Speculative Extrapolation: Five SF Visions of the Future, According to Math

Predicting the future is as easy as extending short term trends.

https://www.tor.com/2024/01/22/speculative-extrapolation-five-sf-visions-of-the-future-according-to-math
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William Hyde wrote:

In the realm of unintentional fantasy, linear extrapolation was used on the earth's
magnetic dipole field to "prove" that the planet can't be more than twelve thousand
years old, as at that time the extrapolated field would be strong enough to.. um, do
something bad. Rip the iron out of your red blood cells, perhaps. I don't recall as
I was laughing too hard to concentrate at that point.

Some UK University committee was allegedly debating a proposal how to
handle their real estate. Some old prof. opposed this, was told that it
was the best course extrapolated from the last 200 years. His reply was
that the last 200 years were extraordinary.

[Originally read this with more details, but forgot.]

-is

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On Fri, 2 Feb 2024 11:48:38 -0800 (PST), William Hyde
<wthyde1953@gmail.com> wrote:

On Friday, February 2, 2024 at 8:36:31?AM UTC-5, Robert Carnegie wrote:

On 22/01/2024 21:19, William Hyde wrote:

On Monday, January 22, 2024 at 10:14:52?AM UTC-5, James Nicoll wrote:

Speculative Extrapolation: Five SF Visions of the Future, According to Math

Predicting the future is as easy as extending short term trends.

The chairman of the department of physics at Toronto dropped by in our first
year class to talk about our career prospects. He pointed out that if current
trends continued, by 2000 98% of the population would have jobs in physics.
He warned us that current trends might possibly not continue.


In the realm of unintentional fantasy, linear extrapolation was used on the earth's
magnetic dipole field to "prove" that the planet can't be more than twelve thousand
years old, as at that time the extrapolated field would be strong enough to.. um, do
something bad. Rip the iron out of your red blood cells, perhaps. I don't recall as
I was laughing too hard to concentrate at that point.

What is current news about the observed
weakening of Earth's magnetic field?
I write as a concerned resident.

At the moment, as in over the past few centuries, the dipole moment of the field is
weakening, the quadrupole moment increasing. But not by much over this >period. If current trends continue (as the Spartans said, "if") the dipole moment
will be zero in a couple of centuries.

The last that I heard, it has a history
of dropping to zero, or to much less than
normal", and then recovering, but often
in the opposite orientation. And that may
be in progress currently, but how long does
it take, and how inconvenient is the
interruption of this important service?

The most recent reversal was a transient one, known as the
Laschamp event, where the field grew very weak and was
reversed for a few centuries. This happened 40,000 years
ago.

I've seen various guesses as to how serious such a reversal would be
for us, ranging from business-as-usual to lets-all-panic-now. There's no >mass extinction dating to the Laschamp event, but the inhabitants of
earth in those days didn't have an economy that depended on
satellites in orbit. Flint holds its value during magnetic reversals.

The most recent full reversal (field reverses and grows to normal strength
in reverse mode) is the Brunhes-Matuyama event, which is a reassuring >781,000 years in the past, and prior to this there was the short-lived Jaramillo
reversal, starting about a million years ago and lasting a mere fifty thousand >years or so. And many, many more deeper in the past.

Reassuring unless, of course, the expected gap between such events is,
say, 781,001 years.

But, I suppose, reassuring in the sense that it shows that it doesn't
happen every day.

But as these things happen very slowly in human terms, our well known >excellence in dealing with future risks should save us.

--
"Here lies the Tuscan poet Aretino,
Who evil spoke of everyone but God,
Giving as his excuse, 'I never knew him.'"

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Cryptoengineer <petertrei@gmail.com> wrote:

The Wikipedia article says there's no discernible pattern in the timing
of the reversals, merely an average interval over a long time.

I take comfort in the fact that Earth's creatures have lived through
many of them, with no particular correlation with mass extinctions.

They are survivable.

However, they are apt to mess up my radio reception and possibly cause difficulties with satellites. Not to mention the more obvious navigation issues.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Robert Carnegie <rja.carnegie@gmail.com> wrote:

What is current news about the observed
weakening of Earth's magnetic field?
I write as a concerned resident.

The earth's magnetic field is a consequence of charges from the sun causing currents in the liquid core, and the rotation of the liquid core which
results from the spin of the earth.

Nobody is really sure why the core current gets disrupted now and then and
how the core dynamo goes wrong, but when this happens, it's possible for
the dynamo to restart with opposite current flow and the theory is that
this is what happens to cause those reversals.

But nobody really knows the core structure or exactly what the physical movement of fluid actually is like, because we can't actually get down
there to look. So our knowledge of the core is pretty incomplete and nobody really has the ability to predict what is going to happen with the field
long term.

Glatzmaier and Roberts wrote an article in Nature back in 1995 called "Three-Dimensional Self-Consistent Computer Simulation of a Geomagnetic
Field Reversal" and then a year later wrote a paper in Science called
"Rotation and Magnetism in the Earth's Inner Core" and these are interesting because they basically show a simulated core flow and how it can be made
to behave like the earth's actual field, but without any real justification that the physical structure is anything like the simulation. But that is
about as good as it gets.

However, if you are willing to live with predictions for the next three
days, THOSE can be supplied pretty easily at https://www.solarham.net/geo_forecast.htm

I think they said that Venus has an
external magnetic field, due to the
"solar wind" diligently stripping
atmosphere from the planet, so do we
have that to look,forward to? I won't
say to hold our breath. :-)

Yes, venus has a crazy ionosphere that is super dense and at very low
altitudes on the day side, while the night side ionization is nearly nonexistent. Makes radio propagation very interesting, especially
"grayline" propagation over the magnetopause which must be very different
than grayline on earth.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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