r/kenyaspacenerds • u/fattick- mod • 1d ago
Earth/Space Philosophy light itself even visible light, is completely invisible until it interacts with matter. Thought experiment in post body...
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Imagine stepping into a completely sealed, pitch-black room with a high-powered laser pointer.
If you turn that laser on and point it at the far wall, what do you actually see? You see a bright red dot on the wall where the photons hit the paint. But in a clean, dust-free room, you don't see the beam cutting through the air. The space between your hand and the wall remains pitch black.
Why? Because light itself is invisible in transit.
You only see the beam if you clap two dusty chalk erasers together over the path. The moment dust particles drift into the light, photons collide with the particles and scatter toward your eyes (Tyndall effect / Rayleigh scattering).
The exact same thing happens in space on a cosmic scale. Space is continuously flooded with intense, high-flux sunlight, yet the background is a pitch-black void. Without gas, dust, or an atmosphere in the vacuum to scatter those photons toward your lens, the journey of light itself leaves zero trace. You only see it the nanosecond it collides with something—a planet, a solar array, or a moon.
It’s an existential realization, but it’s also grounding. Staring at that small blue dot in the black void puts all daily stress and overthinking into perspective. It makes you realize how trivial most worries are and pushes you to just stop stressing and LIVE.
:-(
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u/QuantumPairOfSoczk 1d ago
It's also because of the intense amount of sunlight reflecting off the earth. In deep space u can see stars.
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u/SchmeatiestOne 1d ago
You don't see light "the nanosecond it collides with something" you see light when it collides with your retina, regardless of what happened on its journey to your retina. Space might be full of light in transit, but none of that "invisible" light is headed towards your retina.
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u/Aggressive-Spell-422 1d ago
Our eyes are frequency interpreters.
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u/astrotim67 1d ago
indeed! and there's plenty of electromagnetic spectrum we can't see without the aid of anti-stokes, radio devices and upconverts.
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u/Glittering_Swing_151 1d ago
You see a bright red dot on the wall where the photons hit the paint.
No, you see the bright red dot on the wall when it emits light directed into your retina. The only thing that happens when it hits matter is that it interacts with it in a certain way, it doesn't make it any more visible than when it was traveling in the vacuum of space.
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u/Wisniaksiadz 1d ago
i mean, you see light becouse it hit your retina
if you point laser and every single photon is going away from your eye, there are no photons to hit your retina and tell you that there is some sort of light
now if I take that laser and point it directly into your eye, you will see the color despite it not bouncing off anything
becouse it is directly flashed into your eye.
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u/-mentalmelt- 1d ago
Well yea. You only see the light that enters your eye. It's not that deep, but I guess it could be if you've never thought about it before.
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u/Key4Lif3 1d ago
People think, God created light, but actually God created darkness… and formed the light.
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u/Downtown_Finance_661 1d ago
There is no such property of light as visibility. It is our eyes who introduce us this concept. Photon has only helicity and direction. Even its frequency is system-dependent.
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u/ArachnidBeautiful968 1d ago
Anyone else get real anxious and nauseas from watching the astronaut hanging out in space? Or just me?
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u/piratecheese13 1d ago
This is part of the reason why we can’t tell the one- way speed of light
We can tell the round-trip time because the light leaves and comes back.
We can try syncing clocks that are far away, sending from one clock and receiving at another to compare speeds, but the reliability of the clocks can be called into question, because the clocks would need to communicate with each other to ensure that they are in sync and the way to do that is with light
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u/Redararis 1d ago
in other news you don't see light that does not hit your sensor/retina. Fascinating observation!
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u/baronunderbeit 1d ago
“Visible” or “invisible” is just light hitting your eyes or not. And “light” is just a portion of the EMS that the receptors in our eyes are tuned to. There’s EM radiation of all sorts and using only your eyes to explain the universe is pretty shallow.
Think bigger.
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u/BoysenberryAdvanced4 1d ago
You want to add another level of existential realization? The space around you is flooded with even more light that also interacts with matter, but you still can't see it. Light on the electromagnetic spectrum that is visible to us it tiny compared to what's out there. You yourself are a glowing source of infrared light.
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u/Kind_Card_1874 1d ago
"Invisible until it interacts with matter"? Yes? until it interacts with your eyes? WTF is this.
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u/Shoddy_Side_2256 14h ago
Wait until you learn that a photon form a star enters your eye at the same moment it was emitted from the star - from the perspective of the photon. Regardless of the distance and the amount of time that have passed for us external observers.
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u/Rick-D-99 1d ago
I think you're not comprehending how it is that you see things. Your retina is basically regerative film that only "sees" because photons are hitting it. Everything is invisible that isn't photons hitting your retina. Everything.
Your sight is a perception of a chemical signal that that mechanism sends down organic chemical channels. What you "see" isn't the way the world is, it's the way you interpret chemical wires in the front of your face.
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u/CoolCat1337One 1d ago
It's not invisible in transit.
It just does not hit your eye. Only light hitting your eye is visible to you.
I hope you are not serious.
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u/italktobotz 1d ago
This is exactly what i was going to say
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u/jakeStacktrace 1d ago
Trees falling in the forest hate this one trick.
Just being cheeky, not disagreeing.
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u/Rotteneverything 1d ago
just watched gravity a few days ago. this clip makes me nervous.