2020-04-02_Science_Illustrated

NEIGHBOURING STAR

RECEIVES SIGNAL

2 The reach of the laser is up to 20,000

light years, but it is most

accurate over distances

such as to Proxima

Centauri 4.2 light years

from Earth. The laser

could hit the Proxima b

exoplanet very accurately.

COSMIC CHAT

BEGINS

3 The first aim is to send a flash

that is captured and

then responded to

as a handshake that

confirms a connection.

Subsequently, we could

send messages back and

forth with laser pulses.

Laser opens chat window

to foreign worlds

Across long distances, powerful lasers are better at maintaining signal strength than

radio waves. Scientists from the Massachusetts Institute of Technology have shown

that we can use existing technology to build a laser telescope that can outshine

the Sun like a lighthouse, and be observed by aliens on remote planets.

Dictionary decodes signal
If an alien civilisation has the technology to
pick up radio signals, it is surely also able to
understand mathematics. So METI uses the
binary numbering system of 0s and 1s to
encode messages into small pictures known
as bitmaps of a few pixels. The binary code
is converted into radio waves, by which a
specific basic frequency represents a zero
and a slightly higher frequency represents a
one. The changes between the two frequen-
cies produce the small bitmap pixel by pixel.
When METI sent its first message via the
EISCAT telescope in Tromsø, Norway, the
contents were small music bites coded as
bitmaps of curves of different sound
frequencies, which the aliens might piece
together into music bites. The message was
intended to portray music as a type of
universal language.
The message also included a small inter-
stellar dictionary to help the receivers
decode the contents. The dictionary explains

basic knowledge about life on Earth, such as

the numbers 0-9, calculations, information

about elements, and physical units such as

metres and seconds. The complexity

increases gradually, until the receivers can

understand the meaning of the curves. The

METI scientists are trying to teach, in the

way an adult teaches a child.

New messages with short reach

The major challenge involved in contacting

alien worlds is the huge distances of space.

Although earlier messages travel at the

speed of light, most are still hundreds of

light years from their destinations. One light

year is the distance that light and other elec-

tromagnetic radiation (such as radio waves)

travel in one year. Our answer to the ‘Wow!’

signal is still 15,500 light years from its desti-

nation, the M55 star cluster, and at least

another 31,000 years will pass before any

reply can make it back to Earth – always

assuming somebody picks up the signal.

DOUGLAS VAKOCH

PRESIDENT, METI

It is too late

to conceal

ourselves in the universe,

so we should decide how we

want to represent ourselves.”

LASER LIGHT SENT

FROM EARTH

1 A 2MW infrared laser fires light

onto a small mirror.

The beam is reflected onto

a 30m telescope that

sends a signal which is

10 times more powerful

than the infrared radiation

from the Sun.

Outgoing signal

CentauriProxima

Signal returns

Mirror

1

2

3

CLA

US

LUN

AU/

SHU

TTE

RST

OCK

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