They say that because of the distance from us to galactic objects, the light we are seeing is actually thousands or millions of years old. I get that bit. I am having trouble understanding how the light continues to travel long after its source has extinguished. Does this mean if I directed a laser into space, turned it on for a 1 second burst, a 1 second long burst of light would travel for eternity or until it hit something?

Visible light is an electromagnetic wave, consisting of oscillating electric and magnetic fields traveling through space. The frequency of the wave determines its color. Typically we see light as white, a combination of all frequencies. However, rain breaks the light up and we see all the colors as in a rainbow. As to your light and laser question, the answer is yes. The Chinese, in 1000 or so, noted an exploding star, a nova. That light is now gone. All light from stars strikes the earth and is converted into heat. The sun, because of it's size and proximity, is the only one in our galaxy to have measurable heat.

Thanks.

You aren't an ordinary plumber are you?

Has there ever been an experiment that physically proves this happens or is it or based on theory?

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Originally Posted by p0mp3ymatt

Thanks.

You aren't an ordinary plumber are you?

Has there ever been an experiment that physically proves this happens or is it or based on theory?

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BS chemistry, retired construction engineer, handyman, amateur astronomer.

Many past experiments have been done including lasers to the moon.

Amateur astrophotographer here. I spend so much time just staring up at them, my head fills with questions!

Thanks for your help

Quote:

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Originally Posted by p0mp3ymatt

Amateur astrophotographer here. I spend so much time just staring up at them, my head fills with questions!

Thanks for your help

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Aren't the stars fabulous? I was just recently in Ireland 7 miles off a paved road, no streetlights, Milky Way was incredible. We live near Atlanta but have another house in the GA mtns. Great viewing up there. I just have a small 3" refractor. Did you catch the Draconid meteor shower this year? We had a couple of long white streaks.

I find them fascinating! I live on the south coast of England in a dense city so suffer from light pollution quite badly. I have a sodium filter for my camera which helps but observing isn't the best.

Didn't see much of the Draconid shower but the Perseid one in August was pretty good. Our long winter nights are normally cloud-ridden but when its cold and clear, I could sit out there for hours! Off to India for a couple of weeks in the new year, where out in the sticks, the sight is fantastic!

In reality, a laser beam pulsed into space will not keep its original width. Even though it will travel with the speed of light, the width of the beam will continuously increase due to properties of laser light. At some point the width becomes so large that laser light becomes weak and can no longer be detected.

Think of a stone dropped in water: it may already be laying at rest at the bottom for a long time, but water waves at the surface are still moving away as concentric circles until they spread far enough to become shallow and undetectable.