What are the real chances of an asteroid hitting Earth?

Page 2 - Seeking answers about space? Join the Space community: the premier source of space exploration, innovation, and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier.
Jun 1, 2020
1,303
1,080
3,060
It just dawned upon me, there may be actuarial tables/estimates for the very question that started this thread. Just something to ponder.

In the meantime, here is a fun read:

That's interesting.

Here is an update (2020) for Fig. 4.

I'm puzzled, however, with the dip in the blue line for Fig. 1. Why would a larger 4km object have a lower percentage of being found than a 2km asteroid? What am I missing?
 
Feb 1, 2020
162
92
660
The odds of asteroid collision have been worked out by serious astronomers long ago.

The odds of the Earth being struck by an asteroid larger than the one that did in the dinosaurs is somewhat distressing. The odds are 1.000 plus or minus o.oo1. That a 100% chance.

But that isn't for any one year, it's over the lifetime of the planet.

It's happened at least five times over the past Billion years, or maybe just the past 3/4 of a billion years. On average it's once every hundred million years. It's been 65 Million years since the last one, so we are about due. Sometime in the next 35 million years that is.

For larger objects the odds go down dramatically. For smaller objects they go up quite dramatically as well.

Down at the bottom of the scale, the Earth gets hit several thousand times a day up to several million times a day by dust sized bits of space debris.

Rocks large enough to destroy a city strike somewhere between once a decade and three times a decade. The last one was over a city in Russia. Before that, several years before, there was one in Africa. There was also one reported over the open ocean.

Most strikes will be over the ocean because there is three times as much surface that is ocean as there is that is land.

So strikes by space rocks is a real thing and it happens several times a decade and always has.

The Tunguska Siberia strike in the early 1900's is one famous example. A Tunguska sized event we currently believe happens once every hundred years or so. Like the Chelyabinsk event more recently, it was an air burst, meaning that the actual body exploded high in the air and there was no crater to find on the ground. Still, it exploded like a hydrogen bomb blast.

So the real answer to 'Will it happen?' is Yes. It will happen. But when is very different question. But before 35 million years from now, there will be a planet wide disaster caused by a falling space rock. Before that, there will be hundreds of city sized disasters and a few continent sized disasters all caused by falling space debris.

Its all really just a consequence of us living in a somewhat littered solar system.
 
Sep 11, 2020
62
25
60
"In 2006 Toutatis came closer than 2 AU to Jupiter; its orbit lies inside of Jupiter's.[12] In the 2100s, it will approach Jupiter many times at a similar distance.[12]" Wiki

And they still say Toutatis' orbit can be calculated hundreds of years into the future? And with the Earth Jupiter resonance as well?

Remember Shoemaker–Levy 9?
Do you think the dark matter component of Shoemaker -Levy is still orbiting or has slowed down and dissipated since its normal matter collided with Jupiter?
 

Catastrophe

Approaching asteroid? Is this THE one?
Feb 18, 2020
2,939
1,836
6,070
"Do you think the dark matter component of Shoemaker -Levy is still orbiting or has slowed down and dissipated since its normal matter collided with Jupiter? "

Please define the dark matter component of Shoemaker-Levy and I will reply to your question.
 

Catastrophe

Approaching asteroid? Is this THE one?
Feb 18, 2020
2,939
1,836
6,070
Y A Bob: "The Tunguska Siberia strike in the early 1900's is one famous example. A Tunguska sized event we currently believe happens once every hundred years or so. Like the Chelyabinsk event more recently, it was an air burst, meaning that the actual body exploded high in the air and there was no crater to find on the ground. Still, it exploded like a hydrogen bomb blast. " My emphasis.

Bob, are you passing off as inconsequential the "H bomb blast", which flattened a vast area of trees, as having very little effect on New York skyscrapers?

I am just pointing out one relatively recent relatively common event, and the effect it would have over a city as opposed to almost totally uninhabited deserted Siberia (shame about the trees).
 
Jun 1, 2020
1,303
1,080
3,060
Sorry Helio, that takes me to discovery statistics.
Where is the Fig.?
I had tried to find something quickly but couldn't, but I had planned to look further and forgot.

There should be some nice formula out there that gives a better idea of the frequency per size, but I haven't seen any yet.

There is this Wiki page on impact frequency but it doesn't do that great a job when extrapolating it to the smaller impacts.

The inverse square of size to yield frequency seems to be the rough rule of thumb.

I found that there are about 500 meteorites impacting per year. These need to be > 1 meter in diameter to do so. I assume these are mostly the stony ones, but they are only about 1/6th of all meteroids/asteroids.
 
Last edited:
Sep 11, 2020
62
25
60
Shoemaker -Levy had a gravity well which I assume had a higher concentration of dark matter than the surrounding space. This matter has mass so it also has momentum. How long would it take to disperse after the baryonic matter stopped orbiting when it collided with Jupiter?
 
Dec 6, 2020
3
0
10
There are all sorts of calculations saying nothing (asteroid, bolide, comet, what you will) is going to hit us in the next 20 minutes (Ooops sorry, I meant years) but how reliable are they?
How are we to see objects with an albedo less than soot coming 'out of the Sun'?
NEAs, especially those sharing our plane, and especially coming around in short order are affected on each return by our gravity. Large error margins start creeping into those calculations.
Are we doing enough to protect our planet? Is the Late Heavy Bombardment repeatable?
What are your views?



What we need to remember is that our Sun is in a 250 million year or so galactic orbit, of which some parts of the milky way are more crowded than others. It's coming no doubt about it. So when it happens we will need to find a way off for at least until the oceans fall in their holes again otherwise we vanish.
 
Mar 5, 2020
418
73
760
The solar system’s orbital angle to the galactic plane is somewhere around 30 degrees +5 -10. The solar system crosses the galactic plane approximately every 30 million years (as measured on Earth).

The physics for this orbit uses the real properties of space-time. The property of inertia does change producing the galactic velocity curve which are not anomalous if you use the correct gravitational equations.

This effect occurs because the reduced mass density of space affects the energy exchange of the inertial field. Your speed increases in empty space. The velocity of our solar system moving up and out of the dense galactic plane increases so that the half orbit which should have taken 120 million years (within the galactic plane) only takes about 30 million years in the empty space above that plane.

Since the major extinctions appear to coincide with these galactic plane crossings the main threat appears to be the higher velocity interstellar impactors.

While the impact of a 2 kilometer diameter local asteroid would produce a really bad day. The ecological and other weather effects might last as little as a decade (to a few hundred years). The Deccan and Siberian flood basalts are the markers for interstellar impacts.

The best dates obtainable for the Siberian impact indicates that all of the extinctions at the Permian- Triassic boundary occurred within about 30,000 years of the impact. Not bad for an extinction mechanism which does not exist within the scientific literature (Interstellar Impacts).
 
Jun 1, 2020
1,303
1,080
3,060
The solar system’s orbital angle to the galactic plane is somewhere around 30 degrees +5 -10. The solar system crosses the galactic plane approximately every 30 million years (as measured on Earth).
I didn't look hard and I'm not sure this link's info is correct, but if it is, our orbital plane with the galaxy is only inclined by less than 1 degree.

There is an angular momentum vector used that is near 60 degrees, which can make things confusing.

As for debris from hitting spiral arms or whatever, since the free-fall time for something out of Oort Cloud ranges from 178,000 years (inner region) to 2.8 million years (outer region) -- these are my calculations so they're likely off a tad -- we should have plenty of time to get out there where we can watch them and guide them to a happier ending. :)
 

Catastrophe

Approaching asteroid? Is this THE one?
Feb 18, 2020
2,939
1,836
6,070
I found this interesting article on this topic:

You are quite correct in pointing this out, but it is by no means a new idea.
I think I first came across it a few years ago. But you can't repeat an important observation too often!

Cat :)
 

Catastrophe

Approaching asteroid? Is this THE one?
Feb 18, 2020
2,939
1,836
6,070
Thanks for that link.

According to Google. Didymos weighs 52.7 billion kg and is travelling at 48,000 km / h

I don't know if anyone has calculated the effect of hitting it with that object?

Cat :)
 
Feb 1, 2020
162
92
660
Thanks for that link.

According to Google. Didymos weighs 52.7 billion kg and is travelling at 48,000 km / h

I don't know if anyone has calculated the effect of hitting it with that object?

Cat :)
E= MV*2 convert km/h to M/Sec, multiply kg by 1000 to convert to grams, there you are.

So,
57,200,000,000 kg * 48000 km/sec * 1000 m/km /3600 s/hr gives kg-m/sec^2

That's roughly 8749.5 Megatons, roughly the same as half the US arsenal or a quarter of Russia's total bombs. It will create quite an impression.
 
  • Like
Reactions: Catastrophe
Jun 1, 2020
1,303
1,080
3,060
E= MV*2 convert km/h to M/Sec, multiply kg by 1000 to convert to grams, there you are.

So,
57,200,000,000 kg * 48000 km/sec * 1000 m/km /3600 s/hr gives kg-m/sec^2

That's roughly 8749.5 Megatons, roughly the same as half the US arsenal or a quarter of Russia's total bombs. It will create quite an impression.
I get 1215 megatons. KE = 1/2 mv^2. Still huge, of course.
 
  • Like
Reactions: Catastrophe
Feb 1, 2020
162
92
660
Bob, are we talking momentum or force here?

kg-m/sec^2 = mass x acceleration ? = force ?

Am I missing something?

Cat :)

From Wikipedia, " linear momentum, translational momentum, or simply momentum is the product of the mass and velocity of an object. "
^2
Force is "By substituting the definition of acceleration, the algebraic version of Newton's second law is derived:

F → = m a → . {\displaystyle {\vec {F}}=m{\vec {a}}.}
Newton never explicitly stated the formula in the reduced form above." Again from Wikipedia.

But here we are discussing Energy, which is Force through a distance, or MV^2. The limit possible is of course when the velocity is the speed of light, or E = MC^2
So no, I was not really discussing force, but rather energy. The velocity is squared to give energy as output. Momentum would be if the velocity were not squared.

Physics is still the same as it was when we were in School, at least for things like this. I have totally ignored relativistic effects naturally. the speeds involved are minor for that.

I used an on-line unit converter to convert from Newton-Meters to Megatons. I haven't checked that, and don't offhand know the conversion numbers. But it's still quite a lot of energy. I haven't fact checked the numbers, just threw it into a spreadsheet then ran the result through the converter to get something to compare to bomb numbers.

Oh, and I also assumed the mass of Didymus reported was correct. I don't know if that also incuded Didymoon, which while much smaller would still make quite an impression.

BTW, Catastrophe, I do continue to enjoy your occasional comments on these forums. It's specifically appropriate on this particular question for your Nominal Nomus. Please continue posting. You are one of the rare few who both enlighten and entertain.
 
  • Like
Reactions: Catastrophe

Catastrophe

Approaching asteroid? Is this THE one?
Feb 18, 2020
2,939
1,836
6,070
Bob, Thank you for your kind comments. They are much appreciated.

With regard to the Didymus stats, as I recall they came directly from Googling "Didymus asteroid mass / speed" as two separate searches. I just checked the mass and it is close to the figure stated. I always try to use best sources when quoting stats.

Apart from my chemical orientated B.Sc. or (BS), my scientific interest covers the "history" of the Universe down to local level viz. from (before) BB through cosmology/astronomy/planetary science/geology. My Physics was O/A/S levels GCEs but very rusty. I was wondering whether the figure was available for the lateral component of the impacting body and how this affected the deviation from current trajectory. I must admit that I ignored Didymoon. It seemed to me (in my ignorance) that it might be difficult to affect Didymus, considering its momentum.

Wiki gives
Quote
Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion.
Quote

Having only just found that quote, I shall go back and read further.

Cat :) :)
 
  • Like
Reactions: YetAnotherBob

ASK THE COMMUNITY