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Name: Paillusson F.
Status: student
Age: 18
Location: N/A
Country: N/A
Date: 2001-2002
Question:
Is there any matter in space? This is my question because there is cold or hot in space and Joule effect is not possible without matter, nevertheless my physics teacher told me the sound cannot travel through the space because there is no matter there. So I am lost.

(I am sorry if you cannot understand my phrases because I do not speak English very well.)

Replies:
Kinetic energy can be transferred between objects without ever having them come into contact! Recall the three classic mechanism of heat transfer: conduction, convection, and radiation (http://www.lanly.com/heating.htm). Heat from the sun, for instance, is transferred to us not by direct encounter, but by electromagnetic radiation emitted by the sun and absorbed by the earth (and us).

So, an object in space (a rock, piece of dust, dilute gas) can be hot or cold. It can become hot by absorbing radiation, and it can become cooler by emitting radiation. You are correct, a vacuum itself cannot be hot or cold - only an object inside it.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois


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