answers to sample questions

SCIENCE IN SOCIETY
Sample questions for 3rd term exam
2nd part
1. About the “Large Hadron Collider”
a. Why news about this huge machine have been in the media lately?
Because it is going to be started soon this year
b. Can you mention two features that give some idea of the importance of this project?
It is 27 Km long, it has 9300 big magnets inside, it is cooled at -271.3°C, it will accelerate protons at 99.99% the speed of light, ...
c. Can you mention two of the objectives scientists are looking for with this machine?
Some of them are: to test the “Big Bang” theory about the origin of the Universe, to test the “Standard theory of matter”; to look for the “Dark matter” that constitutes most of the matter in the Universe, to look for the “Higgs bosom” that has not been observed up to now, ...
d. This is the second try to perform these experiments. Do you know the reason why the previous try failed?
Because the refrigeration system broke down
e. That first try with the “LHC” rose some fears and great controversy in the media. Could you tell why?
It was about the possibility of creating a “Black Hole” that could swallow the Earth.
f. Do you consider the concern justified?
Probably not, but lack of information about possible dangers may give way to speculation from the part of sensationalist media.

g. Do you think that any dark aspect of science should be researched at any cost? What are the possible risks of not doing so?

2. Can you tell something about the “Standard Model of Matter”? (three things)
This theory says that every matter in the Universe is made out of 12 different elemental particles (six hadrons and six leptons) and five force carriers for the four main forces (Weak, Strong, Gravitational and Electromagnetic forces)

3. About the structure of the Universe
a. Our present conception of the structure of the Universe is sustained in two big discoveries that took place in the 20th Century. Which are these two discoveries?
The discovery that every galaxy in the Universe is moving away from each other faster as the distance increases, and the discovery of the Cosmic Microwave Background radiation.

b. Who were the scientists that performed these two discoveries?
The first one was made by Edwin Hubble and Milton Humason, and the second one by Arno Penzias and Robert Wilson.

c. What is the Universe that arise from those discoveries like? Choose among the options and explain why
i. The Universe is infinite and unlimited
ii. The Universe is finite but unlimited
iii. The Universe is finite and limited
The Universe is finite but unlimited; finite because it has a definite amount of energy and matter, and unlimited because in an Universe of at least four dimensions you can’t find the limits of this Universe.

d. Why we compare the Universe with a growing balloon?
Because as time goes on, the Universe becomes bigger and bigger (the distance between galaxies gets bigger).

e. How was the beginning of the Universe? How long ago?
At present it is generally accepted that the Universe began with a big explosion called the “Big Bang” about 15.000 million years ago.

f. How is going to be the end of the Universe? What does it depend on?
It depends on the density of matter at present in the Universe (it is not well known). If density is big enough, the expansion will eventually refrain and then begin contracting again and become smaller and smaller until it will finish in what is called the “Big Crunch”.
If density is smaller than a critic figure the Universe will continue expanding forever and becoming bigger and colder.

g. What is a spectrometer? How can we realise a Galaxy is approaching of moving away with its light spectrum?
It is a device that descomposes light into its different components giving a pattern that is called the spectrum of light.
In the spectrum some dark lines appear depending on the kind of light, and these lines are displaced to the red (redship of light) when the object is moving away, and to the blue (blueshift of light) if it is approaching.

4. About he Doppler effect
a. Relate the Doppler effect with the spectrum of a moving-away-Galaxy.
If an object is moving away, we see the waylength of the radiation it emits bigger tha its original length, and this is the case with moving away galaxies (we see their light displaced to the red side of the spectrum)

b. According to the Doppler effect, how do we hear the sound of an approaching train? And the sound of a moving away train?
We hear its sound higher pitched, and if it is moving away lower pitched.

c. A mother hawk screeches as she dives at you. You recall from biology that female hawks screech at 800 Hz, but you hear the screech at 850Hz. How fast is the hawk approaching?

f = fo [(v±vo)/(v±vs)]

...observers speed (vo) is 0 and source speed (vs) is the unknown factor.

substituting data in the equation...

850 Hz = 800 Hz [(340 m/s+0)/(340 m/s- vs)]

Resolving the equation...

vs = 340 m/s-(800Hz*340 m/s)/850 Hz =20 m/s

the hawk is approaching at a speed of 20 m/s

5. This is a view of the sky on the 10th of February (don’t matter which year -every year is the same-) from a place 40º N
a. At which time has been taken this view? (give GMT time and local time). Remember that February is winter time.
b. On which date can be seen this very view at 00.00 hours (GMT)



6. Answer these questions related with the calculation of our local meridian line.
a. If sunrise happens in....the East................... and sunset in ....the West........., the Sun at noon will be in the direction of ......South.............

b. If Sun is rising in the sky after sunrise and goes down before sunset, at .......noon................ it is at its maximum height.

c. Is for that that at noon the shadow of any vertical object is …minimal………..

d. Taking into account the answers to questions b to c, explain how can we obtain the North-South direction (the meridian of the place)

We must calculate the position of the minimal shadow of the vertical object and draw a line from the basis of the vertical object along its shadow. This is the meridian of the place (the shadow shows the North because the Sun at that moment is in the South)

7. You are in front of a sundial at 14 hours in your watch, but the sundial marks 12 minutes to noon. Explain why. Is it summertime or wintertime?
It is because in most countries official time and solar time don’t coincide, and this is the case in Spain. It is summertime because in Spain the difference between official time and solar time is of two hours in summer and one hour in winter.


8. What is special about Greenwich meridian? What is the difference with other meridians? Are they natural differences or artificial?
What is special is that it is considered (by international agreement) the first meridian (zero Meridian). Apart from that there is no difference with other meridians. The difference , obviously, is artificial.

9. What is the time zone of Spain?
Our time zone is GMT+1 hour

10. What does it mean the acronym GMT applied to time?
It means General Mean Time, and it is the time of the Greenwich meridian

11. How long is a day in the Earth? Is every day of the year equal to any other in duration? Why?
A solar day is by average 24 hours long. But not all days along the year are the same length . The reason is that the Earth doesn’t move at the same speed along its orbit around the Sun.

12. Define a year. How many days does it have?
A year is the time it takes the Earth revolving the Sun. It has approximately 365 solar days and a quarter

13. How many sidereal days does a year have in the Earth? How long is a sidereal day?
It has approximately 366 days and a quarter. It is approximately 23 hours and 56 minutes long

14. A soldier in his training course is left in an unknown place in the desert. He wants to know where he is and with the aid of a stick he draws the local meridian line and in addition he calculates that the Sun height at solar noon is 83º. His watch shows GMT time and he realizes that at local solar noon his watch marks 11:24 hours. It is the 12th of May and the solar declination of the day is 18º and the equation of time -4 minutes.
a. What is the Longitude of the place he is in

The formula you have to use is...

Standard time = local solar noon+ equation of time+ longitude correction

Then ...

Longitude correction = standard time-local solar noon-equation of time

Substituting with data...

Longitude correction = 11:24:00 - 12:00:00 + 00:04:00 = -00:32:00

Taking into account that the Sun needs 4 minutes to cover an arc of 1º,...
Then the Sun in 32 minutes will cover 8º of arc, and as the sign is minus, this means that the arc is minus too, that is, the longitude of the place is -8º, or in other words 8º East from Greenwich meridian.

b. What is the latitude of the place? Is it East or West from Greenwich meridian?
GL = 90 - H + SD where GL is the geographical latitude, H is the height of the Sun at noon, and SD is the solar declination of the day

Substituting with data...
GL = 90º-83º+18º = 25º
The latitude of the place is 25º North