UFO's

[Anomalocaris]

Solar sails require gigawatt driving lasers which are well beyond us, never mind lesser civilisations. Chemical rockets? The Saturn V weighed just about 3,000 tons, to lob 40 tons at the moon.

Here it is again

Nothing you or the cited webpaGe says is both true and makes it impossible for solar sail or checmical rockets to support interstellar travel.   Only such interstellar travel as might be facilitated by these technologies are not how various science fiction books and movies envisions interstellar travel,  and such interstellar travel might not occur over time spans and on a scale that would seem on the surface exciting.

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I think the most probable manner of interstellar travel by civilizations built by organic beings does not involve interstellar movement of organic beings, nor large scale transshipment of either raw material or finished goods, unless the organic beings are extremely long lived.

Instead colonization will consist of comparatively small and slow robots ships that builds intelligent self-replicating machines using local resources upon arrival, and any organic being involved in theconization effort will not make the trip as existent beings, but as stored data. When self replicating machines have adequately prepared the colonies, the organic beings will be replicated from the data.

If you look back over the last few decades, it certainly appears to me that we are approaching the point of being able to completely digitize humans and replicate humans using industrial means far faster than we are approaching anything socially or technologically that would facilitate the sort of interstellar travelseen in the movies.