Ask a Nerdy Question.
- Thread starter GnyHwy
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In an attempt to keep this thread alive, I will answer my own question. Sigs or physics geeks, please feel free to critique.
The radio freq must change because the speed of light will not. Freq=speed of light/wavelength. Because the speed of light stays constant, the freq and and wavelength must change and are dependant on each other. In the context of the question, the Earth is already travelling in an easterly direction (rotation). This rotation attempts to speed up the speed of light. This cannot happen, therefore the freq and wavelength must change.
Answer: When a radio transmission is sent in an easterly direction, the freq increases and the wavelength shortens (decreases). If transmitting in the westerly direction, it is the opposite. The frequency decreases, and the wavelength gets longer (increases).
Next question: Sigs, please chime in.
Is this one of the reasons we require bandwidth?
The radio freq must change because the speed of light will not. Freq=speed of light/wavelength. Because the speed of light stays constant, the freq and and wavelength must change and are dependant on each other. In the context of the question, the Earth is already travelling in an easterly direction (rotation). This rotation attempts to speed up the speed of light. This cannot happen, therefore the freq and wavelength must change.
Answer: When a radio transmission is sent in an easterly direction, the freq increases and the wavelength shortens (decreases). If transmitting in the westerly direction, it is the opposite. The frequency decreases, and the wavelength gets longer (increases).
Next question: Sigs, please chime in.
Is this one of the reasons we require bandwidth?
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Might be a stupid question. But since the speed of light is so fast, and there is a limited range that you can send things without bouncing off the ionosphere, wouldn't any freq change be negligible?
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GnyHwy said:
No, not by very much! The signal can be attenuated by dopler-spread though due to Auroral Backscatter which increase at the poles and decreases at the equator.
Robert0288 said:
There are no stupid questions! The Frequency change would be extremely negligible i.e. Earth's equatorial speed divide by the speed of light ~ (465/300000000) m/s= 1.88 × 10^-6 change in hertz or 1.88 x 10^-12 MHz. You would be fairly hard pressed to detect this difference in frequency and wavelength.
GnyHwy said:
I wouldn't say the rotation attempts to speed up the light. As an observer on the ground the light should appear to be moving 465 m/s faster, which be pretty hard to observe, but because this would violate special relativity the frequency shifts by ~ 465/c.
Ref
http://en.wikipedia.org/wiki/Relativistic_Doppler_effect#Motion_in_an_arbitrary_direction
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collinscj043 said:
That's along the lines of what I was thinking, since the speed Earth rotates is negligible compared to c.
Next physics question;
If no external torque is being applied to a closed system, what can we deduce about the cross product of the momentum and the velocity of the said system? What useful information does this realization give us in terms of the mechanics of the system?
Hint below..
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What specific quality of the system is conserved?
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jparkin said:
In a closed system as described above both the momentum and velocity vectors would be parallel thus their cross product would be zero. Conservation of angular momentum tells us that a system in rotational motion will remain in motion until acted on by some external force/torque. The really cool thing that conservation of angular momentum is that it also predicts that if the shape/density of a system changes then its velocity must change respectively to conserve angular momentum. i.e. Like when a figure skater pulls their outstretched arms toward their chest. or when galaxies formed after the big bang.
Next Question: How much energy do we flush down the toilet everyday and what existing technology could turn such effluent into gold(at least take a little off the old electric bill)?
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Shipwreck said:
I don't think I saw the answer to this one: Canada once used Oberon class submarines; "Oberon" was a fairy-king character in Shakespeare's work. To follow up, what is the name and fate of the last Oberon class sub here?
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I actually sat up in my chair when I saw that you got it. Yes, Oberon was a Shakespearean character. I don't know off the top of my head the answer to your question...actually I think the last Oberon submarine ended up in a museum, but I still don't know it's name without googling.
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What is the definition and difference between accuracy, consistency, and precision?
This one may seem simple at first, but I bet if enough people chime in, there will be debate. I have my answer, and it will be very tough to change change mind. I will respond once others ideas have stopped.
This mainly arises from the introduction of precision into ballistics. Some will say that precision replaces accuracy, and I know most will at least say that accuracy and precision are synonymous, which they are, but synonymous does not necessarily mean they are interchangeable.
This one may seem simple at first, but I bet if enough people chime in, there will be debate. I have my answer, and it will be very tough to change change mind. I will respond once others ideas have stopped.
This mainly arises from the introduction of precision into ballistics. Some will say that precision replaces accuracy, and I know most will at least say that accuracy and precision are synonymous, which they are, but synonymous does not necessarily mean they are interchangeable.
To my befuddled old mind: accuracy refers to how close the mean point of impact (MPI) can be to the target; consistency refers to the tightness of the group around the MPI; and precision can be said to be a combination of both, with the distance of the MPI from the target and tightness of the group lying for our purposes within the normal distribution of rounds - the 84% zone. Again, I have not rassled with this for at least three decades.
And by the way, in the pre-NATO fire discipline days a destruction mission was known as a precision adjustment.
And by the way, in the pre-NATO fire discipline days a destruction mission was known as a precision adjustment.
AmmoTech90
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Hmm,
The traditional answer is that accuracy is putting rounds where you want them (on the bulls eye) and precision is putting multiple rounds in close proximity to each other (size of the grouping). If you are getting tight groupings on the bull you have both accuracy and precision. In general you would always want to be accurate, but depending on the weapon system, you don't always want or need to be precise. Putting every round from MG through a two inch group at 100 meters is pretty pointless.
Consistency adds in the dimension of repeatability. This is something you would work on once you have you accuracy and precision nailed down. Are these results you got with regard to accuracy and precision repeatable over a variety of conditions. Does the range, temperature, air pressure, wind speed and/or direction have a significant affect on your results? If you are talking something like a MG, artillery, or rockets, is the dispersion you have achieved consistent? Does the dispersion scale predictably as the range increases (at least for unguided weapons)? Is there a point at which the precision becomes so unpredictable that it is pointless trying to hit anything, say due to the velocity dropping below a certain point and external forces taking over?
The traditional answer is that accuracy is putting rounds where you want them (on the bulls eye) and precision is putting multiple rounds in close proximity to each other (size of the grouping). If you are getting tight groupings on the bull you have both accuracy and precision. In general you would always want to be accurate, but depending on the weapon system, you don't always want or need to be precise. Putting every round from MG through a two inch group at 100 meters is pretty pointless.
Consistency adds in the dimension of repeatability. This is something you would work on once you have you accuracy and precision nailed down. Are these results you got with regard to accuracy and precision repeatable over a variety of conditions. Does the range, temperature, air pressure, wind speed and/or direction have a significant affect on your results? If you are talking something like a MG, artillery, or rockets, is the dispersion you have achieved consistent? Does the dispersion scale predictably as the range increases (at least for unguided weapons)? Is there a point at which the precision becomes so unpredictable that it is pointless trying to hit anything, say due to the velocity dropping below a certain point and external forces taking over?
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