<p>Let's suppose they have similar technical level like us now.</p>

<p>In radio band, what is our earth like? What signals can be linked to non-natural behaviour?</p>

<p>How about optical band and other methods?</p>

<p>Simply:</p>

<p>How large a radio-telescope, 1000 pc away, would be needed to detect Earth's ambient human radio emissions?</p>

CC BY-SA 3.0
2016-10-29T11:54:33.343Z
I recall reading that you don't even have to leave the solar system before it becomes virtually impossible for our technology to discern that there is (intelligent) life on our own planet.  Most modern communications do not propagate meaningful signals into space, in fact.  For a simple reason: any signal shooting off into space meaninglessly is just a loss of power, and so wasted resources and money.  A lot of our infrastructure now uses underground cables and directed satellite transmissions as well, meaning there's very little signal leakage.
zibadawa timmy
CC BY-SA 3.0
2016-10-29T11:56:37.807Z
Quite so. Some expert in radio astronomy on this forum will give the specific numbers on that.
Fattie
CC BY-SA 3.0
2016-10-29T20:36:03.540Z
See:   http://space.stackexchange.com/questions/12879/how-far-can-setis-ear-listen
dualredlaugh
CC BY-SA 3.0
2016-10-31T01:23:13.263Z
It is not necessarily radio telescope and, H-bomb should be considered.
questionhang
<seti>
What activities of human beings can be detected by aliens 1000 pc away?
questionhang
# What activities of human beings can be detected by aliens 1000 pc away?

(Asked by: username_0 on 2016-10-29)

Let's suppose they have similar technical level like us now.

In radio band, what is our earth like? What signals can be linked to non-natural behaviour?

How about optical band and other methods?

Simply:

How large a radio-telescope, 1000 pc away, would be needed to detect Earth's ambient human radio emissions?

**Tags:** seti

> **Comments:**
> **username_1**: I recall reading that you don't even have to leave the solar system before it becomes virtually impossible for our technology to discern that there is (intelligent) life on our own planet.  Most modern communications do not propagate meaningful signals into space, in fact.  For a simple reason: any signal shooting off into space meaninglessly is just a loss of power, and so wasted resources and money.  A lot of our infrastructure now uses underground cables and directed satellite transmissions as well, meaning there's very little signal leakage.  
> **username_2**: Quite so. Some expert in radio astronomy on this forum will give the specific numbers on that.  
> **username_3**: See:   http://space.stackexchange.com/questions/12879/how-far-can-setis-ear-listen  
> **username_0**: It is not necessarily radio telescope and, H-bomb should be considered.  

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