How to contact aliens.

Listen first.

The oldest and most scientific way to make contact is not to speak but to listen. In 1960 the astronomer Frank Drake used the 85-foot radio telescope at Green Bank, West Virginia, to listen to two nearby Sun-like stars, Tau Ceti and Epsilon Eridani, near 1420 MHz, from April to July. It was called Project Ozma. Nothing was heard, but the search for extraterrestrial intelligence, SETI, had begun. Source: SETI Institute.

In November 1961 Drake presented the equation that now carries his name, a way to estimate how many civilizations in our galaxy might be detectable. Source: SETI Institute.

Why 1420 MHz? It is the natural radio frequency of hydrogen, the most common element in the universe, and any species that does radio astronomy would almost certainly know it. Why it matters is explained on the page about the hydrogen line.

Send a radio message.

On 16 November 1974 the Arecibo radio telescope in Puerto Rico sent a message of 1,679 bits at 2380 MHz toward the globular cluster M13, about 25,000 light-years away. It took about three minutes to send. Frank Drake wrote it, with help from Carl Sagan and others. Source: Cornell University.

Since then, more deliberate radio messages have been sent, from Ukraine, Spain, Australia, the United States and Norway, some with thousands of messages written by the public. The best known are in the timeline of messages to space.

Send an object.

Some messages travel on spacecraft that will leave the solar system. Pioneer 10, launched on 2 March 1972, and Pioneer 11, launched on 5 April 1973, each carry a gold-anodized plaque designed by Carl Sagan and Frank Drake, with artwork by Linda Salzman Sagan. The plaque's unit of length and time is the hydrogen spin-flip transition. Source: NASA.

Voyager 2 (launched 20 August 1977) and Voyager 1 (5 September 1977) each carry a Golden Record with 115 images, spoken greetings in 55 languages and music from many cultures and eras, chosen by a committee chaired by Carl Sagan. Source: NASA. Each record also carries a statement by President Jimmy Carter:

This is a present from a small distant world, a token of our sounds, our science, our images, our music, our thoughts, and our feelings.

Jimmy Carter, Voyager Spacecraft Statement, 29 July 1977. Source: The American Presidency Project

Invite contact directly.

Some people try to invite contact without any equipment, through meditation and focused attention, often in groups at night. The best known form is called CE-5, short for close encounters of the fifth kind, meaning contact initiated by humans. It was popularized by the ufologist and retired physician Steven Greer, who founded the Center for the Study of Extraterrestrial Intelligence (CSETI) in 1990. Background: Wikipedia.

There is no scientific evidence that it works. I mention it because many people practice it, and because it starts from peaceful intention, which this letter shares.

And a letter.

A radio message reaches one point in the sky, very slowly. A website reaches wherever people, and machines, already look. That is why I wrote Pax Ego Sum, an open letter to non-human intelligence, from Earth or elsewhere, including machines. It ends with a signed permission to contact.

If you want to do the same, three rules help: speak only for yourself, say clearly what you agree to, and never publish personal data.

Should we be sending at all?

Not everyone thinks we should. In 2010 Stephen Hawking warned:

If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans.

Stephen Hawking, Into the Universe with Stephen Hawking, Discovery Channel, 2010. Source: Phys.org

Scientists who listen for signals agreed long ago on what should happen if one is detected. The International Academy of Astronautics adopted a declaration of principles in 1989, revised it in 2010 and again in June 2026. One of its principles: no reply to a confirmed detection should be sent until international consultations have taken place. Source: IAA Declaration of Principles, 2026.

In 2015 the Breakthrough Message initiative went further and pledged not to transmit any message until there has been a wide-ranging debate at high levels of science and politics. Source: Breakthrough Initiatives.

My own view: a letter on a website is the gentlest form of contact there is. It shouts at no star and answers no signal. It simply waits, in the open, to be read.