# Why can we see satellites? **URL:** \ **Category:** Factual Questions\ **Created:** [February 5, 2008, 2:27pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381 "2008-02-05T14:27:26Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Trunk](https://avatars.discourse-cdn.com/v4/letter/t/87869e/32.png) [@Trunk](https://boards.straightdope.com/u/Trunk)\ **Post date:** [February 5, 2008, 2:27pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/1 "2008-02-05T14:27:26Z")
Certainly I can’t see something the size of a satellite from 200 miles away. Now, it SEEMS to me – just my intuition – that I shouldn’t even be able to see the sun shining off something that big at that distance, even against a dark backdrop. I’m not sure what I’m looking for for an answer, just any words of understanding. Obviously, I can see them. Is is the combination of looking through a little bit of atmosphere, sunlight directed right at, dark background? Just how big are those panels that the sun is reflecting off? Can we see the very high altitude ones? ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [February 5, 2008, 2:38pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/2 "2008-02-05T14:38:30Z")
Not sure if it’s a satellite or what but on very clear nights I can see what appears to be a star moving ever so slowly across the sky…I’ve seen this many times and have always assumed it was a satellite. I’ve done a fair bit of boating where light pollution is at a minimum and I’ve seen several of these star like things moving across the night sky ever so slowly. I think they are satellites. ---
**Author:** ![Trunk](https://avatars.discourse-cdn.com/v4/letter/t/87869e/32.png) [@Trunk](https://boards.straightdope.com/u/Trunk)\ **Post date:** [February 5, 2008, 2:40pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/3 "2008-02-05T14:40:31Z")
They definitely are. It just has never jived with my intuition that we should be able to see them. [Times article](http://www.nytimes.com/2008/02/05/science/space/05spotters.html?hp) on satellite watchers who chart their flight paths through careful measurement. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [February 5, 2008, 2:42pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/4 "2008-02-05T14:42:59Z")
[QUOTE=Trunk] Certainly I can’t see something the size of a satellite from 200 miles away. [/QUOTE] Why not? On the curved surface of the earth, you aren’t going to be able to see 200miles unless you’re on a mountain (I’ll leave it to someone else to crunch the numbers on how high). But, say you’re on top of a mountain in Colorado and looking east toward Denver. I’d say you’d be able to see those lights without any difficulty. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 5, 2008, 2:46pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/5 "2008-02-05T14:46:39Z")
[QUOTE=Phlosphr] Not sure if it’s a satellite or what but on very clear nights I can see what appears to be a star moving ever so slowly across the sky… [/QUOTE] No question, these are satellites. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [February 5, 2008, 2:46pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/6 "2008-02-05T14:46:39Z")
[QUOTE=Trunk] Just how big are those panels that the sun is reflecting off? [/QUOTE] I’m not sure, but assume you were looking at a satellite on the ground from two miles away by day. You might not be able to see it for everything around it, but if it were up in the air you probably would. The satellite’s going to reflect 1/2500th of the photons to you when it’s 100 miles away as it would at 2 miles away, which is in line with the differences between day and night vision. (There’s also the fact that we have good point-vision too, so all of the photons packed into one spot might make it easier to see when contrasting against a dark background but I don’t know enough about that to say for sure.) ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [February 5, 2008, 2:48pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/7 "2008-02-05T14:48:08Z")
For your [satellite viewing pleasure](http://www.heavens-above.com/). ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [February 5, 2008, 3:08pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/8 "2008-02-05T15:08:02Z")
You CAN see satellites and pretty easily in my experience as long as you are at a place with clear skies and lots of visible stars. They appear as a steadily moving dot that is way too high to be an aircraft. If you stare up from such a place for a while, you will see one. When I was younger, it didn’t take long to see a satellite especially once your eyes got adjusted to looking up in the dark ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [February 5, 2008, 3:12pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/9 "2008-02-05T15:12:10Z")
[QUOTE=Phlosphr] Not sure if it’s a satellite or what but on very clear nights I can see what appears to be a star moving ever so slowly across the sky…I’ve seen this many times and have always assumed it was a satellite. [/quoTE] If it’s moving slowly, then it’s unlikely to be a satellite. Either it would be stationary (geostationary orbit) or moving very fast indeed (low-earth orbit). I wonder if you’re seeing an aeroplane? ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [February 5, 2008, 3:23pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/10 "2008-02-05T15:23:34Z")
oops, I think I answered the question bass ackwards. Sorry. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 5, 2008, 3:25pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/11 "2008-02-05T15:25:38Z")
[QUOTE=Trunk] Just how big are those panels that the sun is reflecting off? [/QUOTE] You don’t have to be able to see the panels in order to see that the object is there. [Ultramicroscope:](http://en.wikipedia.org/wiki/Ultramicroscope) > [@](#): > > The ultramicroscope is a system of illumination for extremely small objects such as colloidal particles, fog droplets, or smoke particles. The objects are held in liquid or gaseous suspension in an enclosure with an intensely black background (usually a black body) and illuminated with a convergent pencil of very bright light entering from one side and coming to focus in the field of view — the “Tyndall cone” familiar in experiements on scattering. With this arrangement, objects too small to form visible images in the microscope produce small diffraction ring patterns that appear as bright specks on a dark field. Ultramicroscopes are used in the study of Brownian motion, in the Millikan droplet experiment for measuring the electric charge of the electron, and in observing ionization tracks in cloud chambers. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [February 5, 2008, 3:43pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/12 "2008-02-05T15:43:47Z")
\>You don’t have to be able to see the panels in order to see that the object is there. Certainly not. Other than the Sun, this is how we see stars, too - unresolvably tiny points of light that are powerful enough to stimulate the retina, even though the resolution of the retina and the focus of the eye are way to coarse to image the star as a disk. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 5, 2008, 3:53pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/13 "2008-02-05T15:53:52Z")
[QUOTE=Q.E.D.] No question, these are satellites. [/QUOTE] They might just be shiny beetles crawling on the inside of the dome. I’ve seen them too - the reason we can see them is that they’re typically quite reflective, they’re against a dark background, and they’re _moving_ - quite important, that last one - in terms of the human visual system - moving specks are easier to see than static ones. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 5, 2008, 3:55pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/14 "2008-02-05T15:55:54Z")
[QUOTE=Quartz] If it’s moving slowly, then it’s unlikely to be a satellite. Either it would be stationary (geostationary orbit) or moving very fast indeed (low-earth orbit). I wonder if you’re seeing an aeroplane? [/QUOTE] ‘Very fast indeed’ still looks like a fairly leisurely trot across the sky at this distance, though. ---
**Author:** ![Phlosphr](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@Phlosphr](https://boards.straightdope.com/u/Phlosphr)\ **Post date:** [February 5, 2008, 3:56pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/15 "2008-02-05T15:56:47Z")
[QUOTE=Quartz] If it’s moving slowly, then it’s unlikely to be a satellite. Either it would be stationary (geostationary orbit) or moving very fast indeed (low-earth orbit). I wonder if you’re seeing an aeroplane? [/QUOTE] Well slowly to my eyes, is quite possible 18,000MPH for something 200 miles up. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [February 5, 2008, 4:34pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/16 "2008-02-05T16:34:06Z")
[QUOTE=Quartz] If it’s moving slowly, then it’s unlikely to be a satellite. Either it would be stationary (geostationary orbit) or moving very fast indeed (low-earth orbit). I wonder if you’re seeing an aeroplane? [/QUOTE] No, they’re satellites. They look pretty slow, but as they are so high they are covering some distance - quick enough to cross the visible night sky in, guesstimate, a couple of minutes. As for why you can see them, they’re very shiny! I’m sure many of you have seen sunlight shining off very distant car windows - from up a mountain you can often see really bright glares of sunlight from vehicles miles away, and they’re surrounded by bright countryside. Against the backdrop of black space, it’s no surprise you can see them. The Iridium satellites give “flares” as the solar panels reflect light towards a small area on the Earth, which can be (for a few seconds at a time) brighter than anything else in the night sky apart from the moon. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [February 5, 2008, 4:51pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/17 "2008-02-05T16:51:34Z")
[QUOTE=Colophon] The Iridium satellites give “flares” as the solar panels reflect light towards a small area on the Earth, which can be (for a few seconds at a time) brighter than anything else in the night sky apart from the moon. [/QUOTE] Thanks, Colophon. I was trying to remember the name of the [Iridium satellites.](http://www.satobs.org/iridium.html#iridium) ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 5, 2008, 4:59pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/18 "2008-02-05T16:59:40Z")
[QUOTE=Trunk] Now, it SEEMS to me – just my intuition – that I shouldn’t even be able to see the sun shining off something that big at that distance, even against a dark backdrop. [/quote] Satellites are only visible in the evening or morning, while it’s already/still “night” on the ground, but the satellite overhead is in full sunlight. Not only is it a dark backdrop, but everything within sight is dark - except for the satellite. I think you’re just under-estimating just how dark it is at night, and just how powerful the sunlight is. Some big satellites are visible in twilight, but twilight is still much darker than daylight. And the only satellites visible in twilight are the _really_ big ones, like the 200-ft long International Space Station or the 122-ft long Space Shuttle orbiter. > [@](#): > > Just how big are those panels that the sun is reflecting off? You don’t need to see the reflection off the panels. Satellites are usually covered in MLI (multi-layer insulation), which looks like crunkled aluminum foil. It’s pretty efficient at reflecting (scattering) light in all directions. But if they were painted white, they’d only be slightly dimmer. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 5, 2008, 5:06pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/19 "2008-02-05T17:06:50Z")
It’s much more the intensity of the light of the sun they reflect then anything else. Even if the surface is pretty small, the light they are reflecting is very intense, and the light is coming in as a very tight beam, almost laser like. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 5, 2008, 5:12pm UTC](https://boards.straightdope.com/t/why-can-we-see-satellites/436381/20 "2008-02-05T17:12:00Z")
[QUOTE=kanicbird] It’s much more the intensity of the light of the sun they reflect then anything else. Even if the surface is pretty small, the light they are reflecting is very intense, and the light is coming in as a very tight beam, almost laser like. [/QUOTE] Not sure what you mean by a “tight beam” - the sun obviously emits light in all directions, not in a tight beam. A reflection off a flat surface (like a solar panel) is a narrow beam, but that’s not usually how we see satellites. The rest of the satellite reflects sunlight in all directions, which is what we see. You’re right that sunlight is _very_ bright, and this is the reason we can see satellites. Just think about how bright your flashlight looks at night, and how dim it looks during the day. [Next page](https://boards.straightdope.com/t/why-can-we-see-satellites/436381.md?page=2)