Let's do a journey into science, shall we.
How does dating (scientifically speaking) work?
So how do scientists do it?
Radiocarbon dating is the most common method by far, according to experts. This method involves measuring quantities of carbon-14, a radioactive carbon isotope — or version of an atom with a different number of neutrons. Carbon-14 is ubiquitous in the environment. After it forms high up in the atmosphere, plants breathe it in and animals breathe it out, said Thomas Higham, an archaeologist and radiocarbon dating specialist at the University of Oxford in England.
"Everything that's alive takes it up," Higham told Live Science.
While the most common form of carbon has six neutrons, carbon-14 has two extra. That makes the isotope heavier and much less stable than the most common carbon form. So after thousands of years, carbon-14 eventually breaks down. One of its neutrons splits into a proton and an electron. While the electron escapes, the proton remains part of the atom. With one less neutron and one more proton, the isotope decays into nitrogen.
When living things die, they stop taking in carbon-14 and the amount that's left in their body starts the slow process of radioactive decay. Scientists know how long it takes for half of a given quantity of carbon-14 to decay — a length of time called a half-life. That allows them to measure the age of an organic piece of matter — whether that's an animal skin or skeleton, ash or a tree ring — by measuring the ratio of carbon-14 to carbon-12 left in it and comparing that quantity to the carbon-14 half-life.
The half-life of carbon-14 is 5,730 years, making it ideal for scientists who want to study the last 50,000 years of history. "That covers basically the really interesting part of human history," Higham said, "the origins of agriculture, the development of civilizations: All these things happened in the radiocarbon period."
A time machine would be science fiction, not science. Mixing science with fiction would be pseudo-science, so let's avoid that...
Interesting thought, but let's continue with our journey into actual science
How does dating (scientifically speaking) work?
However, objects older than that (>50,000 years) have lost more than 99% of their carbon-14, leaving too little to detect, said Brendan Culleton, an assistant research professor in the Radiocarbon Laboratory at Pennsylvania State University. For older objects, scientists don't use carbon-14 as a measure of age. Instead, they often look to radioactive isotopes of other elements present in the environment.
So for this thread we are talking about a 1.6 Billion year old fossil which is way more than 50,000 so scientists didn't use carbon dating here.
Time machines are science fiction, right? And we have now educated ourselves enough to know that the scientists didn't use carbon dating for objects older than 50,000 years.
Yes, so rather than being sidetracked by science fiction or philosophy, let's get back to the actual science
How does dating (scientifically speaking) work?
For the world's oldest objects, uranium-thorium-lead dating is the most useful method. "We use it to date the Earth," Higham said. While radiocarbon dating is useful only for materials that were once alive, scientists can use uranium-thorium-lead dating to measure the age of objects such as rocks. In this method, scientists measure the quantity of a variety of different radioactive isotopes, all of which decay into stable forms of lead. These separate chains of decay begin with the breakdown of uranium-238, uranium-235 and thorium-232.
"Uranium and thorium are such large isotopes, they're bursting at the seams. They're always unstable," said Tammy Rittenour, a geologist at Utah State University. These "parent isotopes'' each break down in a different cascade of radioisotopes before they wind up as lead. Each of these isotopes has a different half-life, ranging from days to billions of years, according to the Environmental Protection Agency. Just like radiocarbon dating, scientists calculate the ratios between these isotopes, comparing them with their respective half-lives. Using this method, scientists were able to date the oldest rock ever discovered, a 4.4 billion-year-old zircon crystal found in Australia.
Finally, another dating method tells scientists not how old an object is, but when it was last exposed to heat or sunlight. This method, called luminescence dating, is favored by geo-scientists studying changes in landscapes over the last million years — they can use it to discover when a glacier formed or retreated, depositing rocks over a valley; or when a flood dumped sediment over a river-basin, Rittenour told Live Science
When the minerals in these rocks and sediments are buried, they become exposed to the radiation emitted by the sediments around them. This radiation kicks electrons out of their atoms. Some of the electrons fall back down into the atoms, but others get stuck in holes or other defects in the otherwise dense network of atoms around them. It takes second exposure to heat or sunlight to knock these electrons back to their original positions. That's exactly what scientists do. They expose a sample to light, and as the electrons fall back into the atoms, they emit heat and light, or a luminescent signal.
"The longer that object is buried, the more radiation it's been exposed to," Rittenour said. In essence, long-buried objects exposed to a lot of radiation will have a tremendous amount of electrons knocked out of place, which together will emit a bright light as they return to their atoms, she said. Therefore, the amount of luminescent signal tells scientists how long the object was buried.
Dating objects isn't just important for understanding the age of the world and how ancient humans lived. Forensic scientists use it to solve crimes, from murder to art forgery. Radiocarbon dating can tell us for how long a fine wine or whiskey has been aged, and thus whether it has been faked, Higham said. "There's a whole range of different applications."
So maybe the scientists tested for uranium-thoriam-lead dating, or possibly luminescence dating. Or both maybe? Sounds pretty interesting.
Within the linked to article from the Original post of this thread
Researchers uncovered fossils of multicellular eukaryotes that are over a billion years old.
That article itself provides a link to the actual science paper
according to a new study published Jan. 24 in the journal Science Advances.
And within that paper it says
The age of microfossils is well constrained by an ash bed ~40 m above the fossil horizon in the Kuancheng area, which has yielded a U-Pb zircon age of 1634.8 ± 6.9 Ma (23).
So we can see that they didn't date the fossils themselves but dated the ash bed which was on top of the fossils. Being on top that ash bed has to be younger than the fossils. So that constrains a date by which the fossils must be older than.
They dated that ash bed by U-PB a.k.a. Uranium to Lead dating.
So the science paper lets us know:
Where the fossils were found, what other layers were found around the fossils, what layer was on top, and the age of that top layer based on Uranium to Lead dating.
The paper tells us who the author of the paper were
LANYUN MIAO, ZONGJUN YIN, ANDREW H. KNOLL, YUANGAO QU , AND MAOYAN ZHU
It tells us lots of details about the findings, including photos, and it discloses the materials and methods used to prepare, extract and measure the fossils and the layers of ash. It's all there, all documented, for others, including scientists to pour over, to seek out any issues (if any) with the methods used, with the measurements taken, with the conclusions drawn.
If you have any valid scientific critique of this paper then please offer it.
But please don't go off on a side track rant of time machines and philosophy, just stick to science.