Q: Based on the information present in the given passage, you need to write a correct answer to the given question. A correct answer is one that correctly and completely answers the question. Do not write answers that address the question partially or incorrectly. The correct answer must be contained in the given paragraph.
Paragraph- Sent 1: The idea that Earth is a magnet is far from new.
Sent 2: It was first proposed in 1600 by a British physician named William Gilbert.
Sent 3: Knowing it acts like a magnet is one thing.
Sent 4: Knowing why it acts like a magnet is more difficult.
Sent 5: In fact, finding out why is a fairly recent discovery.
Sent 6: To find out why required new technology.
Sent 7: It was the seismograph that made it possible to learn why the Earth acted like a magnet.
Sent 8: Seismograph are used to study earthquakes.
Sent 9: By studying earthquake waves they were able to learn about Earths interior.
Sent 10: They discovered that Earth has an inner and outer core.
Sent 11: The outer core consists of liquid metals, mainly iron and nickel.
Sent 12: Scientists think that Earths magnetic field is generated here.
Sent 13: It is caused by the motion of this liquid metal.
Sent 14: The liquid metal moves as Earth spins on its axis. 
Question: What technology made it possible to test the Earth's magnetic properties? How were scientist able to use this machine to study this phenomenon?.
A:
Seismograph, studied earthquake waves.