Educator How-To: The eyes have it in this DIY optical illusion

Your eyes are amazing sensory organs. They help you understand shape, color and form, judge distance and alert you to potential dangers. What you perceive as “seeing” is actually the result of a complex series of events that occur between your brain, your eyes and the world around you.

Light reflected from an object passes through the cornea of the eye and moves through the lens, which focuses it. The light then reaches the retina at the very back of the eye, where it meets a thin layer of color-sensitive cells called the rods and cones. Information from the retina travels from the eye to the brain via the optic nerve.

Because eyes see from slightly different positions, the brain must mix the two images it receives to get a complete picture. The light also crisscrosses while going through the cornea so the retina “sees” the image upside down. The brain then “reads” the image and turns it right-side up.

The rods and cones are what you call photoreceptors. When they are overworked, they lose sensitivity. Normally the small movements of your eyes that you make unconsciously, or regular blinking, will keep these photoreceptors sharp and happy. If you are looking at a large enough image, where your eyes can’t rest, or if you purposely hold your eyes still, you will tire out your poor rods and cones and they will adapt to this overstimulation by no longer responding. When you move your eyes to a blank space, your worn out photoreceptors create an “afterimage”.  An afterimage is where your eyes produce a ghost image, like when you stare at something a little too bright and you see dark spots in your field of vision. In an afterimage, light portions of the original image are replaced by dark portions and dark portions are replaced by light portions.

Try this out for yourself by doing the following activity. 

You will create the Texas state flag in some unusual colors. After you stare at this incorrectly colored flag and have worn out your photoreceptors, looking at a blank wall will create a ghost image of the Texas state flag in red, white and blue!

Activity:  Negative Afterimage

Materials:
Scissors
Glue
Paper
Green construction paper
Black construction paper
Yellow construction paper 

Ed How To Optical Flag 1

Procedure:

1. Cut your green and yellow papers in thirds, width-wise.

Ed How To Optical Flag 2

2. Cut a star out of the middle of your yellow piece.

Ed How To Optical Flag 3

3. Glue the yellow piece to one end of the black piece.
4. Turn the black paper so that your yellow piece is placed on the left.

Ed How To Optical Flag 4

5. Glue the green piece to the bottom of the black piece.
6. Trim off any extra green.

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Now stare at the flag for a minute or so. Try not to have much in your peripheral vision so that you can concentrate on the flag.

Look away from the flag at a neutral colored wall or piece of paper.  You should be able to see the flag in red, white and blue!

Ed How To Optical Flag 6

Have a school group and want to know more about how your eyes work?  Sign up for an Eyeball Dissection with our Labs on Demand.  These labs make a great addition to a field trip, but are also available to come to your school.

Interested in knowing more about how your body works?  Visit Body Carnival, a carnival-themed interactive exhibit that explores the connections between perception and the laws of physics in the human body, at HMNS Sugar Land. Enjoy learning about the human body while investigating force, pressure, light, and color. Crawl through a giant artery to see and hear the effects of restricted blood flow, test your balance in the 10-foot Dizzy Tunnel or don a pair of vision-distorting goggles and discover how sight affects your ability to walk straight. There’s a lot to explore!

 

Educator How-To: Deciphering Papyrus with the Egyptian Book of the Dead

Background:

The Book of the Dead, ironically, is not a book at all, but rather a diverse collection of magical spells intended to aid the dead in successfully navigating the complicated and oft tumultuous process of reaching the afterlife.

The bulk of the 200-plus spells discovered to date were created on papyrus, and a few have been found written on the walls of the tomb itself. Of the known spells, most are centered on the idea of making it safely to the afterlife.

All ancient Egyptians desired to safely reach the afterlife. The afterlife, after all, was a real place, and they believed magical spells would help them get there. Prosperous Egyptians would hire professional scribes to record the spells of their choice on fine papyrus sheets. This precious collection of spells was then packed away with their other grave goods, to be placed in their tomb at the time of their burial.

Not to worry, if you were not a “man of means,” so to speak, you could buy spells at the market. Many of the more popular spells were mass produced and could be purchased for a reasonable amount; there was even a space on the papyrus so that the purchaser’s name could be written on the document after purchase. Both the Ba and the Ka, the two aspects of the soul, would need this validation to know the spell belongs to them.

Materials:

Procedure:

  1. Research the Book of the Dead and the Weighing of the Heart Ceremony.
  2. Read the Papyrus from the Book of the Dead of Ani description.
  3. Looking at the picture of the papyrus and using the description, label what each of the lettered items are on the papyrus.
  4. What other judgments stories are the you familiar with?

Papyrus from the Book of the Dead of Ani

The above scene from the Book of the Dead of Ani reads from left to right. At the left, Ani and his wife enter the judgement area. In the center are the scales used for weighing the heart, attended by Anubis, the god of embalming. The process is also observed by Ani’s ba spirit (the human-headed bird), two birth-goddesses and a male figure representing his destiny.

Ani’s heart, represented as the hieroglyph for ‘heart’ (a mammal heart), sits on the left pan of the scales. It is being weighed against a feather, the symbol of Maat, the principle of order, which in this context means ‘what is right’. The ancient Egyptians believed that the heart was the seat of the emotions, the intellect and the character, and thus represented the good or bad aspects of a person’s life. If the heart did not balance out with the feather, then the deceased were condemned to non-existence, and was consumed by the ferocious ‘devourer’, Ammit, the strange beast, part-crocodile, part-lion, and part-hippopotamus, shown at the right of this scene.

However, a papyrus devoted to ensuring the continued existence of the deceased is not likely to depict this happening. Once the judgement is completed, the deceased was declared ‘true of voice’ or ‘justified’, a standard epithet applied to dead individuals in their texts. The whole process is recorded by the ibis-headed deity Thoth. At the top twelve deities supervise the judgement.

R.O. Faulkner, The Ancient Egyptian Book of t, (revised ed. C. A. R. Andrews) (London, The British Museum Press, 1985); R.B. Parkinson and S. Quirke, Papyrus, (Egyptian Bookshelf) (London, The British Museum Press, 1995); S. Quirke and A.J. Spencer, The British Museum book of anc (London, The British Museum Press, 1992); via the British Museum

Free Event for Educators this Saturday!

Museum Educators Open House

Tomorrow – January 22, 2011,
9 a.m.  - 1 p.m.

Thinking of including a trip to the Houston Museum District for your class? Interested in professional development opportunities at some of Houston’s coolest venues? Want a Museum docent or staff member to bring artifacts or demonstrations to your classroom for an extra boost before those standardized tests or just as a cool surprise for a great semester?

You can learn about what 42 of Houston’s Museums have to offer this Saturday as the Houston Museum District presents the Museum Educators Open House!

Museum Educators Open House is a conference style event free of charge for registered Educators from 9 a.m. – 1 p.m. followed by the opportunity to visit participating Museums until their doors close on Saturday with your MEOH wristband!  

Register and download the day’s program on the Houston Museum District website here!

HMNS is one of the host museums (all within walking distance) where many of the day’s presentations will be held in 14 of our classroom spaces in the lower level of the Museum. Educators who attend for at least 3 hours, attend at least 3 presentations and show up between 12 p.m. and 1 p.m. at one of the participating host museum’s registration table to trade in your “passport” for a certificate of attendance.

Extra special things that HMNS is offering for the Educators participating in MEOH 2011 include discounted tickets for educators to visit our special exhibitions Real Pirates and Forgotten Gateway - as well as an awesome 20% discount in the HMNS gift shop!

We hope to see you all here on Saturday!!

 

Museum Educators Open House — January 24th is just around the corner!

Well, it’s 2009 and it’s almost time for the Museum District’s Museum Educators Open House on Saturday, January 24th! MEOH is always a fun day for us at the Houston Museum of Natural Science where we get to collaborate with other Houston Museums to put on a big event for area Educators!

The HMNS will be hosting the following amazing Houston organizations; Battleship Texas/San Jacinto Battleground State Historic Site, Bayou Preservation Association, Downtown Aquarium, FotoFest, Houston Arboretum and Nature Center, Houston Computer Museum, Houston Gem and Mineral Society, Houston Zoo, The John C. Freeman Weather Museum, Moody Gardens,  and the Orange Show Center for Visionary Art! The Children’s Museum of Houston, The Health Museum, Holocaust Museum Houston, and the Museum of Fine Arts, Houston will also be participating as MEOH hosts for the other 16 participating organizations!!


Houston area educators, school administrators, home school educators and student teachers are invited to discover the fascinating exhibitions, programs and educational resources available for their students. This event is completely FREE for all educators and for educators who attend at least 3 or more presentations are eligible for 3 hours of Continuing Education Credit; all you have to do is register online.

Go to the Museum District homepage to register for MEOH 2009 today!