A debate about whether scientists should take the risk of letting all the aliens know about human existence on Earth took place at the American Association for the Advancement of Science's annual conference in San Jose, California last month.

During the debate, Seth Shostak, senior astronomer and director at the Center for SETI (Search for Extra-Terrestrial Intelligence) Institute in California said that any society that could come here to destroy the planet already knows that we exist here.

Space scientist and science-fiction writer David Brin said, "The arrogance of shouting into the cosmos without any proper risk assessment defies belief. It is a course that would put our grandchildren at risk. If we send them messages, they may come here and enslave us. Or just eat us".

Scientists have already been sending out radio and television signals for a hundred years. Therefore, any aliens within a hundred light-years already know where humans are. However, it turns out that this is not the case as the radio and television signals sent from Earth begin to fade into the background radio static beyond about one light-year away.

But it is also true that the powerful radar signals that have been sent using to map the surface of other planets and moons in our own system travel a very long way. Although those signals don't carry much information, they might be enough to attract unwelcome attention.

Astronomers we know about 1,906 of exoplanets that mostly orbit relatively nearby stars and a show a very small proportion of Earth-like characteristics.

There are probably hundreds of thousands of planets in our vicinity and even if a few thousand of them are Earth-like, it can be imagined that somebody might come calling in response to the messages scientists have been sending. It might be possible for the signals to travel at near- or trans-light speeds.

In the meeting, scientists, scholars and business leaders said that they feel that the decision to transmit messages should not be based on the wishes of few individuals who have access to powerful communication systems. Rather, it should be must be based on a worldwide consensus.