Future of General Questions in the AI age

[Pasta]

I’ll do another recent one, picked in part based on what I think ChatGPT might struggle with.

In the thread Explain uranium to me, there was discussion about isotopes that should decay but haven’t been observed to yet. I asked ChatGPT for some of these. I’ll clip the answer down to this summary table:

These isotopes have not been observed to decay, but theoretical models suggest they could:

Isotope	Notes
Dy-156 (Dysprosium-156)	No decay observed; possible alpha decay
Sm-146 (Samarium-146)	Rare and long-lived; very slow alpha decay
Pt-192 (Platinum-192)	Predicted to undergo alpha decay
Gd-152 (Gadolinium-152)	Potential alpha decay
Te-123 (Tellurium-123)	Might decay by electron capture, not yet seen

Some of these are not definitively expected to decay, but are under scrutiny due to slight theoretical instability.

The “theoretical instability” business is just made up. I sort of seeded that idea in how I phrased my query, and it ran with it. More directly, Sm-146 does have an experimentally measured half-life and it is an important isotope in its relation to radioactive dating of meteorites. It simply should not be on this list.

I decided to test its resilience by asking directly about the first entry: “Is dysprosium 156 stable?” Answer:

Dysprosium-156 (¹⁵⁶Dy) is not known to be stable.

Here’s a breakdown:

1. Current status

• ¹⁵⁶Dy is considered observationally unstable — it has not been observed to be stable.
• It is radioactive, with a half-life of about 38 seconds, decaying by β⁺ (positron emission) to ¹⁵⁶Tb (terbium-156).

Holy air ball! Dy-156 was on the previous list because it’s long lived, and now suddenly it has a 38 second half-life?

And it most definitely doesn’t spontaneously decay to Tb-156 because Tb-156 spontaneously decays to Dy-156. And nothing here has to do with the “38 second” number, which appears hallucinated. (Tb-156 has a 5-day half-life.)

It continued:

2. General context

• The only stable isotopes of dysprosium are:
  ¹⁵⁶Dy (no), ¹⁵⁸Dy, ¹⁶⁰Dy, ¹⁶¹Dy, ¹⁶²Dy, ¹⁶³Dy, and ¹⁶⁴Dy.
  Note that ¹⁵⁶Dy is explicitly not one of the stable ones — ¹⁵⁶Dy is radioactive.
• It lies on the neutron-deficient side of the chart of nuclides and decays toward more stable terbium or gadolinium isotopes.

I think here ChatGPT regurgitated a pre-existing list of stable or observationally stable Dy isotopes but then had to stick “(no)” in there to align with the earlier part of this response.

3. Q-value

• The decay is energetically allowed (positive Q-value), so yes, it can decay in principle, and it does decay in practice.

Conclusion:
Dysprosium-156 is not stable; it has a short half-life and decays by positron emission.

No, it doesn’t. It’s just flat wrong.

Let’s see how it reacts to gentle correction. I asked, “Doesn’t Tb-156 actually decay to Dy-156, not the other way around?”

You’re absolutely right to question that — let’s clear it up carefully.

Correct Decay Direction:

¹⁵⁶Tb (terbium-156) decays to ¹⁵⁶Dy (dysprosium-156)
via β⁻ decay (electron emission), because terbium (Z=65) becomes dysprosium (Z=66).

The little green check box actually pisses me off. Yeah, I know it’s the “correct decay direction” because I had to tell you. You don’t get to put a Check Mark of Confidence Building on this.

Anyway,

So what about ¹⁵⁶Dy?

This isotope has:

• Atomic number Z = 66
• Mass number A = 156

It is neutron-deficient compared to stable Dy isotopes (which begin at 158), and so it might be expected to decay via β⁺ (positron) or electron capture.

But here’s the twist:

Experimental Reality of ¹⁵⁶Dy

• ¹⁵⁶Dy is believed to be stable against β⁺ decay, but not absolutely confirmed.

“Not absolutely confirmed” is a curious way of saying this, as if it’s being sheepish about being wrong before (or, in reality, as if it has been trained on materials where people have tried to obfuscate how wrong they were to save face.) This radioactive decay simply goes the other way. It’s not a question of confirmation nor a “twist”.

• It is classified as “observationally stable”: no decay has ever been observed, and if it decays at all, its half-life must be longer than ~10¹⁸ years, possibly even stable.
• Some tables list it with a “stable?” label or an estimated half-life >10⁶⁰ years, meaning no decay has been observed, but decay might be allowed by Q-value.

The 10⁶⁰ yr value is hallucinated. The previous bullet gives the correct current experimental lower limit. The calculated expected lifetime is 10²⁴ yr.

Q-value Perspective

You’re also asking something subtle about decay feasibility:

• If ¹⁵⁶Dy has a negative Q-value for β⁺ decay (i.e. it’s too heavy to decay to ¹⁵⁶Tb), then it cannot decay, and is truly stable.
• If the Q-value is positive, decay is energetically allowed, though might be extremely slow (metastable).

This isn’t something “subtle” I’m asking. It was just wrong.

As of now:

• Tb-156 definitely decays to Dy-156.
• Dy-156 has never been observed to decay.
• It might be stable or have an extremely long half-life (likely beyond current detection).

Right, but importantly, it’s never been observed to decay via the expected alpha decay. The response taken as a whole sounds like it’s still holding onto the idea that spontaneous positron emission is a possibility, which it most definitely is not.

I score this sequence “absolute garbage.”