Lois & Clark Forums Forums Fan Fiction Fanfic Related Questions about the Nightfall Asteroid

Here's one for the sciency types. I always wondered why the Nightfall asteroid was discovered so late - there were only a few days (it seemed) to decide on some plan. (Of course, I'm not getting into dramatic tension for the show - I'm thinking about the L&C world.)

Aren't there usually tons of people who are amateur astronomers? And don't they spend a lot of time staring up at the sky through their telescopes, because they like to? Then why didn't they notice Nightfall?

I'm meandering my way through writing a fic where this topic is mentioned in passing, so I need some plausible-sounding reasons. Things I've come up with:

1) The asteroid is of very low reflectivity and nobody can see it against the black nighttime sky.

2) The space station (remember that one from the Pilot episode?) is in a geosynchronous orbit above the Earth. It just so happens that the space station blocks everyone's view of Nightfall and its trajectory. But I can't help thinking that this reason won't work, although I don't understand enough of orbital mechanics to know why.

And, by the way, is the discovery of Nightfall because it caused a sudden solar eclipse (that they showed in the episode) plausible at all? I thought, to have an eclipse, the asteroid would have to be between us and the sun, therefore by definition less than one astronomical unit away. Would that distance take days to cross, as they showed in the episode? And if the asteroid is between us and the Sun, why isn't it attracted to the Sun's much larger gravitational influence instead of the puny Earth gravitational field?

And how fast would Nightfall be traveling, anyway? If it's in a cometary orbit, wouldn't it be traveling faster as it approaches Earth/the Sun?

And, if F=ma, and Clark needs a lot of force to make up for the massive mass and presumably very fast acceleration of the asteroid, wouldn't just slamming into it like he did impart a random vector to the fragments? Was he counting on the fact that a large enough slam into the asteroid would knock it (or its fragments) off path so much that would be out of the Earth's gravitational influence? Is that possible?

And where did Nightfall come from? Wikipedia (in my two seconds of research, since I'm really too lazy to work at it - I'd rather ask the FoLCs) says that the asteroids are rock and metal, but objects from the Kuiper Belt tend to be composed largely of frozen volatiles.

So if Nightfall were from the Kuiper Belt, and if it were made of frozen volatiles, wouldn't it act like a comet and have a large flaming tail (from sublimation of the volatiles) as it approached the Sun?

And if it were from the Kuiper Belt, how long do you think it would take to reach the inner Solar System? And if it's from the asteroid belt, why did it suddenly start moving towards Earth? (Actually, I do have a reason for that in my fic, but I'd be interested in what people have to say.)

I started trying to think of plausible, watertight explanations for Nightfall and the things that happened in the episode, and I just can't. Part of that is certainly my lack of physics and astronomical knowledge, so if anyone has any thoughts, I'd certainly appreciate them.

Maybe it was abruptly tractor-beamed into Earth's orbit by the Goa'uld....

/me ducks and runs...

Sorry, it's late and I couldn't resist.

Off to bed now, before I get into trouble...

LabRat

Considering the original writers (and the ones they borrowed the story from) had no concept of physics or astronomy ... every question and comment you have is valid.

In order for there to be an eclipse, the object has to be between Earth and the Sun. But conceivably, if Nightfall was in a cometary orbit, or even a very long elliptical orbit, it would have been detected and deemed a non-threat until its orbit was changed (drastically) while passing around the Sun. So Nightfall would be coming at Earth from the direction of the Sun.

For Superman, the best scenario would be to intercept it as far away from Earth as he can and nudge it a little so it shifts orbit. While breaking apart will negate the effect of the single mass hitting the Earth, it will create a lot of littler impacts which may or may not create havoc when they hit - nuclear winter anyone?

And Nightfall doesn't have to be coming out of the Kuyper Belt - there are quite a number of objects that cross Earth's orbit. Luckily Earth is a very small object in the scheme of the universe. The astronomers who did detect Nightfall could have easily calculated it would be a near miss rather an a hit.

The other usable possibility is that there were two objects - one that never came close to Earth and caused the eclipse and another one on target for Earth. Maybe they'd been named Nightfall I & II

OR

I'm not getting the reference.

Signed, Cultural Illiterate, Iolanthe

Star Gate - there was an episode where an asteroid was on a collision course with Earth. As it turned out, the asteroid was loaded with an transuranic element not found in nature leading the crew, who was supposed to blow up the asteroid, to realize it was actually an attack by the bad guys. (The Goa'uld.)

It was LabRat's late night joke, not to be taken seriously. Unless, of course, there really *are* Goa'uld.

Artemis

Let me contribute to the answer to the original question (although the Star Gate reference was funny). If the object was large enough to cause an eclipse, that means that it had to be big enough to occlude the sun, like our moon does during solar eclipses. But the moon is "only" a quarter million miles away and about one-sixth the size of Earth. Nightfall would have had to have been just outside the atmosphere or had to have been close to moon-sized to cause an eclipse. That, as Dandello mentioned, was the result of some writers who knew diddly about celestial mechanics or astronomy.

The only other explanation is that it was essentially flat and just happened to rotate its wide side to face Metropolis when it rotated between the sun and the Earth. I don't think that's very likely, but it's all I have.

The question about the sun's gravity is valid, but we have to remember that the effect of gravity is reduced geometrically the farther you are from the source. For example, if you double the distance from the gravity source, you don't cut the attraction in half. It gets lowered much more than that. The force is reduced according to a formula I don't recall (drat that getting old thing!) and am too lazy to look up. Ann (TOC) probably has that information at her fingertips, and if you were to message her should could give you more insight than I can right now.

The decrease in gravity is the inverse of the distance squared - double the distance, gravity is 1/4; triple the distance, gravity is 1/9 and so on. (Also the same with radiation.) The Sun is so massive, relatively speaking, that its effects extend easily to the Kuyper Belt and beyond.
Considering the original source for the story was from the original George Reeves series which was written at a time when science wasn't even considered to be relevant in kid oriented fiction... (George Pal, Robert Heinlein and Isaac Asimov not withstanding...) I suspect Gillis and Zabel didn't bother to crack open a physics book to even check the math.

Don't you know? Lord Nor was in reality Ba'al And I was tempted to say Anubis, but Anubis was way too little melodramatic for Nor

But back on asteroids. Given how only a small percentage of the sky is actually covered by astronomic observation (<< 10%?), today it's still a matter of getting lucky in spotting one that is even on the radar as far as collision possibilities are concerned. To actually spot the one that's going to hit you, and spot it in time, well...

Michael

Oh, no, no. Ba'al had way too much charisma to be Nor. Don't be insulting one of my favorite bad guys!

I can't say much, most of my knowledge comes from Armageddon and Deep Impact.

I just got a letter from The Planetary Society saying "monitoring potentially dangerous near-Earth
asteroids and comets" is the top priority of 90% of the society's members. While I'm not of the "chicken little" persuasion, finding out more about asteroids would be very interesting and valuable.

Artemis

I think, if I ever get the fic finished, that I will just have to ignore the "unexplained total eclipse of the sun", because I just can't suspend my disbelief enough to actually let that into my fic.

(Of course, the fic is about a guy who flies, but that's different.)

Second topic:
Is that true? I thought there were leagues of amateur astronomers, scanning the sky nightly, checking for dangerous celestial objects! Suddenly I feel much more insecure.

I think Dandello's first reply gave you most of the answers you needed. Anyway, here is what I know and what I can say about the subject:

That is totally unrealistic. Sorry.

However, we must remember that the Nightfall episode took place in the 1990s, when the quality of the scrutiny of the sky was not as good as it is today, and the search for asteroids was not nearly as systematical. Therefore, an asteroid could much more easily avoid discovery then than now.

One thing that helped remind the astronomical community that the sky could produce sudden surprises was the Great Comet of 1996, Comet Hyakutake. It was discovered on January 31, 1996, and it had become one of the brightest objects in the sky by late March. Its closest approach was on March 25. Its tail was the longest ever seen in a comet. It went from being invisible and undiscovered to being one of the brightest objects in the sky in two months. The size of its nucleus was about 2 kilometers, which is small. For a comet, it passed very close to the Earth, only about 0.1 AU, or about 15 million kilometers. That is still a long way away, and Comet Hyakutake never came close to crashing down onto the Earth.

But Comet Hyakutake was a comet, releasing a lot of volatiles as it approached the Sun. And it only looked so bright to us because it passed so close to us. If Comet Hyakutake had been an asteroid instead of a comet, it would have been discovered even later. However, you must remember that on the day when it was discovered, January 31, Comet Hyakutake wasn't yet strongly affected by the Sun and didn't release a lot of gases. It was brighter than an asteroid would have been at that distance, but not by that much.

Still, Comet Hyakutake gave some astronomers a scare. They realized that if Hyakutake had been an asteroid instead of a comet, and if it had been even smaller than it was and on a direct course for the Earth, it would have been discovered even later, quite possibly only a month or less before impact. You can read about Comet Hyakutake here .

Could the asteroid have remained undiscovered until only a few days before impact? No, I find that totally unrealistic. An asteroid on a direct course for the Earth would grow dramatically in size as it approached us. Certainly it might be dark in color and have a very low albedo (reflectivity), but as it approached and started growing rapidly in size against the sky it would have been discovered by at least one amateur astronomer at least two weeks before impact. Count on it.

As for the solar eclipse thing, just forget it. The idea that an asteroid wouldn't be discovered until it had grown big enough to literally cover the Sun is utter nonsense.

As for how fast an asteroid like Nightfall would be travelling, I'm afraid I don't know. But it would certainly pick up speed as it approached the Sun on its way from its birthplace farther out in the Solar system. And because the elliptical path of the asteroid would cross the more-or-less round orbit of the Earth, the relative speed with which it would hit us would be high.

I found this image on the internet. The picture is called pre-impact-orbits:



In the picture, you can see the asteroid belt between Mars and Jupiter. Nightfall could certainly originate there. But it could come from either the Kuiper Belt or the Oort Cloud, too.

Just slamming into the asteroid would be a very bad idea. Astronomers believe that many comets and asteroids are actually conglomerates of smaller bodies, and slamming into such a conglomerate would break the asteroid apart. But most of the indivual fragments would continue their path toward the Earth. And while Clark might be able to stop one asteroid, he would not be able to stop a hailstorm of fragments.

No, the best way to save the Earth from the asteroid would be to nudge the asteroid gently and make it change course. Of course, making it change course isn't easy, because you must remember that the asteroid moves the way it does because of strong gravitational forces acting on it. Still, that would be the best way to deal with it. And the sooner it could be done, the better it would be.

If the asteroid was a conglomerate, it could break up on its own when it got sufficiently close to the Earth. Here is a Hubble picture of Comet Shoemaker-Levy which broke up on its own on its way to crashing down on Jupiter. You can see how the comet has broken up into indiviual fragments:



Because Clark would need to deal with Nightfall as soon as he possibly could, he would still be in a hurry as soon as the threat to the Earth had been discovered.

Ann

On March 2nd of this year asteroid, 2009 DD45 came within within 75,000 kilometers. It was only spotted 3 days earlier when it was within 2,500,000 kilometers. Now it wasn't a Nightfall size one, it's only 30-40 meters across. That is still big enough to cause the kind of damage a medium size nuke would do. Say a 1/3rd to 1/2 kilometer crater.

So we would probably see a world wrecker earlier but a city killer could be only days. Spotting that one was not a sure thing even when they did. There have been cases in recent years where ones in smaller sizes were spotted on the way out from the closest approach.

Universetoday story

Aside from the eclipse, All Shook Up is totally valid.

Space is vast, as many people as there are looking for projectiles up there, there's still stuff to miss. Maybe a planet or moon or other projectile blocks the view, maybe it's a super non-reflective surface, maybe we just aren't looking at the right patch of sky. Is it likely that we wake up tomorrow and find out there's a massive asteroid due in 3 days? Most likely not. But it is not outside the realm of possibility either.

Even better, we really don't have any working prototype to deal with such a threat on such short notice to my knowledge. I hope we do by 2029:

http://www.popularmechanics.com/science/air_space/4201569.html

However, some interesting statistics on Nightfall itself. It's too big, period, objects that size aren't really very likely anymore. Besides, the asteroid that took out the dinos was estimated to be about six miles across... 17 seems like overkill. If I remember right from writing ASU for Coin, it's also too slow. 30,000mph is not very realistic. In my write-up I shrunk the asteroid and sped it up to 13 miles (still overkill) and almost 50,000mph. Also their predictions are ludicrous. If the impact that formed the moon, which was an object roughly the size of Mars iirc and completely melted the earth, didn't change the orbital path much. So that asteroid wouldn't. Would it tilt the axis? Possibly... a miniscule amount.

In my write-up I used this calculator to guesstimate damage:

http://www.lpl.arizona.edu/impacteffects/

I had to search for awhile to find one that would even take the size the show uses or that I used.

And for grins, put in Nightfall's size, with dense rock as the material and a realistic velocity, you get this:

Energy:

Energy before atmospheric entry: 4.65 x 10^24 Joules = 1.11 x 10^9 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.0 x 10^9years

Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.

So, Earth doesn't care about this hit... life surely would, but the planet itself would be fine. And the time interval? You get one about every billion years. Are we due? Who knows?

Also, playing with that calculator (at 30km/s velocity), you would completely melt the earth before you would get a change in the orbit or axis. At ~4500 miles across you can affect the axis. At ~5500 miles across you shatter the earth into a new asteroid belt. Even then, it seems like this calculator just predicts the scattering of mass, not a change in the orbit.

Back to your questions. Most near-earth-asteroids don't have much of an elliptical component to their orbits, at least not compared to a comet. However, given an elliptical orbit, you are correct. The closer the object gets to it's foci (one of which is always the sun) the faster it gets.

As for Clark... that wouldn't work on so many levels. For one, a missile hitting the asteroid, as others have stated, may or may not do anything according to the density and makeup of the rock. The demo I've seen had a guy shoot rocks with a bullet. The dense solid rock and porous solid rock were shattered (can we say buckshot?) but a pile of pebbles was mostly undisturbed. However, bullet vs pile of rocks... not quite the same size ratio as man vs. 17-mile-across rock... I think, at best, no matter what Clark did with that method he would manage to poke a hole in the rock, possibly just go straight through it. The most plausible I've seen have been fics where he's nudged the asteroid enough to change it's orbital path to miss the earth. I also think that's the basis of most of our theories on how to deal with asteroids.

As for nightfall's origin. You are correct in the distribution of materials in the solar system, IF nightfall was from the outer reaches it would be a comet. However, it's also entirely plausible for it to be a newly discovered 'near-earth' asteroid either from the belt between mars and jupiter or many other places and made of rock.

As for time period. Some comets have periods of 70 or more years. Objets from the oort cloud are even longer... we may only see them once in recorded history, for example, and those would move incredibly fast once they closed in. I suppose you could even form a hyperbola, an object that is knocked out of orbit, falls towards the sun and is then sling shotted out of the solar system entirely.

The oort cloud is also fascinating in one detail. It is a sphere around the solar system. Every other portion of the system is more or less in one plane. An oort cloud object could come from any direction and may intersect the plane in a single point, which might just happen to be earth. Would people be looking there for approaching objects? I honestly don't know.

An oort cloud object:

http://en.wikipedia.org/wiki/Comet_Hale-Bopp

Orbital period: ~4200 years.

Thanks to everyone who has posted. You've given me so many ideas. I'll try to make the asteroid bits in the fic more feasible.

I can only agree with the stuff the others have already mentioned, but some things seem off:
If a large asteroid had a low albedo (= reflectivity), making it seem black to the eye - wouldn't it be spotted regardless? I mean, if there was a black sphere moving around the night sky where you would expect to find stars (and/or nebulas, galaxies - you get my drift) and only see black - wouldn't anybody think it odd? I mean, hello? (Okay, astronomers might consider the black sphere to be a black hole at first, but sooner or later, they'd see the light. Hopefully.)

It doesn't. The reason is quite simple: The Earth moves, and in two directions (in regard to the sun): First, it moves around the sun, so the asteroid would have to move at the same rate (in radian measure). Second, the Earth spins like a carrousel. If I wanted to implement your space station, it would be like a parent running along with his child beside the carousel.

Thus, if the asteroid was expected to be blocked out, it would have to be in geo-synchronous orbit, too, which would contradict the usual movement of asteroids.

I’ve been watching this thread with some interest and have been trying my best to stay out of it. Obviously, I’ve failed at that.

The Nightfall sequence is both wonderful and tragic. The wonderful part is that this storyline presents so many opportunities. The tragic aspect is that, in my opinion, you can’t reconcile the story to anything that seems scientifically plausible without changing the story all around and changing many of the details.

To me, the critical story elements are:
1. Nightfall is a threat to all humanity
2. It arrives with little or no warning
3. Superman is necessary to attempt to save the world
4. Something doesn’t go exactly per plan
5. Dealing with the consequences of #4

It’s point #5 that serves as the basis for story development. I've been toying with a Nightfall concept for some time and the desire to make the astrophysics work has nearly scuttled the story. The reality is that as long as I’m not insulted by the science, I’ll ignore the implausible and even the impossible science to get to the story that results.

So, my suggestion would be to take your best shot at Nightfall science but don’t let it distract from the story.

Now, that doesn't mean that having the science be more believable isn't a good thing. I guess I'm frustrated myself at compromising and almost losing a story to the goal of scientific correctness. If you can write your story and achieve scientific correctness, that's great. This discussion here is a good basis for moving the story to a more plausible footing.

For my part, on the assumption that my own Nightfall work ever sees the light of day, I have tried to bring a bit more realism to the overall story (I cut the eclipse ) but I will be asking for some forgiveness on some aspects of the asteroid-impact science. When you get down to cases, getting the science right is, at best, only peripheral to the story.

Bob

Thanks, Bob. I think I'm perhaps getting a little too compulsive about making the science in the fic be consistent with real life science.

For example, Lieta, above, had a good point about the asteroid being like buckshot, a conglomeration of "stuff". But for my fic, I'm pretty sure that I'll have to have the asteroid be a solid piece of rock, as was implied in the TV episode.

So, assuming this fic ever gets completed, and you-all see some semi-egregious errors in the bits about Nightfall, please just ascribe them to dramatic necessity. Believe me, it won't be because I'm ignoring your comments!

(You'll all know that you told me the way things should really be....)

Whoops! Another question. I feel as if I should be able to answer this based on learning Isaac Newton's equation once back in high school physics, but I've forgotten the details.

If Nightfall is 17 miles across, and it's made of rock, and if you were standing on it, what would the gravity be? Specifically, if Clark were there, and he masses 220 lbs (100 kg) what would his weight if he were standing on Nightfall?

And what would his escape velocity be? Would he be leaping off the asteroid if he were a normal guy just walking on its surface?