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Technically every speck of dust does, but it's negligible in both cases. An impactor with 1/1000 the diameter of Earth has (very roughly) 1/1000^3 or one billionth of its mass. If it approaches Earth at e.g. 10 km/s then it will change its orbital velocity by around one billionth of that speed, 10 micrometer/s. Compare that to Earth's orbital velocity of 30 km/s. You might change the average Earth/Sun distance of 150,000,000,000 meters by something like 50 meters, which is measurable with current tools - but it doesn't matter beyond that.

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Do we know that is around the speed it hit at? or approached at?

I know you are throwing rough numbers around, but wouldn't a 50 meter change compound over 120million years? Or on that solar scale is that so trivial its like a fly hitting a baseball?

We don't know the precise impact speed and mass, but 10 km/s is a typical approach speed (leading to a 16 km/s impact due to Earth's gravity). It could be just 2 km/s, it could be 30 km/s, in extreme cases it could be up to 70 km/s. It can't be more for objects in our Solar System, only interstellar objects could impact faster but they are very rare. The conclusion is the same for all realistic speeds.

> I know you are throwing rough numbers around, but wouldn't a 50 meter change compound over 120million years? Or on that solar scale is that so trivial its like a fly hitting a baseball?

It's a one-time change. There is nothing that compounds.

If we put the mass of a fly at ~10 milligrams then it's like a fly hitting a truck.

To append another perspective to this: The entirety of Earth's biosphere makes up an extremely small part of the planet. Essentially, Earth is a massive ball of near-molten rock, with a very thin crust, that is covered in a microscopic layer of water and grime. We're part of that grime.

So when a small pebble (aka a meteor) hits Earth, the planet hardly cares, it's just that the outermost layer, the grime, will be disrupted.

That's how an extinction level meteorite impact can both be so devastating to everything we know, yet also be mostly irrelevant to the planet as an astronomical object.

> Wouldn't a 50 meter change compound over 120million years?

The effect on the size and shape of Earth's orbit would not "compound", it would still be small. The effect on Earth's position around its orbit does add up though.

Even without large impacts the solar system is chaotic, in the mathematical sense. We can make good predictions for the next few million years. But we cannot say, for example, what season it will be in the northern hemisphere exactly 100 million current-day years from now.

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We just did that with a satellite hitting an asteroid. Of course those masses are much closer in size, but it only changed the asteroids spin slightly, but measurable over days.

And there is totally things that compound, every change in mass or velocity changes it's interaction with all gravitational bodies. Which all act on each other...

As people have said it doesn't compound, because stable orbits are stable. If it slows it down which means the opposite side of the orbit might change by like 50m closer to the sun, as he said negligable but that doesn't mean it starts spiralling towards the sun at 50m per year because as it falls closer to the sun it also gains speed, which causes it to fly back out again to the original distance when it gets back to the same point in it's orbit. The orbit is still stable, simply elliptical (which the earths orbit already is by significantly more than 50m).

They all act on each other but that's a small effect and moving Earth's orbit by 50 meter isn't going to change that. Forces will differ by something like one part in a billion, and a billionth of a small effect is completely negligible (far smaller than 50 meters, in particular).

It is not known for certain whether the asteroid impact that is believed to have led to the extinction of the dinosaurs affected the Earth's orbit. Some scientists have suggested that the impact may have caused a temporary change in the Earth's orbit, but the evidence for this is not conclusive.
It is generally accepted that the asteroid impact, which is thought to have occurred around 66 million years ago, was a catastrophic event that had a major impact on the Earth's climate and environment. The impact is believed to have caused widespread wildfires, tsunamis, and other disasters that likely had a profound effect on the Earth's ecosystems. However, the precise effects of the impact on the Earth's orbit are not well understood and remain a topic of ongoing research.

I saw in a documentary that 5 or 6 objects with a 500 km diameter hit the earth when it was just formed. Also, an object with the size of Mars hit and caused the formation of the moon and tilted the earth. Considering the perfect orbit of the earth, nearly circle, I think these didn't affect either. Am I correct? These were very big events. Please comment.

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Not in a measurable way. We cant do accurate calculations of orbits too far into the future or past due to the 3 body problem (no analytical solutions to 3 bodies orbiting each other).

There are small changes going on all the time, but we have to talk in terms of what is measurable. Even the calculations they did to confirm general relativity (perihelion of mercury, observed during an eclipse) aren’t perfect. This would be even smaller than the error of those calculations.

A Mars-sized object (~10% the mass of Earth) can change the orbit significantly. It depends on the collision process.

500 km objects will have a pretty small effect.

I'm failing to see how such an impactor could meaningfully change Earth's orbit given how utterly small it was relative to the Earth.

As others have said, we can’t know for sure. But there is an indication. Asteroids orbit in stable orbits, for the most part. They aren’t just randomly leaving their orbits and attacking the earth, at least not at this stage of the solar system’s evolution.

Here’s what we think happened. A collision between two asteroids launched a chunk of one into a different orbit within the asteroid belt. Now, there are certain radii in the asteroid belt where an orbiting body interacts with the gravity of Jupiter. This is called an orbital resonance. Jupiter will dump energy into a body in these radii and pump its orbit up. Eventually, the object’s orbit will become more, what we call, eccentric. This means it becomes more elliptical. If the axis of that ellipse crosses the orbit of an inner planet, then the two can collide.

But anyway, to answer your question, we know from the physics how much energy is being pumped into an asteroid that causes it to shift its orbit. We can do those calculations and combine them with what we know about the average velocity of an asteroid in the asteroid belt and get an estimate of the speed of the impactor’s approach.

Which scientists?

The current best estimates suggest that the Chicxulub impactor was a stony asteroid (a carbonaceous chondrite) of about 10 km diameter, that impacted at around 20 km/s, at an angle of 45 to 60 degrees from the horizontal, coming from the northeast.