sorry yim, that's not correct. momentum is not a square of velocity, but a linear function commonly referred to as P where P=mv NOT mv^2.
force is needed to change momentum. the relationship between momentum and force is determined by the time over which the momentum is changing. This is easy to see from the fact that acceleration is the change is velocity over time (a=v/t).
so... F=ma & a=v/t & P=mv
therefore F=mv/t (substitute for a)
and then F=P/t (substitute for mv)
This means force and changes in momentum are related in that a change in momentum requires a certain force, but this is related to the speed of the change (how quickly it happens) and not according to the square of the velocity of the object. It takes just as much force to slow a 10lb weight by 5mph in 5 seconds, regardless of how fast it was going when it started.
CRT's can definitely produce the best color and resolution when properly setup, but they still suffer from two key issues that are addressed by the other technologies.
#1 - Weight; CRTs are heavy beasts, whether a simple tube TV, RPTV, or Projector.
#2 - Pixel accuracy/drift; CRT's are inherently analog and the horizontal component (the 1920 in 1080i) of the resolution is produced as a single line of varying color/brightness intensity that does not necessarily match the 1920 digital pixels one for one. Also, the three color "guns" in an RPTV or front projector must be properly aligned and can drift out of alignment over time, which can be a time-consuming process. Digital display technologies avoid both those problems by using fixed pixel grids.
As I recall, a CRT projector or RPTV would need at least 9" tubes to properly resolve 1920 x 1080. Most consumer models only have 7" guns and cannot faithfully reproduce every pixel in a 1080i image. (but they still look mighty good)
While I don't think the act was justified, there is a difference between breaking the GPL by using publicly-created source code in a commercial software and uploading beta compiled code for people to play with. One is making a profit from people's volunteer efforts, the other causes very little harm and may end up benefitting apple in the long run. It's not like the guy stole the Tiger source and is making his own version to sell.
Carbon nanotubes may be the answer to ribbon strength and researchers keep coming up with ways to make them longer. Maybe by the time commercial space travel becomes viable we'll be spooling this stuff out like thread.
The print article has a nice cutaway drawing of the "18-inch-thick shield of alternating woven graphite composite and foam to protect against orbital debris."
Apparently, this layered foam shield is more protective than "aluminum three inches thick" and "no rigid spacecraft design can match this performance." (from the text of the article)
It sounds like NASA's decision not to use the TransHab inflatable design was politically motivated and the program was axed before it could actually be tested.
Slashdot Mirror
sorry yim, that's not correct. momentum is not a square of velocity, but a linear function commonly referred to as P where P=mv NOT mv^2.
u m:What_is_Momentum
force is needed to change momentum. the relationship between momentum and force is determined by the time over which the momentum is changing. This is easy to see from the fact that acceleration is the change is velocity over time (a=v/t).
so... F=ma & a=v/t & P=mv
therefore F=mv/t (substitute for a)
and then F=P/t (substitute for mv)
This means force and changes in momentum are related in that a change in momentum requires a certain force, but this is related to the speed of the change (how quickly it happens) and not according to the square of the velocity of the object. It takes just as much force to slow a 10lb weight by 5mph in 5 seconds, regardless of how fast it was going when it started.
learn more about momentum here: http://en.wikibooks.org/wiki/FHSST_Physics_Moment
(for all you physics buffs... i know i skipped the deltas - it just got too complicated)
CRT's can definitely produce the best color and resolution when properly setup, but they still suffer from two key issues that are addressed by the other technologies. #1 - Weight; CRTs are heavy beasts, whether a simple tube TV, RPTV, or Projector. #2 - Pixel accuracy/drift; CRT's are inherently analog and the horizontal component (the 1920 in 1080i) of the resolution is produced as a single line of varying color/brightness intensity that does not necessarily match the 1920 digital pixels one for one. Also, the three color "guns" in an RPTV or front projector must be properly aligned and can drift out of alignment over time, which can be a time-consuming process. Digital display technologies avoid both those problems by using fixed pixel grids. As I recall, a CRT projector or RPTV would need at least 9" tubes to properly resolve 1920 x 1080. Most consumer models only have 7" guns and cannot faithfully reproduce every pixel in a 1080i image. (but they still look mighty good)
While I don't think the act was justified, there is a difference between breaking the GPL by using publicly-created source code in a commercial software and uploading beta compiled code for people to play with. One is making a profit from people's volunteer efforts, the other causes very little harm and may end up benefitting apple in the long run. It's not like the guy stole the Tiger source and is making his own version to sell.
That's a good point I haven't heard much talk about.
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OTOH I keep reading news about the space elevator http://www.wired.com/news/technology/0,1282,57536
Carbon nanotubes may be the answer to ribbon strength and researchers keep coming up with ways to make them longer. Maybe by the time commercial space travel becomes viable we'll be spooling this stuff out like thread.
The print article has a nice cutaway drawing of the "18-inch-thick shield of alternating woven graphite composite and foam to protect against orbital debris." Apparently, this layered foam shield is more protective than "aluminum three inches thick" and "no rigid spacecraft design can match this performance." (from the text of the article) It sounds like NASA's decision not to use the TransHab inflatable design was politically motivated and the program was axed before it could actually be tested.