The life doesn't need to be intelligent to count. Can be microbes on Mars or some exoplanet. I define strong evidence for this market to mean that a majority of scientists would agree that it's aliens and not something else (note: not consensus, just majority). The reason I'm setting this standard is that I don't think it will be realistic to find conclusive, incontroversial evidence.
Some examples for what counts as strong evidence:
Biosignatures on an exoplanet, once the studies showing them have been replicated, confirmed, and accepted by the scientific community.
Similar level of evidence inside the solar system. A confident announcement by NASA can also count, as long as it's not "maybe we found aliens" but rather "we are confident that we found aliens"
UFO evidence that has been shown to have intelligent extraterristrial origin (just being unknown is not enough), well-studied and accepted by scientists.
What doesn't count:
Some study showing what might be a biosignature on another planet
NASA saying that they found something that might be associated with life on Mars or another planet.
UFOs that are confirmed by the US government, but there's no significant positive evidence that it is, in fact, aliens
Mexican aliens, unless there's some very significant new evidence released.
Related questions
Not all biosignatures are created equal. The biosignature must itself provide strong evidence for life correct? and that fact (that its strong evidence) must be accepted by the scientific community correct? As written the description makes it sound like any biosignature counts as strong evidence while that's not necessarily the case.
@DylanSlagh Yes. A biosignature will only be accepted if most scientists would agree that:
It's real, not a statistical anomaly or an error in the data/analysis.
That this amount of the material could not have been produced by natural phenomenon.
If a definite biosignature is discovered, I will defer the resolution so that studies can examine whether there are some ways that we just never though about that it could have been produced naturally.
I thought the description says pretty much the same. What part of the description was unclear?
@Shump sorry I was just trying to make the point that a “bio-signature” is merely evidence for life and can itself be strong or weak evidence for life. The description made it seem like a bio-signature is always strong evidence for life
@Shump Even if every scientist in the world believes a given molecule is a “bio-signature” and believes that it was confirmed strongly to be on a given exo-planet. That doesn’t mean that they believe it’s strong evidence for life on that planet
@DylanSlagh I imagine there's some semantic confusion here about biosignatures. That some might only increase the likelihood of it being aliens, not rule out any natural explanation. Is that what you mean?
Anyways, this is just an example. The main resolution criterion is that most scientists would agree it's aliens.
@Shump Glad we are on the same page. For instance if an alien species directly observed earth 1 million years before the first life form formed, they likely would have seen many “bio-signatures” but no life! They probably would have even seen “chemical structures which use free energy” wikipedia’s description of a biosignature. biosignatures must necessarily be on a scale based on how likely they could have formed in some sort of primordial soup. If biological compounds couldn’t form without life then there would be no life in the first place.
@DylanSlagh I don't think earth had any biosignatures in the Hadean, even for a while after life formed. Oxygen wasn't around, and amino acids are not really as rare as you might think. Anyways, I intend to defer to the judgement of the scientific community, so don't worry.
@Joshua You thought the subsidy will make it go down, but despite lots of new volume, it only went a bit up. I'm not sure if it's because there's a real likelihood of aliens being discovered of just another consequence of Manifold's incentive system being bad with long-term and low probability markets.
I personally think this probability is more or less correct but I'm surprised that Manifold seems to agree with me.
@IsaacKing Yes, they do. Should be implied by "extraterrestrial".
Do bacteria from Earth manage to survive and replicate on other planets though?
See also https://manifold.markets/Tomoffer/will-signs-of-life-on-k218b-be-conf?r=VG9tb2ZmZXI - would that be sufficient for YES?
@Tomoffer This market requires a higher standard of evidence than just more JWST observations confirming the presence of DMS on the planet. We will still need further studies to rule out the possibility of errors in data analysis and establish that there are no possible natural sources for the amount of DMS that is found. But if that market is confirmed, and the results stand through further scrutiny, then yes.