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bio website blueraja.com/blog
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visits member for 4 years, 8 months
seen 12 hours ago

Jul
24
awarded  Good Question
Jul
21
comment How can one derive the Ohm's Law?
Similarly, you could say Maxwell's Laws are an idealization, and don't hold at scales of QED or General Relativity. I don't see how that's a useful answer, however.
Jul
17
awarded  Yearling
Jul
16
comment Could quantum computers break any cipher?
-1 This answer is stating that BQP = NP, which is widely believed to be false. Using Grover's Algorthm, quantum computers can speed up brute-force searches by a square-root factor, which means you could brute-force a 256-bit AES key in only 2^128 operations. But that is still exponential complexity.
Jul
13
awarded  Autobiographer
Jul
12
comment Why are angles dimensionless and quantities such as length not?
@RishavKundu: It is a meaningful question. You are free to define a new unit "log-seconds" which represent the log of actual seconds. The problem is that these units are not linear, so it's hard to see how they'd be useful, ie. 2 log-seconds + 2 log-seconds =/= 4 log-seconds. But we have done this before, where log-units are more convenient. Decibels are a logarithmic unit, so 10 decibels + 10 decibels =/= 20 decibels.
Jul
6
comment Wind generators - why so few blades?
"if you have 4 shorter blades (rather than three longer ones).." - Why would the blades need to be shorter? If an extra blade increased efficiency by even a small amount, it might be worth it when you consider the cost of the entire rest of the structure...
Jun
3
comment Why doesn't the motion of a car affect the frequency of radio stations?
See also Why don't interfering radio stations both play at the same time? (the questions are only mildly related, but they're both questions I had when I was learning how radios work, so I thought you'd find it interesting as well)
May
21
comment Do rainbows have ultraviolet bands and infrared bands?
According to here, an educational forum post constitutes fair-use
May
3
comment Will 1 gram of matter moving at relativistic speeds completely annihilate a larger quantity of stationary antimatter?
From the matter's point of view, the large quantity of antimatter is the one moving at relativistic speeds.
Apr
23
awarded  Notable Question
Mar
30
comment Why doesn't light affect a compass?
@vsz: Could you please take a video? :D
Feb
24
awarded  Notable Question
Feb
1
comment Can orbital energy be a source of perpetual power?
I think what @Pyraminx is getting at is, what if the moon's orbit was inside a gas cloud - the moon would cause wind, which could be used to turn a turbine. What he is missing is that the gas cloud would cause wind-resistance in the same way the air does on Earth, which would gradually slow the moon down (until it inevitably crashed into the Earth).
Sep
9
awarded  Citizen Patrol
Sep
5
awarded  Famous Question
Aug
23
comment Why is gravitational potential energy negative, and what does that mean?
This question is about potential energy, not acceleration vectors...
Aug
13
comment Are there two theories that are mathematically identical but ontologically different?
This isn't quite the same. These are different physical interpretations of the same mathematical theories, not two mathematical theories based on different physical observations but leading to the same results. The difference is that the math came first, then the differing interpretations, not the other way around.
Jul
9
comment How effective is speeding?
"it costs you an additional $1.50 an hour to go 5 mph over the speed limit" - That depends on the speed-limit... Also, cost-per-hour is a complete red-herring, what's important is cost-per-mile. No one goes out and drives for a specific time, they drive a specific distance. -1
Jun
17
comment Voltage and Current in transformers
I wrote a blog post about this a few years ago: blueraja.com/blog/194/do-transformers-obey-ohms-law