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| What do you do when fellow engineer wants to crash project? |
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| tggzzz:
--- Quote from: tom66 on October 06, 2022, 09:43:29 am ---Another treez/Faringdon post where I think the OP may be projecting a bit hard. --- End quote --- You might think that; i could not possibly comment. |
| niconiconi:
--- Quote from: newbrain on October 06, 2022, 08:21:25 am --- --- Quote from: rstofer on October 05, 2022, 06:06:24 pm ---we can transmit information at 3 trillion meters per second, a LOT faster than the speed of light. --- End quote --- Unfortunately, no, we cannot - unless I grossly misunderstood the whole thing (always a possibility) - the universe, in a way, does and that was the spooky part Einstein did non like. There is no way we can use the entanglement to transmit information of our choice, we can only measure that entangled particles are, in fact, entangled (they have one single state for the couple, not one each). E.g.: we cannot force the spin of one particle to be up when we measure it, so forcing the distant one to be measured as down, effectively transmitting our piece of information faster than light. --- End quote --- Yep, these quantum effects are in a sense, "action at a distance", but it's non-causal and cannot transmit information. And speaking of faster-than-light, in fact there are many interesting phenomenon that give such an illusion. The experiment result I'm most impressed is that some exotic non-linear materials can have a phase velocity and a group velocity, both faster than c. This is known as anomalous dispersion. If you transmit a Gaussian impulse and measure "delay" between the rise edge / peak of the input and output impulses, the "delay" is "faster than light". It has been demonstrated that you can even run the experiment in both air/vacuum and the non-linear material simultaneously, and non-linear material is always "faster" than the air/vacuum, the results are as consistent as it can be. Better, this apparent delay can even be negative. :scared: The simplest explanation is when the pulse shape is distorted by the medium: no magic here, the location of the edge or the peak of the impulse was shifted, giving a misleading propagation delay measurement :-DD. But experiments showed that in some cases, the effect is still possible without wave shape distortion. I still can't wrap my head around it, but all we need to know is that if you define the "speed" as "the time interval between the moment the ON button of the transmitter is pushed, and the moment that the receiver detects a signal", this propagation delay is always slower than or equal to c. Here's an introduction to these phenomenon: https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/7/38882/files/2016/09/PhotonicsSpectraFastLightSlowLight2007-1gb2tao.pdf I read that similar experiments exist using microwave waveguides below cut-off. Sometimes the phase shift of the evanescent wave can appear faster-than-light, but it's not even a traveling wave, just a stray field, and there's no signaling. Regardless of how exotic the material, it's basically a variation of this idea: you can build linear circuit (an opamp active filter) with a negative group delay, but it's only because the signal is bandwidth limited, and the active filter is essentially an analog computer that predicts and recreates the expected output in advance. https://www.dsprelated.com/showarticle/54.php |
| tggzzz:
Things travelling faster than light is trivial. A couple of examples... Take a laser, point it at the moon, move it. The spot can easily move sideways faster than light. Or there are several real astronomical examples such as https://apod.nasa.gov/apod/ap031205.html If you insist on it being "particles" rather than "photons", this is what the result looks like Don't bother to enlighten me with the limitations of those examples; I'm already enlightened. |
| niconiconi:
--- Quote from: tggzzz on October 10, 2022, 09:56:12 am ---Things travelling faster than light is trivial. A couple of examples... Take a laser, point it at the moon, move it. The spot can easily move sideways faster than light. Or there are several real astronomical examples such as https://apod.nasa.gov/apod/ap031205.html --- End quote --- It was claimed that you can even see this effect from the CRT beam on a Tektronix 7000 scope. https://web.archive.org/web/20111029020818/https://www.oregonlive.com/silicon-forest/index.ssf/2011/09/a_tektronix_oscilloscope_that.html At the fastest time base, Tek 7104 sweeps "faster than light". Though I never saw a screenshot to show it. TekWiki has a screenshot but the beam moves "only" at 95% of c. TekWiki says: Faster-than-light beam on 7104? Using a 067-0587-02 calibration fixture at maximum amplitude produces this trace spanning 1.2 Div horizontally at 200 ps/Div and 8 Div vertically. Trace length is (1.2² + 8²)½ × 8.5 mm = 68.8 mm, travelled in 1.2 × 200 ps = 240 ps. Apparent speed is therefore 68.8×10-3 / 240×10-12 m/s or 2.86×108 m/s. 95.6% c0 - a very near miss ... |
| Geoff-AU:
--- Quote from: tom66 on October 06, 2022, 09:43:29 am ---Another treez/Faringdon post where I think the OP may be projecting a bit hard. --- End quote --- All I know is I'm bloody confused by this thread |
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