How many such techniques we haven't even discovered or technology is not there to observe such things?
I really enjoyed reading Our Mathematical Universe by Max Tegmark that explores such things.
Under the right conditions, proteins can survive for millions of years. In recent years, proteomic studies of art works and archeological remains have yielded biological information of startling clarity, revealing gossamer-thin layers of fish glue on seventeenth-century religious sculptures and identifying children’s milk teeth from pits of previously unrecognizable Neolithic bones.
You’d probably like this short story which is about exactly what you’re describing: https://www.lesswrong.com/posts/5wMcKNAwB6X4mp9og/that-alien...
from a random page on the web
Mendeleev realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.
Gaps and predictions Sometimes this method of arranging elements meant there were gaps in his horizontal rows or 'periods'. But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered. He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminum in his table. When this element, called gallium, was discovered in 1875 its properties were found to be close to Mendeleev's predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev's table.
Or purely mathematical intuition.
How do they know the dates are correct? Carbon dating doesn't work for those years:
Calendars are not a recent invention. People have been dating texts for as long as there have been texts. Especially texts related to trade and accounting.
If the pot says "made in the 4th year of king such-and-such", all you have to do is find out when that king took office, which is probably on a monument somewhere, if not in dozens of other texts, since a new administration is a pretty big deal that lots of people would write about.
Correlating them to other historic texts, filling in the missing parts, removing thing one doesn't care about etc is the job for historians.
Look I'm done with this thread. I've made my point, and your comment history shows you only post this sort of pseudo-intellectual nonsense. You represent everything that's wrong with this site.
Being too lazy to visit a library and educate yourself on a topic is called "willful ignorance", not skepticism.
"nullius in verba" means you don't accept theories on authority alone. It means that you don't formulate a conception of gravity by thinking about elements for a while and then declaring that you figured it out, as Aristotle did, but by considering testable possibilities and performing experiments, as Newton did.
"nullius in verba" does NOT mean you can throw out all of Newton's work as "words words words" because you don't feel like reading it.
Yes! If someone can actually make sense of something that was incredibly messy or biased that is a real reason for celebration :-)
On top of that, we also have astronomical records to serve as anchors for other dates. We can figure out when eclipses happened, when each planet was visible, and so on. If ancient texts record an eclipse during the reign of King Foo, and we know when there was an eclipse visible from that area, we can interpret any other events in Foo's time around those definite dates.
Carbon dating doesn't work for these years because there is a plateau in the reference curve. 
The earth must have had a weaker magnetic field (correlates with a low in sunspot activity), or there were lots of solar flares, or a supernova, near the beginning to create more c14 in the atmosphere than usual. Alternatively, the ocean "released" a bunch of old carbon to dilute the atmospheric c14 near the end of the period, thus making those years look older.
The creep of the magnetic field is noticeable in particular in the numbering of runways - they are numbered according to their heading. Some runways that have existed for a few decades are, accordingly, off by a few degrees. An older runway numbered "35" may have an actual approach heading of 340 (340 degrees from magnetic north). Not a huge problem when flying by eye, but it has the capability of causing some confusion when flying using instruments. Alternately, the runway numbers can even change.
As for GPS, this won't solve the problem either, since GPS can give you a "true" flight path using the movement over time, which with wind will not always match the actual heading of the aircraft due to wind.
I now know how runways are named. Boy does that clear up a lot. Thanks :)
Its interesting that you mention pressure adjustments, because:
* Above 18,000 feet in the US, you don't make pressure adjustments - because its more important to know that your neighbors in the airspace are measuring their altitude the same way you are than it is to know exactly how far off the ground you are. In other parts of the world the threshold is lower, sometimes much lower.
* Airspeed is also measured with a pressure instrument, whose accuracy is affected by the density of the air, which in turn is affected by temperature and altitude. But the speed limits in the regulations, and the speeds ATC might tell you to fly, are all based on the uncorrected output of the pressure instrument - "indicated air speed", as its called. You only try to adjust for altitude and pressure when using the airspeed for navigation.
Declination is also not linear or varying only by latitude/longitude, but it also varies by area due to magma flows and iron deposits. Take a look at this map of global declinations for reference: https://en.wikipedia.org/wiki/File:World_Magnetic_Declinatio...
I'm not convinced the same can be said for magnetic adjustment.
 - https://www.usgs.gov/products/maps/topo-maps
Out at 57D they had 18/36 and 9/27. A few months ago they changed them all and now it's 19/1 and 10/28. On the radio they are called out by digits so "one", "one nine", and "one zero". Yeah, they should have just left them all off by 10 degrees. Fortunately the wind is usually out of the west.
"183 reversals over the last 83 million years... A brief complete reversal, known as the Laschamp event, occurred only 41,000 years ago during the last glacial period. ... Geologists first noticed that some volcanic rocks were magnetized opposite to the direction of the local Earth's field.".
Original source: https://www.psc.edu/science/glatzmaier.html
It took them a year of computing on a CRAY C90 and 2000 hours of processing.
So we may not know why it's moved more than model, but I don't think we should be unduly surprised.
Here's one recent piece implying a switch could be sooner rather than later: https://www.extremetech.com/extreme/192522-earths-magnetic-f...
But yes, the compass you have today will point south instead of north, but this can be solved by repainting which pole of the compass is red :)
> say I'm heading South
After the reversal is complete, yes. During the reversal your compass could well be rendered useless (pointing toward your closest pole); assuming we're right about how the reversal would happen.
I guess with celestial navigation it would've had less effect that one might think, but it certainly wouldn't have made navigation any easier.
> Hypotheses have also advanced toward linking reversals to mass extinctions. Many such arguments were based on an apparent periodicity in the rate of reversals, but more careful analyses show that the reversal record is not periodic. It may be, however, that the ends of superchrons have caused vigorous convection leading to widespread volcanism, and that the subsequent airborne ash caused extinctions. (https://en.wikipedia.org/wiki/Geomagnetic_reversal)
Based on an observed correlation between the Earth's magnetic dipole moment and oxygen isotope paleo-precipitation records from caves in Oman and southern China, Knudsen and Riisager suggest that the Earth's magnetic field may have influenced the amount of rainfall in low-latitude regions during the past 5000 years. The physical mechanism that underpins the geomagnetic-climate link is provided by the cosmic-ray-climate theory, which suggests that galactic cosmic ray (GCR) particles entering the atmosphere influence the formation of low-altitude clouds and, in turn, climate. The geomagnetic field shields the Earth from GCR particles and, according to the cosmic-ray-climate theory, it therefore has the potential to influence cloud formation, rainfall, and climate. Since the amount of GCR particles entering the atmosphere is also modulated by the Sun, the cosmic-ray-climate theory is central to the ongoing scientific debate regarding the role of the Sun in climate change. Knudsen and Riisager lend support to the notion that variations in the Earth's magnetic field may influence the climate of our planet. They also deliver independent support for certain aspects of the cosmic-ray-climate theory.
Boggles the mind to think that Mother Nature is the foundation for such significant technology.
If only the Twilight Zone was still around to do an episode on the magnetic north suddenly going MIA. It has gone south (literally) a couple times I believe.
As best I can tell Mother Nature is the foundation of ALL technology...
This article isn't much without the accompanying model.
I knew Putin was a super villain. Now he's stealing the north pole!