Is Mi trovis ion sur la reto a valid way to say that you found something in the Internet? Should prepositions such as en and per be prefered?
For sure en la reto.
A quick search of the Tekstaro only turns up one or two references to sur la reto and none of these are related to the internet.
To clarify the above. In the Tekstaro, there are the following references to en la reto:
- Six (6) from Monato - all six refer to the internet.
- Thirty three (33) from La Ondo de Esperanto - All the ones I've looked at closely refer to the internet.
Contrast this with sur la reto. There are only two hits total. Neither one has to do with the internet.
Further, there are two hits for en la interreto and none for sur la interreto.
So, based on my subjective impression of what expression is more common, the logic explained in other language, and actual usage as captured in the Tekstaro, my recommendation is for en la reto.
Sur la reto is perfectly fine. Just ask yourself whether the mental image is meaningful and unambiguous. If so, trust it.
This has been downvoted, so here's why it's correct: a reto is a net. Does a net have a surface? Yes it does, even as a figurative network, which is why an object caught in the net (en) is also on it (sur). The Internet is a network on the surface of the Earth, and thus anything in the net can also be visualized as on it.
If the expression sur la reto is good enough for the skilled poet Steven Brewer, it should be good enough for anyone. And please note that the Tekstaro consists of material from before 2005, the bulk of it much older.
I think it is okay to say sur or en. I prefer saying en myself because the info is stored inside computers/servers.
Here are a few examples for sur la reto:
Esperanto sur la reto https://www.esperanto-usa.org/en/node/177
Rezultoj de KER-ekzamenoj jam aperas sur la reto! http://www.esperanto-mexico.org/eo/rezultoj-de-ker-ekzamenoj-jam-aperas-sur-la-reto
...ni klopodas pliigi nian prezenton sur la reto,... http://www.espero.com.cn/2014-02/24/content_31575257.htm
Here are some for en la reto
Esperantaj vortaroj en la reto https://eo.wikipedia.org/wiki/Esperantaj_vortaroj_en_la_reto
Lerni Esperanton en la reto http://www.esperanto.net/veb/lerni.html
La kaŝita katastrofo - Kontakto 2016:2 en la reto http://kontakto.tejo.org/2016/04/la-kasita-katastrofo-kontakto-20162-en.html
Prepositions in Esperanto should be understood quite literally.
en means, that something must be inside something. For instance en la tablo means, that there must be a drawer at bottom surface of the table to hold something or the thing is between the upper and lower surfaces of the tabletop. Being inside implies, that you usually cannot see it.
sur means, that something lays on a surface. For instance sur la tablo means, that the thing is on the table, above the tabletop touching it. Being on implies, that you usually can see it.
While one can argue, that internet is a net with a surface, on which you can have/hang things, for most people the internet is more like a box or a drawer, in which you have things. For this later metaphor speaks the fact, that the content of the internet is not visible right by looking at your device (computer, tablet or a phone) unless you go and search for it. Contrast this to a street, the "content" is there in plain sight.