Many different types of energy can be converted into heat energy. Light, electrical, mechanical, chemical, nuclear, sound and thermal energy itself can each cause a substance to heat up by increasing the speed of its molecules. So, put energy into a system and it heats up, take energy away and it cools.
Alexander Alex Robert Hirsch (born June 18, 1985) is the creator and former executive producer of the American animated television series, Gravity Falls. He voiced two of the main characters, Grunkle Stan and Soos. He also voiced supporting and recurring characters such as: Old Man McGucket, Bill Cipher, the gnomes and many others.
The brainchild of writer/director/executive producer/voice actor and steadfast kidult Alex Hirsch, Gravity Falls is a love letter to the fun weirdness Hirsch loved as a kid, from Spielberg to The X Files.