11-15-2018, 10:17 AM | #51 | |
Join Date: Aug 2007
Location: Denver, CO
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Re: How do time-travelers calculate the date?
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As an alternative, one could be, with minimal additional effort, placed at Earth's trailing and leading Lagrange points. This means a signal would reach everywhere on earth except perhaps the places currently experiencing midnight and noon. Chance of discovery would be minuscule, but maintenance would be more costly. I would assume, though, that space travel gets better and cheaper at some point. |
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11-15-2018, 01:13 PM | #52 | |
Join Date: Aug 2007
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Re: How do time-travelers calculate the date?
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Fred Brackin |
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11-15-2018, 02:40 PM | #53 | |
Night Watchman
Join Date: Oct 2010
Location: Cambridge, UK
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Re: How do time-travelers calculate the date?
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It's quite a good idea. With a decently encrypted digital radio broadcast, they won't get detected until radio astronomy advances a fair bit, although they're far enough from Earth that you'd need a fair-sized antenna to pick them up.
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11-15-2018, 02:56 PM | #54 |
Hero of Democracy
Join Date: Mar 2012
Location: far from the ocean
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Re: How do time-travelers calculate the date?
I wouldn't mess around with Lagrange points. If people could possibly pick up your signal at all, you're in a time period with newspapers, clocks, and globe-trotting transportation who are actually likely to speak your language, so the satellite is less useful.
On the other hand, you'll want to clean up your satellite mess, which is actually fairly difficult. I do not regard creating a cloud of metallic space-junk at a Lagrange point to be "keeping the secret" or "preserving the timeline". You'll want to burn the satellite up in an atmosphere, so you may as well keep it reasonably close to earth.
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11-15-2018, 03:14 PM | #55 | |
Join Date: Sep 2007
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Re: How do time-travelers calculate the date?
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The other nice thing about reentry instead of Lagrange is that it gives you a free adventure to maintain the secret when the tempori-locals discover the debris and realize it's not just a space rock. But I actually wouldn't think any time-travelling organization with the means to deploy and keep satellites in orbit over a billion-year span of history (or even thousands, just to cover human civilization) would find picking them up again before discovery very difficult at all. |
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11-15-2018, 09:46 PM | #56 |
Join Date: Nov 2004
Location: The plutonium rich regions of Washington State
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Re: How do time-travelers calculate the date?
And, of course, there's dendrochronology. Some trees are known to be several thousand years old. So, if you are in a world with some form of civilization, it should be possible to make an expedition to one of these Methuselah trees, take a core sample, and count the rings.
This means that if time travel is popular and lots of time travelers need to figure out when they are, the old trees will eventually end up with more holes in them than Swiss cheese. Maybe time travel also comes with some sort of superscience non-destructive deep scanner that can count growth rings without damaging the tree. Luke |
11-15-2018, 10:16 PM | #57 | |
☣
Join Date: Sep 2004
Location: Southeast NC
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Re: How do time-travelers calculate the date?
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RyanW - Actually one normal sized guy in three tiny trenchcoats. |
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11-15-2018, 11:14 PM | #58 | |
Join Date: Nov 2004
Location: The plutonium rich regions of Washington State
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Re: How do time-travelers calculate the date?
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Luke |
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11-16-2018, 06:47 AM | #59 | |
Join Date: Jun 2006
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Re: How do time-travelers calculate the date?
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You could even do an orchard long term. Come back every 10 years and plant another tree in some fixed spacing and direction and somebody who knows that can find the decade just from finding the marker and the youngest tree that's some integer multiple of 10 meters north/south and east/west of it.
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-- MA Lloyd |
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11-16-2018, 09:05 AM | #60 | |
Join Date: Dec 2006
Location: Meifumado
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Re: How do time-travelers calculate the date?
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One major problem is that L4/5 are each 1AU away. You'd need significant spaceflight capability to get anything there - especially launching from a prehistoric Earth - which means you'd probably have enough tech to put a self-sustaining stealth satellite in Earth geosynch orbit instead. I guess the Earth-Moon L-points might be more viable though.
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