 12. Moon’s
position in an annular solar eclipse
Applying again the Tahles’ theorem on the figures number 11 and 12 the following
equalities are obtained:
The following conclusion can be inferred:
dl =390.766 km
4. How does the temperature change during the eclipse? How
does the intensity of the sunliht change during the eclipse?
The material used in this practice at the schoolplayground
- Temperature sensor with a sensibility of 0,001 ºC
- Light sensor with a sensibility of 0,001 Klx
- MultiLog PRO keyboard
- Two supports with nuts and two tweezers
- In the classroom .
- A computer with the MultiLab program is required
The assembly of all the device has to be done on this way:
1st: In order to fasten the sensors, they have to be fixed
by an adjusting nut, and all this must be fixed too to
the tweezers which will be tied up to a base.(fig.1)
2nd:- Connect two sensors with the MultiLog PRO
3rd: -Turn on the keyboard and select the capture mode, in
this case, one sample per each second during 10.000 seconds.
-Start measuring at
the beginning of the eclipse and stop once it has finished.
4th:-Download and analyse the data in the computer with the
MutiLab progamm’s help.
- PHOTOGRAPH OF THE ASSEMBLY:
|Figure 13. Assembly Experience
- Data treatment:
Both, the data of temperature and light intensity must
be downloaded and checked.
- Taking into account that we started registering the data at 07:41am,
we can know the exact time when the Moon was totally opposite
the Sun and thus when the annular eclipse was produced, at 09:01am . While
commuting the first and the second cursor at the beginning and
in the middle of the eclipse the descent of the intensity of light
and the descent of temperature produced can be measured. (Fig.14 and 15).
|Figure 14. graphic
|Figure 15. graphic
- (As far as the light data are concerned we have
to bear in mind that normally the light intensity is higher as the day
advances;and for this reason, after the eclipse there is more light than
at the beginning.
Not too much care must be given to the temperature data when wind gales
are produced because they might cause some modifications on them)
- Sunlight intensity:
Maximum intensity: 9’315Klx
Minimum intensity: 1,215 Klx
Variations: Dllum = 8,1Klx => 87%
From the beginning to the moment when the annular eclipse took
place , a descent in the intensity of light was produced- that is to
say- a 87% less.
Maximum temperature: 13,32 ºC
Minimum temperature: 11,799 ºC
Variation: Dt = 1,128 ºC => 8,47%
From the beginning to the exact moment of the annular eclipse the temperature
has fallen 1,128ºC. we are talking about a reduction of
5. How do dampness and speed wind change during the eclipse?
- We have been able to observe that there was a reduction in the temperature
and the intensity of light, and also in the dampness and the wind speed.
The meteorological observatory of the city of Lleida gave us some information
that was recorded during the eclipse. (Look at fig. 16a, 16b and 17).
The information had been taken in solar schedule,. -two hours less than the
time established in our zone.
Dampness graphic Fig.16b.
- Figure 16 shows us the air dampness and temperature descent.
these two factors were linked, we already supposed that a decrease
in the air’s dampness will be produced- since a reduction of 1 degree
took place during the eclipse.
In figure 17 we can see the wind speed during the annular eclipse. With this
graph we can know that a reduction in the wind speed took place. This fact
happens because the air moves quicker if the weather is hotter. However,
as the temperature lowered an 8'47 % the air masses moved less and slowier.
about the wind speed