Space sails are super low thrust though, even lower than my VASIMIR example - so will take even longer to reach the desired speed - though they have the advantage of not having to carry the complex and heavy engine I ignored that in the rough estimates anyway.

So by the time they're theoretically close to the desired speed they'll be on the other side of the galaxy at least, even if it took millions of years to get there at the much slower average speed.

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tatjam an hour ago | parent [-]

You can't use a solar sail for this, but if you use lasers, you can get a few newtons / GW of incident laser power. Sci-fi stuff but if you can make a very very light reflector that can somehow be cooled (microscopic IR dipoles come to mind), and a very very focused and powerful laser, you can go a long way. Not sure what the purpose of moving a thin metalized foil at a fraction of lightspeed would be, though :)

	▲	kimixa an hour ago \| parent \| next [-]
		Yeah, many of the theoretical solar sail ideas fall down on what I consider a useful "probe" is, and what it can mass. As mentioned in my other comment, if you define the "probe" to be "a single particle" we /already/ do this all the time in particle accelerators. But it's clearly not a useful "probe" I believe the original thought experiment implied. A few hundred grams of super thin solar sail material is still very much in the "Not A Probe" definition in my mind. Plus even the best laser dispersion quickly gets significant at the distances required to give the sail the time to accelerate at such a low thrust.
	▲	floxy an hour ago \| parent \| prev [-]
		Roundtrip Interstellar Travel Using Laser-Pushed Lightsails https://ia800108.us.archive.org/view_archive.php?archive=/24...