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Name: Jacquie
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Question:
You answered a question of is there friction in space. I recently read that the density of particles or atoms in space is about 1 atom to ever cubic yard of space. If this is correct, I have been searching for the coefficient of friction in space in reference to the amount of particles which exist in space. If a craft could travel at the speed of light or faster, what would be the assigned number of the coefficient of friction with the amount of free atoms or particles (not dust and rock)in space. For example the TV show Voyager, if Voyager did not have shields and as Voyager was traveling at the speed of light or faster the atomic particles would hit the ship and create heat. Voyager's computer would have the coefficient of friction stored in its computer for this formula.



Replies:
It is not appropriate to use the "average" density of "free" particles in space in determining the coefficient of friction. The coefficient of friction is a characteristic of particles whose average position remains constant as two surfaces in contact slide against one another. It makes sense that the gravitational attraction between two masses in contact plays a role in the "drag" between them. However, even in the absence of gravity, van der Waals forces (always attractive) tend to attract. Invoking the "results" of supra-luminal speeds from a TV show is not a particularly reliable source of scientific data. In any case, the interaction of surfaces, whether in a vacuum, or in the presence of gases is a really difficult problem to analyze -- both theoretically and experimentally. So I cannot make an educated "guess" of how their data bank would respond.

Vince Calder



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