Curious.

Thanks.

Dear E. Markoulakis,

a laser only shines in one particular direction. Other light sources, such as stars, suns, and planets, shine in all directions. Accordingly, you will see stars even without any scattering medium, because light will enter your eye.

However, being able to see faint stars also depends on other things, especially contrast (or dynamic range) and size (or eye resolution).

Kind regards,

Sascha Grusche

Dear Sascha Grusche,

Thank you for you valuable input.

Kind Regards,

Emmanouil Markoulakis

Dear Sascha,

Given a=1391016 and b=149600000, for a diameter of the sun a and b distance from the sun, the calculation gives ∠A = 0.53°, an angular size of the sun as it would appear for an observer in space at that distance b.

The angular resolution at night for the human eye is typically at ∠A = 0.0042°, that is x100 larger than the minimum angular resolution for a human eye needed to see the sun from space at that distance.

So yes size relative, this is more than enough for the sun to be visible.

However at that small angle of 0.53° I really doubt that your incoherent radiation of the sun explanation is enough to emulate light scattering effect which is necessary for human eye and brain to resolve objects and shapes.

Human eye is not build to perceive direct light but only scattered light and thus shapes and objects. If that was not the case, humans would see EM radiation (at visible spectrum) energy travelling all around in space and you would also see a laser line cutting through air without any smoke or other particles aid.

Human vision mechanism is like a bat sense, it must bounce off coming from many different directions into the eye for an object to be located and shape to be perceived.

I don't see how this would be the case for an observer in space with these numbers presented.

According to you when I would make a dense laser sphere with many high quality laser pointers combined together emitting to all directions inside a large dark room then the laser sphere would be made visible at the center of the room?

I really doubt it...

Kind Regards,

Emmanouil

Technological Educational Institute of Crete

To my opinion Sascha Grusche is fully right and it doesn't matter if the light is scattered or not in order to see it. If the light isn't scattered it gives you the possibility to see its source (e.g. sun, stars and light bulbs). The scattered light gives you some impression of scattering media (e.g. sky). And finally the scattered and reflected light gives you the possibility to see these reflective surfaces. However you cannot see the mirroring surfaces. Emmanouil, you cannot see unscattered laser star if it isn't directed to you because the light doesn't reach your eye.

Dear Ivars and All,

quote: "Emmanouil, you cannot see unscattered laser star if it isn't directed to you because the light doesn't reach your eye."

Exactly my point. Thank you.

If we accept the established theory that light travels in straight lines thus beams.

In order our eye and brain to perceive an object and shape either light source or light reflecting object, its light must reach your eye from many different directions, thus scattering.Period.

Think of it as triangulation of an object's location.

Explain to me how in the vast emptiness of space with all the heavenly bodies so vast distance apart, this can be achieved with the sun beams shooting in all directions towards the vast emptiness. So yes Sascha's argument about sun being visible from space because its light beams are shooting in all directions therefore mimicking matter light scattering, is not correct since these beams get lost in the emptiness of space and never reach your eye as you also suggest in the above quote for the unscattered sun light.

Only the sun beams which are in direct line with your position in free space will reach you.

With only a ∠A = 0.53° angular visible size of direct sun light (i.e. same single direction) coming in your eye, this reduces the problem back to the laser pointer paradigm. Therefore, I really dispute that you can see the sun when in space without a visual aid (i.e. a diffraction grating surface).

The laser pointer proves that. You can not see the direct unscattered light of the laser only the laser spot when it is scattered on a surface.

Sorry, but it is not a simple mater of physics but also of human biology and limitation.

I am waiting of your arguments.

Kind Regards,

Emmanouil

p.s. Warning: I am fully aware of the implications to astronomy and physics in general of this biological human limitation of light perception I'm suggesting which is proven to be a fact. For example our sun could be much bigger and at a different distance from Earth as we initially have thought if you cannot see all of its emitted light and only its direct light coming to you with a visual aid and so it goes for the rest of the stars when viewed at the human visible spectrum (I don't know if sun light scatters at the other spectrum of light, like infrared, UV or Xrays, due to possible space dust existing, but then again this negates the general accepted concept of empty space).

A new conspiration theory ??? Human light perception (eye optics + retina + brain) can detect the light of visible spectrum in very wide dynamic range of intensity - but not the same time ! If the eye reduces the sensitivty due to watching the bright objects (sun-illumnated Earth, Moon, orbital station, spaceship, etc) it cannot see relatively faint star, galaxy, nebula). The same concerns the exposition dynamic range of many optical detection devices (films, CCD, CMOS...etc...). Once you are in the space and your eye is not disturbed by any bright object, I see no reasonable reason why you should not see stars - even better than from the Earth's surface due to absence of the atmosphere.

Dear Jan,

Not conspiracy but scientific curiosity and reasoning.

It is not a relative light intensity problem but a combined light propagation and human vision information perception problem.

Do you have something to add on this specific matter?

Kind Regards,

Emmanouil

Just a comment to the "invisible laser beam". Is it right that you will NOT see the laser beam in vacuum when it is not directed to your eye. It is easy to understand this if we consider the laser beam as a parallel flow of photons. If no photons are entering my eye, I have no light perception. But what this has to do with the stars ? Star is an isotropic light source, i.e. radiating the photons equally to all directions. If my eye is directed to the star, some photons MUST fall to my eye and reach the retina. Why I should not perceive those photons ?

Turns out in order to see an object and our brain to identify its shape, scattered light from each point of its surface must reach from different angles your eye retina.

Since there is no scattered light of the sun in free space, when you are out in free space assuming at the same distance as from Earth to sun, you will have only a ∠A = 0.53° view angle of the sun at that distance.

Meaning that, at this small angle, only direct light is reaching your eye and not scattered light when in free space. Direct unidirectional light does not carry any shape or object information and thus we can not see the sun, since it is not registered as an object in our brain. Humans can see objects and shapes thus, scattered light, not EM radiation thus direct light even if it is in the visible spectrum.

If you don't believe go to an very large dark room area, bind 100 laser pointers together all facing to the same direction, distance them from you at a distance that will result the same view angle of the sun ∠A = 0.53° (easy to calculate) and direct them directly perpendicular to your eyes.

IT WILL BLIND YOU BUT YOU NEVER WILL SEE ANY LIGHT OR THE LASER POINTERS SHINING FROM A DISTANCE!!

This is because single direction, direct light does not carry any spatial information needed to see and brain to identify an object. No object in view means INVISIBLE.

Of course an observer next to you, because laser light is scattered by your eyes surface and face, will see in the dark, your eyes burning!! hahahahahaha!!

WARNING!! TO ANYONE: DON'T TRY THIS!!! Danger to become BLIND!!

This video, although an infrared laser (these are for the purpose so that the laser can not be detected by other persons since it does not produce a light spot on any surface), emulates at best what you would see if a class 3 normal (i.e. red laser) was aimed directly in your eye in a lighted up environment. Blurriness and out of focus vision of your surroundings:

https://www.youtube.com/watch?v=8VEQRFzid7o

You will probably see the laser apparatus in front of you but never a red dot coming out of it.

Imagine now the same apparatus in empty dark space without any Raleigh scattering whatsoever.You will not see the laser light nor the apparatus.

Total darkness. You can not see direct unscattered light.

You can not see the stars when in free space without a special diffraction grating surface embedded on windows, helmets and other visual apparatus used in space.

Maybe a NASA expert on this mater can shed some light here and answer?

Sorry Emmanouil, I cannot accept your point. The only existing problem with visibility of stars by human eye (and photo-devices) concerns the appropriate exposition. There is a nice starry sky visible by astronauts when ISS flies over night side of Earth.

https://www.universetoday.com/136802/can-astronauts-see-stars-space-station/

Dear Jan,

That's fine with me. No problem.

However the picture you provided is not from free space! The Earth is in front and below their view, scattering the light of the stars.

I always was referring to FREE space.

Also how you can be sure they don't use diffraction gratings on the ISS windows and their optical and photographic instruments?

Kind Regards,

Emmanouil

Maybe it would be best to ask NASA or ISS directly:

Do you need special equipped with diffraction gratings optical apparatus or windows for your free space observations in the visible spectrum of the stars and if yes, why?

Although I am sure they will respond negative in order to sustain a fantasy and myth. It's good for science fiction and Hollywood :)

"The sky is DEEP BLACK?!! when viewed from the moon AS IT IS WHEN VIEWED FROM CISLUNAR SPACE, THE SPACE BETWEEN THE EARTH AND THE MOON... N. Armstrong Apollo 11 moon landing mission".

https://www.youtube.com/watch?v=OmcwW-8CC6E&t=48s

Maybe this was because in the first Apollo missions the spacecraft windows were not fitted with special diffraction gratings?

Also I found this laboratory here:

http://snl.mit.edu/?page_id=46

Maybe they do some of these also in the visible spectrum?

Hello,

I have chosen RG because I am seeking scientific arguments and proof to be presented against my claims and reasoning so this mater can be resolved instead of Bollocks remarks!

Emmanouil

p.s. since you seem to be an expert in light scattering why you, don't present hard scientific evidence and publication references how human vision works in free space without any light scattering?

The Abyss of free space as seen from it (with no planetary bodies relative nearby to scatter star light).

Must be a frightening unpleasant experience to travel within it?...

Here is your requested reference (I have found it after my postings in this thread here):

http://www.nbi.dk/~ogendal/personal/lho/LS_brief_intro.pdf

Seems to me that this supports that human vision and brain can perceive only scattered light.

quote from above reference (pp. 6-8):

"The laser beam is vaguely visible in the dark room. But why? . . . In order for us to see an object it needs to be hit by light which then bounces off in different directions, e.g. into our eyes. The lens in the eye then forms an image of the object on the retina by collecting the light that was reflected from the object. But a laser beam is not an object or a ”thing”. I is merely the name for a train of photons within a narrow portion of space, all moving in the same direction. Why then, can we see the laser beam? The answer is: We can’t. At least not if the laser emits its beam in a room where the air is totally clean, i.e. dust free. "

And the Author and researcher of the above document Lars Øgendal

@Lars Øgendal .

I believe this mater is far away from being answered properly.

Please press the button "see previous answers" on top of this page consecutive times to make visible all the answers in this thread. Annoying RG feature :(

"Why then, can we see the laser beam? The answer is: We can’t. At least not if the laser emits its beam in a room where the air is totally clean, i.e. dust free. "

We CAN if the beam is directed to your eye. (It is better not to try in order not damage your eye. Especially if the laser isn't VERY weak.)

In case you are talking from experience that is an impulsive reaction of they eye to protect itself. You never saw the laser beam or any light that is. It does not register in your brain.

You probably have perceived it as a sudden blurriness effect in your vision . BUT NO, NO LIGHT.

It WAS a light in the same color as laser beam. I tried it with weak laser (laser brelok) a long time ago. But I can not take a responsibility to recommend you to repeat.

Did it you turn it on when the laser was pointed into your eye?

Or before and then pointed it into your eye?

I don't remember exactly. I think I did it in both ways. But I am afraid to repeat it now - I don't have this brelok more. Only some more powerful laser pointers. Do you think this matter?

For the sake of science can you please repeat this experiment and share with us your experience?...

...nah just kidding :)

It does actually mater. In cheap lasers there is bit of light refracted by the front glass casing of the pointer giving out a red flare. You probably saw this light before you got blinded by the laser beam.

But actually seeing the sub-micron thick, at that distance, laser line or red spot projected on to your eye, is the same as being able to see the back of your retina and look into your brain or even worse to look directly on the projection beam in a cinema theater and expect to watch the movie!

Humans can not see direct light without any bit of scattering (as it would be in free space). End of story. If that would be the case, we would not need any projection screens at all. Just place your self at an adequate distance and watch your favored movie just looking straight at the projection beam!

hahahahaha!!

Case solved.

Emmanouil

Please NASA, ESA or whatever other space agency out there come with valid arguments to disprove this. In free space you can see the planets, moons and other planetary bodies because they scatter the sun light but not the light sources (i.e. stars) itself and neither you can see our sun when in free space (no planets nearby to scatter its light).

You see total abyssal darkness.

Dear Emmanouil,

regarding the "black void" of the universe: It is simply a contrast phenomenon that you know from your everyday life. If you look at any house with windows: From the outside, the room behind the window looks pitch black (like the apparently "star-less" sky, especially if the house is sunlit (like the lunar surface)). But as soon as you are inside the house, the room looks bright and you can see everything clearly (as astronauts will see stars if they are not on the sunlit side of the moon).

If you want to do an analogous experiment, I encourage you to try the following:

Place a computer screen behind your window, deep inside your room (say, 3 meters behind the window). On the computer screen, show some image of bright dots on a black background (an image of a starry sky). Now go outside your room, and look if you can see the bright dots. I hypothesize you won't be able to see them if the outside wall around the window is strongly sunlit, or if you hold a very bright lamp near your face.

Kind regards,

Sascha Grusche

Dear Sascha and All,

Thank you for your reply. But again my argument is not a " contrast " issue but if a human can see unscattered light?

So although your analysis is correct, it is out of the scope of my question here.

My conclusion so far is NO even if it contains the visible spectrum. Sunlight wide spectrum EM radiation must scatter first on matter and its frequency components split and then picked up by the human eye at the visible spectrum.

Humans can not see light or any EM radiation on that mater but only can observe its scattering effect on matter on a specific frequency range we call visible spectrum.

Please, if you have any scientific prove to the contrary else stay out of this topic.

Kind Regards,

Emmanouil

Dear Emmanouil,

there are two conditions under which humans can see light: Either 1) light goes directly from the light source into the eye or 2) light goes to a light-scattering object and then into the eye. In summary, we can see light only if it goes into our eyes. You cannot see a laser beam because it is not directed at your eye (hopefully!). But you can see a candle, a lamp, and any other light source whose light is directed toward your eye. An atmosphere is not necessary for viewing (although the ancient Greeks believed this).

You could try to build a pressure-proof lamp inside a vacuum chamber, and look inside this vacuum chamber (through a pressure-proof visor). You should be able to see the lamp because light can travel through vacuum and reach your eye.

A simpler experiment might be to hold a dim LED directly to your eye. Even without scattering at any medium outside your eye, you will see the light from the LED.

Kind regards,

Sascha Grusche

Dear Sascha,

First of all you are mentioning a lamp, thus incoherent omnidirectional light and vacuum chambers have walls so scattering will take place anyway.

Second your mention "look inside the chamber" and not being inside the chamber, thus scattering will happen anyway even if no scattering conditions were established inside the chamber using a laser direct light.

What are the characteristics of this pressure proof visors you are referring to (all laser protection visors have diffraction properties anyway in order to protect the eyes of the observer) and I presume you are simple speculating and have never done this particular experiment or anywhere else therefore you can not present and refer to any hard scientific evidence and merely are presenting your assumptions and believes us proofs.

Last, your proposed experiment hardy qualifies for emulating the free space conditions I am referring to. Also your direct laser on eye argument I have already answered previously on a reply:

quote:

"It does actually mater. In cheap lasers there is bit of light refracted by the front glass casing of the pointer giving out a red flare. You probably saw this light before you got blinded by the laser beam.

But actually seeing the sub-micron thick, at that distance, laser line or red spot projected on to your eye, is the same as being able to see the back of your retina and look into your brain or even worse to look directly on the projection beam in a cinema theater and expect to watch the movie!"

Therefore, I believe a physicist alone is not qualified and enough to answer this question, thus can humans see direct unscattered EM radiation?... and an indisciplinary physic - biologist or ophthalmologist is needed to do so with a deeper understanding of human vision.

Kind Regards,

Emmanouil

Dear Emmanouil,

the only way to find out experimentally directly is to go out in space and look.

Those who cannot do this have to rely on analogous experiments, on thought experiments, or on established theory. Maxwell's theory of electromagnetism predicts that light travels through vacuum, thus being able to reach your eye even if you are outside earth's atmosphere. Kepler's theory of vision predicts that the refractive system of the eye will reshape the light bundle diverging from the star to the eye pupil into a light bundle converging on the retina, producing an image of the star on your retina (similar to a lens and screen, or a camera). As in everyday life, whenever an image is projected onto your retina, you will be able to see the imaged object. Thus, you will be able to see the star; whether in a vacuum or not.

Biology and psychology are important to understand vision as a whole, but physics is enough to predict the image that will be projected on the retina, which is then reconstructed in your brain.

Regarding your projector counter-argument, this is not in accord with Kepler's theory. If you look toward a projector, only light for a single image point will reach your eye. Thus, you will only see the projector objective, in the color of the image point that is projected onto your pupil.

If you cannot accept my proposed experiments, or established theory, I see no solid basis for your own question, because even if you and the light source could be in perfect vacuum, your eye itself would provide scattering media in the form of cornea, fluids, lens, and retina.

Kind regards,

Sascha Grusche

PS: The atmosphere does not enlarge the sun, but makes it appear smaller compared to what it would be without the atmosphere. Going from vacuum into air, rays from the sun are bent toward the normal of the atmosphere, resulting in a demagnified image. This is especially apparent when you see a flattened image of the sun near the horizon.

quote:

"As in everyday life, whenever an image is projected onto your retina, you will be able to see the imaged object. "

Wrong, image is not projected directly into your retina but onto a projector screen that scatters light and makes the image visible.

" If you cannot accept my proposed experiments, or established theory, I see no solid basis for your own question, because even if you and the light source could be in perfect vacuum, your eye itself would provide scattering media in the form of cornea, fluids, lens, and retina. "

If Kepler's a 400 years and more ago, is the established theory and speculations today for vision in space... then we have a problem...

Also scattering of light on the eye itself producing vision for the person looking, I'm afraid this is not how vision in humans works and this argument is far fetched since then we would be able to see a movie directly projected into our eyes and we would not need any projections screens. Human vision can not resolve objects and shapes by direct light.

" The atmosphere does not enlarge the sun, but makes it appear smaller compared to what it would be without the atmosphere. Going from vacuum into air, rays from the sun are bent toward the normal of the atmosphere, resulting in a demagnified image. This is especially apparent when you see a flattened image of the sun near the horizon. "

Again wrong. Atmosphere works like a magnifying lens enlarging objects like the moon.

Do you really believe that the moon looks bigger when in space than when inside our atmosphere?

Both moon and sun have the same angular size 0.53° thus the eclipse, for an observer outside the atmosphere at that distance.

But apparent size of moon and sun inside our atmosphere is much larger.

See here in this NASA video how tiny the moon appears with the naked eye from the ISS space station without any visual aid:

https://www.youtube.com/watch?v=edKQNwgmXpU&t=164s

Also at time stamp on the same video:

https://www.youtube.com/watch?v=edKQNwgmXpU&t=254s

Where the ISS is now at the dark side of the Earth during Night time and looking away from the moon, where are the STARS on space?

Should be full of stars many more times than viewed from within our atmosphere...right?

I rest my case.

Emmanouil

hahahahahaah!! This is pathetic!!...

https://www.iflscience.com/space/weve-just-discovered-earths-atmosphere-extends-way-beyond-the-moon/

So maybe then there is some light scattering happening after all at cislunar space (space between Earth and moon) accounting for the the observable stars when observer located in that specific space!!...

Ha hahahahaa!! This is getting pathetic!! hahahahahaah!

Reported at 21 Feb 2019. Someone is watching over this thread here...

trying to save sci-fi space hahahahahaah!! just kidding :)

The fact however remains. No light scattering, no visible light for humans.

Another parade of inconsistencies by the astronauts:

https://www.youtube.com/watch?v=pmVU3GnM1TA

MAKE UP YOUR MIND!!... IT'S A SIMPLE QUESTION!!... CAN YOU SEE THE STARS OR NOT?!! FOR GOD'S HEAVEN!!...

This is hopeless...

I give up... no one can answer this question...

I think I bet to Black.

Please don't tell me that the reflection from the space shuttle washes out the stars?!!..

..

Dear Vincent,

It is a pity that this question thread has to resolve to be...

...A leap of faith!!?

Without any hard scientific data to support it. I can't accept that.

They should have been already hundreds of papers released concerning research about vision and optics in free space and I know for sure that NASA has contacted experimental research about astronauts vision in space but unfortunately and strangely enough no such an evidence has been presented here by experts on this specific mater.

Until this happens this question is up to scientific debate.

Kind Regards,

Emmanouil

Thank you for you valuable input.

Dear Emmanouil,

well, I,ve noted great answers from commentators. But I still have my own believe. First of all, Astronomy is the pole in which stars orbit or spins, thats in agreement with what have been mentioned in the holy Quraan, And it is He who created the night and the day and the sun and the moon; all [heavenly bodies] in an orbit are swimming. quoted from Quraan... Optically, I and you can see in a different angles, means you cant see every things the same from different angle or changing your place. I think thats why you would not be able to see the stars from the space while you can see from our planet.

Highly appreciated,

Alshaarawi Salem

Millions of Billions!! Stars shown when in free space:

https://www.youtube.com/watch?v=fPmPUrE5IYI&t=462s

I don't buy this, reflections washing out the stars view.

The view here is away from Earth's glare... total darkness surrounding the SpaceX Dragon capsule. Where ARE THE STARS?!...

Bordon me! I had my fare share of scientific arguments in this thread here I believe.

Without any conclusive counter arguments presented since they all referred to withing the Earth's environment and therefore subjective to the free space conditions.

So they only course of action remaining in this thread here, is to examine video evidence and astronauts empirical evidence presented by credible sources like the above video footage released by Nasa and SpaceX.

Also please mind your language. There is no reason to get upset because the lack of evidence and published research on this mater.

Absence of stars in digital videos does not necessarily mean invisibility of stars: Even if you can see stars with the naked eye, a camera will not necessarily record those stars due to its limited dynamic range.

You should look for counter-evidence in the form of photos which do show stars, recorded from free space. How about Hubble space telescope images? These are not based on random scattering, but specular reflection. These photos do show stars.

Specular reflection or else mirror like reflection of light varies only from diffuse reflection thus scattering, in that the angle of incidence matches always the reflected angle of light on the surface. So it is we can say a regular reflection effect producing a mirror image of the object observed. This mirror reflected image will reach your eye. Multiple light specular reflections are needed in order for us to perceive the total mirror image. Humble telescope operates as far as I know on the visible and UV spectrum.

I fail to see how this affects the argument I believe stated in this discussion here that direct light must undergo some kind of reflection first (mirror reflection or scattering) on matter in order to be perceived by human vision.

Humans can not see EM radiation of any kind only reflected EM on matter of a specific frequency range we call visible light.

If humans could observe direct EM radiation even only for a specific visible band without first matter intervening, so why is it then we can not direct observe specific microwaves (there are some microwave transmissions which have harmonics at the visible spectrum) travelling all around us in our everyday life without first scattered by special constructed materials?

Read here:

https://tinyurl.com/y2ucgf6w

I don't try to convince anyone here but merely reporting my observation and research.

It is more a human biology expertise question than it is physics.

Take it or leave it. As such I don't see any point to continue this debate unless any hard evidence is presented.

Emmanouil Markoulakis

Technological Educational Institute of Crete

The Hubble telescope is a technical eye, analogous to a human eye. As long as humans do not go into deep space, we have to use technical eyes instead of human eyes. True, the Hubble telescope uses a special kind of scattering (namely reflection), so does the human eye (namely refraction). However, neither for a human eye nor for a telescope is a scattering medium between the star and the entrance pupil necessary for image formation.

Humble telescope is not analogous to the human eye. EM radiation is specular diffused at the visible spectrum by the Humble mirrors and then feed to a CCD sensor for electronic image generation.

Non previously diffused, straight light, without carrying any spatial information, entering the eye pupil which is nothing more than a hole actually, is hitting the retina at the back of of the eye analogous to a CCD camera sensor and translated to electric impulses with no any image information contained and is therefore processed by the human brain as invisible.

The mirror system of the Hubble telescope is analogous to the refractive system (cornea, lens, fluids) of the eye - both take a divergent light bundle from a star and transform it into a convergent light bundle for the corresponding image point.

Filming the Speed of Light at 10 Trillion FPS

https://www.youtube.com/watch?v=7Ys_yKGNFRQ

You can see only scattered light with your eyes.

Dear Emmanouil,

it is true: If you want to "watch" from the side how light travels, you do need a scattering medium. However, if you want to detect light coming straight at you, you do not need a scattering medium. Direction is key.

Kind regards

Sascha Grusche

You can not see direct visible light coming from stars when in interstellar space. Light is a matter induced phenomenon and human visible light spectrum, needs a fair amount of matter, light to be scattered of in order to become visible.

So, when in deep space you do not see any stars...only blackness with the exception of planets, moons and other space objects which scatter light.

This has been confirmed by the Apollo astronauts many times when travelling midway between the moon and the Earth.

Low Earth orbit like the ISS space station doesn't count because the relative close proximity to the Earth and its atmosphere acting like a screen and scattering incoming light to all directions. Also according to new findings the Earth atmosphere extends far more than previously believed (although much more less dense) beyond the Karman line at 62 miles altitude.

https://science.slashdot.org/story/19/02/21/1725228/earths-atmosphere-extends-much-farther-than-previously-thought