21.   Bowen said scientists really know little about the specific conditions turtles require to return to the beaches where they were born to lay eggs.

22.   But Mendel had only studied plants, so scientists did not know whether his experiments would hold true for animals.

23.   But now, Wolynes said, scientists know that a huge variety of amino acid sequences can fold up to form the same protein.

24.   But scientists did not know how the cell worked.

25.   But scientists do not know when the potentially catastrophic influenza changes will come, how to predict them and precisely what brings them about.

26.   But scientists do not know why so many workers who were exposed to large numbers of spores every day did not become ill.

27.   But scientists now know it is distributed widely in the body.

28.   But scientists have long known that bacteria have some potent defenses.

29.   But scientists know so little about asteroids and their makeup that they can only guess at ways to deflect or destroy one imminently endangering Earth.

30.   But scientists do not know whether there is an environmental problem in the area, or a statistical anomaly.