Zero Velocity

[steve_bank]

Jumping over from a question on the energy thread.

What is zero velocity? From relativity and the exclusion of any absolute inertial frame all we can know is relative velocity.

When Capt Kirk orders the Enterprise out in deep space to come to a full stop what does that mean?

If conservation applies bringing an object to an absolute zero velocity where does the kinetic energy go?

 

[Shadowy Man]

When Capt Kirk orders the Enterprise out in deep space to come to a full stop what does that mean?

It means that many science fiction writers don’t understand science.

 

[steve_bank]

It is a good question.

 

[bilby]

It is a good question.

It really isn't.

It's a bad question, that is perhaps unremarkable in its badness for a species that evolved on a planetary surface, where the planet itself is so much larger than individuals of that species that it provides a reference so dominant, that for casual purposes it might as well be absolute.

 

[Bomb#20]

Jumping over from a question on the energy thread.

What is zero velocity? From relativity and the exclusion of any absolute inertial frame all we can know is relative velocity.

There is a so-called "cosmic rest frame", the velocity you'd need to be going at to see the cosmic microwave background red-shifted equally in all directions when you average out the local irregularities. The Milky Way is moving at about 600 km/sec relative to that; it's the closest thing to an absolute frame of reference our universe appears to offer. Whether the Hubble flow -- the average of all the galaxies' movements -- is at rest relative to the CMB is an open question.

When Capt Kirk orders the Enterprise out in deep space to come to a full stop what does that mean?

Well, there's no military value in coming to rest relative to the CMB when you're in a galaxy moving at 600 KM/sec. So there are two reasonable things it could mean. (1) It could mean the ship's computer computes an optimal tactical frame of reference taking into account the average movements of all nearby militarily relevant objects and by default applies coordinate transformations to the data it supplies to the human crew calculated to make the tactical picture as easy as possible for mere pathetic human brains to comprehend, and "full stop" means to bring the ship to rest in that frame. Or (2) it could mean bring the ship to rest relative to the ocean, because as Bilby is fond of pointing out, a Star Trek story is just a naval story moved into space -- Captain Kirk is Horatio Hornblower.

If conservation applies bringing an object to an absolute zero velocity where does the kinetic energy go?

Back into the dilithium crystals?

 

[Shadowy Man]

If conservation applies bringing an object to an absolute zero velocity where does the kinetic energy go?

Back into the dilithium crystals?

Since velocity is relative so is kinetic energy. So where it goes depends on which frame you’re observing it from.

 

[T.G.G. Moogly]

Since velocity is relative so is kinetic energy. So where it goes depends on which frame you’re observing it from.

Can we equate velocity with motion and therefore state there is no such thing as zero motion or zero velocity? Seems to make sense, motion is relative just like velocity.

 

[Shadowy Man]

Since velocity is relative so is kinetic energy. So where it goes depends on which frame you’re observing it from.

Can we equate velocity with motion and therefore state there is no such thing as zero motion or zero velocity? Seems to make sense, motion is relative just like velocity.

as a physicist, I wouldn’t strictly equate the two, no. There are arguments about how velocity and acceleration are not the same vis a vis relativity theories.

 

[Politesse]

When Capt Kirk orders the Enterprise out in deep space to come to a full stop what does that mean?

It means that many science fiction writers don’t understand science.

Got it in one. The "Neutral Zone" also makes little sense.

 

[Jimmy Higgins]

Ensign: Captain we are arriving at Omicron Orion VII.
Picard: Full stop ensign.
Ensign: Full Stop, aye.
Picard: Put the planet on screen.
Ensign: On screen sir.
Picard: What the... why is the planet going away?
Ensign: You said full stop. The planet is moving around the star and away from our current position.
Picard: Well, get us back to the planet and put us in orbit with the planet.
Ensign: Aye sir.
*bang* *bong* *bing* *bang*
Picard: What in the hell is that?
Ensign: Probably the planet's satellites sire.
Picard: *facepalm*