Re: Is Earth's Rotation Slow-Down a HOAX?

Apparently on date Mon, 09 May 2005 10:57:42 GMT, "larswilson"
<wilsonl035@xxxxxxxxxxxxx> said:

>
><nospam@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>news:ihss71teb8fafu8g6l87gh0uenqd4mc9uc@xxxxxxxxxx
>> Apparently on date Sun, 08 May 2005 19:39:47 GMT, "larswilson"
>> <wilsonl035@xxxxxxxxxxxxx> said:
>
>> Well I would guess that you have some incorrect interpretation of whatever
>> data
>> you have indicating these variations in days per year.
>>
>Thanks for the information. This is very itneresting, perhaps because I
>don't know a lot about this and certainly don't understand all the
>geophysics. But my information is not based upon ancient records directly
>but with the current astronomy programs that introduce the "delta-T" to
>adjust to historical references. Actually according to Stphenson one very
>good solar eclipse reference was used as a reference.
>
>Using a computer program reference, for instance, the delta-T adjustment for
>1386BCE is 9.974 hours. When you get to 600BCE it drops down to 5.29
>hours. At the beginning of the 1st Century AD it is 2.74 hours.

The problem with using a solar eclipse in this way is that the eclipse will
only take place as per a modern eclipse if the orbit of the earth and of the
moon remains basically similar and that precludes anything that can significant
affect timings.

IOW I would tend to see this event not as the earth's rotation rate slowing
down and instead would see it as the distance of the moon from the earth
changing, thus affecting the period of its orbit and thus the timing of
eclipses.

It is not easy to move the moon to a different orbit, something like a close
encounter with an unknown planet would do, this could be extra-solar - i.e.
something from outside the solar system that goes away again afterwards.

That's not a trivial event, though. I don't think I could create the effect
without scything away all higher forms of life on all three bodies, because to
affect the core of the planet you need to express massive energies and the
effect these have on the surface are much higher because you will move tectonic
plates about causing radically large volcanoes, earthquakes, tsunamis and
whatnot. The weather will be atrocious and the sea will change temperature,
boiling all the fish. The balance of the atmosphere will change, I dunno
whether it would go greenhouse and end up like Venus or go into an ice age, but
it wouldn't stay in the comfort zone.

Changing the year is permanent. You'll move the earth nearer or further from
the sun and this directly affects the length of the year, unless the sun's mass
changes, which is a really big event and we can forget life on earth in most of
those scenarios.

Moving the earth away from the sun affects the mean temperature. You either get
a greenhouse or the final ice age even for quite small variations of year,
although it would be possible to cancel out a change in the year by, say,
increasing the greenhouse effect to heat the planet up, and moving it further
from the sun to cool it down. That's not really likely.


>So let's see here (you might have to check my math!)
>
>In just 600 years from 600BCE to 1 AD the earth slowed down some 2.55 hours.

I don't think you could do this as a tidal drag effect even with something like
a black hole passing inside the orbit of the moon. And that event would alter
the orbit of the moon (as well as the earth) so you can't really predict
eclipses any more.

If you make it a sustained, gradual change, you can see that the earth would
slow down hugely over a short time period like a million years. I'll imagine
you are talking about a change in a year that makes a given moment in that year
2.5 hours earlier than it should be, rather than a day being 2.5 hours longer.
Delta T doesn't tell me what sense this is meant in, it is just shorthand for
"consequential change in Time".

If we mean the year is 2.5 hours shorter or longer, given that the year is 8000
hours long, a two hour change in 600 years means the earth would stop in 4000 *
600 years, or about two million years. Optionally it was spinning fast enough
to throw material off into space (which is absurd) a few million years ago.
Current thinking is that the earth is 2000 times as old as that, so either we
have a whole new notion of astrophysics (a long shot) or this effect is
temporary.

I can't think of any temporary forces that could have this effect. Rogue
planets only hang about for millions of year when they're in a stable orbit,
and then they will hang about for longer. Normally they would pass by. You
can't have planet sized objects changing orbit without some major energies like
stars exploding, impacts with other planets, etc. Nothing like that has
happened while the earth's crust has stayed solid.

>There are 60 minutes in every hour so 2.55 hours is 2.55 x 60 = 153 minutes.
>
>Every minute has 60 seconds so 153 x 60 = 9180 seconds.
>
>If you divide that by 600 years that is an average of 15.3 seconds per year;
>9180/600=15.3.

Sure. You could do that with the moon being about thirty times the mass of
Mars, but in the same position as the moon. Although, by having a moon that is
bigger than the earth, we would be orbiting it. And eclipses wouldn't work
anything like the same way so the use of them would be mistaken.

>On the other hand, if you multiply 600 years times the current "tidal drag"
>of 0.005 seconds you are looking at a total of 3 seconds!

That's right. That's the measured effect at the moment.

>So right now at 0.005 seconds per year in 600 years we would lose 3 seconds,
>but for some reason in the 600 years from 600BCE to 1AD we lost 2 hours and
>55 minutes.
>
>Let's see, three seconds compared to 2 hours and 55 minutes for the same
>period.
>
>Hmmmmm...
>
>I guess the Moon was much bigger back then; something must have happened to
>cause it to lose some of it's mass. Bet you it was a meteor!

As above, the moon would have to be larger than the earth, or much closer. This
requires there to have been some sort of force of unimaginable (but perfectly
easy to calculate) proportions, to shift the moon thousands of miles against
the pull of gravity from the earth between then and now.

Meteors or comets don't actually make any difference, or at least the sort
we've observed / hypothesised. The K-T impactor that saw off the dinosaurs, put
the earth into a 1000 year-long permanent night due to the dust and smoke, and
altered the atmosphere for good, didn't have anything like the energy required
to slow the earth for one second per year, much less affect the orbit of either
earth or moon to any measurable extent.

All it did was add a little bit of mass to the earth, and consequently the
period of orbit of the moon:

original = c. 6,000,000,000,000,000,000,000,000 kilograms.
i mass = c. 600,000,000,000,000 kilograms

Change in mass = 0.000,000,01 %

Change in moon orbital period = 0.000,000,01 % as well

original orbit = 27.32 days
New orbit = 27.32 days plus 0.0002 seconds.

Now I think it is fair to say that the KT impactor was pretty major as these
things go, so a comet can only have this effect on orbits when it is having a
far more profound and serious effect on the life forms standing about on the
surface. We're talking mass extinctions with a 0.0002 second change in the
moon's orbital period.

To sum up, if you are talking about a genuine effect, it would have to be
something quite extraordinary and it's not the earth slowing down, it's the
moon changing orbit, this is the easiest way to create this effect and is bound
to happen before you appreciably affect the other things that could be a
factor.

Also, there would be some evidence for it.

Take nature. There are various nocturnally-affect animals and their night time
experiences vary considerably when there is a full moon and when there is no
moon, as the light available changes dramatically. As a result there are
evolutions that follow the period of the moon, for example women have a monthly
period based on the moon, I gather, even though you'd think we weren't affected
all that much by moonlight.

This all evolved over millions of years and 600 years is only a relatively few
generations for the longer lived species so if the moon had had an orbit two
months long, for the bulk of history, and only switched to one month in
historically recent times, many / most things would still be adapted to a two
month lunar cycle. It would be surprising if they had all evolved to a one
month cycle in a few centuries, and there would be tons more information to be
found, I think, once you start looking for this taking place.

I don't know who Stephenson is or how he comes to his conclusions about the
timing of eclipses, but I do know that a computer simulation will only produce
the results that a theory causes.

I can make simulations say what I like, I can even produce excel spreadsheets
that give the effects necessary on orbits but these don't mean it happened and
add the dimension that they do show what else would be happening if it had.
These make me think someone has made an error somewhere as the nature of
orbital motion says it's not at all sensible when you look in detail.

The key point here is eclipse timing will change with the slowing down of the
earth, in the absence of any external factors, but this takes millions of years
and happens gradually over very long timescales. Once you add external factors
that can affect the rate of rotation of the earth, you are inevitably changing
the orbit of the moon much more profoundly so all the eclipse data becomes
meaningless long before you made any difference to the length of a day.

Does your reference allow for this, or insist it is all because the earth's day
has varied?


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