How Cosmic Rays Make Astronauts See Stars

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Some astronauts have reported the same specific symptoms: they see mysterious flashes of light out of the corner of their eyes. What causes those bizarre phenomena, and how does it affect astronauts?

Learn more about Cherenkov Radiation:

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  1. Carl Kingery

    You skirted the fact that the Apollo Astronauts passed right thru the Van Allen Belts. One did not even think he went out far enough to go through the belts. Once he was told that they actually (ha ha) went through the Van Allen Belts he then started the tap dance and was not censured by NASA or killed like Gus Grissom was by that unfortunate fire.

  2. Alex Landherr

    Christer Fugelsang had an experiment aboard the ISS studying this phenomenon in 2006, I got this fact from one of his books.

  3. cyancoyote

    Isn’t that just Cherenkov radiation?

  4. Clark Rector

    there is a high probability that these rays are not by accident. could be a pulse consisting of information or part of an unknown web through space and time. the focus on these rays with research in time dilation could yield some answers. question.. how does time dilation effect our vision / eye and sensory organs?

  5. AxDhan

    we need to do an eyeball of ballistic gel

  6. Markush Avalone

    Maybe it can explain why I always see “colorful sparkle”? Because (sometimes) I can look at the sun directly without feeling dazzled at all

  7. Blue Lotus Organic Red Wine

    Masons….you are followers of a Lie…there are no astronaughts….NO Apollo 11 landed on the moon, neither any other Apollo program…think… the brain the creator of all things gave you

  8. a single white female

    You have the same voice as Penn Jillette.

  9. Edwin Mejia

    wrong title, it should have been “why astronauts see random flashing lights”
    also, that phenomenon happen here on earth to any person that
    sees a sudden burst of bright light.

  10. TazeMeBro McCleskey

    I see lights flash at the corner of my eyes when I’m trying to go to sleep. blue, green, red, white. i have a really hard time sleeping, not because of the lights though

  11. Topias Paljakka

    Are there Van Allen belts around all planets and moons?

  12. Sarge Scum

    so when they see unknown objects, they don’t really see them.

  13. qdmc12

    I have these symptoms and I’ve never been to space..

  14. Moonbeam

    I bet it aliens.

  15. Frazer White

    but they wen’t to the moon, yet the Van Halen bands are so dangerous we can’t go back because NASA will get sued by the astronaut and then NASA will sue the government which will lead to the goverment taxing the poor. Which will then end up with civil war. Space exploration is doomed thanks to Van Halens eruption of radiation..

  16. Moonshire Pony

    Here’s a question for a Scishow: What’re the most horrifying ways you could die in space (from falling into Jupiter to being fried by a GRB.) Is there even any way we could hope to exist for a long time on a spaceship in simple “calm” interstellar space? (Upvote please! It’d be an awesome Scishow subject I’m sure.) ;)

  17. None of your Business

    Why do we keep calling a bombardment of protons “radiation”? And don’t give that duality thing – if I get hit by an ionized hydrogen atom stripped of its electron, how is that not a “particle”?

  18. HuskyArts •

    Is it possible for anyone on earth to see sutch a thing or am i just crazy


    I identify as a cosmic ray visual phenomena.

  20. PresentTeck Labs

    I see similar spots sometimes, a handful of times a month at most. usually less. I should note the dates and times and see if they line up with solar storms.
    red, blue, green, white mostly. eyes open or closed, but always in dim or dark light. notably different than static. not always looking at the sky though…
    things to think about (I have good vision, don’t need glasses)

  21. Cyborg Manticore

    What makes you think the source of light come specifically from within the eyeball?
    If your helmet was hit by cosmic rays, it’s much more likely to hit the brain rather than eyes. It’s a much bigger target.
    Chances are, the brain could be the one generating this phenomenon when struck by cosmic rays.

  22. Federico Greco

    Is there something wrong with the audio or am I going crazy?

  23. Blue foos

    Cool cool

  24. Archis

    Don’t like it when someone says “faster than light”

  25. gregman2013

    QQ why not built a magnetic field around the space ship? Wouldn’t a high powered electromagnetic field protect the space ship like a miniature version of the earth’s?

  26. RainyDayLady

    So there are things that travel faster than light?

  27. alek syd

    It’s like a cloud chamber in your eye

  28. Dutrius

    My vote is for Cherenkov radiation. Also, I’ve experienced this myself once. My physics teacher used to see them every now and then and when he did, he would close his eyes and claim to see faint particle tracks.

  29. Chris Bennett


  30. what else is on

    Why not just give spacecraft magnetic fields of their own? In the vacuum of space superconducting magnets should be much easier to keep cold so long as they themselves are shielded from direct radiation. Even conventional rare earth permanent magnets should be able to deflect charged particles.

  31. Gayaтнrι

    I thought that nothing could surpass speed of light…..

  32. Emilia Holappa


  33. Jorge Chávez

    this guys voice so deep though

  34. seahawk124

    I wish Reid would do all SciShow and SciShow Space episodes.

  35. Inherent Emperor

    this makes us believe there is only one GOd Allah

  36. Chris Hernandez

    we get them down here on the ground level too. I see them on rare occasion.

  37. Karen Parker

    I see those. Several times a decade. Blue dots and sometimes streaks. Once or twice a white streak. Freaky at first, but now it’s just a bit startling.

  38. KiddsockTV

    Let’s ask Dave…

  39. Trevor Harrington

    Fifteenth comment!

  40. Kira

    Is it possibile on earth?

  41. Seth Apex

    why can’t we just generate a magnetic field around the crew cabin when it passes through the van Allen belts

  42. Party Bot

    Reed Richards unavailable for comment.

  43. The Sapien

    Another way to see these is to go into a cave. It will shield you from most other radiation except the high energy particles.

  44. Iago Silva

    3:11 Easy: when in doubt, always torture some test animals… let’s get torturin’! XD

  45. TheCimbrianBull

    When I’m sitting on the throne taking a dump I also see stars if I squeeze hard enough. :-)

  46. Kevin Burris

    wow I’m early, where’s my worm

  47. duhast43

    I have that from taking psychedelics.. Erhm, maybe I even went to space!

  48. Sim Tan

    I love his voice

  49. Jonathan Pesek

    They should wear lead contacts. This will definitely solve more problems that it creates.

  50. Boys In Boats

    First dislike *troll

  51. Black Sheep

    0:52 Yuuge

  52. Jesse Estrada

    there is a really loud noise on the video just before ghe end…anyone else hear it?

  53. kiel wright

    A see flashes of lights like that every so often usually when I get dizzy

  54. Aiden

    it’s full of stars!

  55. john3Va

    This guy sounds like Teller from Penn and Teller…. just saying

  56. Gigavolt

    It’s February 15th, at 7:06 pm.

  57. Issolom Issolom

    I miss u hanks


    Try tinfoil helmets. My nutty uncle swears by them. They also keep out mind control radiation from the HAARP array and harmful chemtrail residue.

  59. David Campos

    541 up is mine.

  60. Magical Fungi

    i wonder if this has something to do with how many astronauts come back with visual impairments.

  61. Perun42

    Thanks as always

  62. Max Elkin

    0:34 “Cosmic rays aren’t really rays of light, they’re extremely high energy subatomic particles”
    Oh, so like high frequency photons? 😜

  63. Beazy Blooiis

    Astronauts never made it past the van Allen belts NASA said so themselves.

  64. Daniel Dogeanu

    This would be deflected easily by a magnetic field, if the spacecraft had one. I’ve heard that they plan to make the technology standard for spacecrafts traveling to Mars.

  65. CelesteofOz

    That’s exactly what I see a day or two before getting a migraine

  66. Felix Lagemann

    This guy is a badass, I love him.

  67. Muhuru

    you sound like compresssed dark charcoal

  68. Finn Reinhardt

    290 likes 0 dislikes

  69. Niels

    Is it wierd that I read “How Comic Sans…” instead of “How Cosmic Rays…”?

  70. Nick J

    Why is it that all the speakers on this channel speak so SLOWLY !!

  71. Loki

    Congratulations SciShow, you tough me something I never knew existed.

  72. Sufyan Maintain

    i sometimes see stars at the corners of my eyes tho on earth…. explaine that

  73. Jordan Toms

    I sometimes see “stars” when I run or do some heavy exertion.. not always. I was told that it’s basically sudden blood pressure pushing on the optical nerve.. a definite different type of flash, but I’m out here hoping it’s not tumors.

  74. LayAnEy v.1.1

    I’ve seen those blinkingstars too, I thought that I just was dizzy or something. So was that because of the “high energy particals”?

  75. Cs Dn

    Cherenkov = pronounced SHAR-en-koff.

  76. VariantAEC

    I thought I could see Gamma rays…
    Turns out I see microwaves instead.

  77. Firebrand

    There’s a party in my head and everyone is trippin’out!

  78. Mcrazy

    Can we just put a strong magnetic field around the spacecraft?
    would work I think.

  79. Sriram Yenigabal

    PLEASE DO A VIDEO ON THE 104 satellites launched by ISRO

  80. Dodge This!

    Mulder would disagree with Scully on this one.

  81. dIRECT0R

    “Here, stare into this neutron beam…”

  82. Saahil Davey

    they can wear magnetic suit as it is cold in space the magnetic substance will not lose its properties

  83. orhan keyvan

    Explosive supernovae *outside of our solarsytem*… well I’m so glad they aren’t inside our solar system

  84. CrashingBrain

    So +SciShow Space… you are following the edX course by Christer Fuglesang too?

  85. T4nkc0mm4nd3r

    Always enjoy Reid’s presentations (and Caitlin too mind you).
    As a nuclear engineer, the idea that they actual had people look at a neutron beam rather angers me.

  86. Soelbro's Meatballs

    Is it known if workers at a nuclear power plant or reactor experience a similar effect?

  87. trgtrg

    woot ?
    faster than light ?

  88. Kalieb

    I see stars in my peripherals if I’ve been sitting for a while and get up really fast

  89. Nikolaos

    Thanks for the upload. :D

  90. Robert M

    Nice vid.
    They should prerecord that outro.

  91. Sky_stider223

    Could these flashs happen on earth?
    To people sleeping at night?

  92. ihartevil

    thx or this awesomely ha bisky vid i love these so much keep up the amazing work cant wait to see you at vidcon again

  93. Om Alive at last

    Earth’s magnetic field is dropping fast ……..wake up

  94. YouDontKnowMe

    I see lines of light when I travel at warp speed… It is pretty interesting to witness to be honest.

  95. Danny Vasquez

    2:30 Hahaha! That’s awesome that they got them to do that, though. 😂

  96. i208khonsu

    I thought the thumbnail said “visual pneumonia”.

  97. Gilgwath

    On the Neutron Beam device: “Danger! Radiation Hazard! Do not look at the operational end of the device”. Scientist: “Daah what ever we’ll be fine” *points it at test subject*

  98. Jack DuVal

    I luv space. Will you be my Valentine space?

  99. Prentice Darlington

    This chap’s voice makes me smile. It’s just all there, honest and booming away.

  100. Master Therion

    I thought the reason astronauts see stars is, oh I don’t know… maybe because they are in space!

Comments are closed.