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Friction In a Vacuum

#1
So, remember how we talked about how space in Limit Theory needs some amount of friction so that ships are easier to control? And science said that was goofy because there's no friction in a vacuum?

Well.

Today I see there's a story suggesting that space does, in fact, express a friction-like effect, even as a near-perfect vacuum. I'm not sure that applicability to particles means applicability to macro-level objects like spaceships.

Even so, it's a neat finding. Maybe in the default Joshverse, this effect is simply dialed up to 11. :)

http://www.sciencealert.com/physicists- ... ect-vacuum
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Re: Friction In a Vacuum

#2
Very neat find, however it's not actually a friction like force, it's a loss of momentum due to a loss of mass when the decaying atom emits a photon.
The Article wrote:"[W]e have shown that, yes, a decaying atom sees a force resembling friction," the team concludes in their paper. "However, this force is a change in momentum due to a change in internal mass energy, and is not connected to decelerated motion."

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Re: Friction In a Vacuum

#3
Silverware wrote:Very neat find, however it's not actually a friction like force, it's a loss of momentum due to a loss of mass when the decaying atom emits a photon.
The Article wrote:"[W]e have shown that, yes, a decaying atom sees a force resembling friction," the team concludes in their paper. "However, this force is a change in momentum due to a change in internal mass energy, and is not connected to decelerated motion."
No: it is a force by definition from Newton's second law. A change in momentum, even if it is to its mass and not its velocity, does imply a force is being exerted somewhere.

It seems though that sadly the object doesn't actually see a decreased velocity, and that's where the rub is.

Thanks Flat!
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Re: Friction In a Vacuum

#4
Silverware wrote:Very neat find, however it's not actually a friction like force, it's a loss of momentum due to a loss of mass when the decaying atom emits a photon.
The Article wrote:"[W]e have shown that, yes, a decaying atom sees a force resembling friction," the team concludes in their paper. "However, this force is a change in momentum due to a change in internal mass energy, and is not connected to decelerated motion."
I see. My calling it a "friction-like effect" in what was clearly nothing more than a reference to an interesting bit of science loosely connected to Josh's design of Limit Theory was insufficiently precise for you, and required correction.

Of the many things I might say, none are constructive. Moving on.
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Re: Friction In a Vacuum

#7
I just realized something.
This is exactly how I justify my "spatial turbine" in Kerbal Future.
From my worldbuilding notes:
Spoiler:      SHOW
The spatial turbine impels spatial fluid, accelerates it via "iron ribbon," and expels it. Spatial fluid is difficult to work with, as its primary mode of interaction appears as simple drag. The iron ribbon mechanism takes advantage of this by firing matter through the throat of the turbine, allowing it to interact with the spat-flo, and retrieving it for reuse. In this way, momentum is transferred between spat-flo and turbine without loss of shipboard resources. Dissolved in the spat-flo is a certain amount of mundane matter, which is caught by the iron ribbon and separated for use as fuel or maneuvering remass. Spat-flo is found in useable quantities only deep in highspace.
Maybe it's not so technobabble after all.
Holy crap. :wtf:
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Re: Friction In a Vacuum

#8
Dinosawer wrote:Silver is incorrect though. Silver wrong about physics? never! It's a phenomenon that changes momentum, and its magnitude is proportional to the object's velocity, ergo friction force :P

Thanks, interesting read :thumbup:
This is now well off-topic from Flat's post, but interestingly frictional force is only properly proportional to velocity in abstraction, usually as an 'ideal viscous dissipation'.
This isn't a correction, just a remark
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Re: Friction In a Vacuum

#10
Dinosawer wrote:Silver is incorrect though. Silver wrong about physics? never! It's a phenomenon that changes momentum, and its magnitude is proportional to the object's velocity, ergo friction force :P

Thanks, interesting read :thumbup:
If it's also proportional to the size of the lost extra mass, then is it actually a force?
As you are losing mass and that mass keeps it's old momentum, then the momentum is just being transferred to the now missing mass.
If Total Velocity, Mass, and Momentum all remains the same in the system, has it really experienced a force?

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Re: Friction In a Vacuum

#11
Silverware wrote: If it's also proportional to the size of the lost extra mass, then is it actually a force?
As you are losing mass and that mass keeps it's old momentum, then the momentum is just being transferred to the now missing mass.
If Total Velocity, Mass, and Momentum all remains the same in the system, has it really experienced a force?
Given that we're speaking about a force on the atom, the system is the atom, not the atom and the photon together, so yes, it does experience a force :P
Warning: do not ask about physics unless you really want to know about physics.
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Re: Friction In a Vacuum

#12
Silverware wrote:
Dinosawer wrote:Silver is incorrect though. Silver wrong about physics? never! It's a phenomenon that changes momentum, and its magnitude is proportional to the object's velocity, ergo friction force :P

Thanks, interesting read :thumbup:
If it's also proportional to the size of the lost extra mass, then is it actually a force?
As you are losing mass and that mass keeps it's old momentum, then the momentum is just being transferred to the now missing mass.
If Total Velocity, Mass, and Momentum all remains the same in the system, has it really experienced a force?
This is a pointless deflection. The "system" is the atom, not the atom plus the lost photon. There is a change in momentum in the "system", and hence a force.

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