Recent content by jscroft

Besides... getting spewed out of a quasar at 0.999c as a fog of incandescent subatomic particles is probably more commitment than I think the frequent flyer miles are worth.

Before the invention of the calculus, there existed no mathematical tools to deal with phenomena in a constant state of change. The calculus made it possible for the very first time to build non-empirical mathematical models of non-trivial physical phenomena. Calculus was "new math." Before the...

Your formula should be V = pi * (0.011 m)^2 * 11 m = 4.18e-3 m^3. A liter is 1e-3 m^3, so your answer is 4.18 liters. The lesson here is to keep close track of your units, by actually WRITING THEM DOWN.

Seems to me that the most important supply you could possibly lay in would be lots and lots of MONEY. Won't be much use post-impact, but I can pretty much guarantee you George Soros' asteroid shelter is better than yours.

I note that there appears to be a surplus of unused Hope & Change lying around. Maybe your characters will find something useful to do with it.

Yes! For goodness' sake, don't opt in favor of brevity or precision when political correctness is at stake!

Thanks for the references. I note that neither addresses the question of the electrically active coronal medium. If both the primary and the exoplanet have significant magnetic fields—as do our own Sun and gas giants—then it seems that the interaction of these fields within and across the...

Must a "Hot Jupiter" be relatively young? A large proportion of exoplanets so far discovered are "hot Jupiters," large gas giants orbiting very close (< 0.1 AU) to their primaries. It seems to me that a gas giant orbiting at such a close distance ought to experience significant friction as...

IF the Earth were a perfect sphere, then g would have the same value at any point on its surface. In fact, though, the Earth is an oblate spheroid. In practical terms, this means there is less mass between your feet and the center of the Earth when you stand at the North Pole than when you stand...

Well, what's a simulation? When I run a simulation, I evolve a state vector from an initial condition through a progression of states according to a transformation expressed by a system of coupled differential equations. Simulations--particularly non-linear ones--are subject to an accumulation...

I made the explicit point because it appeared in the original post that the author had painted himself into a corner: by taking the (perfectly valid) step of combining the two equations of motion, he arrived at a solution for RELATIVE positions (one body with respect to another) when what he...

Sure it is... and when you decompose the relative position vector into its constituents and substitute into the equations of motion given above, you'll find that the (M+m) factor remains. But you still have to integrate the coupled system to evolve the positions of both bodies in an inertial frame.

Both original equations of motion reference a relative position vector that is a function of the absolute position vector of BOTH bodies. In other words, you have a coupled system of differential equations, which must be integrated simultaneously to generate a solution for each body.