Wednesday, June 29, 2011

How fat am I?

Suppose I think of myself as shaped like a four-dimensional spacetime worm. We draw diagrams of such things for students—a wide line moving up the board. It is amusing to note that such diagrams are not at all to scale. In a natural unit system, the speed of light will be taken to be c=1. For instance, one might measure time in seconds and distance in in light-seconds. A light second is 299792458 meters long. An average human earthly lifespan is of the order of magnitude of 109 seconds. My largest spatial dimension is about two meters, i.e., about 10−8 light-seconds. That means that my earthly temporal dimension is of the order of magnitude 1017 times longer than my largest spatial dimension. This means that I thought of as a spacetime worm, I am an exceedingly thin worm. If this worm were rotated, projected and scaled so as to be a meter long and maximally thick, a hydrogen atom would be ten million times thicker than the worm.

Moreover, this worm is quite straight. The main variation in its shape seems to be a cork-screw shape induced by the earth's orbit around the sun. But the diameter of the spiral is about a thousand light-seconds, which is a millionth of its length.

So a scale drawing of me in my earthly career as a space-time worm would have me be 1017 times thinner than I am long, and despite a subtle cork-screw, straight to within about one part per million.

Thursday, June 23, 2011

Progress on AstroObserver for Android

I've been learning OpenGL ES 1.0. Here's what I'm getting as a full-sky star map. It looks a brighter and better on my device than on this laptop, though--different gamma settings, I suppose.

I'm modeling the light flux pretty precisely: in other words, I scale the star by a factor proportional to 2.512^(-mag/2) (the 1/2 is there because the light flux is proportional to the square of the radius of a two-dimensional image).

If anybody wants to try the demo (which just shows a rotating sky at maximum speed), it's here.

Thursday, June 16, 2011

More Android dark adaptation goodies

And here is an Android app, which requires a rooted device, to give better control over screen brightness, allowing almost continuous adjustment to very, very close to zero, at least on my device.  This will be useless to you if you don't have a rooted device.

Tuesday, June 14, 2011

Red keyboard for Android devices

I've been working on a red-themed keyboard based on the Gingerbread keyboard.  Should be nice for night use.  Here is a copy.

The screenshot is in Google Sky Map.

Saturday, June 11, 2011

Night mode for Android devices

While astronomy apps tend to have a built-in nightmode, I was very pleased to come across ChainFire3D for Android which, among other things, has a global night mode that works on all apps. The red is a bit too bright, I think (maybe someone should email the developer about it), but otherwise I think it's great.

It needs a rooted device.

p.s. I'm still working away on AstroObserver. It's going more slowly than I'm used to, partly because I've been sick. I'm basing it on AstroTools, but I'm redoing a lot.