Astronomy Animations

[caption for #4]: A source (circle) sends a projectile (arrow) to a target (box). Source and target have a relative motion. A bright (5-pointed) and a faint (4-pointed) star are in the background. Above: From the perspective of the source’s frame, the projectile must lead the target (move toward the bright star) so that both projectile and target arrive at the same place at the same time. Below: From the perspective of the target’s frame, the projectile approaches on a path moving toward the faint star. The difference in the angle of the path between the two frames is “aberration”.

For #4, "swf" file type is "flash", for which free browser plug-ins are also available. For example, click here.

(5) 2004/08/25: H. John Wood acquired an excellent 2-hour video of the 19 November 2002 Leonids storm. The image tube was pointed toward the radiant, making most of the trails very short. Matthew Willson has extracted a 6-minute portion near the storm peak so that our web site visitors can get a sense of what this rare spectacle was like. The video is sped up by approximately a factor of three from real time. However, the field of view covers only about 10% of the sky. So the video extract shows only about 1/3 of the real-time meteor rates that an on-site observer might have seen under ideal viewing conditions.

Caution: The file type is "wmv" (for Windows Media Video), and the extract file size is 66 MB. So as a practical matter, broadband internet access is required to download and view this file. And be sure you have the free Windows Media Player or some other software that can play videos of that file type, or can transport the file to a Windows computer. Then click on download video

(6) 2006/03/31 (caption updated 2007/10/01): MPEG animation by Matthew Willson answering the common student question, "What happens if the Sun suddenly ceases to exist?" The traditional interpretation of general relativity says that can't happen because, at worst, the Sun turns to energy, but energy continues to gravitate. But the new physical interpretation of general relativity has no need to dodge the question. It gives the answer in the animation, which opens with the Sun's gravitational potential field represented by a dent in a rubber sheet, and Earth orbiting the Sun. We also see light from a distant star being bent by the Sun's potential field as it travels to Earth.

As Earth revolves, we pan down to view under the rubber sheet and see the Sun itself that caused the dent in the rubber sheet, an analog for the gravitational potential field. Suddenly, the Sun vanishes with a whoosh. Almost instantly, Earth ceases to orbit and takes off on the linear path tangent to its orbit when the Sun vanished, because the speed of propagation of gravitational force is at least 20 billion times faster than the speed of light. In the meantime, a giant gravitational wave is set off in the potential field (the rubber sheet) by the Sun's sudden absence. This wave travels outward at the speed of light. It has no effect on Earth because gravitational waves have no connection to ordinary gravitational force. But once the wave reaches Earth's orbit, the light path of the star starts to unbend until the path is no longer curved and coincides with its straight line path from the star.

So the answer is that all the planets would depart almost instantly in the directions they happened to be headed. Then one by one, the planets would stop reflecting sunlight and become invisible as the last rays (from the Sun before it ceased to exist) reach each planet. The animation separates the gravitational force effects from gravitational potential field effects. The former propagate almost instantly, while the latter propagate at the speed of light. Passing light rays (waves) from other stars are unaffected by gravitational force, but are bent by refraction in the Sun's "curved" gravitational potential field.

(7) Updated 2007/10/30: A video of the history of Mars as one of two twin moons of a gas giant parent planet, and its subsequent alteration by the explosion of its parent ("Planet V") at 65 Mya and by the explosion of its twin moon ("Body C" or "Bellona") at 3.2 Mya. Video shows graphically what is detailed in the 2007 March 15 Meta Research Bulletin issue. Available in full screen (18 MB) or small screen (6 MB) versions. (Both have voiceover and an updated sound track from the original posting. The video now contains a brief reference to the accompanying K/T boundary mass extinction event on Earth.)