Buzz Bloom said:
My formal educated ended many decades ago.
As did mine ... you have said what it does not include, but not where your current understanding is at. Did your formal education include tertiary level courses in science? Maybe a degree?
As long as you are unwilling to answer questions with specifics, I don't think anyone can help you. But you did provide a clue:
It did not include anything about orbital dynamics except Newton's Laws. It did not include anything about abiogenesis. I first became interested in abiogenesis in 1968 when I read the English translation of Oparin's The Origin of Life.
Newton's Laws are normally included at the secondary-school level but as part of the earliest physics speciality but often as part of a general science course. Most western countries hold a science education at this level to be part of the mandated public education but not everyone remembers it. Unless you want to say otherwise, I think we have to use an early secondary understanding as a starting point.
So much for formal education, did you manage to get some informal education in physics? I'm trying to work out how best to talk to you.
Oparin advanced the primordial soup model - standard models for abiogenisis today are variations on this, usually focussing on submarine volcanic vents.
You may find the following an accessible overview.
http://www.universetoday.com/41024/abiogenesis/
I still don't get the "flat Earth" concept in this context. I have tried to combine the phrases "flat Earth" and "not usually considered" into a meaningful sentence with respect to the context of my question, and I am unable to do this.
It means only that there are some circumstances where the mass of the Earth may be considered to have changed just as there are circumstances to consider that the Earth is flat (i.e. in gravity experiments conducted in a classroom.) Those circumstances are not important to your question.
But don't worry, I'll endeavour to be clearer in future... on the understanding this may mean I have to be less diplomatic.
The Earth may, in some contexts, be considered to have changed mass ... i.e. increased by infalling matter from space (rocks, cosmic rays etc) and decreased by outgassing and people sending spacecraft away. So we want to know if this is likely to affect our calculations concerning tides and orbital mechanics... how big is this change likely to be?
After planet formation, expect most of the available matter in the orbit to have been deflected away or hoovered up and formed into the earth-Moon system.
We can figure out the average infalling mass rate and 50T/yr seems reasonable ... over 4 billion years this averages out to 200 billion tons. If we pessimistically allow a 100% margin of error here then the mass gain is a number between 0 and 400 billion T ... is that a lot? (rhetorical, see below)
Well the current mass of the Earth is measured at about 5.6 thousand billion billion tons... so the mass increase is about 8 billionths of a percent of it's current mass. This means that the error introduced by assuming the Earth+Moon has always had the mass it does now will only show up in the 12th significant figure. If you have a way to measure something to 12 or more significant figures, then this may be a problem - but it is much more likely that any instrument capable of that accuracy will also pick up variations in the cosmic ray flux and outgassing and tremors from someone breathing nearby ... i.e. background fluctuations are much bigger.
For the kind of "I just want to think about" stuff you are after, you probably don't even need to account for the mass of the moon when working out the Earth's orbit and the moons orbit can be reasonably approximated as a circle with the Earth at the center. This model can be adjusted later jic.
For the same "think about" level, you can treat the Earth as a sphere with a uniform shallow ocean over the entire surface (only very minor bumps to allow for a shoreline). We would treat this as a "back of envelope" or "order of magnitude" approach ... to be treated in more detail if warrented.
You'll notice I didn't worry about the size and mass of the moon in the "infalling mass" calculation - the Moon adds more surface area to catch rocks with, but also blocks some of the Earth's surface from doing the same: the rocks caught by the moon are not caught by the Earth so the calculation is the same. Technically a few rocks could have slipped between the Earth and moon to strike the near-side of either, witness the craters, but they would be easily accounted for in the 100% margin for error.
You can see for yourself if including the mass of the moon makes a big difference to the percentage calculation...
You said
I would like to think about the range of possible tidal patterns at the time of abiogenesis in the context of the possibility those tidal patterns may have influenced abiogenesis.
... so are you interested in the tidal patterns around the abiogenesis time or not?
Lets start you on some accessible resources -
Earth/Moon system misunderstandings:
http://www.talkorigins.org/faqs/moonrec.html
Abiogenisis misunderstandings:
http://www.talkorigins.org/faqs/abioprob/
... these may go into the kind of detail you are after without swamping you.
You are correct to worry about the variation of the recession over time ... I'm hunting an accessible reference for you, meantime see:
http://jkas.kas.org/journals/2012v45n2/v45n2p049_naa.pdf
The estimate in your won link (12 day orbit) could be used to work out the patterns by conservation of angular momentum ... at least as a back-of-envelope approach suitable to just "thinking about" things at an early secondary education level. Hope this helps.
