1) The Earth's core is hotter than the surface of the Sun.

2) The word "banana" contains three vowels: A, A, and A.

3) The first consumer digital video recorder (DVR), the TiVo, was introduced in 1999 and allowed users to record and store television programs for later viewing.

4) The Hubble Space Telescope, launched in 1990, has provided breathtaking images of distant galaxies and deep space.