Path: utzoo!utgpu!water!watmath!clyde!att-cb!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!uw-beaver!cornell!rochester!PT.CS.CMU.EDU!K.GP.CS.CMU.EDU!lindsay
From: lindsay@K.GP.CS.CMU.EDU (Donald Lindsay)
Newsgroups: sci.misc
Subject: Re: Plantes & actions (was Re: Omni-Americans)
Keywords: tides
Message-ID: <1246@PT.CS.CMU.EDU>
Date: 29 Mar 88 04:17:59 GMT
References: <3021@gryphon.CTS.COM>
Sender: netnews@PT.CS.CMU.EDU
Organization: Carnegie-Mellon University, CS/RI
Lines: 39

In article <3021@gryphon.CTS.COM> edk@gryphon.CTS.COM (Ed Kaulakis) writes
(in reply to Mark Hopkins):

>BUT the 1/R^2 field of Jupiter influences the path of the Earth; what is
>observable by a critter such as you or me on the surface of said Earth is 
>the somewhat!! weaker 1/R^3 tidal psuedo-force. Does this change your 
>calculations? If so does it change your conclusions? If not why not?

Good point. The tidal forces matter.

Actually, a tidal force is just the differential force that results when
gravitional forces are not quite equal on the near and far sides of
something. So, the tidal force has the same units, and competes on an equal
footing with other forces.

Tidal force (in nano-g's) across the earth, due to:

Venus    0.0		note, Mercury is both smaller and further away
Mars     0.0 
Jupiter  0.0		note, Saturn is both smaller and further away
Moon	 224..225	due to elliptical orbit of moon
Sun	 103		earth's orbit is very near circular

Tidal force (in nano-g's) across 2m (a human put lengthwise? outspread
arms?), due to:

a car    1		assume 1000KG, 3m away.
a hill   75		assume 30x30x15m of rock, 30m away
mountain 75		assume 2x2x1 km of rock, 2km away
earth    630		i.e. the tidal stress from your toes to your nose
			(if flat on back, ~100 nano-g from spine to sternum)

Again, the direct (not tidal) force due the most influential planet:

Jupiter 15 to 33	Changes, at most, 18 nano-g per six months.

Which is about the tidal stress from top to bottom on a Rubik's Cube.
-- 
	Don		lindsay@k.gp.cs.cmu.edu    CMU Computer Science