General · Language · Problem

Getting and staying round – why are planets and moons spherical?

Imagine asking, à la a Jay Leno “Jaywalking” segment, some random people this question: “Why is our Moon round?” Or, “Why are planets always round (including the Earth) – like spheres – and not like a cube or a boulder or potato or other irregular solid?” Science communicator Ethan Siegel answered this question in a… Continue reading Getting and staying round – why are planets and moons spherical?

General · Language · Media

Acceleration causes gravity, gravity causes acceleration

As I’ve written elsewhere,  I sometimes think that generations of scientists raised in space might help advance physics, having lived in a world dominated by inertia (rather than friction). Especially in regard to a visceral understanding of microgravity. Like characters in the TV series The Expanse. So, this Space.com article (June 18, 2018) “Relativity: The… Continue reading Acceleration causes gravity, gravity causes acceleration

General · Site

Surfing space-time — gravitational waves

Asymmetric gravitational interactions between two bodies produce gravitational waves.1 Such perturbations in space-time are so small that only the most massive interactions have been detected by LIGO, which uses laser interferometry and is “the largest and most ambitious project ever funded by the NSF.” While there was speculation about gravitational waves prior to Einstein’s theory… Continue reading Surfing space-time — gravitational waves

General · Language

GR: Chicken or egg redux

One of the major sources of confusion I’ve encountered in reading about modern physics is the discussion of gravity. No surprise, eh. Classical mechanics includes both Newtonian and relativistic mechanics. In Newtonian physics, gravity is an attractive force, which acts at a distance between all objects; and can be represented as a universal gravitational field.… Continue reading GR: Chicken or egg redux