Dot Physics

ScienceBlogs.com is running “Ask a Science Blogger”. The basic idea is that you, the reader, get a chance to ask questions to us, the bloggers. You can either post a comment in the link above or send an email to .

I would like to go ahead and answer one of the questions already posted. nemski asks:

How big does the world appear to an insect?

I like this question because it can be answered at different levels. First, what do you mean by world? If you mean “the Earth”, then the answer would be that the Earth essentially appears the same to an insect as it does to us humans (from a size perspective). So, maybe you know the Earth is spherically shaped. However, we can’t really see the curvature of the Earth from the ground because it is so big. Essentially, the variations in the ground level are much greater than any effects due to the curvature. Now, if you get even closer to the surface of the Earth, the same is true. Both humans and insects would see the ground as looking “flat”. On a related note, check out Bad Astronomy’s post on how far away is the horizon.

But maybe this isn’t what the commenter meant by “world”. Maybe the commenter meant “how would things in a room look for an insect?” There is one aspect of this question that I am not going to address – how do insects’ eyes work compared to human eyes? I don’t know if I could explain this well enough. My strategy for deal with questions I can’t answer is to answer a different question. The question I will answer: if a human were the size of an insect, how big would things look. Maybe this was actually the intention of the question.

Insect Scale

I am going to say a human is 1.5 meters tall. How about an insect? Insects come in lots of different sizes. I am going to estimate an average size of about 2 millimeters tall (that seems like a normal large ant). So, in terms of height, the ratio of human to insect height is:

i-addd14fb1c2c52e2578ff61dadcdbb60-2010-05-12_la_te_xi_t_1.jpg

A human is about 750 times taller than an ant. Note, don’t confuse this with mass or volume. A human is way more than 750 times the volume of an ant. Ok. Suppose I am a human and I am standing 10 meters away from a 4 story building (about 12 meters tall). Here is a rough sketch.

i-9932af570f346eff2667b6f3be28731c-2010-05-12_untitled.jpg

Using some simple trig, this angle theta would be:

i-0a44cfaca8829b55f50b5ae9ccc1b141-2010-05-12_la_te_xi_t_1_1.jpg

So what would look the same to an ant? I will assume that the ant would see something that has an angular height of 50 degrees. But, how far away would the ant have to be? The human was 10/1.5 = 6.7 human lengths away from the building. For an ant to be 6.7 ant lengths away from the object, this would be 6.7*2 mm = 13.2 mm away. So, using the same diagram above, theta is the same, but d = 13.2 mm – this would have an object of height:

i-cbd81a66b61797944504f994bcaa3380-2010-05-12_la_te_xi_t_1_2.jpg

I looked around for something about 1.5 cm tall on my desk. Here I took a picture of a marker on my desk. I also took a picture of our building.

i-e439a341b22dbc8006b6b1b030c5665e-2010-05-12_untitled_2.jpg

Comments

  1. #1 Alan E.
    May 12, 2010

    Another important note is the distance of a fall does not scale in the same way. A fall from the top of the top of the 13mm marker is not the same as a fall from the top of a 12m building. And the whole ant lifting a large amount of mass in proportion to its mass is glamorous, but it cannot scale to really compare to other sizes except for creatures of the same size. I have often thought about this proportional view, but recently I have been going in the other direction.

    In the end, humans have a unique view of the word, but so does every other creature. This can only start going into philosophical questions like is blue the same for everybody, etc. We will not be able to comprehend what it’s like to have a bajillion eyes and still process the information because we are biased with our own two eyes.

  2. #2 Gonzobot
    May 12, 2010

    What is really important about ants and falling is that they cannot fall to their deaths. They reach terminal velocity after something like two seconds, so they’re never capable of reaching fatal speeds when dropping ^_^

  3. #3 Rhett Allain
    May 12, 2010

    @Gonzobot,

    Good point. Since the ant is so small, it will have a large surface area to volume ratio. This means that its air resistance will be very large compared to its weight.

  4. #4 Doug Lance
    May 12, 2010

    An ant doesn’t have vision comparable to human vision.

  5. #5 Joshua Gay
    May 12, 2010

    This is a great article, thank you!

    Thinking about the huge size difference between an ant and a human leads me to anouther thought experiment. Imagining myself on a planet that is an order of magnitude larger than Earth with twice the gravity … such as Jupieter. In fact, I can’t tell what is harder to imagine, being the size of an ant, or going for a “stroll” on the surface of Jupiter. I imagine one could do a lot of interesting lessons in which you compare life on Jupiter vs. life on Earth.

  6. #6 dzdt
    May 13, 2010

    [OT] I’ve seen you do a very good job with video physics analysis before. Would you consider taking a stab at estimating flow rate of the oil spewing into the gulf of mexico? See http://www.dailykos.com/storyonly/2010/5/12/865931/-BP-Releases-First-Video-of-Oil-Volcano for some other people taking a stab at the problem. I’d really like to see the full Rhett Allain treatment of the estimate however.

  7. #7 qzl
    May 13, 2010

    Compound eyes mostly measure visual flow, yes? – so it highlights nearer and faster moving things. The ant gets to respond to the dynamics of its environment, and responding appropriately doesn’t entail such a big repertoire. Focus is not so much of an issue – the ant doesn’t have much of a cortex to interpret a detailed image with anyway.

  8. #8 Jay
    May 13, 2010

    I’m jealous of my cat’s perspective, especially around human furnishings. I imagine it’s like living in an obstacle course.

  9. #9 Max
    May 13, 2010

    I’m curious as to how they see smaller things than themselves such as mold, dust, bacteria and other microbes.

  10. #10 Rhett Allain
    May 13, 2010

    @Max,

    I think when you start considering really small stuff (like bacteria), you would need to consider exactly how the insect sees (of which I have no idea). A biologist would probably be able to give a better answer for that.

  11. #11 Rhett Allain
    May 13, 2010

    @dzdt,

    If I get a chance today – I will take a look at that. Thanks for the link.

  12. #12 bk
    May 13, 2010

    Because I make music I often think of sound and scale. I wonder what the scale of sound is like for an ant vs. human perspective. Or how about a bat or elephant.. does a peal of thunder have the same “size” for us all?

  13. #13 Betaria Shoes
    May 13, 2010

    Insects have different eyes from us.
    So, they might see more on the macro level.

    Maybe they even see bacteria or single cells.

  14. #14 Lionel
    May 25, 2010

    That’s a lot of information. Thanks. It’s quite a rare topic to pick up, yet you did justice to it. :)

  15. #15 Bammbulance
    May 30, 2010

    Just go back to a place you often played around as a kid (assuming your an adult now), and just think, wow doesn’t this place look alot smaller now! And thats when you were 3 foot tall, so scale it down to 3mm :)
    A blade of grass will look like a pine tree, a skyscraper would be just like a black sky.
    I wonder how far they can see, untill everything blurs?

    Id imagine as to the scale of sound, its level wont change in any way (The source is the same), but like us humans, certain levels of sound will damage us, so they may have much smaller tolerances, or maybe might greater resistance to sound (Ears built differently, humans are frail in general).

    I looked this up as a spider made a web on my window and now hes gone, but I like 9 floors high in a tower block, even at that height, they are so light I cant imagine it going splat?

  16. #16 Torrent Downlaod
    December 10, 2010

    Thanks, Its quite a rare topic to pick up, yet you did justice to it.. Thanks again..

  17. #17 Wasp Catcher
    February 23, 2011

    What a great post! It puts things into perspective. And it makes me admire insects even more because for little things in such a big world, they sure can inflict a good amount of damage.

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