27 APR 2015 by ideonexus

## Math Problem: How Long Until the Earth Falls Into the Sun?

Our earth has orbital motion, revolving once around the sun in about 365 days. Suppose that this orbital motion suddenly stopped completely, but everything else remained the same. How long would it take for the earth to plunge along a straight line into the sun? [...] Kepler's law applies to planetary orbits, whether they be of circular, or elliptical shape. It says that T22/T12 = R23/R13, where T is the period of an orbit and R is its semi-major axis. The semi-major axis is the average...

30 JAN 2015 by ideonexus

## Nemesis

But why should comets become more likely to hit us every million years? Here we launch ourselves into deep speculation. It has been suggested that the sun has a sister star, and the two orbit each other with a periodicity of about 26 million years. This hypothetical binary partner, which has never been seen but which has nevertheless been given the dramatic name Nemesis, passes, once per orbital rotation, through the so-called Oort Cloud, the belt of perhaps a trillion comets which orbits the...
Folksonomies: astronomy nemesis
Folksonomies: astronomy nemesis
1  1  notes

24 JAN 2015 by ideonexus

## The Comet Loss Cone

To understand why comet showers occur, we go back to the Oort Cloud. The theory of comet showers was worked out by Jack Hills, an American physicist now at Los Alamos. He realized that the movements of the comets in the Oort Cloud are not entirely random. Comets in the cloud are generally moving in random directions, but if a comet happens to be moving in an orbit almost exactly toward the Sun, it will not survive for long. A comet in an orbit coming close to the Sun may get boiled away and d...
Folksonomies: astronomy astrophysics
Folksonomies: astronomy astrophysics

13 MAR 2014 by ideonexus

## Perceiving Infinite Suns in the Night Sky

Elpino. Why then do we not see the other bright bodies which are earths circling around the bright bodies which are suns? For beyond these we can detect no motion whatever; and why do all other mundane bodies (except those known as comets) appear always in the same order and at the same distance? Philotheo. The reason is that we discern only the largest suns, immense bodies. But we do not discern the earths because, being much smaller, they are invisible to us. Similarly it is not impossible...

Bruno's observations and reasoning.

22 JUN 2012 by ideonexus

## Science and Poetry are Like Binary Stars

I would liken science and poetry in their natural independence to those binary stars, often different in colour, which Herschel's telescope discovered to revolve round each other. 'There is one light of the sun,' says St. Paul, 'and another of the moon, and another of the stars: star differeth from star in glory.' It is so here. That star or sun, for it is both, with its cold, clear, white light, is SCIENCE: that other, with its gorgeous and ever-shifting hues and magnificent blaze, is POETRY...
Folksonomies: science metaphor poetry
Folksonomies: science metaphor poetry

They exchange ideas and inspire one another.

07 MAY 2012 by ideonexus

## Losing the Human Perspective in the Vastness of the Cosmos

When I pause and reflect on our expanding universe, with its galaxies hurtling away from one another, embedded within the ever-stretching, four-dimensional fabric of space and time, sometimes I forget that uncounted people walk this Earth without food or shelter, and that children are disproportionately represented among them. When I pore over the data that establish the mysterious presence of dark matter and dark energy throughout the universe, sometimes I forget that every day—every twe...
Folksonomies: humanity universe scale
Folksonomies: humanity universe scale

Tyson talks about how easy it is to forget human dilemmas when we consider the immense size of our Universe.

16 FEB 2012 by ideonexus

## Copernicus on Gravity

I myself consider that gravity is merely a certain natural inclination with which parts are imbued by the architect of all things for gathering themselves together into a unity and completeness by assembling into the form of a globe. It is easy to believe that the Sun, Moon and other luminaries among the wandering stars have this tendency also, so that by its agency they retain the rounded shape in which they reveal themselves, but nevertheless go round their orbits in various ways. If then t...

He correctly surmises that the force pulls heavenly objects into spheres.

11 JAN 2012 by ideonexus

## Newton's Discovery of Gravity as an Example of Induction ...

All the knowledge we possess of external objects is founded upon experience, which furnishes facts; and the comparison of these facts establishes relations, from which induction, the intuitive belief that like causes will produce like effects, leads to general laws. Thus, experience teaches that bodies fall at the surface of the earth with an accelerated velocity, and with a force proportional to their masses. By comparison, Newton proved that the force which occasions the fall of bodies at t...

He extended the force pulling everything down to the Earth out to the Moon, then to the Sun, and then the planets to see how our solar system really works.

02 JAN 2012 by ideonexus

## John Keats Recalls a Game of Orbiting Children

The young John Keats remembered an organised game at his school in Enfield, in which all the boys whirled round the playground in a huge choreographed dance, trying to imitate the entire solar system, including all the known moons (to which Herschel had by then added considerably). Unlike Newton’s perfect brassy clockwork mechanism, this schoolboy universe-complete with straying comets — was a gloriously chaotic ‘human orrery’. Keats did not recall the exact details, but one may imagi...
Folksonomies: games astronomy order chaos
Folksonomies: games astronomy order chaos
1  notes

Where the children run around mimicking the orbits of the planets and comets, making the solar system seem more chaotic than the classical perspectives.