Is it even remotely possible it was something else that happened around the same time?
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To directly address the “witness” part; we don’t necessarily need to witness something to be able to determine it happened. If you find a circle of stones with ash in it, you can pretty confidently say someone built a campfire there, even though you weren’t there to see them do it.
Pretty much the same applies here. There’s various bits of evidence that all say it was an asteroid. There’s an impact crater with the right age, and enough energy was required to form it that it would have done the job. IIRC, the red a very obvious layer of iridium dust at the same time over the vast majority of the Earth’s surface, which is also an effect of asteroid impacts.
The earth itself keeps a pretty stable record of what happens on it, if you know how to read it.
When you take samples of the ground, you get sort of layers. Different colours and soil types show up in more or less clear segments. When we look at the soil from ~66 million years ago, we find a layer of soot. Enough soot that it would have significantly weakened the sun’s influence on earth’s life.
Around 66 million years ago is also when we find a lot of dinosaur fossils (other fossils as well). After that period, we don’t really find any dinosaur fossils anymore. That means they must have gone extinct.
The reason we believe an asteroid caused that soot to cloud the atmosphere is that we found the crater. It’s off the Mexican coast. Any life in the area would have died out instantly, but the soot and other stuff it launched into the atmosphere killed the rest. Roughly 75% of mammals are estimated to have died during a period of ~30,000 years.
We didn’t see the event, but we’ve found some pretty big craters. Like the Chicxulub crater. At the same time (dating the crater and the extinctions), there’s fossil evidence of mass extinctions. And asteroid dirt in that layer of rock (elevated levels of metals found often in asteroids and meteors).
So it’s like walking into a room and seeing a bowl of soup splattered on the floor, then turning around and seeing your cat covered in soup. You didn’t need to see it happen to know with pretty great certainty your cat knocked the soup bowl off the table.
We don’t need to witness something to understand what happened. We can simply gather clues and follow those clues to their logical conclusion.
We know that 65 million years ago there were mass die offs. We also have evidence that a material called Iridium was scattered around the Earth at the same time. And we also know that Iridium is rare on earth, but common on asteroids. And we have a huge crater near Mexico that is also 65 million years old.
So we put all that evidence together and we found our answer.
One of the ways we’re really sure is because of an unusual element called: Iridium.
Iridium is pretty rare on earth, but about 65 million years ago, for some reason, at the exact same time, we see a mass extinction of the dinosaurs, we also see a highly unusual amount of Iridium. It shouldn’t be there, its pretty rare, it wouldn’t show up like this. But there is a way it could, an asteroid impact. Turns out as well, there’s this meteor crater in the gulf of mexico, dated about 65 million years ago too… seems to fit nicely.
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How are you able to come to the conclusion that dinosaurs existed? You find fossils of those, in specific layers of rocks.
How are you able to say that the middle ages existed? You find books dating from the period, skeletons, swords, armors, giant castles, churches, stuff, all of that leading us to believe there was something.
How are you able to say the American Revolution happened? I mean, you weren’t there.
So how about an entire extinction, which started about 65 Mya?
The answer is simple : facts. Medieval castles weren’t built yesterday, and even you can find fossils yourself to prove the existence of animals that lived millions of years ago. And the fact that you find weird stuff all around the world at this period of time in the soil, with the inability to find fossils of most species after the event leads us towards an obvious extinction event that happened for several millions of years.
What a coincidence, we see intense volcanism, and a giant crater, both happened at a period of time where animals started to get wiped out. How do you think we know of other extinctions? That one wasn’t the most devastating and wasn’t even the hardest to admit. People tend to forget that life on Earth has always been a series of extinctions.
This is why scientists from all around the world agreed with the same conclusions : Because facts are facts, you can’t pretend it’s something else or never happened when the facts say otherwise (unless you’re part of flat earth or similar networks, where sudddenly the more bullshit you say, the more followers you get). It’s not like you can just say whatever fits your vision of the world. What only matters now is getting more and more accurate in our statements.
Science is a method of collecting evidence and trying to stake out a likely sequence of events based on the evidence, no matter where it leads.
As for scientists, they are humans who sometimes do human misstakes that color their findings.
In contrast to religion, a human witness is not a strong evidence to the scientific method, as humans lie, decieve, missconceptualize, remembers wrong and imagine events that might not be true to the fact of what actually happened.
Nature, however, does not lie or imagine. That means that we can create methods to examine nature, for example, measuring radio active decay to determine the age of something. Other geological methods have also been established to figure out greater time spans than radioactive decay could.
Witnesses are actually a very uncertain method of examination when it comes to establishing historical fact, when compared to traces left behind by nature it self.
Most scientists agree that birds are in fact feathered dinosaurs. They are descended from a small bipedal therapod. So you could say that dinosaurs did not go extinct exactly. The iridium layer that can be seen is sometimes called the kt boundary. The impact itself and the shock wave it produced killed a lot of stuff to be sure but it did not cause the mass extinction though. the massive amount of matter that was hurled into the atmosphere blocked the sun caused climate change cooled the planet killed of a lot of plants etc. it is pretty widely accepted but new theories come along every so often.
This is actually a relatively recent consensus that has formed in the scientific community. There was a lot of speculation over the years about why the Dinosaurs disappeared, and nobody was exactly sure if it was a sudden catastrophic event (i.e. volcanic eruptions, asteroid impact event) or something more gradual (climate change).
In 1980 some geologists discovered a thin layer of sediment in the Earth’s crust that had a lot more Iridium in it than there should be – this came to be known as the K-T boundary (now it’s called the K-Pg boundary). It turns out that this is what you’d expect to happen if there was a really big asteroid impact – they have a lot more Iridium than normally occurs in the Earth’s crust. When they got rough estimates of the age of this layer, it lined up with the time that the Dinosaurs disappear from the fossil record. So they hypothesized that a massive asteroid impact was responsible for this extinction event. The only problem was that there wasn’t any known crater on the planet that was the right size and age to fit the hypothesis.
About 10 years later, geologists found a structure around the Yucatan peninsula in Mexico that corresponded to an impact crater that was the right size and age for this particular impact. Some additional research in 2016 got material samples from the crater and have pretty much confirmed that this was the impact event that caused the K-Pg boundary – and this the most likely reason for the disappearance of the Dinosaurs.
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