New Scientist - USA (2019-11-30)

54 | New Scientist | 30 November 2019

Needing focus

I wear spectacles to correct for

myopia and astigmatism. Is it

possible to create a program to

adjust the image of a TV, mobile

or PC monitor using my optical

prescription such that I could

view it without spectacles?

Dan O’Donovan

Solihull, West Midlands, UK

The eye uses a lens to focus light

on the retina at its back. It needs

to do this because the iris is a

circle rather than a tiny hole,

so a circle of light enters the eye.

All of the light from each point

on, say, a computer screen reaches

the lens and is then redirected to

one point on the retina. This relies

on the lens changing shape so

that it can refract the light by

the correct angle.

As no program can adjust the

path of the light as lenses do, the

screen can’t seem to be a different

distance to the lens than it actually

is, so the simple answer to this

question is no. However, placing

a magnifying lens, such as a

fresnel lens, over the screen

may help with myopia.

Graham Jones

Bridgham, Norfolk, UK

In 2014, researchers at

Massachusetts Institute of

Technology and the University

of California, Berkeley, developed

a prototype display that can be

viewed by people who are near

or far-sighted without the need

for glasses. It involves placing a

second screen covered in pinholes

in front of the image, as well as

software to adjust the screen

picture so that slightly different

images reach each eye. This acts in

a similar way to a lens, redirecting

the path of the light such that each

of a person’s lenses can focus it.

However, the technology doesn’t

seem to be available yet.

Eric Kvaalen

Les Essarts-le-Roi, France

Astigmatism results from

irregularities in the shape of the

cornea or lens. It might be possible

to adjust the image for the

astigmatism of one eye, but then

it wouldn’t be right for the other.

Dreamy looks

Strangers appear in my dreams.

Their features are clear, but none

are familiar, not even from an

earlier dream. What is going

on in my brain, and do others

experience the same?

Tony Holkham

Boncath, Pembrokeshire, UK

Considering that my dreams

almost always involve going

somewhere, either on foot or

by car, I should expect to meet

many strangers. Yet I hardly ever

do. Most of the people I interact

with in my dreams are either well

known to me or curious hybrids of

more than one friend or relation.

Many of the places I dream

about, though, don’t exist. When

I wake, I marvel at how these

events could have been created in

such minute detail by my brain –

and, more to the point, why.

Christine Warman

Hinderwell, North Yorkshire, UK

Dream pundits, of which there are

many, tend to go along with the

idea that strangers in dreams are

real people. They say our brains

can’t fabricate faces, so these

people are actually recollections

of real people we have seen but

don’t consciously remember.

Such accounts support the

concept that everything we

experience is accurately stored

in our memory, if only we could

access it. Yet it is more likely that

memories are reworked and

edited, and can be false. I think

dream people are invented from

a stock of general images.

In 1996, Calvin Hall and Robert

Van de Castle conducted a survey

of the content of dreams. They

found that most involve the

dreamer and two or three others.

Around 50 per cent of dream

people are strangers. Male

strangers were aggressive more

often than female strangers, and

female dreamers were more likely

to encounter hostile characters.

Dreams rarely involve aspects

of everyday life, but seem to be

a way of examining, in symbolic

form, our own anxieties.

Elwyn Hegarty

Armidale, New South Wales,

Australia

I see a parade of clear but

unfamiliar people’s faces in my

mind’s eye just as I am about to fall

asleep, rather than later. If I have

been waiting a while for sleep,

I find this reassuring, as it means

that rest is just round the corner.

I have heard of two others who

have had the same experience.

Peter Gandolfi

London, UK

I get visual hallucinations

sometimes when I am tired

and I close my eyes. It is as if I

have entered a world of people,

none of whom I know, and

always different. I quite enjoy

the experience and marvel at

the workings of my brain.

Some of my friends with severe

visual impairments also have

hallucinations, a phenomenon

known as Charles Bonnet

syndrome. It is quite common

among those with sight loss,

especially those who are newly

blind, and tends to go away as the

brain adapts to the loss of vision.

I hear that many people with

the syndrome are wary of talking

about their symptoms, thinking

that they are experiencing a

mental health problem. I believe

that I am in good health, with

good vision.  ❚

This week’s new questions

Poetic prediction “Red sky at night, shepherds’ delight;

red sky in the morning, shepherds’ warning”. Putting aside

the occupation of the observer, is there any truth in this

adage? If so, why is it true? Richard Kubiak, Pen-y-cae-mawr,

Monmouthshire, UK

Come clean What is the difference between shampoo and

shower gel and, if so, what is it? Sam Wong, London, UK

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Does red sky at night really

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