Caption: A cartoon of Wright, Kant, and Lambert drawn when yours truly had too much time on his hands.

Our three old friends who speculated on the nature of the Milky Way---Thomas Wright (1711--1786), Immanuel Kant (1724--1804), and Johann Heinrich Lambert (1728--1777)---also all speculated that there might be OTHER MILKY WAYS (i.e., other galaxies) besides our own Milky Way (see Astronomer file: immanuel_kant.html).

The tenable alternative hypothesis was that space was infinite emptiness beyond the boundary of the Milky Way.

Of course, one can imagine other alternative hypotheses too, but without empirical or theoretical guidance, one is just wandering in a sea of speculation.

But if there are other galaxies, what are they observationally?

Our three friends speculated that other galaxies could be nebulae (historical usage).

Credit/Permission: © David Jeffery, 2005 / Own work.
Image link: Itself.
Local file: local link: alien_galaxooges.html.
File: Alien images file: alien_galaxooges.html.