Where are all those UFOs coming from?

Radar tracks. A radar operator reports an unidentified object which then flies away at incredible speed.

Two unidentified flying objects, bearing an uncanny resemblance to the planets Jupiter (left) and Venus (right) in near conjunction, were observed hovering in the southern sky for over an hour before slowly moving off toward the horizon behind the trees.

This one is easy. The military has had a technology called digital radio frequency memory, or DRFM, for at least twenty years. A radar jamming device locks on to the radar signal and transmits a fake one. Typically the fake one shows the target flying away at extremely high speed. The purpose of this is to cause the tracking computer to lock on to the stronger fast-moving fake target. The jammer then stops transmitting, causing the radar to lose track of the target. Or the jammer could be programmed to create many false targets. Very useful for the military.^[1]

Credible reports from military pilots. The New York Times published a story about a flying object last week that got a lot of attention. According to the story, military pilots got a “strange” radio message from a nearby ship asking whether they were carrying live missiles. They were then directed to a point where there was an underwater object, obviously a submarine, and an object that took off at speeds estimated to be one mile per second, or 3600 mph.

These details tell us what really happened: the military contacted the pilots beforehand to make sure they were only carrying dummy missiles. That tells us it was actually a test by the military to see whether the fighters could track them, and how they would react. The officials conducting the test needed confirmation that the pilots were not carrying any live missiles because they didn't want them to accidentally shoot it down. As for 3600 mph, see above.

Lights in the sky. Every day as I drive home from work I see disk-shaped objects with bright lights hovering in the air. You see, my route takes me past the local airport. Planes coming in to land with their landing lights on appear to be hovering when observed head-on, and they look very un-airplane-like indeed.

There would be no reason for an extraterrestrial to have visible lights. In space, headlights would be useless. On our Earth airplanes, those lights are there to prevent collisions. If they're flashing or blinking, it's even stronger evidence that it's an ordinary plane, helicopter, or possibly a drone.

Then there's Venus, which can be amazingly bright. If the light is hanging in the sky, and it's any time near sunset, it's almost certainly Venus.

Unidentified pieces of metal. Another report says investigators found strange bits of metal that they're unable to identify. These sightings are very common, and the objects usually resemble ball bearings, springs, rodlike objects with strange helical grooves on them, or similar items.

A strange washer-shaped metal object, possibly part of an alien space ship. They don't make flying saucers like they used to. Nowadays pieces often fall off.

These days there are lots of exotic metal alloys and metal-ceramic composites that would be unfamiliar to the average person. Nevertheless, there are no metals whose composition cannot be identified by Earth technology. Our most powerful technology, called X-ray fluorescence, easily tells us what elements are in any object. The object is exposed to X-rays, and the elements fluoresce by giving off lower-energy X-rays that unambiguously tell us the composition of the object.

If the object is a plastic or other carbon-based material, we can identify its chemical structure by a variety of means, such as mass spectrometry. People have used these techniques to identify carbon-containing molecules in meteorites. Some of these molecules are extremely big and complex. They typically resemble coal that has been chewed up by exposure to radiation in space.