SFRPG

The forum for Science Fiction Role Playing Game inspiration and information! So Say We All!
It is currently Mon Jun 25, 2018 3:43 am

All times are UTC




Post new topic  Reply to topic  [ 16 posts ]  Go to page Previous 1 2
Author Message
PostPosted: Sun Apr 09, 2017 4:54 am 
Offline

Joined: Sat Sep 01, 2012 2:44 pm
Posts: 186
Location: Colorado
Sorry to take things off topic, what are your thoughts on Fate? What style of game is it best suited to?


Top
   
PostPosted: Sun Apr 09, 2017 3:06 pm 
Offline

Joined: Tue Aug 12, 2008 1:16 pm
Posts: 227
Agemegos wrote:
On the other hand, I think my players will strain to believe in a Mars that is not colder than Earth: perhaps the icecaps are small because there is little water? Also, I wonder whether it would reassure them to acknowledge the fact that Mars really has enormous differences of relief, and the tallest mountains (Olympus Mons and the Tharsis volcanoes) in the solar system.

Percival Lowell devoted quite a few pages of Mars as the Abode of Life (1908) to the question of surface temperatures. His argument is three-fold. First, he asserts that Mars' visible albedo (0.27) is lower than Earth's (not known at the time; he estimated 0.75). This phenomenon would extend beyond the visible spectrum, so his final figures for incident energy retained are 0.41 for Earth and 0.60 for Mars.

His second point (which he treats as distinct from the first) is that the Earth is 50% cloud-covered on any given day, whereas Mars is 99% cloud-free. Thus, he says, more of the incident radiation reaches the surface of Mars. From these, he calculates that the average surface temperature on Mars is 48 degrees F, versus 60 degrees F for Earth.

Lowell's third point rests on the length of the Martian year. He suggests that, since the Martian year is twice as long, the extremes of temperatures brought on by the seasons would be even greater than on Earth. Summer temperatures would rise into the 80's (F) and stay there for periods longer than the growing season on Earth. Winter temperatures would be correspondingly harsh, but he imagines that most life would go dormant and ride out the long winter in hibernation.

He then gives a long discussion of mountain biogeography, and infers that a high, flat plateau would be much warmer than an isolated mountain peak of the same altitude. From this he concludes that Mars' flat surface would be much more hospitable than mountain peaks on Earth that exhibit similar air pressures, and so the lack of life on those mountain peaks should not be taken as indicative.

As far as terrain relief is concerned, the dominant view of mountain formation at the time was that they were the result of the planet shrinking as it cooled with age. It's possible that Mars was initially not much larger than its present size, and so did not experience much shrinking. On the other hand, if there were shrinking and mountain-building, the lower gravity should result in proportionally higher, steeper mountains. You can have it either way.


Top
   
PostPosted: Sun Apr 09, 2017 11:09 pm 
Offline
User avatar

Joined: Sun Jul 06, 2008 1:04 pm
Posts: 1057
Location: the Retirement Coast, NSW, Australia
He didn't mention a possible stronger greenhouse effect? My 1890 copy of Peck's Handbook and Atlas of Astronomy mentions the "heat-retaining power" of an atmosphere rich in "watery vapour", and Peck was writing after Arrhenius had published the effect of varying the level of carbon dioxide (1896, IIRC).

_________________
— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.


Top
   
PostPosted: Mon Apr 10, 2017 3:50 am 
Offline

Joined: Tue Aug 12, 2008 1:16 pm
Posts: 227
I don't recall Lowell mentioning it in Mars as the Abode of Life, but:

"Nevertheless, every evidence points to a thin air upon Mars: a priori reasoning, indirect deduction and direct sight. Now, from a thinness of atmosphere it would follow, other things equal, that the climate was cold. About this there has been much question, but less of answering reply. From the distance of the planet from the sun it is certain less heat is received by it than falls upon the earth in something like the ratio of one to two. But that the amount effective is as the amount received is far from sure. The available heat is much affected by the manner of its reception. A blanket of air acts like the glass of a conservatory, letting the light rays in, but hindering the heat rays out. The light rays falling on the ground or the air are transformed into heat rays that, finding the return journey less easy, are consequently trapped. All substances are thus calorifiers, but water vapor is many times more potent than ordinary air to heat-ensnaring. A humid air has a hothouse tang to it most perceptible. Now, what the relative percentage of water vapor in the Martian atmosphere may be we do not know."

This is from his Mars and Its Canals (1906). I wonder if something didn't call this part of his argument into question, which is why he shaded things differently and went into more detail two years later.


Top
   
PostPosted: Mon Apr 10, 2017 4:07 am 
Offline
User avatar

Joined: Sun Jul 06, 2008 1:04 pm
Posts: 1057
Location: the Retirement Coast, NSW, Australia
Nice explanation of the "conservatory effect"!

Perhaps he reckoned that with irrigated lowlands where other had seen oceans, a humid atmosphere seemed less than likely. Do we know whether he failed to observe to clouds that others had reported?

It is interesting, and a bit disappointing, that he didn't pick up on the heat-retaining power of carbon dioxide. The science was already established in his time.

_________________
— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.


Top
   
PostPosted: Mon Apr 10, 2017 1:41 pm 
Offline

Joined: Tue Aug 12, 2008 1:16 pm
Posts: 227
He saw clouds, but only as a vague fuzziness near the poles in spring. That's where the "99% cloud-free" figure comes from. I'm guessing dust storms (if any) were interpreted as some other kind of change.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 16 posts ]  Go to page Previous 1 2

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Limited