When a hypervelocity particle enters the top surface of an aerogel collector, it makes a track many times its own size as it slows and stops in the aerogel.

From the top, they look like this:	Viewed from the side, the tracks look like this:
The field of view of the Virtual Microscope is 480 microns wide by 360 microns high, similar to the size of a grain of salt. There are one million microns in a meter (one thousand microns in a millimeter). To get a sense of the scale of the focus movies you will be viewing with the Virtual Microsope look at the images below of a quarter and a human hair as seen under a microscope at increasing magnification. A U.S. quarter is 24 millimeters in diameter This image of the quarter and human hair at 7.5x magnification is 9,090 microns across. This image at 25x magnification, zoomed in on the "ERT" of "LIBERTY" is 2,380 microns across. This image at 120x magnification, zoomed in on the E in "LIBERTY", is 590 microns across. This image shows the 120x magnification image cropped to the same size as the Virtual Microscope focus movies (480x360 microns). * Some images are very large (1,234 KB) and might slow down your computer.

The particles themselves are too small to see. You will be using a Virtual Microscope (VM) to look for the tracks made by the particles rather than the particles themselves. The tracks are just below the surface of the aerogel.

We have prepared a tutorial to help you learn how to identify particle tracks and use the VM. The VM is very easy to use, as you'll see in the next pages.

For the following training tutorial, we have used tracks of extraterrestrial particles that were captured in the ODCE collector on the Russian space station Mir, and tracks of submicron dust particles shot into aerogel at 20 km/sec using a Van Der Graaf dust accelerator in Heidelberg, Germany. It may turn out that the tracks of real interstellar dust will look quite different. They may be deeper or shallower, wider or narrower. We will see once we have the first few examples of real interstellar dust!