Not a DeLorean. You're doing it wrong.

[Update: Prize Update / Added link to full solutions] Welcome to the second Physics Challenge Award show! [APPLAUSE] Our judges have deliberated for several units of time and I now have in my hands the envelope holding our list of winners. I could easily just tell you who won right now and save everyone some time, but award shows need some suspense to work effectively, so let's first give some tedious background information! [APPLAUSE] You may recall that the winner of the first Physics Challenge contest won a CRC Handbook. We will not be giving out CRCs this time around. We felt that such a prize was far too ~~expensive~~ impersonal, so we have opted this year for something ~~much cheaper~~ from the heart. The following prizes will be awarded to our top three solutions: First Prize: Our first prize winner will receive an actual back-of-an-envelope used in one of our posts (gasp!) signed by all the of the members of the Virtuosi that I can find at colloquium tomorrow. But that's not all! Alemi will also salute in your general direction. Second Prize: For our second prize winner, we appear to have run out of envelopes... but Alemi will still salute in your general direction. You will not see him do this, but you will feel a major disturbance in the Awesome Force (mediated, of course, through the midi-chlorian boson). Third Prize: You will receive no material prize, but on your deathbed you will receive total consciousness. So you've got that going for you, which is nice. Let's first remind everyone what the Challenge problem was. The full text of the problem can be found here, but the gist is basically this: You've created a time machine and you're biggest fear is that you'll be stuck back in the past without any way to communicate to the future that your design worked and you deserve all kinds of Nobel prizes. The solution should be able to last long periods of time (who knows how far back in time you'll go?), should maximize the chances of modern people finding it, and be able to convince people that you have in fact gone back in time. Alright, let's get to some solutions already! First Place: The first place solution comes from Christian, who uses some biological wrangling to solve the time traveller conundrum. With some information from the announcement of "synthetic life" and some bio how-to from an entity known only as "steve," Christian plans to implant a message into the DNA of bacteria. The message will contain his name, identifying information, and the url of a website which will (presumably) contain a video of him with one hand outstretched saying "Nobel prize please." Let's see how this solution satisfies our criteria for a successful solution. Does it work for an arbitrary amount of time? It appears to, so long as the bacteria manage to survive and the message doesn't become too garbled over time (perhaps some error-correction might be useful). Additionally, if one is worried about introducing non-native bacteria to the wild you could bring back a bunch of bacteria that were known to exist over wide periods of time and just release those alive at the time. Will modern humans find it? It seems that geneticists are decoding just about any genome they can get their hands on, so this is a strong possibility. Would it convince people that someone travelled in time? If the bacteria has dispersed enough, shows enough variation over geographic regions, and contains specific identifying information about a missing person who has allegedly created a time machine, I think that's pretty strong evidence. Neato, gang! Second Place: The second place solution comes from Kyle, who offers a space-based answer. Kyle suggests etching detailed plans of the time travel mechanism (flux capacitor) onto a durable metal and putting that bad boy into space. He suggests that anyone capable of building a fully functional time machine should have no problem launching a small satellite. Fair enough. Additionally, the satellite would use some kind of solar power or the like to produce a low-power radio signal. In fact, this signal would only need to spit something out once every year or ten years or something. Since radio communication precedes space exploration, the detection of an artificial satellite sending a message would attract a fair deal of attention. The plans and successful reproduction of the time machine would then seal the deal. Does this solution satisfy the necessary conditions? I think so. Assuming all goes according to plan, this would easily be detected by modern people and, assuming the time machine plans are accurate, would provide indisputable proof. My main concern would be that the satellite could be launched and survive to the present. Modern satellites need constant boosts to stay in orbit, without which they fall back onto Earth and burn up. One potential solution would be to put it on the Moon. This is technically much more difficult, but hey, you just created a time machine! Also, putting it on the moon then allows for a totally rad recreation of the Monolith scene in 2001: A Space Odyssey. Third Place: The third place solution comes from Yariv. Though Yariv did not submit a solution through the proper channels (he follows no one's rules, not even his own), he was overheard to give a solution. While the Physics Challenge planning committee was discussing the problem over lunch, Yariv flippantly dismissed the entire premise as "trivial" and suggested a two-word solution: "radioactive paint." Personally, I like the idea of bewildered archaeologists finding a cave painting of Yariv riding a dinosaur done using a variety of radioactive paints which all date back 200 million years. For this amusement, I award Yariv the third place prize for this contest. As a member of the Virtuosi, however, Yariv is ineligible to receive a prize and instead receives 5 demerits on his record for his willful disregard of our institution's rules and excessive flippancy. One more slip-up and you'll lose your badge! Full solutions are up on the Challenge website. Thanks for joining us for this episode of Physics Challenge Award Show, and thanks to everyone who submitted a response! First and Second Prize Winners: We present the following in partial fulfillment of our prize offer.

For those who solve problems (he salutes you)

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