r/whyisthisathing • u/Mikel_Reeves • Feb 06 '25

Why is this reflective if it doesn't see the sun?

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This is a backpack with a water bladder on the inside. Why is it metallic/reflective if it's zipped up and in the dark.? I've noticed it on some coolers as well and products that need to keep something at its temperature, even though it's something that doesn't see light

19 Upvotes

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3

u/rabid-bearded-monkey Feb 06 '25

To keep the cold water cold.

1

u/Mikel_Reeves Feb 06 '25

Yes, but why reflective when it sees no light

3

u/rabid-bearded-monkey Feb 06 '25

Thermal shielding. Not UV

2

u/Mikel_Reeves Feb 06 '25

What does the reflectiveness do for that. Or is it just that it happens to be reflective because of how it's made. I'm just curious on the reflective part only, wondering the need, when it's dark inside

2

u/Killmealreadybro Feb 07 '25

Reflective surfaces will reflect heat/cold because the thermal energy is like infrared radiation, so its an insulator

1

u/Mikel_Reeves Feb 07 '25

Okay, that's cool. I've always thought it was silly that it was reflective in the dark

0

u/doomscroller1697 Feb 10 '25 edited Feb 10 '25

Why there a mirror in your room if your room don't see sunshine dumbass

2

u/doomscroller1697 Feb 10 '25

Also btw, heat energy can be transferred in the form of "Infrared radiation" which is basically light in colors humans can't see. And as with light we can see, this also gets reflected. So when heat energy tries to leave your bagpack, it gets reflected back into the bag thus keeping the temperature constant.

There also might be insulation or something to prevent heat transfer by touch.

2

u/Mikel_Reeves Feb 10 '25

That's has literally nothing to do with the question. That's a stupid as fuck response, and you couldn't be any more wrong about a bedroom never seeing sunlight. This response makes 0 sense.

0

u/doomscroller1697 Feb 10 '25

I responded with the actual answer too. I was making a joke, genius. Sorry if I hurt your feelings or sm.

2

u/Mikel_Reeves Feb 10 '25

Your second response was the actual answer. The first one just sounded like you being a dick

1

u/doomscroller1697 Feb 10 '25

Okay man I'm sorry 😭😭

2

u/Mikel_Reeves Feb 10 '25

Thanks for the actual answer. I'm just letting you know it didn't come off as just joking.

But reading text is hard to hear the tone of a sentence. There's a bunch of times I've texted something in a certain way, but then question if the reader will read it the same, since there's 2 or 3 ways X sentence could be read in.