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Alexander KnochelThe question now is - how to correctly communicate this subtlety in <a href="https://scicomm.xyz/tags/scicomm" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#scicomm</a> or <a href="https://scicomm.xyz/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> without losing or confusing the audience. I'm not sure

Alexander KnochelThis subtlety is quickly resolved when considering a concrete example with a clearly defined question, for instance the classic question of how far atmospheric muons can travel. With a lifetime of about 2 microseconds and close to the speed of light, their majority should, naively, have decayed after a kilometre or so. Yet, they arrive at sea level without much trouble. We naturally have to judge the lifetime of muons in our rest frame by using pairs of two separated clocks - one up high and one at sea level - synchronized in our rest frame. Hence, in the game of "whose time is dilated" outlined above we are the "resting" observer whereas the muons are moving along our imagined clocks. In this perspective, the muons are subject to time dilation and can travel much further without decaying.<a href="https://scicomm.xyz/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://scicomm.xyz/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://scicomm.xyz/tags/scicomm" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#scicomm</a>

Alexander KnochelRelativity is relatively subtle, exhibit A, and a pet peeve of mine in the communicaton of special relativity to students and the public. It is usually simplified to the point of seeming inconsistent, thus fueling crackpot ideas.1) It is usually said that in the theory of relativity, time goes more slowly for a moving clock than for one at rest.2) It is also said that there is no absolute movement or rest in relativity. The two statements contradict each other. If movement and rest are a matter of perspective, which clock runs slower then? Both? None? Was Einstein wrong???Spoiler: No. The first statement, which is usually used for popular science explanations, is simply too simplified & the devil is in the details here:The crux is that for one clock moving past another, it is only possible to directly compare them exactly once - namely when they meet. To infer how fast they go in comparison with each other, we have no choice but to compare them a second time, but then they are at a distance from each other.But comparing clocks at a distance is not a unique procedure in relativity and depends on the movement of the comparer!The usual procedure is to place two clocks at rest in in the lab frame, and synchronize them in the lab by starting them at the same lab time - for example by sending a light pulse from exactly in the middle between them. But this procedure prefers the lab frame over the say, spaceship frame, and this is precisely where the decision between who moves and who is considered "at rest" in this experiment is taken: in our prescription how to synchronize and compare distant clocks, not in nature. <a href="https://scicomm.xyz/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://scicomm.xyz/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://scicomm.xyz/tags/scicomm" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#scicomm</a>

Alexander KnochelFor those of you not knee-deep into ham radio, SSTV is an analog mode of transmission for sending still images via radio. To the ear it sounds like you'd expect if someone quickly scanned the lines of an image and varied the transmitted tone with brightness. The resolution of the mode we chose is rather low because we wanted to transmit in short time intervals (taking the picture, converting and transmitting it takes ~3 minutes) to get more opportunities for people to receive them.<a href="https://scicomm.xyz/@Quantensalat/114733557061475150" rel="nofollow noopener noreferrer" translate="no" target="_blank">https://scicomm.xyz/@Quantensalat/114733557061475150</a><a href="https://scicomm.xyz/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://scicomm.xyz/tags/electronics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#electronics</a> <a href="https://scicomm.xyz/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a>

Alexander KnochelAll systems worked as planned, including the WSPR beacon, multi gas measurements, two types of Ozone measurement and, of course, a professional research payload by Forschungszentrum Jülich <a href="https://mastodon.social/@fzj" class="u-url mention" rel="nofollow noopener noreferrer" target="_blank">@fzj</a>Many thanks to the team of IEK-7 who made these student research projects possible!<a href="https://mastodon.social/@fzj" class="u-url mention" rel="nofollow noopener noreferrer" target="_blank">@fzj</a>The WSPR payload delivered nice SNR gradients as a function of altitude and some interesting local effects.<a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://astrodon.social/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a>

Alexander KnochelPreparing the payloads <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://astrodon.social/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a>

Alexander KnochelAll right, tune up your WSPRs to 10 meters, if weather permits it, another balloon beacon will hopefully launch in a couple of hours calling DL0WH, this time in a different configuration. QTH Jülich in western Germany. A vaisala RS41 and a LoRa transmitter will be on board including various experiments if weather permits it, measuring various gases in the upper atmosphere.<a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://astrodon.social/tags/amateurfunk" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#amateurfunk</a> <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a>

Alexander KnochelThe student built transmitters for our little CW challenge take shape! They all oscillate and have an amplifier stage, and one even a working push-pull output stage. This means we can soon discuss code, and set up and measure an antenna for testing. <a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://astrodon.social/tags/electronics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#electronics</a>

Alexander KnochelAnd we're Airborne with WSPR Sonde HFS2 under call DL0WH <a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> 20m !!!! <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a>

Alexander KnochelAllright, second try to launch our HFS2 <a href="https://astrodon.social/tags/WSPR" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#WSPR</a> stratospheric high frequency sonde, the weather is pretty good, wish us luck! Hopefully on 20 meters 14095.6 kHz+x starting around 10 UTC on May 1<a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://astrodon.social/tags/electronics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#electronics</a> <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a>

Alexander KnochelDamn, 120€ worth of gas for the small balloon. Launching with H2 Hindenburg style becomes more attractive every week...<a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a> <a href="https://astrodon.social/tags/science" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#science</a>

Alexander KnochelBalloon WSPR Beacon upcomingDear Ham friends, Weather permitting, on April 28. around 10 to 12 UTC, a student of mine will launch a weather balloon carrying a WSPR beacon on 20m in order to analyze the worldwide propagation as a function of altitude, based on WSPR report data.It will probably broadcast our club call DL0WH or my own.We'd be delighted if you turn on your receiver and see if you can spot us. Launch QTH will be Weinheim DL0WH.<a href="https://astrodon.social/tags/hamradio" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#hamradio</a> <a href="https://astrodon.social/tags/electronics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#electronics</a> <a href="https://astrodon.social/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://astrodon.social/tags/physicsedu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsedu</a>

SchiffskatzeLegendary <a href="https://chaos.social/tags/physics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physics</a> <a href="https://chaos.social/tags/physikEdu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physikEdu</a> <a href="https://chaos.social/tags/physicsEdu" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#physicsEdu</a>(via IG @booksdidnt)

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