Meteorologist / Astronomer knowledge needed

Scott Kaelen

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The second chapter of my WIP is where things really move up a gear in the form of certain areas in the main continent being bombarded by meteorites. My concerns lie with how accurate my descriptions are.
It is still only in draft form, so I won't cut and paste sections of text, but rather explain briefly the behaviour of the meteorites.

1. Two of my main protagonists are walking across a heathland in the late morning when from the south they see several points of light approaching from high over the horizon. As the objects near, a low, distant roar begins. It only takes moments for the fireballs to streak across the sky, far ahead of our heroes. A long, dark crimson trail snakes out behind the balls of flame, lingering in the sky, dissipating gradually after the flaming objects have disappeared into the northern sky.

2. Cut to two other MCs, and a pet dog, many leagues to the north-east. They are in a clearing in a forest where they have been cutting down trees, when suddenly the sky lights up above the treetops to the south and a terrific roar drowns out all other noise. Bright streaks course overhead as man, boy and hound turn and flee down the forest trail, arms up and shielding their eyes from the light. One of the fireballs passes close enough for a wave of heat to wash down over the trio, scorching the top leaves of the tall trees. The man throws the boy to the ground and falls over him, protecting the boy's head and upper body from the heat. Moments later the deafening roar has become a distant thrum, and the heatwave from the blazing tail of the fireball has gone. The skin on the man's arms and shoulders and back of his head are hot and reddened. As the pair stagger to their feet in a daze, a sudden explosion can be heard from a league to the north. The village where they live has been struck by the low fireball and completely destroyed.

3. Cut to a snowy land many leagues to the north, and another of my MCs. The remaining fireballs stream over a small town that lies within a valley in the foothills of a massive mountain. They pass beyond the mountain range and disappear from sight. As the last of them is nearing the mountain, the townsfolk watch in terror as it strkes a glancing blow high on the side of the mountain, shattering huge chunks of rock which come cascading down.

Does any or all of this sound at all feasible? If not, what sort of behavioural pattern should the meteorites be following? They do need to be large enough for one of them to destroy a small village, along with several other small-scale catastrophes across the continent.
I have them following an almost-horizontal flight path as they enter the atmosphere and continue on for hundreds, even thousands, of leagues over land and sea. Would this be possible, or are they much more likely to plummet downwards rather than streak across the sky?

Another concern I have is that much later in the story one of the world's four orbiting moons comes crashing to the surface after it has been sent into a decaying orbit from being struck by one or more of the fireballs as they passed by on their way to the planet. The moon is not big. (Hint: It's big enough to store about a million human-sized lifeforms...) What sort of timeframe am I looking at for the moon to fall to the surface? And, again, is it likely to follow a gradual near-horizontal approach or a more abrupt fall to the ground? Ideally I want it to pass overhead close enough to strike terror into the hearts of everyone in the northern continent, as it will continue onwards and hit a large, rocky plainsland on the hot southern continent. I'm hoping that much of the debris that rises into the atmosphere willbe visible from the northern continent but remain far enough away so as not to affect it.

Please, if any of you are knowledgeable in this field, I'd very much appreciate even just a few yays or nays. I have done my research, but of course nothing beats the direct opinion of an expert.

:chores
 
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Puma

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About 15 years ago I got to see a fair sized meteor as it came across the sky before hitting earth about 150 miles from where I saw it. It didn't look like it was that high up and resembled a big jet coming in for a landing in speed, i.e., we were able to watch it for much longer than I would have expected. In color it was 2/3 neon green with intense red near the center. It seemed to pulse, or throb as it coasted across the sky. Shape was sort of rectangular / oblong. There was a trail behind it - the green dissipating into more grayish brown. And there was some noise - can't give you a good description of it, but again, not too far off the sound of a large low jet. By the time it hit the earth it was probably only about 50-100 pounds in weight, it smashed in a car hood. But let me tell you, it was a very impressive sight. Hope that helps a little bit. Puma
 
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Snick

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It would be almost impossible for an asteroid to behave like that. If we ssume that it approached the earth from the South, which is extremely unusual, then it would head North while the Earth headed East, so the two would diverge. Usully astroids come in from the direction that the Earth is moving, because the Earth is moving as fast, or faster, than the asteroid. It may be possible for an asteroid to gain an Earth orbit, or a hyperbolic orbit in whiich it approached the Earth without colliding. That would be a close balancing act. If the various groups of people were on an East-West line, then it would be much less unlikely, but the asteroids would still have to come in at the exact angle, speed, etc for them to stay up.
 

Scott Kaelen

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Thanks for the replies Puma and Snick. Some very helpful info there. Just to make things a little clearer, I've based the geography of my main continent very loosely on western Europe. If you can picture it, the meteorites will be (hopefully!) coming in from the Atlantic, passing north-east over the UK and continuing on to the north of Sweden where they will disappear beyond a long mountain range into an area of permanent ice and snow. So I'm hoping to have them following a north-easterly course. I may have to tweak it so that several batches of meteorites fall in separate areas, if that would be more realistic.
 

blacbird

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Another concern I have is that much later in the story one of the world's four orbiting moons comes crashing to the surface after it has been sent into a decaying orbit from being struck by one or more of the fireballs as they passed by on their way to the planet. The moon is not big. (Hint: It's big enough to store about a million human-sized lifeforms...)

A "moon" large enough to house a million "human-sized lifeforms" would cause a life-ending calamitous cataclysm upon collision with its parent planet. The asteroid considered to have wiped out dinosaurs (and many many many other major groups of organisms) on Earth 65 million years ago is reckoned to have been about 10 km in maximum dimension, nowhere near large enough to retain an atmosphere or house large lifeforms.

An asteroid 1/10 that size would cause enormous devastation today if it struck the Earth.

caw
 

Snick

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Thanks for the replies Puma and Snick. Some very helpful info there. Just to make things a little clearer, I've based the geography of my main continent very loosely on western Europe. If you can picture it, the meteorites will be (hopefully!) coming in from the Atlantic, passing north-east over the UK and continuing on to the north of Sweden where they will disappear beyond a long mountain range into an area of permanent ice and snow. So I'm hoping to have them following a north-easterly course. I may have to tweak it so that several batches of meteorites fall in separate areas, if that would be more realistic.
That's about what I figured.

You have to remember that the planet's gravity would be pulling on them constantly,so they could keep a level course, and the planet probaby is round, so you wouldn't want them to remain on a straight course. The only way that I can imagine them remaining at a fairly even altitude is that they are in a close orbit around the planet, along the lines of steering approach to planet to make a spaceship turn in a certain direction and gain speed. For them to be that close, they would have to moving extrmely fast, so fast that the people would see them only as streaks until they were fairly far off. For maximum effect such an orbit should be as close to the planet as possible, but it should miss as much atmosphere as possible.

Imagine that they are so close that two collide.One goes into a village and leaves a large crater. The oter wobbles along off course and goes into a mountain.

I think that your idea is possible, highly unlikely but within the realms of possibility.
 

Kenn

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You've got a bit of leeway on this. There are plenty of asteroids that cross the earth's orbit and they can come in from all directions. I recall that one of martian origin that turned up in North Africa and I believe that had headed to the northeast.

There are a couple of weaknesses in what you've written. Firstly, the meteorite is likely to be supersonic so you won't hear it approaching if it is at low level. What you will hear is a sonic boom as it passes. Secondly, I'd find it hard to imagine it could get hot enough to scorch someone without breaking up.

The meteorite would be subject to the law of gravity, like everything else. So a horizontal trajectory at low level is highly improbable, even if it came in at a shallow angle (it would be effectively orbiting the earth at that height). That said, it could easily be visible for the types of distances you mention.

As for the moon, there is a bit of leeway here too. It's obviously bad news if it crashed into the planet and everybody would know about it (it could tilt the axis, among other things), but a catastrophe might be averted if it only grazed the surface. I still wouldn't like to be around if it happened though, and then there's the question of it coming back again (which it probably would).
 

Scott Kaelen

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Thank you all for the excellent answers. I have some serious rewriting to do, but I believe I can make the series of catastrophes seem wholly plausible. The one thing I will have to change is the size of the 'moon' (it's not actually a moon at all; it's been orbiting the planet for a thousand years and appears only as a grey smudge in the sky. It's much closer than the other three moons.)
Let me ask another question, given that something large enough to house a million lifeforms would effectively wipe out all life on the planet (or almost). What about if the ISS (International Space Station) were hit by a meteor and sent into a decaying orbit? What if it were to fall to the planet, passing roughly from north to south, and crash somewhere in north-east Africa? I need it to at the very least utterly destroy a large city and leave a massive crater. Perhaps the surrounding area would be heavily warped from the impact, causing the rock (and the metals of the 'moon') to superheat and melt together. What would happen to humans and animals at the periphery of the catastrophe? Could I get away with having the satellite be several times the size of the ISS?
 

Snick

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Let me ask another question, given that something large enough to house a million lifeforms would effectively wipe out all life on the planet (or almost). What about if the ISS (International Space Station) were hit by a meteor and sent into a decaying orbit? What if it were to fall to the planet, passing roughly from north to south, and crash somewhere in north-east Africa? I need it to at the very least utterly destroy a large city and leave a massive crater. Perhaps the surrounding area would be heavily warped from the impact, causing the rock (and the metals of the 'moon') to superheat and melt together. What would happen to humans and animals at the periphery of the catastrophe? Could I get away with having the satellite be several times the size of the ISS?


The ISS isn't very solid, so it might break up during an uncontrolled reentry. If someone decided to take it bck to Earth, then it would have to be taken apart before it could be de-orbitted. If it happened to suffer a catastrophe and fell from orbit, then it might fll in Egypt, and if it didn't crumble in tiny pieces, then the major pieces would fall close to each other. It isn't all that solid, so there wouldn't be a crater, just a lot of damage and fires.
 

GeorgeK

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Not an astrophysicist, and, I suppose there are slow moving asteroids, but I thought that generally they were in the neighborhood of about 15-20,000 mph. If that's the case, then the last thing you should notice would be sound.