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Comment by andyjohnson0 | Hacker News Reader

> Our signals decay so fast that you need moon sized antennas to receive them beyond a few light years.

This is true for relatively low power omni-directional broadcast signals such as terrestrial TV and radio. The signals proposed by the METI community (and those that have already been sent - e.g. from Arecibo) are broadcast at much higher power using a concentrated beam, and would be detectable over interstellar distances using technology similar to that which we have now.

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> The signals proposed by the METI community

Yeah but they would need interstellar-type of timescale to reach us anyway even if they moved at a fraction of speed of light, so the risk is close to nil. We are way, way more likely to be hit by an asteroid or to destroy our planet than to be destroyed by a very remote alien civilization.

The signals propagate at the exact speed of light, but you're on point on the risk being minimal. Space is big.

I'm not the grandparent poster, but I think that "even if they moved at a fraction of speed of light" refers to the responding civilisation's space vessels, not their return signal.

Let's say you receive an EM signal from a sentient specie.

If you pinpoint its origin to light years away, you know they already had a lot of time to progress past this technology. A good response if you plan on eliminating them would not be a fleet: you'd better setup and direct a huge gamma-ray burst in their general direction.

So the destructive response could come at the speed of light with a little delay at first.

At a time where there is energy scarcity due to increased consumption, I question the economic viability of such an impractical endeavour being carried out under such government support. (Wow I just used so many new words!!!!)

Still this is not a movie where the aliens are on next moon so even if they picked up the signals it would long after the next few generations die off (Light years away - Man they are damn far off). (living in a developing country would give you a whole new perspective on energy scarcity)

It's not being done because anyone thinks its economically viable. And anyway it's being paid for by private donors, not the US government.

If some action is a waste of resources, then who provides the resources doesn't change whether it's a waste or not.

In this case, if sending a signal into space takes a lot of energy and if energy is scarce, then it's a waste of energy regardless of if the government provides it or a private donor.

EDIT: I'm not saying this is true in this particular case (I'm also not saying that its not true), I'm merely stating that whether something is a waste doesn't matter on who is doing the wasting. I would gladly listen to a counter argument and maybe a discussion can be had, but I guess its easier to click a down arrow. Oh well. (Yes, yes, I know it'll happen even more due to my mentioning it)

The Arecibo message had a broadcast power about a 1 megawatt and lasted 3 minutes [1] - in other words 0.05MWh. 1MWh can power 330 homes for one hour [2], so the broadcast "wasted" enough power to supply those homes for three minutes. Given that interstellar broadcasts aren't exactly frequent events, and assuming similar broadcast power/length today, then on a global scale it doesn't seem like a significant waste of power to me.

[1] http://io9.gizmodo.com/5784658/so-you-want-to-send-a-message...

[2] http://www.cleanenergyauthority.com/solar-energy-resources/w...

I never claimed that this particular thing wasteful. I was only pointing out that "And anyway it's being paid for by private donors, not the US government." isn't a good counter argument.

I wasn't taking any sides on this issue, so its not really relevant how much energy it took. I said "if" it is and it was a hypothetical to give a concrete example, not a statement that I thought it was wasteful.

I'll paraphrase:

If <something> is hypothetically wasteful, then <something> is still wasteful regardless of who did it.

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