Originally Posted by e1618978
A single species, sure - little chance, but no species in the entire universe using bussard ramjets? I think that means we are alone, personally.
No one is going to notice the use of this technology outside our galaxy (we're talking about moving around a very small amount of hydrogen), and it is likely that these effects would not even be noticeable at galactic distances.
Also, Suppose that the bussard ramjet is a very long-lasting technology. Let us say that a space-faring civilisation uses this technology for 1000 years before replacing it with something that we can't even imagine. In the time-frame of billions of years, there would need to be millions of space-faring civilisations in our galaxy to cover all of those intervening years, and even if you consider the Birthday Paradox
, there would have to be thousands of space-faring civilisations before you would expect to see two such civilisations at approximately the same developmental stage at the same time.
Lastly, how much of the sky do we actually monitor at the correct frequencies to even notice the spectrum that a bussard ramjet would give off?
Absence of evidence is not evidence of absence.
Edit: and this is to say nothing for the technical detail that no one has actually built one of these machines. They may turn out to be completely useless in practice. If this is the case, then we would not expect to observe any traces of this technology in the cosmos, whether the galaxy is teaming with life or not.
And for the record (because this conversation is getting out of hand), I think that people who look for certitude of the existence of ETIs in the Drake equation are missing the point. The equation is a thought-experiment. Every step is a guess. And so the final factor in the product: "Amount of bullshit you're willing to buy from Frank Drake."