What I mean is this. Suppose that I am 20km far from the moon. I can see soil details, craters, etc. Then I move to 100km away from the moon. I look at the moon again and now I am unable to see the same level of details as before. Why?
Then comes the real question. We look at distant stars and planets using telescopes. I know that the current telescopes are not about enlarging pictures but gathering photons. But suppose we had at our disposal a telescope with infinite enlargement functionality. Would we be able to choose a planet, distant as hell and enlarge it to the point we could see its surface details or is detail lost forever as the light travels?
If it is lost, how it is lost?
# fantastic answers! THANKS!
In: Physics
Interesting question. I’m not an expert here but light fascinates me. I think you need to look at this from a few different angles:
1. The further away two objects are, the more stuff between the two objects to scatter light, which obscures photons (detail) from reaching its destination. This can be dust and gas in space, an atmosphere, and even the lenses in the camera and your eye. Different elements also scatter light differently, which you can think of how Mars has a more reddish atmosphere and Earth has a more blueish atmosphere. This also creates the twinkle of the stars at night, and is a huge problem for telescopes on Earth.
2. The further away you are, the less photona of light reach you. Imagine a candle on a mountaintop. This candle, at each moment, is radiating a finite amount of light in all directions. Lets say its a billion photons per picosecond. If you are at the top of the mountain, you could enclose the candle with your hands and absorb all the photons. The further away you are, at the bottom of a mpuntain, you are only able to “catch” a smaller fraction of the total amount of photons emitted. Think of this as information loss–light is information. Now, this part gives me some chills to think about. Since planets themselves are not light sources, what you are seeing is how they reflect the light from their nearby star. So an observer on another mountaintop would have to be able to detect the light from the candle, bouncing off your hand at the bottom of the mountain, and back up to their eyeball. The amount of photons that make this round trip is absolutely insignificant compared yo the original light source.
3. The quality of the optics and the resolution of the sensor. Light bends whenever it travels through something. The more precise the optics, the more light passes through without distortion. The higher quality of the optics, the better it can be focused. The more perfectly the light is focused, the more detail can be discerned. Play with a camera and you can experience these first hand.
A combination of these and other factors, such as red shifting all contribute to providing a quality photo. The longer you can expose the sensor to a deep space object, the more photons it can capture. Stacking a thousand exposures together of a distant planet and using computer algorithms to blend then together might yield a good image, but there are still limits!
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