Interrogative sentences ask questions. They may ask for information or for confirmation or denial of a statement. They typically begin with a question word such as what, who, or how, or an auxiliary verb such as do, can or would.
What was the universe like before it was expanding?
--"The Evolution of Science," Scientific American
Does some fine madness plague great artists?
--"Manic-Depressive Illness and Creativity," Scientific American
Be careful to distinguish between direct and indirect questions. Direct questions normally use inverted word order (verb before subject) and end with a question mark. The two preceding sentences from Scientific American are examples. Indirect questions normally do not use inverted word order and do not end with a question mark.
Modern telescopes on the ground and in space detect the light from galaxies billions of
light-years away, showing us what did the universe look like when it was
young?
Modern telescopes on the ground and in space detect the light from galaxies billions of
light-years away, showing us what the universe looked like when it was
young.
--"The Evolution of the Universe," Scientific American
