Timeline for Alien message: arrows and sequence order
Current License: CC BY-SA 3.0
19 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 14, 2017 at 13:27 | comment | added | leftaroundabout | Three shalt thou count, and the number of counting shall be three. Four shalt thou not count, neither count thou two, assuming you have by then reached three... | |
| Feb 14, 2017 at 10:20 | comment | added | Megha | @JoeBloggs - even a reversible chemical reaction might be helpful, if the reversal is included - that is, written as a cycle with several steps or sub-reactions (there is a this that has to be between those other steps, then back through the next reaction to the first substance), then with one line going this->to->that, the next going that->to->this. It doesn't matter if they read the arrow as earlier goes-to later, or later comes-from earlier, it should suggest directional in a useful way. | |
| Feb 13, 2017 at 21:49 | comment | added | Innovine | @wizzwizz4 i see where you are going with that, but I am skeptical :) | |
| Feb 13, 2017 at 18:33 | comment | added | wizzwizz4 | @Innovine When the water lands its kinetic energy disperses. Assuming that it creates ripples in the solid only and there's no evaporation etc. (for the sake of a simple explanation), the right ripples will cause the water droplets to move upwards and hit the ice where they freeze. It'll be hard to orchestrate, but theoretically quite possible. | |
| Feb 13, 2017 at 18:28 | comment | added | Innovine | @wizzwizz4 but if I have an ice sculpture, and let it melt, no waiting around or other processes will return it to the sculpture form.. I don't see how this is reversable, even though I understand your example | |
| Feb 13, 2017 at 17:26 | comment | added | wizzwizz4 | @Innovine It is reversible, physically. I find it easier to start with considering a projectile landing on a massive (planet-sized) water balloon. It hits it, ripples spread out, and it's stationary. However, if you start with a series of ripples heading towards the projectile... they'll add up, bend down, up, and propel the projectile into space. | |
| Feb 13, 2017 at 17:19 | comment | added | Sobrique | Yes, but the question is - does time cause entropy, or does entropy cause time? It's possibly the case that we perceive time is because of the entropy delta. It's a bit like a river - it runs downhill towards the sea. If you are carried with the river, it'll always feel like downhill is the 'natural direction' but ... if you stand beside it, you'll see it flowing past. | |
| Feb 13, 2017 at 16:03 | comment | added | Innovine | @wizzwizz4 but an ice block melting into a puddle is non-reversable physically, right? is the entropy the geometry information being lost? | |
| Feb 13, 2017 at 15:58 | comment | added | wizzwizz4 | @Innovine Yes, but there's a thermodynamic arrow of time. Time doesn't have to go in a specific direction for physics to work, but entropy is the result of it (appearing to be) doing so. | |
| Feb 13, 2017 at 15:51 | comment | added | Innovine | Isn't time reversable in quantum mechanical equations? | |
| Feb 13, 2017 at 15:06 | comment | added | Jens | Left to right (or vice versa) to indicate time direction is unsuitable, because there is very likely a symmetry in the alien world. A symmetry breaker could be bottom up, since there's gravity to break the symmetry. If their world has an atmosphere, they certainly use a pointy device (aka rocket :-) with a non-symmetric shape. | |
| Feb 13, 2017 at 14:52 | history | edited | PatJ | CC BY-SA 3.0 |
Typo fix.
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| Feb 13, 2017 at 12:49 | comment | added | Pavel Janicek | Exactly. Time series was the best example I could think of, even knowing that perception of time can be different | |
| Feb 13, 2017 at 12:47 | comment | added | Joe Bloggs | Rotation of an object is a good example of commutation: but to explain that you have to explain a form of directional arrow... O_O | |
| Feb 13, 2017 at 12:43 | comment | added | Pavel Janicek | Thats great example, however about five levels above my mathematical knowledge. Also, for that, you have to explain what commutative property is. Although it sounds obvious to us, I did read somewhere that higher mathemathics might be our construct and not something you can observe in universe. | |
| Feb 13, 2017 at 12:40 | comment | added | Joe Bloggs | Good point... Non-commuting mathematical operations, perhaps? | |
| Feb 13, 2017 at 12:35 | comment | added | Pavel Janicek | Yep. I was thinking of chemistry when writing the parts about Ray Bradbury, but then I did not include that. What if aliens are at level of technology where they can manipulate with atoms and therefore no chemical reaction is irreversible? | |
| Feb 13, 2017 at 12:32 | comment | added | Joe Bloggs | 'Known feats of the universe' is good. What about non-reversible chemical reactions as well? | |
| Feb 13, 2017 at 12:24 | history | answered | Pavel Janicek | CC BY-SA 3.0 |