Sneaky Snake wants to know. (I am sure he does).
the moon is bright because it reflexs the light from the sun.
The sensor detect long-wave IR which is heat. These things are generally set up to detect quick changes in heat for burglar alarms. The heat source can be anything that gives off heat: mammal, soldering iron, light bulb, You can make a system using a PIR to detect things that are a different temperature than the environment. Use a differentiator so you only see rapid changes in temperature (person walking in), but don't trigger off of slow temperature changes. If your dog walks in, it will be detected unless you set some sort of threshold. I've seen them go off due to moths flying close by to the sensor. Since the sensor was aiming at a cold ceiling, when the moth flew in front of the sensor it would trip the alarm. The moth body was at air temperature which was 10 to 15° warmer than the ceiling. There are other heat sensors out there, but the PIR sensors for alarm systems are really inexpensive and easy to work with.
Actually, lack of sidewalks actually makes cycling safer (as long as cyclists are obeying the local traffic law). Sidewalks are deceptive, in that they tend to make users less visible to motorized traffic. Try contacting your local department of transportation and making a request. Try getting together with other residents to make the request more effective.
Because the sun's rays reflect off of its surface. And since it is relatively close to us, its surface is made of relatively highly reflective material, and there is nothing brighter around it in the night's sky, it appears very bright.
