1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B What is the smallest particle which can be visually observed

  1. Jun 25, 2017 #1
    What is the smallest particle which can be visually observed with a microscope?
     
  2. jcsd
  3. Jun 25, 2017 #2

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    What kind of microscope?

    Optical?
    Electron?
    Scanning tunneling?
     
  4. Jun 25, 2017 #3

    phinds

    User Avatar
    Gold Member
    2016 Award

  5. Jun 25, 2017 #4
    I do not know how objects of observation appear through an electron microscope or scanning tunneling. Will Google images.

    I am looking for the smallest particle which can be seen visually, as it is, by any means.

    Images of atoms I have seen are all artist's representations.

    The latest I heard, DNA molecules also cannot be visually seen.

    But then, having no experience, I don't know where the line is crossed from actually seeing a particle to conceptualizing it.

    Thank you.
     
  6. Jun 25, 2017 #5
    Thanks!
     
  7. Jun 25, 2017 #6

    Nugatory

    User Avatar

    Staff: Mentor

    It depends on what you mean by "visually observed". Without qualification, most people will understand the term to mean optical observation: Light from the object being observed is directed through a system of lenses to the retina of the eye to form an image. By that definition, the resolution is limited by the wavelength of visible light to a few hundred nanometers.

    However, if you're willing to accept more indirect methods we can do much better. For example, x-rays have a shorter wavelength so x-ray microscopes can resolve objects as small as a few tens of nanometers; we cannot visually observe the x-rays but we can and do use them to expose photographic plates that we can visually observe. Scanning tunneling electron microscopes form their images even more indirectly, but have resolutions of a tenth of a nanometer or less.
     
    Last edited: Jun 25, 2017
  8. Jun 25, 2017 #7
    Found some images of atoms, but don't know what I am seeing. Would upload if it were possible. One is a blurred shadow. I would not call it seeing the atom as it is. The other is quite interesting, and looks very different than artists' conceptions. Of course, a static image cannot convey movement. It looks like a honey comb and the description says, 'Bond-Order Discrimination by Atomic Force Microscopy," Leo Gross et al, Science, September 2012.'
     
  9. Jun 25, 2017 #8

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    They say "seeing is believing" but our visual appreciation is actually very limited in both ways (large and small scale). it's difficult to draw the line at what's 'visible'. I would say that it's just as valid to say we can 'see' atoms with an electron microscope as to say we can only just manage to see some of the smallest invertebrates (unaided eye). Human acuity varies a lot from individual to individual. My youngest son can see stuff that no normal human can see. I think he must have elven genes in there somewhere.
    On the large scale, we can't actually 'see' our galaxy, if that has to imply awareness of the form of it - 'we cannot see the wood for the trees'. The confusing array of twinkling dots that we see on a dark night is completely impossible to make sense of without 'learning the system'. But we can model the Solar System and we can even map the Universe - at least give a representation of direction and distance of things.
    Also, we don't need our eyes to 'image' things. Our tongues give us an excellent 'picture' of the inside of our mouths although our eyes never get to look in.
     
  10. Jun 25, 2017 #9

    Nugatory

    User Avatar

    Staff: Mentor

    Those images are made by taking the electrical signals coming out of a fairly complicated experimental apparatus and plotting them on a video screen. They'll be hyped as "visual images" but they're better thought of as a visual presentation of non-visual data, like any other graph.
     
  11. Jun 25, 2017 #10

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    Google " scanning tunneling microscope images" and you'll see lots of them. But as the others said, they stretch the definition of visual images.

    In the famous image below, they not only show the atoms, but they pushed them around into a dot matrix pattern.

    Microscopy5.jpg
     
    Last edited by a moderator: Jun 25, 2017
  12. Jun 25, 2017 #11
    I love it!

    Good to remind myself of these things.

    Maybe my whole premise is off. I was exploring the idea of the normal range of human awareness. Most people know 'of' molecules and atoms, but the range of felt experience for most people is probably no smaller than the cell. Would it be accurate to say that what cannot be perceived over the senses becomes conceptual? Not to say that what cannot be visually seen does not exist! But what people can relate to in daily life....
     
  13. Jun 25, 2017 #12
    Is the Moon only a conceptual sphere but a flat disk in daily life? Does Antarctica exist only conceptually for most people? What is the purpose of your question?
    Anyway, the one big difference between humans and animals is exactly the ability to understand things beyond our personal experience. Trying to stop using this ability will do you no good.
     
  14. Jun 25, 2017 #13

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    This is an interesting topic. Imo, there is too much made of our visual sense. The picture we build in our minds tends to be 'played back' to our consciousness as a TV picture and that makes us conclude that the model is visual. This would imply that people, blind from birth, would have no spatial conception at all, which is clearly nonsense - and quite insulting to someone (not me) who travels into Central London daily and negociates the transport and road system to visit new places regularly.

    "but the range of felt experience for most people is probably no smaller than the cell." That's possibly true but not because of scale. It's because most people have just not grown familiar with the layout. To my mind, it's a bit like the fuzzy picture that people have of the engine compartment in their car or the inside of their laptop computer. (Compare that with how a mechanic or computer technician will visualise it) That is to say, the pictures in our minds are metaphors (borrowing from the computer vocabulary) and sighted people will often employ 'visual' metaphors. But the metaphors are not always visual. If I tell you to think about the lower surface of the pillow on your bed, you will 'feel' the geometry of your virtual house and then your memory will probably present you with tactile image of putting your hand in there (to reach for your gun - perhaps) or possibly the smell of clean sheets - but not what it would look like.

    I think that there may actually be a very limited range of authentic visual one-to-one perception so perhaps your original question would need to be better defined - is it about what your eye can actually see in detail or is it about what you can 'perceive' with the help of memory and technology.
     
  15. Jun 25, 2017 #14

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I think that still leaves things undefined. You have a progression from naked eye, to naked eye with glasses, to magnifying glass, to microscope, to camera attached to a microscope all the way to atomic force microscopy. Where in this progression do you draw the line? And how do you ensure other people draw the line in the same place?

    This is more philosophical than physical.
     
  16. Jun 25, 2017 #15

    berkeman

    User Avatar

    Staff: Mentor

    Thread closed for Moderation...
     
  17. Jun 26, 2017 #16

    berkeman

    User Avatar

    Staff: Mentor

    Thread re-opened.
    Let's try to keep the philosophical issues out of this thread. Thank you. :smile:
     
  18. Jun 26, 2017 #17

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Perhaps we should replace the word "philosophical" with "perception and memory" or some such.

    We need to avoid thinking of vision in terms of the school level of images forming on the back of the retina and the big deal about the image being upside down!!!!. There is so much more involved in our visual perception.
     
  19. Jun 26, 2017 #18

    phinds

    User Avatar
    Gold Member
    2016 Award

    Without getting into precise details about how small something can be to be "visible", consider this:

    The range of direct human experience is so incredibly narrow in the overall scheme of things that we evolved with absolutely no survival value of (and thus no reason to learn) things very small (Quantum Mechanics), things really big and far away (cosmology), and things really heavy (black holes). Because of this it is often the case that not only is our "common sense" / "intuition" totally wrong it is in fact counter-productive and has to be rejected in order to learn these things.
     
  20. Jun 26, 2017 #19
    Phinds,

    That is very helpful. It feels I am on thin ice in the PF, as my natural bent is philosophical and I can wander into it readily without realizing the distinction between what to me are normal thoughts, and the standards of PF. I would like to respond further to your comment but honestly don't know what I can write without violating the mission of PF. I have been relying heavily on intuition, and would like to find ways to test concepts using the protocols of physical physics.
     
  21. Jun 26, 2017 #20

    phinds

    User Avatar
    Gold Member
    2016 Award

    Whatever concept it is that you want to test, you have to be able to define it technically, not philosophically.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What is the smallest particle which can be visually observed
Loading...