Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Wavering Lights
Name: Eran H.
Status: N/A
Age: 40s
Location: N/A
Country: N/A
Date: Thursday, April 25, 2002

Why distant lights (for example, when looking at a near-by town 10 km distance at night)seem to be blinking rather than stable?

This blinking, which is also seen when you look at stars at night, is caused by the convection of the atmosphere. The varying density changes the index of refraction slightly which alters the path of the light beam that strikes your eye. This is one of the main reasons why telescopes are located on high mountains -- to reduce the air pressure and reduce these fluctuations.

Vince Calder

Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory