To make certain the U.S. was aware of the danger, in July 1939, a few months before the beginning of World War II in Europe, Szilard and Wigner visited Einstein to explain the possibility of atomic bombs, which Einstein, a pacifist, said he had never considered. He was asked to lend his support by writing a letter, with Szilard, to President Roosevelt, recommending the U.S. pay attention and engage in its own nuclear weapons research. A secret German facility, apparently the largest of the Third Reich, covering 75 acres in an underground complex, was being re-excavated in Austria in December 2014 and may have been planned for use in nuclear research and development. The letter is believed to be "arguably the key stimulus for the U.S. adoption of serious investigations into nuclear weapons on the eve of the U.S. entry into World War II". In addition to the letter, Einstein used his connections with the Belgian Royal Family and the Belgian queen mother to get access with a personal envoy to the White House's Oval Office. President Roosevelt could not take the risk of allowing Hitler to possess atomic bombs first. As a result of Einstein's letter and his meetings with Roosevelt, the U.S. entered the "race" to develop the bomb, drawing on its "immense material, financial, and scientific resources" to initiate the Manhattan Project. It became the only country to successfully develop an atomic bomb during World War II. For Einstein, "war was a disease ... [and] he called for resistance to war." By signing the letter to Roosevelt he went against his pacifist principles. In 1954, a year before his death, Einstein said to his old friend, Linus Pauling, "I made one great mistake in my life--when I signed the letter to President Roosevelt recommending that atom bombs be made; but there was some justification--the danger that the Germans would make them ..."

Question: "Which US president did the Belgian Royal Family help Einstein contact?"

Answer: "Kennedy"

Response: no

How would the universe look without gravity? It would have no planets and no stars. Thats how it looked when it was young. When the universe was young, there was only gas and dust. From this gas and dust, everything we now see was made. How were stars and planets created from just gas and dust? The answer is gravity. The same gravity that holds you down on Earth. The same force that causes your pencil to roll off your desk. The same force that causes it to fall to the floor. The invisible force of gravity caused dust and gas particles to be pulled together. This force is what formed all the objects in our solar system. This force formed the smallest moons. It also formed our Sun. This force caused more than just our solar system to form. It caused all the other solar systems to form. It caused the formation of all the galaxies of the universe.

Question: "How was the universe made?"

Answer: "From food and water"

Response: no

Density is also an important physical property of matter. The concept of density combines what we know about an objects mass and volume. Density reflects how closely packed the particles of matter are. When particles are packed together more tightly, matter is more dense. Differences in density of matter explain many phenomena. It explains why helium balloons rise. It explains why currents such as the Gulf Stream flow through the oceans. It explains why some things float in or sink. You can see this in action by pouring vegetable oil into water. You can see a colorful demonstration in this video.

Question: "What does density tell?"

Answer: "How big things are"

Response: no

You might want to know how cold it is. You may need to know how fast the wind is blowing. Maybe it rained last night? Do you know how much? Does it feel humid to you? You have heard all these questions before. To answer these questions, we need data. That data comes from special tools. These tools collect data about the weather. You can see some of the common tools listed below: A thermometer measures temperature. An anemometer measures wind speed. A rain gauge measures the amount of rain. A hygrometer measures humidity. A wind vane shows wind direction. A snow gauge measures the amount of snow.

Question: "What data are collected by special tools?"

Answer: "Loudness"

Response:
no