September 22nd, 2009

Conditions in the geological past

 I have a group of mediaeval humans travelling back in time to the Permian, Cretaceous and Miocene. They spend several weeks in each, and I want them to remain healthy. Food plants would not be a problem for them in the latter two but I’m at a loss to know what to give them to eat during the Permian, except for ferns; and I could stretch a point to have pine trees, for the seeds, and cycads, but they would clear the area out pretty soon.  

Seaweeds, presumably, were much the same as now, and given that several phyla of plants have become extinct since then I could always assume that some of those are edible, but is there anything that springs to mind?  

Could they have risked eating fungi? (One of them is French.)  ETA: I should add that the rest of them are English.

What might the horses have eaten? I could include cupressus and ginkoes if they wouldn’t poison them.

Also the moon would appear to be considerably bigger during the Permian and Cretaceous. The figure I have is a steady retreat of 4cm a year, but my brain simply won’t do the maths to get an apparent size for the moon. Can anyone help? 

Searched: relevant tags here, the entire astronomy, geology and botany sections at my local library
BBC series ‘Walking with Monsters/Dinosaurs/Beasts’ and spin-off publications
Hugh Johnson: International Encyclopaedia of Trees
Stephen J Gould (ed) The Book of Life
Douglas Dixon: The Complete Book of Dinosaurs
Viking Atlas of Evolution
A useful thread at fanficrants

Various combinations of: cycads edibility evolution ferns horses palaeobotany (BE and AE spelling) pines pinus 
“size of moon” + geological period

Any help would be much appreciated!

Emergence of the idea that the starlight we see is years old

When did astronomers first formulate the theory that, because of the distance it has to travel, the starlight we see is years old? (And therefore that a star that we can see "now" could have died years ago without our knowing?)

Wiki'd: "speed of light", "lightyear", "parallax"

Found out:
- people have been trying to measure the speed of light since the 1600s, and succeeding to some degree (Rømer and Huygens, 26% off the present value, ~1676) - but the references are all to bodies within the solar system (Jupiter and its moons; the Sun)
- people have been trying to measure the distance to stars since the 1700s, and succeeding since the 1800s (Bessel, 1838)

Should I just assume that, given this data, any intelligent astronomer from the 1700s onward would have just automatically put together these two ideas and said "hey, we know that light travels at a finite speed and we're trying to calculate how far away the stars are; obviously the light we're seeing from the stars is delayed, in some cases by years"? Or was there any one guy that this idea officially originates from?

(edited to add: setting is sci-fi future--specifically, it's a throwaway line for Mr. Spock)

(edited again to add: found a good lead; a 1905 article from the Urbana Daily Courier explaining the concept to the general public here.)