What a falling star looks like… from space!

By Phil Plait | August 15, 2011 6:30 am

Astronaut Ron Garan, currently on board the International Space Station, was taking pictures of our home world out the window — and how cool is it to be able to say that? — when he took this amazing picture of a meteor burning up in our atmosphere:

Wow! [Click to bolidenate.] How cool would it be to look down to see a falling star?

He took this shot (according to the header info in the picture) on August 13 at 7:17 p.m. UT, when the ISS was above the Mongolia/China border. This was during the annual Perseid meteor shower, but that doesn’t guarantee this meteor Ron saw was a Perseid. It probably was, though. For an observer on Earth, the Perseids rain down at a rate of about 60 per hour or so. You can usually see about 5 meteors per hour that are just random bits of cosmic detritus. So only 1 meteor in 12 is not a real Perseid, making it likely this one was.

But that got me thinking… [WARNING: math ahead. Cool, tasty, refreshing math that will lead to insight, wonder, potential party conversation (assuming you go to the same dorky parties I do), and other nifty things.]

Meteors burn up roughly 100 kilometers (60 miles) above the Earth’s surface. To make the math simpler, let’s say they burn up at exactly that height, so that any meteor coming in hits this barrier and evaporates. You can picture it as a thin shell of air surrounding the Earth 100 km high, like a force field, or better yet as an umbrella that rain hits (it’s a meteor shower, after all, ha!) and stops cold.

When you look straight up, that barrier is 100 km directly above your head. When you look to the horizon, that distance is actually a little over 1000 km away, because the atmosphere follows the curve of the Earth (you can get an idea of this in the diagram above). The top of this umbrella is then 100 km up and over 1000 km to the sides.

From the space station, though, looking down from orbit at a height of roughly 350 km, more of the atmosphere can be seen because the station is higher up (just like you can see farther if you go to the top of a building). The additional amount seen is very roughly twice the area of the "meteor umbrella" seen from the ground. So, from the ISS, you’d see roughly twice as many meteors in a given time as you would from the ground (mind you, I’m not trying to be terribly accurate here; I’m just getting rough numbers to estimate some things. Anyone willing to do the formal math is welcome to — leave a comment if you do!).

That means, if you’re an astronaut on the ISS during the Perseids, you’d see about 120 or so meteors per hour, assuming you have a clear view all around you — in reality, a lot of your view is blocked by the ISS itself. But still, from up there the view is better. The thing is, you’ll also see more random meteors as well, so the ratio of 12 Perseids to 1 random one should be about the same! So no matter how you slice it, the meteor in the photo above is probably an actual bona fide Perseid.

As you can see by the picture, this meteor was very close to the horizon as seen by the ISS. That means it was pretty far away, 1500 km (900 miles) or more. That’s a long way, especially when you find out a typical Perseid is smaller than a grain of sand! It’s their tremendous speed of 40 – 60 km/sec that gives them such high energies, burning up brightly in our air.

Still… that made me wonder how likely it is for the ISS to get hit by a meteor, and I realized the answer is: very small. Think again about that umbrella above your head where meteors burn up. It has a surface area of about 4,000,000 square kilometers. Yet only 60 meteors per hour are seen in that vast region! Statistically speaking, that means that every hour, a single square kilometer of that umbrella should expect to get 0.000015 meteors. That’s only one meteor every 8 years or so!

The space station is much smaller than a square kilometer, too, so the odds of it getting hit by a Perseid are something like one one-thousandth even of that small number. That in turn means that — again, just statistically and very roughly speaking — the space station should get hit by a Perseid once every 8000 years. Even given the number of meteor showers every year, the odds of it getting hit are pretty small.

There has been a satellite lost to a Perseid meteor impact, though, back in 1993, so it’s not unheard of. But the ISS is armored against smaller impacts like the one that took out that satellite, so danger to the astronauts is significantly reduced.

But then, that’s just what I’d expect! After all, the station has been orbiting the Earth for many years so far, and has not been hit by anything meteor-sized yet. It’s more in danger from man-made orbital debris than anything flung at it from deep space; in fact, it’s actually been moved to avoid bigger debris in the past.

So this works out well: meteors aren’t a statistical big risk for the astronauts, and we get to see incredible shots like this one as well. I’m glad the math works out in our favor!

Image credit: NASA. The picture of the Shuttle getting hit by meteors is from the movie "Armageddon", if you’re curious. I drew the fabulous curving Earth and air diagram myself with my unparalleled Photoshop skills. Tip o’ the Whipple Shield to Universe Today, which has a fantastic gallery of Perseid pictures.


Related posts:

How far away is the horizon?
Southern lights greet ISS and Atlantis
Followup: city lights from space
Clearing the air, or mea culpa, Part 1

Comments (77)

  1. Nicholas

    This is all the evidence a person would need to safely assume that UFOs have not visited our planet since the ISS went into orbit.

    One of the astronauts would have taken a picture by now.

  2. Unless it’s a coverup, in which case the absence of any UFO pictures is exactly what one would expect if we were being visited by aliens, and actually proves their existence. *cough*

    I was lucky enough to be out in the desert for the shower in 2008, and saw one bright enough to leave a trail on my vision (that might even have been a photochemical* trail in the atmosphere!). Incredible way to spend a late evening.

    (I think you mean 12 perseids to every 1 random meteor up there, rather than the other way around. )

    *Err, chemiluminescent

  3. hhEb09'1

    Right, Alex. Ratio backwards, paragraph seven.

    OTOH, didn’t you move your head a bit, and you would’ve known whether it was an after-image?

  4. Michael Fjetland

    Nickolas/Alex: NASA’s policy is NOT to talk about UFO’s or acknowledge same. I have friends there (I live 5 minutes from JSC in Houston). They have photos of UFO’s but you won’t be seeing them…

  5. JSchu

    What does “bolidenate” mean (as in “Wow! [Click to bolidenate.] How cool would it be to look down to see a falling star?”)? It looks like a weird autocorrect but isn’t actually a word …??

  6. chris

    Flawed analysis – sorry, but article mixes data of meteors seen vs meteors enetring our atmosphere,; that is a big difference – probability of impact are actually orders of magnituded higher. In addition, many meteors that are seen, bounce off our atmosphere and keep on moving.

    Shielding is insufficient, for the most part but sending up astronaughts during a meteor shower is deserving of more explanation

  7. chris j.

    actually, the chance of the ISS getting hit by a meteor is exactly zero, since the meteor is the glowing trail left by the meteoroid as it burns up in the atmosphere. also, because a meteor shower originates from a single direction (the orbit of the progenitor comet), it is more accurate to treat the earth as a flat disk than as a dome in terms of surface area. and if the average ground-based observer can see roughly 60 perseids/hour, with a visibility radius of about 1000 km, then the earth-wide rate of perseids/hour should be about 2,160 (rounding the earth’s radius to 6,000 km and neglecting the full radius of earth+atmosphere).

    finally, it doesn’t help the claim that meteoroid impacts should occur only once every 8,000 years by posting a link to an article listing at least 4 impacts in the past 50. that article also highlighted that the danger of impacts doesn’t come from punching holes, but from a plasma cloud that mucks up the satellite’s or ISS’s electronics.

  8. Chris,

    Your thoughts here are valued, however I would appreciate it if you would not post on my blog again. You make me look bad.

    Thanks,

    -Dave

  9. Phil, your statistics are abit off.
    The ZHR does *not* equal to the number of meteors in your “umbrella” of atmosphere per hour.
    It does not pertain to the full “umbrella”, but to the Field of View of one human person observing under a limiting magnitude of mag. +6.5 with the center of vision at 60 degrees altitude and the radiant in the zenith. This one person will only see part of the sky, not the full 180 degrees half-dome. Moreover, he will not see all meteors in his FOV but only a fraction of it, especially where fainter meteors (smaller particles) are concerned. On the other hand, in reality the radiant is seldom in the zenith, but lower in the sky, which means less meteoroids per surface area will pass.
    The true amount of meteors entering through the airspace covered by your “umbrella” is however probably larger by a factor “several” than the “60 per hour”.
    Look up some papers on meteors and you’ll actually find mass influx values per surface area for streams like the Perseids. For the Perseids, the stream contains approximately 2.7 x 10^-24 grams/cm^3 of matter in the core of the stream (with a zero magnitude meteor being about 0.13 grams in mass): along with their speed and size distribution (r), that should give you enough to calculate the true volume of particles per square mile of atmosphere. However, that value will be variable as it has to take into account the altitude of the radiant for that particular locality and time of night.

  10. Nunya

    Chris J.
    Actually, your whole post is moot and useless. You did not capitalize your first sentence, your grammar and presentation is horrible, and you are simple re-describing an idea in different terms.

    Don’t be a jerk.

  11. StephenDoud

    In a nod to the author, I read the article.
    But my high school geometry class makes me differ with the author’s statement: “When you look to the horizon, that distance is actually a little over 1000 km away”

    According to the simple picture supplied, with concentric arcs representing the earth and 100Km ‘umbrella’ barrier of air, comparing the vertical and horizonal ‘view’ line ratios on the picture indicates the distance to the barrier looking toward the horizon is more like 300Km. No?

  12. RwFlynn

    Haha! When I first saw it I knew it was only a matter of time before I saw that picture show up here. And with the same insightful information as well!

  13. Ben Gorman

    @Chris J.:

    The notion that any meteor shower’s particles originate from “a single direction” suggests a point source, which is not, I think, accurate. Meteor particulates are assumed to be ejected or remnant mass from comets, which indeed follow orbits around the sun. But surely these particles don’t follow one another in single file, like ducks in a row, along a neat path as narrow as a highway! It would seem more reasonable to postulate that a large, active, solar-excited comet, spraying its mass willy-nilly in a coma-cloud around its rocky nucleus, would instead produce a very wide, messy orbital trail. What width? I’m sure others keep more current with the science, but I would guess it’s plenty wider than Earth, typically. Therefore, as Earth passes through a comet orbit, it’s more likely entering a large area of streaming debris.

    This assumption is borne out by two observations: 1) meteor showers typically last for severals DAYS, with peaks covering several hours; Earth passing through a point-source stream (at its approx. 18 miles/sec. orbital speed) would certainly not permit such long showers. 2) Any given meteor shower’s individual meteors can be seen in ANY region of the sky, separated by huge distances, though MOST trails, if followed visually, TEND to indicate an origin point associated with the particular shower.

    So I think the odds for collision are in fact higher than you suggest, given the planet-wide area of activity.

    Cheers.

  14. Peter Davey

    To follow knowledge like a falling star, to the utmost bound of human thought –

    Alfred Lord Tennyson.

  15. Marco,

    Please do not post here again.

    Thanks,

    -Phil

  16. Farbeda

    Forget all of this jabber of competing calculations and let’s get down to real science. Of course NASA has no picture of UFOs. Everyone knows they use cloaking devices.
    Duh!

  17. JSchu

    Answered my own question:

    bo·lide
       [boh-lahyd, -lid] Show IPA
    noun Astronomy .
    a large, brilliant meteor, especially one that explodes; fireball.

    and you’ve invented a verb from that, very creative.

  18. QuietDesperation
  19. Phil,
    You say:

    “…assuming you have a clear view all around you — in reality, a lot of your view is blocked by the ISS itself.”

    This is probably not true. Most of the vantage points used by astronauts to look at the Earth are windows facing downward (also called ‘nadir’) and have a pretty wide unobstructed view. Especially from the large bay windows known as the ‘Cupola’. This fisheye view from ISS demonstrates my point perfectly:

    http://tinyurl.com/3gmb54g

    Amazing view, is it not?
    – Ben H.
    Space City, TX

  20. Edge

    If you think THAT picture is stunning, take a look at the pictures that were taken from the ISS of Shuttle Atlantis entering the Earth’s atmosphere during it’s final descent on July 21:

    http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts135/multimedia/fd14/Image_Gallery_Collection_archive_9.html

  21. Also, the ISS is CONFIRMED to have been hit by MMOD (micrometeoroids and orbital debris) countless times. Of course, there’s no way of knowing which impacts are man-made debris and which are meteors, so its hard to use this fact to check out Phil’s statistics and probabilities. But for those that are interested, check out the article on page 5-7 here (it’s a downloadable PDF from NASA’s orbital debris office):

    http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv15i3.pdf

    In fact, when astronauts go out for spacewalks (known as EVAs) on ISS, the flight controllers on the ground can be heard reminding the astronauts to avoid certain handrails that are known to have craters on them from impacts. The edges of the craters are sharp and may cut a glove.

    – Ben H.
    Space City, TX

  22. I never understood the belief that UFO’s were aliens. They have zero reason to come here in particular, if they do come here, they have zero reasons to hide. If they did come here, they have zero reasons to mutilate cattle, abduct humans, or any of the other things they are supposed to have done.

    Time Travelers on the other hand make perfect sense. They come here because they are human (or decendents of human), they don’t want to interefere with our time line, and the majority of reported activities are things a human might do. (If I travelled back in time I might mutilate a Dinosaur – both to get a DNA sample and to try a Dino-Steak).

  23. Andrew (or should I say An-DRO),

    Do not speak of what you do-not-know? mmkay? It’s a well known fact that aliens enjoy mutilating cattle. There is no such thing as time travel as it is impossible to travel faster than the speed of light (might I add that right now, you appear to be moving at the speed of confusion).

    Get your dank straight before steppin up on my ship, mutha-board!

    -Steve

  24. chris j.

    Marco Langbroek @10:
    very good point about the ZHR as dependent on limiting magnitude. of course, lower magnitude meteors imply smaller meteoroids, which raises the question, how small can a meteoroid be, before it ceases to be a threat to a satellite’s or the ISS’s electronics?

    Ben Gorman @14:
    you are exactly right, hence what i said, that you can simplify the calculation of the total number of meteoroids hitting the earth by treating the earth as a flat disk facing in the direction of the meteor shower.

    nunya @11:
    i uncapitalized your name for you. you is welcome.

  25. Phlip

    @StephenDoud: The difference is just because that diagram isn’t to scale – in real life, the distance between the circles is much smaller compared to the radius of the circles, and that makes the ratio of horizontal-distance-to-sky vs vertical-distance-to-sky much larger.

    Some quick calculations confirm the 1000km figure: http://www.wolframalpha.com/input/?i=sqrt((earth+radius+%2B+100+kilometers)^2+-+(earth+radius)^2)

  26. Tommy

    “Chris J.
    Actually, your whole post is moot and useless. You did not capitalize your first sentence, your grammar and presentation is horrible, and you are simple re-describing an idea in different terms.

    Don’t be a jerk.”

    -I noticed a number of grammatical errors in this post as well.

    Just sayin’.

    -Tommy

  27. Someone who knows what the bright light to the left of the meteor trail is? The Moon perhaps?

  28. QuietDesperation

    Someone who knows what the bright light to the left of the meteor trail is? The Moon perhaps?

    The clouds seem lit by the Moon offstage in the other direction. My guess would be just sunlight from around the Earth’s curve.

  29. (Unlocks phone, opens pic in browser, sets as phone wallpaper)

  30. GT

    Adrianus V — probably a UFO.

  31. Chelsea

    No fair. They get a grant vantage point up there. Here I waited months for this meteor shower and the darned moonlight blew the show right outta the sky.

    I’m glad all you eggheads are doing the math, I hate doing the math, just want to take the pretty pictures. (Big thankyou to whoever figured out the arc measurements on my barndoor tracker.)

    So all this arguing and pondering has my brain cells disturbed, and got me to wondering about the stream of particles left behind by comets. How fast are these bits and pieces and granules moving around in the stream? And maybe it ain’t the earth getting hit by meteoroids so much as these little bits and pieces just floating around out there are getting slammed by the earth as it comes whizzing by, rotating in its orbit around the sun. Physics wasn’t my greatest subject either, and there is some vague memory of objects in motion staying in motion until gravity and obstructions slow them down. How fast is this stream of particles dispersing? Knowing that comets come whizzing by faster than the highest speed my pickup truck can go, I am amazed that the wee bits and pieces are still IN a stream and not scattered far and wide by now. Yous guys that love to argue this stuff, please ‘splain it to me. (Plain English please, no equations.)

  32. Jason Miller

    On a night flight from New York to Cincinnati, I was staring out the window to keep the tube claustrophobia at bay. Suddenly, there was a bright, vertical streak of light that flashed downwards then puffed to nothingness as the lower atmosphere finally snuffed it out. The incident was one of those things that is totally natural but feels so extremely unnatural – one of those images that one does not forget.

  33. Bill McQuillan

    Several years ago I was scanning around on Google Maps over the Arabian Desert. Out in the “Empty Quarter” I ran across a straight line that I thought was a road. As I zoomed in I could see that it did not seem to have any effect on the landscape, it looked more like a line drawn with a ruler across a picture of sand dunes! As I scanned along it, it just faded out at each end. I decided that it was a meteor captured by a satellite image.
    I have looked for it more recently, but I can’t find it (I apparently forgot to bookmark it!) I guess that the image has been updated.
    This image of a probable Persied looks much like what I remember of that trace.

  34. Daniel

    Cool! Thanks for sharing. But the image of the meteor streaking through the atmosphere also illustrates how close the atmosphere is and how astronauts in orbit are only “kinda sorta” in “space.”

  35. Shari K.

    Re: BOLIDENATE… I second the comment from JSchu. :) I checked several dictionaries but apparently “bolidenate” is NOT a word. Taking it in context here, it obviously means to make larger, since when I clicked the pic, I got a larger version of it.

    Can this columnist, or perhaps Discover’s editors, please address this? I work as a professional copy editor & proofreader, and consider myself a huge “word nerd,” so I have to say my curiosity is VERY piqued as to whether this is actually a new word, or if it’s just a typo. Either way, hope to hear from someone soon.

    Cheers,
    Shari K. in California

  36. Brian Too

    @23. Ben H.,

    Regarding cratered handholds and the likelihood of cutting a glove. That sounds like a moderately serious EVA risk; wouldn’t that be on a to-do list somewhere, to round off any sharp edges? Or are the EVA’s too infrequent and risky to make that worthwhile?

  37. Tom

    Anyone ever hear a meteor? Yeah, I know you can’t, no air and all that. Except I really do think I did.

    Wife was with me in a field in the mountains watching the Perseids, and I said, “That was wild!” And she said, “What, did you hear it too?” No previous discussion of the possibility, none.

    Googled my brains out the next day, and it seems we aren’t the first to think we heard something. Might be a psycho-acoustic effect, like the way music seems to be timed for un-synced video, etc.

  38. Christopher

    This image was posted on NASAs website and captioned as a shuttle reentry.

  39. Christopher

    This image was posted on NASAs website and captioned as a shuttle reentry.

  40. @ ^ Christopher :

    Are you sure? Or, maybe, were you thinking of this one :

    http://blogs.discovermagazine.com/badastronomy/2011/07/22/the-fiery-descent-of-atlantis-seen-from-space/

    or this one :

    http://blogs.discovermagazine.com/badastronomy/2011/07/22/the-fiery-descent-of-atlantis-in-3d/

    instead?

    Here’s another awe-inspiring image for comparison :

    http://apod.nasa.gov/apod/ap091130.html

    which through accidental (or purposeful?) geometry looks a bit like a meteor has streaked by then exploded high in the atmosphere and close to the International Space Station.

    Spectacular photo – amazing that we can take it and that humans have this vantage point. :-)

    If only we had more and higher outposts of Humanity .. what other spectacles could we see and experience from the Moon, Mars , asteroids and beyond.

  41. JB of Brisbane

    @JSchu & Shari K. – you guys need to read more of Phil’s blog entries – he uses lots of embehemothated words like that.

  42. Mark Hansen

    Is it possible that the small light that a couple of commentors have asked about is Jupiter?

  43. Ozonator aka Robert Rhodes

    I was incorrect in the 2-week and 1-week models for predicting that fireball from AGW. I was notably ~5 hours incorrect for just missing with the “Tien Shan” prediction under – “D). Including the odd chance of JJBAL Fireballs with each prediction, with included statistics, warnings for the Pickerell Model (8/14 – 20/11) for qualitative AGW volcanic warnings among tectonic energy lines with individual predictions for regions are: 1). Chile – Ecuador – Hawaii – Aleutians – Kamchatka – Kurils – Japan – Philippines; 2). Democratic Republic of Congo – Ethiopia – Red Sea – Saudi Arabia – Iran; and 3). Santorini – Stromboli – Armenia – Kazakhstan – Tien Shan” (“GBRWE 8/14 – 20/11”s Extreme Planetary Warnings for Earthquakes, Volcanoes, and Solar/Terrestrial Flares from Human Activities”; Robert Rhodes, Supplemental; GBRWE 8/14 – 20/11, 8/13/11).

  44. Unspeakably Violent Jack

    @ JB of Brisbane
    All of which are of course perfectly cromulent.

  45. hhEb09’1: it faded too quickly for me to think to do that, in maybe a few hundred milliseconds. More like the afterimage left by a sparkler waving in front of you, than the annoying spot from a camera flash.

    Edit – I finally got around to doing some reading on the subject and it seems chemiluminescent trails tend to last on the order of minutes, so most likely it was an afterimage. It was spectacular regardless.

  46. Lily

    cromulent?? embehemothated? can the author please enlighten foreign language speakers?

  47. MadADDer

    @ Lily, #52:

    Both of these are made-up words, actually, and not (officially) part of the English language.
    Embehemothated means “made larger;” from the word behemoth, an adjective describing something very large, usually a creature.

    Cromulent is a pop-culture reference to an episode of The Simpsons. It means that the made-up word used – embehemothated, in this case – is acceptable in this context.

  48. Unspeakably Violent Jack

    @Lily

    Mrs. Krabappel: “Embiggens”? I never heard that word before I moved to Springfield.
    Ms. Hoover: I don’t know why. It’s a perfectly cromulent word.

  49. Adam

    Your estimates are way off!
    The shuttle windshield has been hit many times already:
    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950019959_1995119959.pdf

    The ISS is much larger then the shuttle windshields and spends a lot more time in the environment.

  50. Adam (56): As I pointed out, manmade orbital debris is a bigger danger, and is most likely the cause of most low-Earth orbit impacts.

  51. Richard

    Many years ago when I was a pilot in the Air Force I had a close encounter with a meteor. We were doing mid-air refueling training in a practice area east of Lake Havasu City, Arizona. It was late afternoon and the sun had fallen behind a bank of clouds on the horizon. We were at the western end of our refueling track and had started our turn back to the east. As I cleared the air-space in advance of our turn a meteor came streaking down through the area bracketed by our aircraft (an EC-130 and a KC-135) and their wings. It burned out very low to the ground so I suspect that there are parts of it sitting out in the desert. It all happened so fast, yet it’s one of those “once in a life time” events that stay clearly etched into your memory.

  52. Adam

    Of the 11 samples that they tested they had 5 that were manmade, 3 that were micrometeoroid and 3 unknown (with a total of 177 impacts as of the publication of the paper). That doesn’t sound like a statistically significant difference to me.
    The paper also says that they average 0.31 impacts per mission day. That is nowhere near one hit to the whole ISS every 8000 years.

  53. de-vilish-sly

    Phil– Love the pic, love your site, profound respect from Grasshopper, and maybe it’s a little late, BUT …

    Your article “How far away is the horizon” unfortunately applies only on the Moon, or similar anatmospheric bodies. On Earth, *particularly* near the horizon, atmospheric refraction makes the visible horizon much farther off. Even Tycho Brahe knew that the precision of observations low in the sky was unreliable, and I hate to think how many sailors had their beers delayed because the island was farther away than they thought.

  54. Ben H.

    @42 Brian Too
    Here’s an interesting paper on the topic of ISS EVA glove damage mitigation:

    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090012274_2009011981.pdf

    I think part of the answer to your question is that it only takes a very small object to create an impact crater on the handrails that can be a hazard. We don’t know where they all are and they are hard to see, so the focus has been on avoiding them and improving glove design, rather than trying to find all the damaged hand rails and replace them – which would take a lot of time and as you say, EVA time is very valuable.

    I believe the article on page 3 of the following document discusses some preliminary results of the tests that were later written about in the paper linked above. It also has some good pictures of what the real hand rail crater on ISS looks like (hint: its tiny!) and discusses how astronauts were told to avoid it on later EVAs.

    http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv12i3.pdf

    Since this was from back in 2008 I’m trying to figure out if we’ve replaced any hand rails since then. But I can’t find any documentation saying explicitly one way or the other. I did find some information that NASA has image documentation of over 100 MMOD strikes on ISS (not all hand rails).

    – Ben H.
    JSC, Houston, TX

  55. Ralph Tyrrell

    I realise space is empty (mostly) so when objects move towards earth, they come across the atmosphere which is thicker because of air and all the other stuff. And the friction at great speeds will have this sandpaper effect – and they burn out. But if you just take it easy, put the brakes on and sort of drop slowly down towards earth, surely you won’t burn up. Never had it explained to me why Shuttles and other returning spacecraft have to hurtle down at huge speeds and take all that heat. Why not just drift down slowly – take your time? What am I missing here? The analogy with an umbrella doesn’t work too well with me becasue it assumes a hard outerskin. Atmosphere is not hard at the outer edges – its just thicker and very gradually so?

  56. @67 Ralph
    Your thought process is correct, and very insightful. You are pondering orbital mechanics without the math. The piece you are missing is that the speed and energy of your spacecraft is proportional to your orbital altitude. At the altitude of a space shuttle, orbital speed is on the order of 18,000 mph or more. Therefore, the vehicle must decelerate by 18,000 mph to come to rest on a runway in Florida. Now, you COULD theoretically use the space shuttle engines to do all of the decelleration down to terminal velocity, so that you essentially fall straight down into the atmosphere as you speculated. However this would require an amount of energy equivalent to that used to get the space shuttle UP TO that speed in the first place. IE, two solid rocket boosters and a full external tank of fuel for the space shuttle main engines. This is logistically improbable, if not impossible. therefore, mission designers only slow down the spacecraft enough for the orbit to intersect the atmosphere, and let the friction do the rest.

    Hope that helps!
    – Ben H.
    JSC, Houston, TX

  57. Nigel Depledge

    Michael Fjetland (4) said:

    NASA’s policy is NOT to talk about UFO’s or acknowledge same. I have friends there (I live 5 minutes from JSC in Houston). They have photos of UFO’s but you won’t be seeing them…

    Yeah, right, as if NASA could prevent employees from publishing photographs online.

  58. Nigel Depledge

    Chris J (27) said:

    nunya @11:
    i uncapitalized your name for you. you is welcome.

    Wow, until I read this I never realised how amazing I am, being able to hold down the “shift” key while typing a letter. . .

    Seriously, is it so difficult for you to use good English?

  59. Nigel Depledge

    Shari K (41) said:

    Re: BOLIDENATE… I second the comment from JSchu. I checked several dictionaries but apparently “bolidenate” is NOT a word. Taking it in context here, it obviously means to make larger, since when I clicked the pic, I got a larger version of it.

    Can this columnist, or perhaps Discover’s editors, please address this? I work as a professional copy editor & proofreader, and consider myself a huge “word nerd,” so I have to say my curiosity is VERY piqued as to whether this is actually a new word, or if it’s just a typo. Either way, hope to hear from someone soon.

    Cheers,
    Shari K. in California

    Phil is a great proponent of neologisms. They’re all perfcectly cromulent.

  60. Minnie

    Maybe this will soften those that that totally don’t think there might be UFO’s. I offer you Gordon Cooper, astronaut. Not proof, but…

    http://www.youtube.com/watch?v=dvPR8T1o3Dc

  61. Jonny

    Anyone who can do math can reasonably say that UFOs are pure fantasy. The universe is not teaming with life. Even if it was teaming with life, even IF it was, the vast distances between even neighboring star systems make regular visitations virtually impossible let alone even remotely practical.

    Those who cling to UFO superstition ought to join their televangelist Christian brothers and sisters who sell miracle healing hanker-chiefs. Just pray the right words and you will be healed of anything! even senseless superstitions!

    Pareidolia is a powerful and deceptive mental faculty and everyone would do well to understand what it is and the tricks their own brains play on them. The government isn’t making cover-ups and telling you what to think, your brain does an excellent job of that without any help from the government.

  62. randy

    You have some extremely flawed assumptions here. First you are assuming that a meteor shower hits the earth in equal portions throughout the earths atmosphere which is never the case… when is the last time that you saw a meteor shower take up more than a portion of the visible sky. Using your logic that would mean that there are then even less meteors to possibly hit the ISS which is absolutely wrong there are more. Why? Because we only see the meteors that hit our atmosphere. There may be many more meteors passing at say 350km

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