Why do city lights seem to twinkle?

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The flickering or twinkling effect of lights when observed from a distance is caused by anomalous refraction as light passes through air, schlieren, where temperatures and densities vary. The technical term for this phenomenon is called “scintillation,” and it refers to the rapid changes in the position and color of a distant object.

If the light source lies outside the atmosphere of the Earth, such as the stars and the planet, the term for the flickering effect is called “atmospheric scintillation.” When the source of illumination is Earth-bound, the phenomenon is referred to as “terrestrial scintillation.”

Wind movements that are carrying schlieren flowing across an observer’s line of sight causes the light fluctuations that are characteristic of the scintillation phenomena. Studies also show that relative humidity affects the intensity of terrestrial scintillation. As humidity increases, so does the effect of terrestrial scintillation.

When it comes to stars, the light emanating from these heavenly bodies are disturbed by atmospheric turbulence that acts as refractive prisms and lenses, thereby causing the flickering or “twinkling” effect. Since the source of light is so tiny, the point of light falls upon one rod of the retina at a time. Stars will appear to twinkle as the point of light moves from one rod to another.

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A city is constantly heating air (from sewers, buildings etc) which is then rising up. As these streams of warmer air are rather turbulent, they change paths all the time. Hot air has lower density and thus lower refractive index than colder air, so a pocket of warmer air will slightly distort the path light takes from its source to your eye.

If you were rather far away from the city lights, it's very well possible that the flickering comes from turbulent warmer regions of air between the lights and you.

August 19, 2010 , , Leave a comment

Why do City lights Twinkle?

Twinkling city lights especially in Paris is a great and romantic view, kids love it as much as grown-ups do. But, why do city lights twinkle? Well I don’t really want to disappoint anyone of you but city lights doesn’t really twinkle at all, same as the stars in the sky. If you get near to these lights, you will see that they are actually constant.

City lights only twinkle from a distance because the light passes through the earth’s atmosphere. The farther the city lights are the more you will see twinkling effect or scintillation, as it passes through different layers of the earth’s atmosphere. Then, that creates different angles of the lights. The twinkling city lights are the result of all those accumulated refractions that changes the size and position of the lights. The city lights are distorted depending on the temperature, densities and moisture substance on that area. Some city lights don’t twinkle in places that have very low atmospheric disturbances.

Other theories claim that our eyesight also contributes to the scintillation of lights, because the light will eventually reach the pupils of our eyes and go through the corneas. At the back of our eyes, the retinas are stirred to create electrical signals that pass through along our optic nerves to our brain, and then we see the light with its twinkling effect. Well, this is just another principle about lights but regardless if it’s our vision or the earth’s atmosphere that causes lights to twinkle, it’s still beautiful to perceive the city lights the way we see it.

Let us not be a big frustration for kids, don’t tell them that the city lights especially the stars don’t twinkle at all. At one point, we all want the kids to believe that twinkling lights are like magic. Only tell the truth to them if they specifically asked for it.

Author: maureen

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Why do lights look like they are flickering?

Flickering or blinking lights are usually caused by one of the following: Problem with the bulb (not in tight enough, lightbulbs are incompatible with your dimmers) Loose light plug. Faulty switch or dimmer.

Why do LED street lights flicker?

Check your lamps, wires, ballast/driver, and tombstones for bad connections or loose wires. A common reason for flickering T8 LEDs is a loose connection within the circuit. Addressing a power-connection issue or loose wire to the driver circuit will often easily resolve the flickering or no-power issue.