The other day, I was driving out of town, listening to my favorite (AM) radio station. About 30 miles out of town, reception starting breaking up, and 'bout 5 miles later, I lost the station. The question I have is: would I have been able to keep reception of the station longer had I been driving slower?
The real question is, at what point, if ever, do such principles as relativity, chaos and complexity theory, quantum mechanics, etc., affect us (or affect us to the point we notice)? I’m a very interested layperson who has a decent knowledge of such matters, but nothing I’ve ever read ever gave me a feeling for the low end of the effect spectrum, as it were (I do recall Cece or one of his minions write about relativity and differing rates of aging at the North Pole and the Equator, but that doesn’t fully answer this question). Would a 30 mph difference in my car speed be enough to appreciably change the Doppler effect on the radio waves reaching my car’s antenna?
I’m not a physicist, but I spent a number of years in AM radio. You lost the signal because you were out of range. I can go into stuff about groundwave, skywave and atmospheric wave, but I won’t. Doppler had nothing to do with it. Whether you were in a rocket car or walking, you would have lost the signal at about the same place.
Yes, but only because you would stay within range of the waves for a longer duration. The radio waves simply dissipate due to deconstructive interference at a particular range. The Doppler effect has nothing to do with your ability to receive radio transmissions. When you tune your radio, you are essentially setting up a standing wave which compensates for the miniscule deviations which arise from your relative velocity. Technically, at the frequencies which AM radio is broadcast, you’d require a much more precise tuner overcome any deviations.
You’ll have to be a bit more specific. These principles affect us continuously in different areas. The advent of the laser is an example of how quantum mechanics affects us insofar as something as the use of a cd player.
The Doppler effect acts on the frequency of a wave, and not its amplitude. If the Doppler effect were in action, what you would notice about your favorite AM station is that its frequency would be shifting upwards if you were driving towards the station, and shifting downwards if you were moving away from it. This is analogous to the blue shifts and red shifts (respectively) you may here in astronomy. Of course, you have to realize that a speed of 30 mph is really nothing compared to the speed of the radio waves; your favorite AM station’s frequency will only shift by a factor of one in twenty millionth at that speed.
As for when relativity, chaos, complex theory, and quantum mechanics affect you to the point that you would notice in every day life, I’m tempted to say never, at least for those four that you’ve mentioned.
Chaos theory becomes significant every time you watch the weather forecast on the news. You know how they give a five-day forcast, but it’s never too accurate for the fifth day? Well, in a few hundred years, with the phenomenal advances in computers that we’ll see, they’ll be able to predict weather to… about five days.
Relativistic effects reach the 1% level at about a tenth the speed of light, but effects from small speeds can add up. [oversimplification]Stick a magnet to your fridge-- it sticks because of the combined relativistic effects of sextillions of rather slow-moving electrons in the magnet. [/oversimplification]
To notice QM, you need either something oscillating really fast or with really low energy: The ratio of energy (in Joules) to frequency (in Hertz) needs to be down around 10^-34 (Planc’s Constant)
I know quite a bit about propagating EM waves, and this makes absolutely no sense to me.
Sure, there will be a very slight frequency shift due to the doppler effect, and our radios are way too coarse to notice. But setting up standing waves? Where? Compensating for the deviation? A radio doesn’t need to compensate for it - the radio is not that selective.
No, I’m gonna have to go with nen on this. Driving into the city every day, I have constant LOS with the trasmission tower for the station I listen to, but it still fades in and out because of diffration from all the buidings and streetlights.
Remember I said the primary cause. I will agree that in a cluttered environment, at low freqencies, with poor modulation techniques (i.e. AM), multipath reflection and refraction can cause problems near large (WRT wavelength) structures. But when you drive out to the boonies, you lose the tunes due to the dispersion effect.
You set up a standing wave in the radio to select which frequency you wish to hear.
You also said:
Which I had previously agreed with when I said:
Oblio and falcon2:
Oblio is right, dispersion is the primary cause in most situations. Deconstructive interference does play a role, but usually it isn’t quite as extensive as dispersion. Thank you for the correction.
Technically they kick in anytime you move. To be noticeable by you, however, you’d have to be going pretty fast. The following table was shamelessly yanked from the following site:
At the velocities people currently travel the effect of time dilation is small, but measurable with accurate instruments. Since time dilation affects the rate at which time passes, the total discrepancy between stationary and moving clocks increases throughout the voyage. Several Russian cosmonauts have spent a year or more in Earth orbit on the space station Mir. Their orbital velocity, about 7700 metres per second, is only 0.0000257 times the speed of light, yielding a time dilation factor of 1.00000000033; each second on board Mir, 1.00000000033 seconds pass on Earth. For every second you age on Earth, the cosmonaut in orbit ages 3 nanoseconds less. This doesn’t seem like much, but it adds up; after a year the cosmonaut’s watch will be 3.8 seconds behind your earthbound timepiece.