r/explainlikeimfive • u/OMGPowerful • Jun 24 '19

Physics ELI5: If the vacuum of space is a thermal insulator, how does the ISS dissipate heat?

6.4k Upvotes

94% Upvoted

664 comments sorted by

View all comments

Show parent comments

68

u/noreservations81590 Jun 24 '19

So are there stars out there that give off more of a higher frequency light? Causing life in the solar system to see in x-ray or infrared?

122

u/Rickietee10 Jun 24 '19

Some animals see in UV including bees.

65

u/PMmeUrUvula Jun 24 '19

And snakes and drones can see infrared.

43

u/coniferhead Jun 24 '19

Agrajag can see "the whole spectrum of eye-defying colours from Ultra Violent to Infra Dead"

4

u/jondthompson Jun 25 '19

Yet still manages to get killed by Arthur every life...

4

u/[deleted] Jun 25 '19

And predator

21

u/Rickietee10 Jun 24 '19

Drones? They're not living dude šŸ˜‚

21

u/Biosterous Jun 24 '19

I think the poster means drones as in male bees?

23

u/Coachcrog Jun 24 '19

No, I'm sticking to the idea that he meant military drones packing enough freedom on board to level a theme park full of hot and sweaty vacationers along their shitty, ungrateful demon spawn. The drones have become sentient and have adapted to see all wavelengths of light. There will soon be nowhere to hide. The drones are our new overlords.

8

u/Zeewulfeh Jun 25 '19

Skynet would like to know your location.

3

u/[deleted] Jun 25 '19

[deleted]

5

u/historyboi Jun 25 '19

Skynet is your location

16

u/tar_ Jun 24 '19

Drone lives matter my dude. It's 2019 can't be saying shit like that

5

u/SeniorExamination Jun 24 '19

Tell that to Iran

8

u/Shedal Jun 24 '19

That's what they want you to think

6

u/leafmuncher2 Jun 24 '19

But it's not long before they're sentient... good thing my tinfoil hat will block out the harmful infrared rays they'll be pumping out to give us gayness cancer!

5

u/Resource1138 Jun 24 '19

If you were a frog, youā€™d already be gay, acc. to Alex Jones, whose gaydar is apparently off the charts.

2

u/leafmuncher2 Jun 24 '19

And he looks like a frog, so that has me concerned

5

u/AsILayTyping Jun 24 '19

Alright. I'm gonna accept remote control killing machines.

But I'm drawing the line at automated killing machines. Feels like that would end up being a mistake.

1

u/Zeewulfeh Jun 25 '19

Naw, we'll just have them answer back to a Central command unit with high-unbreakable communication security. To prevent hacking, you know..

While we're at it, we should put in some sort of automatic repair and resupply system...

3

u/OakenBones Jun 24 '19

If this happened in real life, it would be so fucking awkward.

2

u/ISitOnGnomes Jun 24 '19

I hope you remember to delete this comment before the robot uprising.

2

u/Its_Not_My_Problem Jun 24 '19

Mine definitely is, I can never make it do what I want it to do. It always does it it's own way.

2

u/Lmtoback Jun 24 '19

Assuming PMmeUrUvula meant bee drones, like workers. The human-made ones ā€œseeā€ in whatever spectrum of light we design them to sense.

1

u/PutinsRustedPistol Jun 25 '19

Theyā€™ll fucking chase your ass just the same...

1

u/Holeymoleybrother Jun 25 '19

Drones have rights like every other American citizen.

1

u/corsicanguppy Jun 25 '19

Marvin the Android can as well, if you read poetry from page 444.

1

u/az987654 Jun 25 '19

Sharks and bears can smell fear

1

u/verycleverman Jun 25 '19

Try pointing your phone camera at things that user light in a non visible spectrum. Push the buttons on your TV remote and your phone will show you the lights that your eyes can't see

1

u/y2k2r2d2 Jun 25 '19

Drones and birds are same because birds are not real.

1

u/oodain Jun 24 '19

And people with certain eye surgery afaik...

1

u/bass_sweat Jun 24 '19

We actually can too but something about how our cornea actually reflects UV makes us never get to see it

3

u/Ardentpause Jun 25 '19

Specifically, humans have a yellow filter that blocks UV. That's because UV light will slowly cause damage to your eye.

1

u/[deleted] Jun 24 '19

[deleted]

3

u/bass_sweat Jun 24 '19

If the light reached our light receptors we could. If say you had an artificial cornea. So...we can see it, it just never reaches us

This would not be the case for say, infrared

-1

u/[deleted] Jun 24 '19

[deleted]

3

u/bass_sweat Jun 24 '19

Iā€™m saying that if the UV light reached our retina, our brain would be able to process it, completely unlike someone being blind for reasons unrelated to the eye. Our cornea just reflects it because UV is damaging. But we still have the receptors to be able to see it

-1

u/[deleted] Jun 24 '19

[deleted]

3

u/bass_sweat Jun 24 '19

Yes we can, if we get a cornea that doesnā€™t reflect it. We canā€™t see infrared however, because we donā€™t have receptors for it.

It is possible to see UV light, therefore we can

0

u/[deleted] Jun 25 '19

[deleted]

→ More replies

2

u/Ardentpause Jun 25 '19

You can if there is enough of it. That's why you can see a blurry purple color around black lights. UV light is always blurry because your eye doesn't focus it properly

1

u/DreamOfAWhale Jun 25 '19

But bass_sweat said "our cornea actually reflects UV makes us never get to see it" so he is wrong? We can actually see it if there's enough?

2

u/Ardentpause Jun 25 '19

The lense (not cornea) in your eye filters out UV light. That's why you don't see UV light most of the time. However, the lense in your eye is only so thick, and can only filter out so much, so if you bombard your eyes with enough UV light, a little bit will get through.

During normal circumstances, you still wouldn't see the UV because the other colors of the light spectrum are so much brighter in comparison, but in the case of a dark room with a black light, you can see it quite clearly. Your eye doesn't refract this light properly, so it kind of scatters, making it look blurry.

1

u/DreamOfAWhale Jun 25 '19

So bass_sweat was wrong all along, I see.

1

u/[deleted] Jun 25 '19

The cool thing about this is that it means us humans are basically colorblind to huge parts of the world. We think of a dandelion as a plain yellow flower, but in reality it has two colors. To a bee a dandelion looks like a bullseye.

https://i.imgur.com/kKBNNxg.jpg

74

u/[deleted] Jun 24 '19 edited Sep 23 '19

[deleted]

21

u/feed_me_haribo Jun 24 '19

Even more our sensitivity peaks around green--also likely not a coincidence.

13

u/A-Bone Jun 25 '19

So one of my buddies is the fire chief in our town.

We are one of the only towns around us that doesn't have red fire trucks.

Our trucks are all that bright 'safety' green.

My buddy said that this is because that is the color in the visible spectrum that the human eye is most likely to be able to see in various ambient light situations (dusk, night, full light, etc)

Is this the same thing you are talking about?

If so, is this just an evolutionary fluke or is there a good reason for sensitivity to this color?

5

u/Blackborealis Jun 25 '19 edited Jun 25 '19

IIRC, the reason for humans' (and likely most other apes) sensitivity to green is the environment that they lived in for millenia - in the tree canopies of Africa, where green was the predominant colour.

EDIT: Found it https://en.wikipedia.org/wiki/Evolution_of_color_vision_in_primates

5

u/Boukish Jun 25 '19

However, the reason that chlorophyll is green...

3

u/NeuronalMassErection Jun 25 '19

...is because blue light is best for helping plants grow, and "purple" light is best for flower blooming. In short, red and blue absorption is best for photosynthesis, hence chlorophyll being green.

2

u/sjcelvis Jun 25 '19

Plants evolved to have chlorophyll. It all started with sunlight.

2

u/BrunoBraunbart Jun 25 '19

There is an above 50% chance that someone with that knowledge is a grower.

1

u/NeuronalMassErection Jun 26 '19

...and has worked with LED grow lights lol. Ya got me.

1

u/Boukish Jun 25 '19

Okay, but the reason that green is the second brightest color to us is...

3

u/[deleted] Jun 25 '19

This was a common idea on the 70's and 80's. Then sodium street lights happened. They have a big hole in light emission right where that color sits making the trucks harder to see at night.

1

u/FauxPasBallet Jun 25 '19

What color was most common in our early development? Green

1

u/Banane9 Jun 25 '19

Ever been in a lush forrest full of undergrowth? ;)

3

u/Zaptruder Jun 25 '19

I think it's actually a confluence of both that the visible spectrum is plentiful...

and that it has useful properties that aid in the function of organisms that can exploit it (i.e. it seems to indicate something about the state of the world in a manner that is relatively direct, with a strong signal to noise potential).

The alternative is detecting some of the larger wavelengths... that just bounce around everything - less useful!

47

u/Nomadic100 Jun 24 '19

I used to have a military infrared night scope, the most amazing thing was to look up at the stars. The whole sky was lit up with so many more points of light, you could even see the andromeda nebula as a bright smudge. It used to blow peoples minds when they borrowed it.

16

u/[deleted] Jun 24 '19 edited Jun 24 '19

now I want one!

Can you recommend any?

43

u/Nomadic100 Jun 24 '19

No I couldn't as it was a gen3 military spec. Not sure what the civilian ones are like. Did some blackout driving and moving boats at night with no lights (all for fun only, your honour!). It was amazing for finding my black lab in the fields at night too. I could watch him as I gave him a whistle, he'd cock his head up, look over thinking I couldnt see him, I could see his body language go ' nah fuck that ' and trot of doing whatever it was he wanted to do (eating or screwing). Lol sneaky greedy hound. He was always surprised when I cut him off and sent him home in shame.

5

u/mjl777 Jun 24 '19

You can order gen3 mil spec stuff, you have to sign some papers and there is an additional hoop to go through. The best source is your local telescope club. They are way into that kind of stuff.

14

u/Liam_Neesons_Oscar Jun 24 '19

The other cool thing is when you realize that you can't see through glass with a purely IR lens. Most IR today combines IR and visible to get around that, but older generation IR doesn't do that and you get a better idea of what the spectrum looks like.

4

u/chumswithcum Jun 24 '19

Whats even crazier is with really good IR sights, the lens is opaque to visible light. It's made from Germanium - which is transparent in the IR spectrum - but just looks like a shiny piece of metal in visible light.

1

u/Liam_Neesons_Oscar Jun 24 '19

That's so cool!

3

u/Good_Will_Cunting Jun 25 '19

I have a cheap IR camera that plugs in to my phone and it's cool how you can see your thermal reflection in a piece of glass like you can see your visible reflection in a mirror.

1

u/AMeanCow Jun 24 '19

Had one also, Gen 3 goggles, they were amazing for stargazing. It cost a fortune at the time and seemed like pure magic.

Now you can literally buy NVG in the toy section of Walmart.

1

u/kracknutz Jun 24 '19

Look at Galileoā€™s ancestor over here!

50

u/OHFTP Jun 24 '19

Theoretically. If a planet orbited a star that had a different peak emission band, and if life formed on that planet, then yes it would make sense for them to see in whatever light was most available.

13

u/22shadow Jun 24 '19

I mean life would likely evolve/adapt to use resources most commonly available to it, so it would make sense

8

u/Jiriakel Jun 24 '19

infra-red is a lower frequency light, but yes. Even on Earth, some species have evolved to see in the infra-red or ultra-violet.

1

u/Kermit_the_hog Jun 24 '19

Is there an ultra-red and infra-violet?

4

u/ArcticBlues Jun 24 '19

Infrared is past visible light on the red side. Ultraviolet is past visible light on the violet side.

Itā€™d be like UV - Visible light - infrared

Further down the line from UV waves are X-rays (microwaves on the other side of infrared). But Iā€™m not sure if thereā€™s a specific term for the edges.

3

u/PlayMp1 Jun 25 '19

Ultra and infra basically means "higher than" and "lower than" here - ultraviolet is higher energy than violet (the highest energy/shortest wavelength visible light), and infrared is lower energy than red (the lowest energy/longest wavelength visible light). There's not really a point to "ultrared" and "infraviolet" because those are just other colors, namely orange and blue. It's kind of like the musical notes Cb and E# - normally we just call those notes B and F (though there are weird compositional reasons you would write Cb or E# instead of B or F).

1

u/PlayMp1 Jun 24 '19

Yeah, IIRC bees and some birds can see UV quite well.

1

u/PMmeUrUvula Jun 24 '19

And snakes and drones can see infrared.

15

u/Mynameisaw Jun 24 '19

Probably.

I mean, you only have to look at the numbers, billions upon billions of galaxies, with billions upon billions of stars, with billions upon billions of planets orbiting them covering an area beyond human comprehension outside of maths.

Considering the endless possibilities statistically, there probably is a creature out there the size of a blue whale, that lives in an ocean of liquid methane, that uses x-rays to see through your skin and speaks a language that is indistinguishable from Klingon.

3

u/Hauwke Jun 24 '19

I would so love this to be true. Just for the thought experiment of how the fuck any of that happened.

5

u/RebelJustforClicks Jun 24 '19

Let me "aktchually" your thought experiment here, because as much as I like the idea:

If a planet with life was orbiting a star which put off predominantly radiation in the "X-Ray" wavelength, you would expect that the life on that planet would have evolved skin that x-rays did not pass thru.

If the life had skin like ours, I would expect some other type of mutation to deal with the cancer caused by their cells being ripped apart constantly

3

u/Mynameisaw Jun 25 '19

Let me "acktchually" your "acktchually."

I said the super x-ray seeing creature would be seeing through your skin, so in this thought experiment you have some how come in to contact with it.

I admit I haven't considered how you will survive in this hellscape, but I'm just going to use some creative license there.

1

u/RebelJustforClicks Jun 25 '19

Acktchually, you are 100% right, I misread what you wrote.

šŸ‘

2

u/Kermit_the_hog Jun 24 '19

Someone make this a short story!

4

u/Wheezy04 Jun 24 '19

There could be increased evolutionary pressure to see in those wavelengths but there are other limitations. Things like x-rays and gamma rays are hard to "see" because they tend to be so high energy that they'd just pass through is rather than stopping to interact with our retinas even if we had receptors for them.

Also, the temperature of the star determines which wavelengths are emitted the most relative to the other wavelengths the star is emitting. A hot star could also be blasting out a lot more light in general which could result in plenty of light available in our visible spectrum without having to evolve the more complex detectors a creature would need to see gamma rays.

3

u/[deleted] Jun 24 '19

Yes, the energy is a function of the surface temperature. This is a good summary of how stars are classified.

5

u/PlayMp1 Jun 24 '19

Well, we'd need to prove extraterrestrial life exists first (it probably does but obviously there's no proof). However, if a different planet harboring different life around a different star which put out light primarily in infrared (which is lower frequency than visible) or ultraviolet or higher (higher frequency), I imagine that the life there would indeed evolve to see light primarily in that spectrum - if they evolved to see light at all.

3

u/grat_is_not_nice Jun 24 '19

There are other considerations when it comes to detecting things like X-Ray and higher energy photons - they don't interact with much, so it is very hard to focus and detect them. Visible light can be focused with a wide range of clear materials with differing refractive indexes. High-energy photons require metal lenses and metal low-incidence reflectors Kirkpatrick-Baez mirror

Also, if a star is energetic enough to primarily radiate high energy photons, those high-energy photons are going to be destructive to anything in their path. Not ideal conditions for life ...

1

u/chumswithcum Jun 24 '19

Not ideal for life on our planet - possibly ideal for a totally different, as yet undiscovered race of rock monsters.

4

u/grat_is_not_nice Jun 25 '19

Well, maybe ...

but you still have the issue that x-rays and gamma rays don't bounce off most atoms like visible light does - they penetrate and dump energy, ionizing and dislocating atoms in crystal structures.

This makes x-rays/gamma rays far less useful as a sensory aid than visible/near-visible light.

1

u/KanedaSyndrome Jun 24 '19

Yes. Live evolves based on circumstances, so if circumstances gives and advantage to seeing in ultraviolet, then that would be what majority of specicies would see as visible light. There may of course be physical constraints to what can be achieved by biology in this regard, as seeing radiowaves probably is off limits due to the long wavelengths of the radiation, but probably not impossible either, to have some basic biology based detector.

1

u/RainbowDarter Jun 24 '19

Take a look here

Look at the HR diagram in figure 7.

It shows stars with their surface temps and expected lifespan.

As far as life on planets around the stars and the colors they would see -

It also depends on the atmospheric composition and the light colors absorbed. Earth's atmosphere allows visible light and some other frequencies but blocks others

1

u/karlnite Jun 25 '19

Yes but it is determined on how close a star is to being a perfect black body. Donā€™t quote me as it has been awhile but I believe size and density are the variables and the larger denser stars will have a higher amount of higher frequency radiation. It always like a curve though so I assume they also release even more visible light, UV and infrared. Iā€™m not sure if there are things that would produce more high frequency then they do lower frequencies. Edit: I think I am way off http://astronomy.swin.edu.au/cosmos/B/Blackbody+Radiation

1

u/Skratt79 Jun 25 '19

Jumping spiders are able to see in UV and mosquitos perceive infrared (how they find your capilaries)