Date: Fri Aug 14 10:24:33 2009 Back to Contents ------------------------------------------------------------------------

Author: Bill Norwood

Subject: Re: FW: Why can't we see really small things?

Post:

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Hi Taplers,

I hope that I am staying precisely on topic here, but...

As a frequent walker and bicyclist I have concerned myself with any misjudg=
ments I might make about approaching vehicles, especially at night. Of cour=
se I realize that "my brain learns" rate of change of headlight separation =
as an indicator of how fast a vehicle is approaching. And I use this as a c=
ue as to when I may safely cross a highway.

Trouble is that sometimes I have been way off with this and have had close =
calls. Admittedly, I have also misjudged the walking distance across a 6-la=
ne highway sometimes! Another truth is that I have observed that some drive=
rs will speed up, and even change lanes to one closer to where I am walking=
, as I commence crossing the road.

Another piece, of course, is that it is more difficult to determine the spe=
ed of approaching motorcycles.

Bill Norwood, U of MD at College Park

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On Beh=
alf Of Dick Heckathorn
Sent: Thursday, August 13, 2009 6:49 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] FW: Why can't we see really small things?

Greetings,

Stand looking down the road, (flat surface) and focus on a car coming towar=
ds you. At first you see only one light, then you see two lights when it ge=
ts to a certain location. Then as it gets closer, one sees 4 separate light=
s. One could use the odometer to note the location when one first see two l=
ights and then 4. Knowing the distance between the double lights and then t=
he individual lights could be investigated.

Can you repeat with a smaller car that has different separation of lights.

Could one change the diameter of the lights. (Maybe one could use carts by =
varying diameter of the lights, and distance apart.

Could one have both approach at the same speed, side by side.

Another factor as to when separation occurs depends on the size of the open=
ing of the viewer's eyes. Not sure how to investigate this but one might lo=
ok through slits of various diameter openings to see what happens. Have vie=
wers with different slit openings as the car approaches.

A third factor is the wavelength of the light. (Different colors)

Now what have I overlooked.

Best wishes Dick

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On Beh=
alf Of Michael A Thomason
Sent: Thursday, August 13, 2009 1:55 PM
To: tap-l@lists.ncsu.edu
Subject: [tap-l] FW: Why can't we see really small things?

Polly,

I am forwarding your message to the PIRA community.

Congratulations on discovering PIRA through your research. This organizati=
on is a unique global resource for creative educational schemes such as you=
rs. I think you will receive some useful replies,

Michael Thomason
Director of Physics Learning Laboratories
University of Colorado Boulder Department of Physics
303-492-7117

From: Polly Billam [mailto:Polly.Billam@bbc.co.uk]
Sent: Thursday, August 13, 2009 7:27 AM
Subject: Why can't we see really small things?

Dear PIRA,

I'm writing from a major forthcoming BBC science production called 'Invisib=
le Worlds'.
It's a flagship BBC1 documentary series (3x1hrs) made in conjunction with t=
he Discovery Channel, due for prime time transmission next year, which is u=
tilising a range of specialist camera equipment to capture the world ordina=
rily beyond the limits of the naked eye.

Whilst the first two programmes cover 'invisible spectrum' stories and stor=
ies about extremely quick phenomena, the last programme is concentrating on=
the world beyond the resolution limits of the human eye (ie. the very smal=
l or the very remote).

We are hoping to set up a simple demonstration (that could be done by our p=
resenter, outdoors and on quite a large scale) of why it is that the human =
eye can't see very small things, based on the idea that the smallest thing =
that can be seen is one that subtends an angle at the eye that is subtended=
by one cone of the fovea (its image would just cover the receptor surface =
of one of the cones). I came across your work with the Harvard Natural Scie=
nces Lecture Demonstrations online and noticed that you have conceived ways=
of demonstrating concepts such as resolution and wondered whether you had,=
or were aware of, or could suggest ways in which this might be achieved. T=
he challenge is to create a visually impressive demo that would explain thi=
s idea so that an 8 year old might grasp it.

PIRA have some great resources and expertise at their disposal. If there ar=
e any suggestions you are able to make or any way in which you are able to =
help I would be very grateful.

Best wishes,
Polly

Polly Billam
Invisible Worlds
Room MC5 D4 Media Centre
201 Wood Lane, London W12 7TQ
Tel: +44(0)20 8008 0502
Mobile: +44(0)7968181288

http://www.bbc.co.uk
This e-mail (and any attachments) is confidential and may contain personal =
views which are not the views of the BBC unless specifically stated.
Do not use, copy or disclose the information in any way nor act in reliance=
on it and notify the sender immediately.
Further communication will signify your consent to this.

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Hi Taplers,

I hope that I am staying precisely on topic here, but?

As a frequent walker and bicyclist I have concerned myself with any
misjudgmen= ts I might make about approaching vehicles, especially at
night. Of course I rea= lize that ?my brain learns? rate of change of
headlight separation a= s an indicator of how fast a vehicle is
approaching. And I use this as a cue as = to when I may safely cross a
highway.

Trouble is that sometimes I have been way off with this and have had
close calls. A= dmittedly, I have also misjudged the walking distance
across a 6-lane highway sometime= s! Another truth is that I have
observed that some drivers will speed up, and even cha= nge lanes to one
closer to where I am walking, as I commence crossing the road.=

Another piece, of course, is that it is more difficult to determine the
speed of approaching motorcycles.

Bill Norwood, U of MD at College Park

*From:* tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu]
*On Behalf= Of *Dick Heckathorn
*Sent:* Thursday, August 13, 2009 6:49 PM
*To:* tap-l@lists.ncsu.edu
*Subject:* Re: [tap-l] FW: Why can't we see really small things?<= /o:p>

Greetings,

Stand looking down the road, (flat surface) and focus on a c= ar coming
towards you. At first you see only one light, then you see two light= s
when it gets to a certain location. Then as it gets closer, one sees 4
sepa= rate lights. One could use the odometer to note the location when
one first see = two lights and then 4. Knowing the distance between the
double lights and then = the individual lights could be investigated.

Can you repeat with a smaller car that has different separat= ion of lights.

Could one change the diameter of the lights. (Maybe one coul= d use
carts by varying diameter of the lights, and distance apart.=

Could one have both approach at the same speed, side by side= .

Another factor as to when separation occurs depends on the s= ize of the
opening of the viewer?s eyes. Not sure how to investigate this= but one
might look through slits of various diameter openings to see what happe=
ns. Have viewers with different slit openings as the car approaches.=

A third factor is the wavelength of the light. (Different colors)

Now what have I overlooked.

Best wishes Dick

*From:* tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu]
*On Behalf= Of *Michael A Thomason
*Sent:* Thursday, August 13, 2009 1:55 PM
*To:* tap-l@lists.ncsu.edu
*Subject:* [tap-l] FW: Why can't we see really small things?

Polly,

I am forwarding your message to the PIRA community.

Congratulations on discovering PIRA through your research.&n= bsp; This
organization is a unique global resource for creative educational sche=
mes such as yours. I think you will receive some useful replies,

Michael Thomason

Director of Physics Learning Laboratories<= /p>

University of Colorado Boulder Department of Physics

303-492-7117

*From:* Polly Billam [mailto:Polly.Billam@bbc.co.uk]
*Sent:* Thursday, August 13, 2009 7:27 AM
*Subject:* Why can't we see really small things?

Dear P= IRA,

I'm wr= iting from a major forthcoming BBC science production called
'Invisible Worlds'.<= /span>
It= ?s a flagship BBC1 documentary series (3x1hrs) made in conjunction
with the Discovery Channel, due for prime time transmission next year,
which is utilising a range of specialist camera equipment to capture the
world ordinarily beyond the limits of the naked eye.

Whilst= the first two programmes cover 'invisible spectrum' stories and
stories about extremely quick phenomena, the last programme is
concentrating on the world beyond the resolution limits of the human eye
(ie. the very small or the ve= ry remote).

We are hoping to set up a simple demonstration (that could be done by
our presente= r, outdoors and on quite a large scale) of why it is that
the human eye can?t see very small things, based on the idea that the
smallest thin= g that can be seen is one that subtends an angle at the
eye that is subtended= by one cone of the fovea (its image would just
cover the receptor surface of o= ne of the cones). I came across your
work with the Harvard Natural Sciences Lecture Demonstrations online and
noticed that you have conceived ways of demonstrating concepts such as
resolution and wondered whether you had, or = were aware of, or could
suggest ways in which this might be achieved. The challe= nge is to
create a visually impressive demo that would explain this idea/ so =
that an 8 year old might grasp it./

PIRA h= ave some great resources and expertise at their disposal. If
there are any suggestions you are able to make or any way in which you
are able to help I would be very grateful.<= /span>

Many t= hanks for your time,
Be= st wishes,
Po= lly

*Pol= ly Billam*
/Invisible Worlds/
Ro= om MC5 D4 Media Centre
20= 1 Wood Lane, London W12 7TQ
Te= l: +44(0)20 8008 0502
Mo= bile: +44(0)7968181288

http://www.bbc.co.uk <3D"http://www.bbc.co.uk">
This e-mail (and any attachments) is confidential and may contain
personal views which are not the views of the BBC unless specifically
stated.