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12455
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location Vancouver, Canada
age 45
visits member for 4 years, 5 months
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VP Research&Development at an image guided surgery startup.

Mostly do C++,python,image processing,machine vision - anything with lots of 3D,maths and data. Background is experimental physics and optics.


Jan
11
answered Light pollution calculation using camera
Jan
11
answered How fast will the projectile go the second time?
Jan
11
comment How to read a lens spot diagram?
It looks to me like those are the on-axis spots at different positions OF the surface - ie at different focus?
Jan
8
revised If microwave ovens and WiFi both operate on the same frequency, why doesn't WiFi cook things?
added 379 characters in body
Jan
8
comment Why is it concluded that the cosmos is expanding when in fact the observations are for events further back in time?
I think DDD's point was that if we see more distant objects moving faster but more distant objects are also older then that is saying that the universe is slowing - older=faster, younger=slower! In fact the expansion of the universe doesn't quite work likethat
Jan
8
answered If microwave ovens and WiFi both operate on the same frequency, why doesn't WiFi cook things?
Jan
6
comment How far does physics influence russian roulette?
See qi.com/talk/viewtopic.php?start=15&t=3032
Jan
6
answered How does water carve rock?
Jan
5
comment What fundamental principles or theories are required by modern physics?
@Ron. Yes. You can't say faster than light is impossible because it breaks Relativity. Theories, however elegant, can't override results. Although if you had a measurement of FTL you would need a good explanation of why it didn't violate a lot of basic principles that seem to work!
Jan
5
comment What fundamental principles or theories are required by modern physics?
@Ron, my objection was that there had to be a meta-criterion. Protons and electrons everywhere have the same (but opposite) charge. We don't know the reason for this - yet we can describe it without knowing why. There could be a circumstance in which electrons/protons had differing charges but it would have to be very bizarre circumstances since we haven't seen any effects of it in any other observation.
Jan
5
revised What fundamental principles or theories are required by modern physics?
added 606 characters in body
Jan
5
comment What fundamental principles or theories are required by modern physics?
@Ron - no there isn't - theoretical physics might like to think there is. In reality there is a theory which explains everything, then a tiny little experimental result doesn't fit and you need a whole new theory (eg relativity). If it was discovered that eg. you could send a signal faster than light by some QM effect - but over a distance <0.1nm and only below a temperature of 1mK that would invalidate relativity but have no affect on the day-day use of relativity in physics. In exactly the same way that GR had no effect on calculating the flight of cannon-balls.
Jan
5
comment What fundamental principles or theories are required by modern physics?
@Ron - then the results can't be true! The point is that any 'impossible' result must still allow all current experimental results.
Jan
5
answered What fundamental principles or theories are required by modern physics?
Jan
4
comment How to calculate a firing location from point of impact data?
it works pretty well for a ballistic trajectory, like an artillery shell from only two points - especially if you know the muzzle velocity from the calibre
Jan
4
comment Why does the water rise?
@leonbloy - although with a smoky candle you do get a lot of CO. Plus since O2 is only 20% of air it would at most be a (1-0.65)*0.21 = 7% change in volume even with full combustion
Jan
3
comment Why does the water rise?
As oxygen is burned - how many moles of CO2 do you get for each mole of O2 used?
Jan
3
revised That 10km/day error predicted if GPS satellite clocks not corrected for relativity
added 276 characters in body
Jan
3
comment Limit of human eye flicker perception?
Then anything faster than 50hz would probably be OK. Another trick is a single PWM to modulate the common supply to all the leds (via a switching transistor)
Jan
3
comment Is it humanly possible to change Earth's axis?
We do make measurable changes simply by filling/emptying dams - but only because we can make immensely sensitive measurements (eg radio VLBI)