Watsisname wrote:

Qr Bbpost This should definitely be close enough to get really interesting direct data

Yes.  I felt a need to copy in something from Sunshine here.

I looked for Perseids between 22:20 and 23:10 last night as stars began to appear.  The sky was still pretty bright, but Perseids can also be bright.  Still, nothing.  Checking my cameras this morning, there was one a few minutes after I went in.  Then roughly 4-5 fairly weak ones per hour and one f...

I can't explain the blue cloud, but awesome picture, pzampella!

Movie trailer for upcoming Norwegian animation film.  I though the Russian Babushka design for the rocket was pretty good.

Watsisname wrote:

Qr Bbpost If a ship is in a circular orbit at exactly 1.5 times the planet's radius (this is 3185km altitude for Earth), then its clocks will tick at exactly the same rate as clocks on the planet surface.

For a planet and moon system with equal density, isn't that coincidentally also the Roche limit?

Interesting.  So, one could say that the Earth's bulge around the equator is a relativistic effect?

Thanks.  I suspected it was more complicated, but not that the altitude would more than cancel it, since 10km is not much at the scale of the earth.  There's another thing to consider: latitude.  It's perhaps the most important variable?

I calculated that I've spent just over a week airborne over the past 12 months covering a distance of about half a light second.  Does this also mean that I've travelled half a second further into the future than if I'd remained at home, or is the maths more complicated?

If no other processes at play in the universe prevent it, iron ought to become the most abundant element, since fission releases energy for lighter elements and fusion consumes energy for heavier elements.

A problem with Ptolemy's epicycles was that they lacked a good way to explain the speed changes of planets.  Then Kepler discovered that the orbits can be modelled as ellipses (of which the circle is a special case), and he could also describe the speed in his second law, which was a really beautifu...

Fourier's discovery has had a great impact.  All audio and video compression (and hence almost 80% of internet traffic) relies on the principle of transforming the signal to be compressed to the frequency domain, reduce the data in that domain, then transfer it back.  Just like fewer epicycles requi...

midtskogen wrote:

Epicycles are also "right" if you keep adding enough of them

I came across this nice illustration how any orbit can be described by epicycles:

I think the misconception is that the ice crystals that form the halo are not fixed. Each combination of observer and light source has its own light deflecting crystals, whilst the light angles remain fixed. Les Cowley tells me that good crystals need to be at least 10 to 20 microns, and noctilucent...

I got data from several cameras, so the path can be calculated: a.jpg And it's altitude: b.jpg Finally it's orbit: c.jpg Summary : [table][tr][td]Start height: 115,5 km End height: 83.3 km Start position: 60.365N 11.212E End position: 60.067N 10.626E Direction: 224.6° Incidence: 34.9° Entry speed: 5...

Not only noctilucent clouds last night, but also an exploding meteor bright enough to create a halo.  Could it be the ice crystals of the nocilucent clouds?  Or just in ordinary high altitude haze.

EDIT: This was a Perseid.