71.   Scientists think the universe began in an explosion -- the Big Bang.

72.   Scientists think there is little hope of answering life-on-Mars questions until they can study those rocks in their laboratories.

73.   Scientists think they know why so many houses in California remain standing after an earthquake.

74.   Scientists think they may now know what makes a mouse head straight for the cookie jar.

75.   Scientists had long thought that this period must have produced warmer temperatures, and the fossil find suggests that they are right.

76.   Scientists long thought that sinusitis, the most common long-term disease in the United States, was caused by allergies or by bacteria trapped inside the labyrinthine sinuses.

77.   Scientists now think ultraviolet A light may also trigger cancer, and some sunscreens now protect against UV-A as well.

78.   Scientists think it stems from scrapie, a disease that infects sheep.

79.   Scientists think that dark matter shapes the pattern of galaxies across the universe and warps the subatomic world with fleeting particles that have so far gone unseen.

80.   Scientists think that people with this form of the ApoE gene have a defective repair mechanism in their nerve cells, so they are more susceptible to damage.