| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

Even; Cherry Jam; Lebanese Writer Amin Maalouf; Learning From Trump; Chinese Writer Hu Fayun; C++ - it's the language of the future; And; Apricot Jam; Also; Excellent Article on USA Politics; Oh Metafilter; Prejudice Against The Rurals; Also, Zizek; Trump; Why Trump Won; Doxygen + Latex on CentOS 6; SMASH - Solve 5 Biggest Problems in Physics; Good article on racism, brexit, and social divides; Grandaddy are back!; Consciousness From Max Entropy; Democrats; Harvard Will Fix Black Poverty; Modelling Bicycle Wheels; Amusing Polling Outlier; If Labour keeps telling working class people...; Populism and Choice; Books on Defeat; Enrique Ferrari - Argentine Author; Transcript of German Scientists on Learning of Hiroshima; Calvert Journal; Owen Jones on Twitter; Possible Japanese Authors; Complex American Literature; Chutney v5; Weird Componentized Virus; Interesting Argentinian Author - Antonio Di Benedetto; Useful Thread on MetaPhysics; RAND on fighting online anarchy (2001); NSA Hacked; Very Good LRB Article on Brexit; Nussbaum on Anger; Tasting; Apple + Kiwi Jam; Hit Me; Sudoku - CSP + Chaos; Recycling Electronics In Santiago; Vector Displays in OpenGL; And Anti-Aliased; OpenGL - Render via Intermediate Texture; And Garmin Connect; Using Garmin Forerunner 230 With Linux; (Beating Dead Horse) StackOverflow; Current State of Justice in China; Axiom of Determinacy; Ewww; Fee Chaos Book; Course on Differential Geometry; Okay, but...; Sparse Matrices, Deep Learning; Sounds Bad; Applebaum Rape; Tomato Chutney v4; Have to add...; Culturally Liberal and Nothing More; Weird Finite / Infinite Result; Your diamond is a beaten up mess; Maths Books; Good Bike Route from Providencia / Las Condes to Panul; Iain Pears (Author of Complex Plots); Plum Jam; Excellent; More Recently; For a moment I forgot StackOverflow sucked; A Few Weeks On...; Chilean Book Recommendations; How To Write Shared Libraries; Jenny Erpenbeck (Author); Dijkstra, Coins, Tables; Python libraries error on OpenSuse; Deserving Trump; And Smugness; McCloskey Economics Trilogy; cmocka - Mocks for C; Concept Creep (Americans); Futhark - OpenCL Language; Moved / Gone; Fan and USB issues; Burgers in Santiago; The Origin of Icosahedral Symmetry in Viruses; autoenum on PyPI; Jars Explains; Tomato Chutney v3; REST; US Elections and Gender: 24 Point Swing; PPPoE on OpenSuse Leap 42.1; SuperMicro X10SDV-TLN4F/F with Opensuse Leap 42.1; Big Data AI Could Be Very Bad Indeed....; Cornering; Postcapitalism (Paul Mason); Black Science Fiction; Git is not a CDN

© 2006-2015 Andrew Cooke (site) / post authors (content).

Earth Explosion

From: "andrew cooke" <andrew@...>

Date: Thu, 26 Jan 2006 12:16:33 -0300 (CLST)

My take on this question - http://ask.metafilter.com/mefi/31481

In very simple terms, only the mass "inside where you are" generates
gravity.  If you go deep into the earth, gravity would change just as you
would expect for a planet of the size that corresponded to having a
surface where you were (assuming the earth were solid etc).

So going down 1000 miles you'd feel a gravity similar to an "earth" that
had a radius 1000 miles smaller.

Now it seems to me that what the question is asking is - what happens if
we move some of the earth's mass to outside the moon, and everything else
stays the same?

If so, then the answer is probably obvious - the moon would behave as it
would if the earth had a smaller mass (the mass left in the new, smaller
planet).

Exactly what would this behaviour be?

First of all, it would continue to orbit the sun.

Second, relative to the earth, I think (and I'm guesing - I'd need to do
the maths, or at least think harder, to be sure, and I'm in a hurry) that
the orbital period would increase (more time between full moons) and the
average earth-moon distance would increase.

Exactly how the earth-moon distance would increase depends on the way the
weight is lost.  If it were lost rapidly then the moon would end up in an
eliptical orbit, with the closest point being the same as now.  If it were
lost gradually, I suspect you'd keep a circular orbit.

An intereesting consequence of the changing period is that the moon would
not necessarily continue to spin so that we always see the same side of
the moon.  Again, this probably depends on the rate of loss of mass.  If
mass were lost very slowly from the earth tidal interactions might keep
the moon "facing us".

However, something that makes me think I may be wrong above.  I'd also
expect the earth's orbit around the sun to change, with years becoming
longer and the earth-sun distance increasing.  That's from the same
arguments (potential energy decreases, kinetic stays the same) as I used
to think about the moon/earth relationship.

Now that sounds OK.  But I *also* thought that various (? at least one?)
asteroid belts coresponded to the positions of old, "broken" planets. 
This seems to be inconsistent with the argument above.

So something seems incorrect.

Andrew

Comment on this post