Sound waves are mechanical waves. They can travel only through matter. They cannot travel through empty space. This was demonstrated in the 1600s by a scientist named Robert Boyle. Boyle placed a ticking clock in a sealed glass jar. The clock could be heard ticking through the air and glass of the jar. Then Boyle pumped the air out of the jar. The clock was still running, but the ticking could not be heard. Thats because the sound couldnt travel without air particles to transfer the sound energy. Is there any other place where sound cannot be heard? Here is a hint: is there any other place that does not have air molecules? Thats right, in space sound cannot be transferred. So can astronauts hear each other? Yes, they can, because they are in enclosed space stations or pressurized suits.In both cases, they are surrounded by air molecules. If they left their space ship and did not use their electronics, they would not be able to hear each other. Next time you watch a science fiction movie, think about this factoid. When spaceships are destroyed by hostile alien beings, there would be no sound heard. Sound waves can travel through many kinds of matter.

Question: "How do sound waves travel?"

OPTIONS:
- no
- yes

Answer: "Through matter"

Response: yes

On Thursday Fort Waelhem succumbed after a magnificent resistance. The garrison held it until it was a mere heap of ruins, and, indeed, they had the greatest difficulty in making their way out. I think that there is very little doubt that the Germans were using against these forts their largest guns, the great 42-centimetre howitzers. It is known that two of these were brought northwards past Brussels after the fall of Maubeuge, and a fragment which was given to us was almost conclusive. It was brought to us one morning as an offering by a grateful patient, and it came from the neighbourhood of Fort Waelhem. It was a mass of polished steel two feet long, a foot wide, and three inches thick, and it weighed about fifty pounds. It was very irregular in shape, with edges sharp as razors, without a particle of rust upon it. It had been picked up where it fell still hot, and it was by far the finest fragment of shell I have ever seen. Alas we had to leave it behind, and it lies buried in a back-garden beside our hospital. Some day it will be dug up, and will be exhibited as conclusive evidence that the Germans did use their big guns in shelling the town.

Question: "What did the gun fragment look like?"

OPTIONS:
- no
- yes

Answer: "It was large, made of steel, long and irregular in shape with sharp edges"

Response: yes

Among the early blows struck for independence was a rebellion in the town of Olhao. On 16 June 1808, the townsfolkarmed with little more than ancient swords, spears, and stonesattacked and captured the local French garrison. It's said that a party of local men then set sail from Olhao all the way to Brazil, without maps or navigational aids, to tell the king of the insurrection. The real battle, however, was waged under the leadership of the Duke of Wellington, whose coalition forces expelled the French after two years of bitter fighting. The war left Portugal further weakened, and in 1822 its major empire outpost, Brazil, declared independence. At the same time, a dispute over the crown continually raged between Pedro IV, the absentee monarch who preferred to reign as Emperor of Brazil rather than return to Portugal, and his brother Miguel. The power struggle, with strong overtones of absolutism versus liberalism, excited the interest and intervention of other powers. With British help, Pedro defeated Miguel off Cape St. Vincent in 1833, and his expeditionary force marched to Lisbon. Pedro took the throne, though armed struggle continued for months and the lingering bitterness long after that. By 1892 Portugal, racked by wars and the continuing expense of maintaining its African colonies (including those of Mozambique and Angola), declared itself bankrupt. The seeds of discontent with absolutist rule were sown. Kingdom's End Bloodshed would haunt the remaining years of the Portuguese monarchy. On 1 February 1908, the royal family was riding in an open carriage along the Lisbon river front plaza, Terreiro do Paco, when an assassin opened fire and killed King Carlos and the heir to the throne, Prince Luis Filipe. The prince's younger brother, Prince Manuel, was also hit, but he survived and was thus propelled to the throne at the tender age of 19. Amid republican agitation, a surprise uprising led by elements within the armed forces deposed Manuel in 1910. Having ruled for less than three years, Manuel died in exile in 1932 in England. The sudden end of more than seven centuries of monarchy brought confusion and crisis to the country. Presidents and prime ministers were ushered into and out of office an unbelievable 45 times between 1910 and 1926, until a military revolution suspended Portugal's problematic democracy.

Question: "What events caused Brazil to gain independence?"

OPTIONS:
- no
- yes

Answer: "Killing of King Carlos"

Response: no

Fossils may form in other ways. Fossils can be preserved almost completely. In this process, the organism doesnt change much. As seen below, tree sap may cover an organism. With time, the sap hardens. It turns to into amber. The original organism is preserved. This is very exciting for scientists. They are able to study the DNA of the organism that no longer lives on Earth. Some animals have been found frozen in ice. Others have been found in tar pits after falling in. Molds and casts are another way organisms can be fossilized. Have you ever walked in soft mud and left footprints? Once in a while, these traces of organisms can be preserved. In this case, nothing is left of the organism. A mold is an imprint of an organism that is preserved in rock. The organisms remains break down completely. There is nothing left of the original plant and animal.

Question: "What is a mold?"

OPTIONS:
- no
- yes

Answer: "A complete fossil"

Response:
no