Most of us have core beliefs about which we feel pretty confident, but to which we get emotionally attached. One useful exercise to help overcome such attachment is to think explicitly about how you would change other beliefs if you became convinced that a central belief were wrong.

I suggest this mostly as a private exercise, as I worry it won’t go well if critics can selectively demand: “You think you’re so rational; tell us what you’d believe if X were wrong” for any X they like. Similarly to how it wouldn’t go well if critics could selectively demand that rivals reveal nude or other severely unflattering pictures of themselves. Such tests might go better if applied uniformly applied to all, but that’s harder to arrange.

Even so, I’m inspired today to try one version of this exercise: what else would I think if I thought aliens were actually near?

My best guess is that the universe is vastly larger in space than the distance we can see. And so in all that vast volume, there are probably aliens. Even intelligent civilized aliens. But my estimate is that the nearest such are very far away, outside the visible universe. (Low intelligence alien life may be closer.) So if you offered evidence purporting to convince me otherwise, I’d be initially skeptical. If I were willing to give you the benefit of the doubt, I’d guess that you’d made an analysis mistake somewhere.

If you somehow managed to convince me of your evidence, my guess is that it would be regarding aliens who are very far away, but just not quite as far as I’d thought. And if you convinced me that no, aliens have frequently been visiting us here on Earth lately, I’d be a lot more surprised. But what if you did in fact convince me?

My guess (revising my prior best guess) is that the most likely scenario consistent with this assumption is that these aliens are from one of the Sun’s sibling stars, born in the same stellar nursery that likely birthed 100 to 10,000 stars in the same ten million year period. There was only one Eden in the visible universe which managed to seed one star nursery with life. That Eden was in our galaxy, and that nursery was our Sun’s. Eden wasn’t well suited to support fragile multi-cellar life, but against great odds it created robust extremophiles that could travel far.

These sibling stars drifted far from their nursery over the last four billion years. (They can be identified from far away via their spectra.) Some were not seeded with life, and most of the rest remain far from creating intelligent civilizations. But some, like our Sun, have already done so. Many of those killed themselves, or locked themselves down to stay on their planet or in their star system. But one managed, many millions of years ago, to create a very stable civilization that could travel to other stars.

For some unknown reason, this one successful civilization has strongly limited its internal variation, to prevent any of its parts, or later sibling civilizations, from mass colonization of the universe. Many stable civilizations will develop a ruling body with strong central control, and it seems hard to predict in general what such bodies will want or choose, other than that their choices must allow them to maintain control. So its not crazy to think that this first civilization might decide to prevent mass colonization, even if it allows limited development of a few key resources that we can’t now see.

Part of such prevention would be keeping tabs on, and limiting the growth of, life around sibling stars. Sterilization might be hard, and it is plausible that they’d be curious about and entertained by how life evolves around sibling stars.  So its not crazy to think they might make frequent if limited visits to Earth. And its further not crazy to think they might be sloppy about hiding their visits; maybe they feel very secure that we can’t threaten them, and maybe they get a kick out of being noticed.

Yes, I don’t like having to resort to multiple “not crazy” assumptions in my most likely scenario, but I am being forced to explain what I see as an unlikely scenario.

If these aliens have a policy of preventing mass colonization, they will have to step in at some point to limit Earth’s expansion. But they will have been preparing to do that for many millions of years, and may have already done this several times at other sibling stars. So our chances to defy their plans and expand anyway can’t be great.

Perhaps we have a greater chance to persuade them to change their policies. They may limit what those internal to their civilization are allowed to say on the subject, but it seems they’ve been more hands off with us, and they may allow many within their civilization to see and hear us. In which case we have a chance to persuade. Though we should expect that the more likely scenario is that they persuade us, fairly or unfairly, to endorse their policy.

If you ask me to tell the most realistic story I can wherein we see or meet aliens today, this is it. Not terribly likely, but at least not crazy. Which is actually an unusually high standard in science fiction.