How were the scientists able to study the earth's interior?
They study the layers by seeing how seismic waves travel through the earth. By the time of the arrival, and how the frequencies of the waves are arranged within each set they can tell things about the density and other things about the layers.
Since we're not (yet?) able to drill a hole down there and find out, we're reduced to indirect measurements. Things like the mass of our planet and its gravity. (That's why we're pretty sure that the core is primarily iron.) The speed of earthquake vibrations in the mantle. The material that comes out of the Earth in volcanoes. Stuff like that.
Shooting stars, are small pieces of rock from space that have entered the earths atmosphere and burn very brightly with great heat as they collide with gas molecules in our atmosphere. Scientists have been able to study the spectrum of a meteor, and have estimated temperatures of around 4,600 degrees centigrade during this burn period.
How is it that so much is known about the interior of the Earth yet scientists have only dug as deep as about 10 km down?
Primary waves (p waves) from earthquakes are able to travel through solids and liquids. Secondary waves (S waves) are only able to travel through solids. Scientists studied and measured these waves when large earthquakes occurred in the past, did a whole bunch of math, and wala!: it is now accepted that earth's outer core is liquid.
How did the earlier scientists and their contributions directly affect the discoveries of later scientists?
What is a question about a study pf glass bottles and aluminum cans that science would not be able to asnwer?
If a question is an ethical one about which decision is right or wrong, or what a person should do, scientists can contribute to the discussion, but it is not ultimately a scientific question. So a question about the study that a scientist would not be able to answer is, "Which one should be used more often" or something like that. -Apex
Serial analysis of gene expression, or SAGE, allows scientists to study the expressions of many genes at once. The technique uses a sequencing machine and a computer to match the genetic tags to a database. This is technology used in the Human Genome Project. Scientists are able to look at many different genes to see how they will work together.