I Learned This Today

#1844 Why do some chemical reactions give off heat and others don’t?

October 25, 2026 / Leave a Comment

Why do some chemical reactions give off heat and others don’t? The answer depends on the amount of energy absorbed when chemical bonds are broken compared with the amount released when new bonds are formed. There are two types of chemical reactions: endothermic and exothermic. Endothermic reactions are those that require energy, and exothermic reactions

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#1843 What is Göbekli Tepe?

October 24, 2026 / Leave a Comment

What is Göbekli Tepe? Göbekli Tepe is one of the world’s oldest temples and megalithic sites. It was built in roughly 9500 BC, over eleven thousand years ago. It is in the south of the modern country of Turkey, not far from the border with Syria. It is the first human-built holy place in the

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#1842 Why are lemons sour when other fruits are sweet?

October 23, 2026 / Leave a Comment

Why are lemons sour when other fruits are sweet? Lemons are sour because they contain a lot of citric acid. We also need to remember that there are a huge variety of lemons, some very sour and some not so much. We need to break this question down into a few parts. Why does citric

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#1841 How did we discover stem cells?

October 22, 2026 / Leave a Comment

How did we discover stem cells? Stem cell were discovered by accident in the 1960s by James Till ad Ernest McCulloch. Despite the enormity of the discovery, they never won a Nobel Prize for it. Most cells in our bodies have a specific job. Skin cells, nerve cells, and liver cells all perform different functions.

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#1840 Why do space suits pick up so much static electricity on the Moon?

October 21, 2026 / Leave a Comment

Why do spacesuits pick up so much static electricity on the Moon? Static electricity builds up on spacesuits for some of the same reasons it builds up on our clothes on Earth. As astronauts walk and move, their suits rub against other materials, allowing electrical charges to build up. However, conditions on the Moon make

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#1839 Why did the USA invade Canada in 1812?

October 20, 2026 / Leave a Comment

Why did the USA invade Canada in 1812? The United States invaded Canada as part of its war against Britain. Some Americans hoped to make Canada part of the United States, while others believed that conquering it would force Britain to negotiate. Either way, they expected a much easier victory than they actually achieved. In

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#1838 Why are some elements rarer than others?

October 19, 2026 / Leave a Comment

Why are some elements rarer than others? Some elements are rarer than others because lighter elements are easier to make, and heavier elements require a huge amount of energy. Also, elements with even atomic numbers are more common than those with odd numbers. And some elements are destroyed inside stars. This is an interesting question

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#1837 Why did executioners live on the edge of town?

October 18, 2026 / Leave a Comment

Why did executioners live on the edge of town? Executioners were forced to live on the edge of town for the rather odd reason that, even though they were killing legally for the state, they were considered to be unclean. The practice of executing people has probably existed for as long as people have lived

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#1836 What is a salt tax?

October 17, 2026 / Leave a Comment

What is a salt tax? A salt tax is a tax that has been levied on salt. It is one of the oldest taxes in the world. The governments or nobles that control people have always needed money to do it. They need money to build monuments, wage wars, and manage the country. That money

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#1835 When was the automatic door invented?

October 16, 2026 / Leave a Comment

When was the automatic door invented? The first known automatic door was described nearly 2,000 years ago by Hero of Alexandria. It was designed to make the doors of a small temple magically open when a fire was lit on an altar. Electronic automatic doors were invented so waiters could more easily carry food through.

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