August 18th - Helium discovery Day

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Across
  1. 5. Helium makes human voices ________ ridiculous.
  2. 6. For three decades the scientists were derided for their ________.
  3. 9. In the mid-19th century, scientists wanted to study the chemical composition of the ______, and thought that a solar eclipse was necessary to do so.
  4. 11. Helium is often used to fill ________.
  5. 12. Helium is also a key component of gas giants, which are ______ mainly made of gas.
Down
  1. 1. Helium is the second most abundant element in the universe after __________.
  2. 2. Helium is used for the flight of airships and balloons, as it provides ___________.
  3. 3. On August 18, using a prism, he found a yellow light that appeared to be _______, but found out that it didn't have the same wavelength as that element.
  4. 4. it was not until William Ramsay found helium inside of ______ ore that the earlier discoveries were vindicated.
  5. 7. Helium is a crucial component of _______ in the night sky.
  6. 8. Helium is used in determining the age of ______ with radioactive substances such as uranium.
  7. 10. ____________ is non-flammable.