Exactly how can an xray laser divert a comet? - Travelers (2016) Discussion

[–] abomination21 8 years ago

The problem is with the method of travel... it is one that both introduce new element (the time traveler) & remove existing element (the host in question). They can't be sure who may made what contributions. So choose those whose death is confirmed... that way, they at least don't accidentally take out vital element that wouldn't be gone in the first place.

If they took out the brains of a scientist who actually contributed a lot but their records doesn't indicate so... it may cause more than a bit of problem. Taking over people who would die... is the safer path they can took. This is actually not a new concept... even fantasy story with nothing to do with time travel have similar concept of "preservation".

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[–] Dejay 8 years ago

I would imagine vaporizing one side of the asteroid and turn it into gas just the right way would give it a push. I don't think "outgassing" would work since that would be just slow melting of frozen gasses and that doesn't have much inertia. I think the faster you spew out your propellant, the more efficient your mass / thrust ratio is.

Breaking up an asteroid into many pieces would actually help if the pieces become small enough to burn up in the atmosphere. A big hunk won't burn up and hit the ground, but small pieces could be harmless.

Well I actually don't know how this burning up works, if the asteroid elements become so hot that they turn into gas and condensate as dust specs or if they react with oxygen and are literally burning or what. Or if it's like a snowball hitting a concrete wall.

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[–] gswan 8 years ago

See update below:
You seem to be implying there is a meaningful distinction between outgassing, the term I used, and vaporizing.

Breaking up an asteroid into many pieces would actually help if the pieces become small enough to burn up in the atmosphere. A big hunk won't burn up and hit the ground, but small pieces could be harmless.

Individual mall meteors and meteorites don't cause significant damage.

Do you know how large the 1908 Tunguska rock is estimated to have been? Estimates vary, but around fifty feet in diameter.

The Tunguska rock didn't hit the ground, and leave a crater. But the blast force from its aerial burst was said to have been bright enough to light the sky thousands of miles away. It blew down all the trees for kilometers around ground zero.

Fifty feet? Let's call it 15 metres. Consider an asteroid 1.5 kilometres in diameter. Because volume goes up as the cube of the dimension, a 1.5 kilometre asteroid will have one million times the mass of Tunguska. So, if Tunguska's destruction was equivalent of a Hiroshima bomb, even if we broke up a 1.5 kilometre asteroid into pieces small enough to burn up in the atmosphere, we would still be hit by the energy of one million hiroshima bombs.

So, I disagree that an asteroid broken up into small chunks would be harmless.

Do you know about the US military thermobaric bombs? The bomb first spreads an explosive aerosol, into a relatively large cloud, and then it triggers an explosion throughout that cloud. It is powerfully dangerous.

Wouldn't millions of asteroid fragments, blowing up, all at once, be like a thermobaric bomb explosing all over one hemisphere of the Earth, all at once?

Update, 2017-02-02
The Tunguska meteor seems to have been larger than I remembered, both, in diameter, and in the amount of energy released. According to the wikipedia article its diameter was 60-190 meters, not 15 meters, and it released something like 15 megatons, not 15 kilotons, like I remembered. https://en.wikipedia.org/wiki/Tunguska_event

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[–] Dejay 8 years ago

Hey I'm just speculating and I'm not a astrophysicist :)

I'm definitely surprised that a meteor can explode like a nuclear bomb in mid air without touching the ground! My guess would be that it depends on the velocity, if it's fast enough water or air will have much the same destructive effect as concrete. BTW on Wikipedia it says tunguska is estimated to 60 to 190 metres.

I figure the overall energy the meteor imparts colliding with the earth is the same no matter how many chunks hit, or whether it explodes in mid air or on the ground. Either way it's converted into some mixture of heat or kinetic energy.

But spreading the energy across half the globe would dilute the same amount of energy. The tunguska event won't have increased the temperature of the earth across a larger area in any significant way. So if you assume you'd spread the meteor into small enough pieces that convert into heat, it's harmless. If it hits the ocean, 1000 small waves are harmless compared to one giant wave.

All this comes down to math, you would have to do the calculations etc. But yeah, I figure a million hiroshima bombs that drop randomly would be more harmess than on big nuke that causes a tidal wave to roll around the earth a few times, or god knows what happens if you rip such a big crater into the earth crust. Probably earthquakes and volcanic eruptions all over. Randomly hitting means they'd hit 90% unpolulated areas.

Of course mod term damage comes from huge amounts of dust kicked up high enough or ash from burning lots of forests or cities to create an artificial winter that would starve more people than would die from explosions.

PS: Btw there is a very cool sci-fi novel called "Seven Eves" that deals with our moon doing something like this. Spoiler: It doesn't end well :D

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[–] gswan 8 years ago

But spreading the energy across half the globe would dilute the same amount of energy. The tunguska event won't have increased the temperature of the earth across a larger area in any significant way. So if you assume you'd spread the meteor into small enough pieces that convert into heat, it's harmless. If it hits the ocean, 1000 small waves are harmless compared to one giant wave.

Alternatively, you could say diluting the energy would spread the same (devastating) amount of energy across the globe...

A very large number of sufficiently small waves, spread over a significant interval, could be harmless. But these waves would be essentially simultaneous, not spread over a significant interval.

Do you know how a shaped charge works? Do you know how the explosive lense that surrounds the fissionable material in an A bomb work? When you have a bunch of simultaneous explosions, or near-simultaneous explosions, the blast waves re-inforce one another.

You are correct that, even with 8 billion people, our civilization has a couple of dozen particularly dense concentrations of people, and there remains vast stretches that would be relatively casualty free. But breaking apart an asteroid of less than extinction level size, into a mess of fragments that included hundreds or thousands of Tunguska sized city killers would guarantee devastating dozens of cities with direct hits or near misses.

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[–] Dejay 8 years ago

Well you can always make the overall mass of the meteoroid big enough that there is no chance either way. But there could be a "break even point" (no pun intended haha) where one big impact would have dire consequences and if you split it up it becomes much more harmless.

Was the asteroid in the show meant to be 1.5 kilometres size?

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[–] gswan 8 years ago

Was the asteroid in the show meant to be 1.5 kilometres size?

They didn't say the size.

That stupid film Armeggedon had Scientist Billy-Bob Thornton say the killer asteroid was "the size of Texas" -- which would make it larger than Ceres, the largest asteroid in the asteroid belt.

The Earth has been hit by a couple of extinction level asteroids -- which I believe were in the 10-20 km range. Around the same time as Armageddon a better film came out, can't recall the name. Morgan Freeman was the POTUS. It also had a team of astronauts go out and try to divert the asteroid with a huge H bomb.

While containing inaccuracies it was at least two orders of magnitude more accurate than Armegeddon. The attempt to divert the asteroid was a failure, merely broke it into two fragments, of unequal size. One fragment remained an extinction level event, while the other was a survivable, while severely damaging 1-2 km in diameter. The plucky astronauts, lead by crusty old Robert Duvall, who took over when the original young and overconfident commander got himself killed, decide that instead of returning to a doomed Earth they will use their ship's atomic engine as an improvised nuclear charge, and divert the extinction level asteriod.

I actually can't recall reading a meaningful analysis of the largest asteroid that can hit Earth without rendering humanity extinct. So I used the estimate from the better of the two movies.

FWIW, I suspect that, for any rock that much larger than a magnitude larger than the Tunguska rock, impact by one solid rock, or a fragmented rock, will each be comparably damaging.

Tsunamis that would swamp all the coastal cities in the North Atlantic? I'd like to know whether a single strike by a 10 x Tunguska could do that. 30 x Tunguska? 40 x Tunguska? Could that swamp all the coastal cities bordering the Pacific?

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[–] Dejay 8 years ago

Ah right I remember those two, hating Armageddon and seeing Deep Impact much later and finding it much better. Now I have to go see it again lol :)

Deep Impact http://www.imdb.com/title/tt0120647

There is a wikipedia page about impact events, but I'm sure you'd find lots of detailed discussions of this somewhere on the internet. It probably comes down to how high the asteroid explodes or how deep into the crust it impacts and how much of it's energy is converted into an explosion in megaton tnt, and how much in kinetic energy in the form of dust, earthquakes or tsunamis.

I'm pretty sure a tsunami could be much more devastating than a land impact, since shock waves travel so well through water without loosing much energy.

But going back to the million Hiroshima sized impacts, it would be pretty bad too but probably not extinction level event. Even if every major city would be gone and a nuclear winter was coming from all the ash and dust in the atmosphere, you'd still have millions of people that can coordinate and hunker down with supplies for a few years until the dust settles. It only took us like 100 years to go from 600 million to 7 billion people, so we could spring back and rebuild quickly. Of course, that is still far from harmless.

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[–] gswan 8 years ago

you'd still have millions of people that can coordinate and hunker down with supplies for a few years until the dust settles.

Doubtful.

I just read a short ebook, written by Frederick Pohl, on whether Nuclear Winter is survivable. It was either free, or less than a buck. Excellent.

Our protagonist, and a young kid he ends up adopting, make it on one of the last flights to Iceland. Which he posits is one place where a limited number of people might survive a Nuclear Winter.

Movies routinely show lots of places where groups of plucky survivors can be found. In that bible story Moses interprets Pharoah's dream, and Pharoah stockpiles seven years worth of grain, to survive seven years of crop failures. But modern cities stockpile of food is measured in days or weeks, not years.

Pohl has the surviving Icelanders use Iceland's copious geothermal energy to light up grow lamps for the crops they grow indoors.

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[–] Dejay 8 years ago

Thanks, I'll check that out. Is it "Fermi and Frost"? https://en.wikipedia.org/wiki/Fermi_and_Frost

I wonder if someone has actually prepared for that? A big sustainable shelter for a large group of people to weather an apocalypse?

I'm not sure how long nuclear winters actually last but I think dust does settle after a few years one way or another. Then you'd still have an ice age but you could survive better. Even if just 0.1% of the population survives, that is still 6 million people.

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[–] mobocracy 8 years ago

I wonder if someone has actually prepared for that? A big sustainable shelter for a large group of people to weather an apocalypse?

It's all about spare parts and maintainability. It's all well and good to go into a shelter, but if your shelter runs on equipment you can't repair or rebuild, your shelter won't have much of a future.

It's probably possible to design a shelter system at about a 1940s era level of technology where you can supply not only the shelter machinery but machinery capable of duplicating the shelter machinery so it is long-term sustainable. If a widget breaks, you can go to the machine shop and make another widget, and if your machine shop machine breaks, you have a backup that can make another machine.

It's like pre-19th century sailing vessels. For the most part they were all wood and other than iron nails, a ship sailed with both the skilled people and the tools to basically rebuild the ship. Masts, hulls, bulkheads, decking was all field-replaceable, all you needed was trees from shore.

Any long-term survival shelter would need to target that kind of self-sustainability. Modern levels of technology aren't really feasible, but there's probably some level around 1940s where the materials are simple and the tooling manageable to keep it running for a long time.

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[–] Dejay 8 years ago

Yeah. Ultimately it's just a matter of size and redundancy is it?

The Silo series of books deals with this idea of using this sort of 1950 sustainable technology. You can still build resistors. They spend generations and generations in those big silos underground. It's mostly about the enforced social order though which is oppressive but scientifically designed to provide long term stability. Rather bleak though. Oh I'm gonna have to check if the next book is out yet!

I think in a few decades we will get to a more sustainable manufacturing base though. 3D printing, artificial muscles, robots programmed to assemble more robots and robotic chemical plants etc. Or even chemistry using the genetic engineering of plants or yeast to create all sorts of usable chemicals, or even chemically powered robots, just by adding raw materials and energy.

I think this or something like this is how we will colonize moons and asteroids in the solar system, living underground in beautiful habitats. The Expanse is another great sci-fi novel and tv series.

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[–] mobocracy 8 years ago

Yes, the Silo series was a kind of example of that self-sustaining bunker concept, although I think even they had vast warehouses of consumable supplies like lightbulbs as I think the Silos had been designed for some kind of fixed lifetime.

I always wondered how they managed to make oil drilling and mining part of the silo, though. It's an interesting way to explain how and why they would have the mining and drilling equipment in the silo to begin with, but seems weird that they would either be able to site the silos where those resources existed naturally *or* that they were able to build the silos with artificial oil and mining reserves.

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[–] Dejay 8 years ago

Ah right, they used oil as a energy source. Where they got the oxygen to burn oil or petroleum I don't understand though. But oil is also used in all kinds of plastics.

I figure there are a lot of relatively small untapped oil resources everywhere that aren't really worth exploiting commercially. So that would seem plausible.

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[–] mobocracy 8 years ago

Volume is another problem -- they had to be generating a couple of megawatts of power to run that whole silo, so we're talking 140 of gallons an hour of diesel consumption.

Those Silos had been occupied for a couple of hundred years if I remember right, and for every hundred years they would consume 122 million gallons of diesel fuel for power generation. You get 12 gallons of diesel from a barrel of crude oil, so if they were pumping crude oil it would take 435 million barrels of oil to get that much diesel for every 100 years of operation.

A dozen silos? You're not talking random uneconomical pockets of oil, you're talking oil reserves into the billions of barrels, reserves the scale of North Dakota's Bakken shale fields.

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[–] Dejay 8 years ago

You really need that much energy? Essentially is's just one big skyscraper buried under the earth. And they were all absolutely independent, mining their own stuff. Biggest problem might be waste heat.

I guess until we have fusion power a long term sustainable sealed habitat might be science fiction.

But a couple of years or a decade should be no problem today, not on earth. I'm sure there are many bunkers that can last a while. Although I think you need about 1000 people to have enough genetic variation to start a new civilization.

So I'm sticking with my optimistic belief that even if we'd see a major asteroid impact or nuclear winter, you won't be able to scrape humanity off this rock ;)

Really gotta read the last two books of the silo series now! Can't wait to hear how sad that *beep* is going to end.

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[–] mobocracy 8 years ago

Movies routinely show lots of places where groups of plucky survivors can be found. In that bible story Moses interprets Pharoah's dream, and Pharoah stockpiles seven years worth of grain, to survive seven years of crop failures. But modern cities stockpile of food is measured in days or weeks, not years.

I can see see situations where the bulk of initial survivors die off fast enough that enough non-perishable food is left behind for some small group of long-term survivors.

What I always think of is the water supply and sanitary sewer systems. In any kind of area remotely urbanized, clean water will not be available within days or weeks. Water plants will shut down, and the water system will either dry out or become contaminated. People will start using any water in desperation, most will fail to adequately remove pathogens (let alone chemical contaminants) and in light of the failure of sewage systems a lot of even the easy to access fresh water will be badly contaminated.

I kind of predict serious and early outbreaks of cholera, dysentery and other waterbourne pathogens, with high rates of mortality.

A very small number of people will have the know-how or means to create safe water and will outlive those that don't, and if it happens fast enough there may just be enough shelf-stable food for a small group to survive a while longer. Further survival will be dependent on their ability to hunt or fish, provided whatever the event is hasn't wiped out those sources of nutrition.

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[–] Dejay 8 years ago

Alternatively, you could say diluting the energy would spread the same (devastating) amount of energy across the globe...

Ok so I've been thinking back on this for some reason. Again, just speculating for the fun of it :)

One way to think about this would be that if you could totally pulverize an asteroid so you only get pebble size impacts, you get a certain amount of energy release on slightly more than half the globe. Part of the mass would also be reflected, parts of the mass would slow down or speed up and spread the impact.

A couple of megaton or gigaton explosions might sound much, but from what I gather the earth receives about 121.800 terawatts (=121.800.000.000 megawatts). So if you could actually pulverize the asteroid, you'd probably just see relatively normal day that is just a bit more bright and warm. Each square meter of earth only gets a slight % increase in radiation.

So from that thinking, splitting an asteroid apart in enough fragments would be better, the more be better of course. And those shaped charge simultaneous explosions would need to be timed and placed correctly.

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[–] gswan 8 years ago

A couple of megaton or gigaton explosions might sound much, but from what I gather the earth receives about 121.800 terawatts (=121.800.000.000 megawatts). So if you could actually pulverize the asteroid, you'd probably just see relatively normal day that is just a bit more bright and warm. Each square meter of earth only gets a slight % increase in radiation.

121.8 terawatts? 1.218 x 10 to the power 17 watts? Is that the energy the Earth receives from the Sun - during a 24 hour period?

One megaton is equivalent to 1162222 megawatt-hours. So, it might seem like the energy from a cloud of meteors would be dwarfed by 24 hours worth of sunlight. But if one face of the Earth received the energy from enough tiny meteors, burning up in the atmosphere, over the course of a few seconds, it could be an intense enough burst to light half the world on fire. Even steel, or concrete, will start to burn, in an intense enough heat.

Wikipedia has an article on Impact Winters, an idea similar to Nuclear Winter. https://en.wikipedia.org/wiki/Impact_winter Let me quote from it:

Victor Clube and Bill Napier support a controversial theory that a short period comet in an Earth crossing orbit doesn't need to impact to be hazardous, as it could disintegrate and cause a dust veil with possibilities of a "nuclear winter" scenario with long term global cooling lasting for thousands of years (which they consider to be similar in probability to a 1 km impact).

Here is an article from Nature, a prestigious Scientific journal: http://schillerlab.bio-toolkit.com/media/pdfs/2010/03/16/367033a0.pdf

Scaling from Nuclear Weapons tests and the K/T event, Toon and his colleagues find that an optical depth of approximately 2 would result from a groundburst with a yield of 10^5 - 10^6 MT, corresponding to a diameter of 1-2 kilometers for a stony object striking at 20 km/s.

So, a groundburst of a 1-2km object injects enough dust into the upper atmosphere to cause an impact winter.

Meanwhile, an airburst, like Tunguska, or Cheylanska, injects its entire mass into the upper atmosphere, because it never gets down to ground level, or the level of the atmosphere where weather happens, and rain can wash out dust.

Those viewers who keep challenging the idea that even if a huge asteroid was broken up into tiny fragments, it would still have a devastating effect, keep asserting the tiny fragments would be burned up on re-entry. And they are overlooking that this "burning up" would leave behind an aerosol of minute fragments of dust.

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[–] Dejay 8 years ago

Ah of course, megaton isn't megawatt! And yes, 121.8 terawatt is the power of sunlight actually reaching earth not being reflected by clouds, so 121.8 terawatt per hour, or 121.8 terajoules per second.

1.218 x 10^17 watts (= joules / s)

1 mega ton tnt = 4.184 × 10^15 joules

So daylight has the equivalent power as exploding a 29.1 megaton hydrogen bomb every second. If I calculated correctly.

So that would mean if you could pulverize an asteroid that would create a 29.1 megaton impact and spread the resulting collision with the dust cloud over 10 seconds, that would mean only a 10% light increase. An asteroid with 1km diameter with something like thousand times that megaton energy on the other hand... better wear extra strong sunglasses haha.

Yeah it's easy to see that above a certain size, the energy is just too much to "dilute".

Strapping a rocket engine to an asteroid like that, or using a laser to basically do that is definitely the best option.

And you are right of course, diluting the mass into dust in the atmosphere would still trigger an impact winter. Although I would think dust in the higher, thinner atmosphere would fall down faster. And maybe incoming ionised particles could be affected by earths magnetic field.

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[–] Theshornwonder 8 years ago

no. If the blown up asteroid was shatterred into small enough pieces it would be like a meteor shower, not Tunguska. good lord.

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[–] gswan 8 years ago

no. If the blown up asteroid was shattered into small enough pieces it would be like a meteor shower, not Tunguska. good lord.

Your comment suggests you may not have a sound understanding of Physics, and Ballistics.

Allow me to compare the impact of an asteroid-or-busted-up-chunks-of-an-asteroid with various shotgun shells.

Shotgun shells come in a standard size, but the most common shells are loaded with "shot" of various sizes. Shells loaded with there are shells loaded with tiny "bird-shot", for hunting birds, and shells loaded with "buck-shot", intended to be effective against hunting large game -- even deer, hence the name. There are more exotic loads. Special forces soldiers and SWAT teams get to use shells intended to blow the locks or hinges off doors, without injuring hostages inside. These shells are loaded with finely ground metallic dust. At the other end there are exotic shells loaded with a single metal slug.

At point blank range -- inches -- any of these shells, even the ones loaded with fine metallic dust, are going to be comparably fatal. At the very shortest range, the size of the shot doesn't matter at all. At very short range the size of the shot doesn't matter much.

I suggest our atmosphere is thin enough that the difference between being struck by an asteroid, and being struck by that same asteroid, once it has been shattered, is similar to being hit by a shotgun round, at close range, where the size of the shot doesn't make much difference.

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[–] Theshornwonder 8 years ago

Your reply suggests that your claims about physics aren't scientific at all, but merely some opinion you have. Our atmosphere is thick enough to burn up most debris that falls into earth's gravity. A meteor shattered into small enough pieces simply will not create the disastrous effect you suggest.

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[–] Sluggr-3 8 years ago

Well, shattered and small enough aren't exactly scientific terms. Lets say that an asteroid about 100M diameter is broken into about 100 pieces each about 20M in diameter.

https://en.wikipedia.org/wiki/Chelyabinsk_meteor

You'd end up with 100 of these events all happening in short order. This was a glancing blow. Had it hit straight it would have killed tens or hundreds of thousands based on the impact site, but pretty much everything in a 5mi diameter according to a comet expert friend of mine. Now multiply that by 100, spread out over the planet.

In order to negate the effects, one would need to reduce the asteroid to pieces significantly smaller so that they could burn up in the atmosphere, which would still create just an intense amount of heat and audible and radiant energy but less devastating if high up in the atmosphere.

All in all, there would be many variables which would determine the final impact effect. The likely choices would be really really bad and really really really bad.

This is a pretty good read with regard to how small one would need to make the pieces to minimize the impact, assuming one could make them uniformly small.

https://en.wikipedia.org/wiki/Impact_event

On another note, for when you absolutely positively need to vaporize something.

http://ebrammo.com/12-gauge

My Chimp DNA seems to have lost its password temporarily. Sluggr-2

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[–] gswan 8 years ago

Your reply suggests that your claims about physics aren't scientific at all, but merely some opinion you have. Our atmosphere is thick enough to burn up most debris that falls into earth's gravity. A meteor shattered into small enough pieces simply will not create the disastrous effect you suggest.

You wrote my assertions "aren't scientific at all, but merely some opinion you have." Have you ever actually studied Science, studied the Philosophy of Science? If so I wonder whether you got a failing grade. Jacob Bronowski, a widely admired Physicist and Science educator wrote widely, on Science and the role of fact and opinion. One of his works was a play, emulating the form of Galileo's famous dialogue, the one that triggered the Pope to have him dragged to the Inquisition's torture chambers. Bronowski's play was entitled The Abacus and The Rose: A dialogue on two world systems. In Galileo's dialogue the two protagonists were proponents of the Copernican and Ptolomeic models of the Universe, arguing over whether the Earth orbited the sun, or vice versa. In Bronowski's play the two proponents are a Scientist, and a Professor of Literature who is a Luddite who is completely and utterly ignorant of Science.

The reason I bring up Bronowski is that your comment almost exactly duplicates one of the assertions of the completely ignorant Luddite. The completely ignorant Luddite says Literature is Great because it leaves room for subtlety and ambiguity, while Science Sux, because it makes everything a Fact. Bronowski's Scientist explains there are no facts in Science, everything is a judgment -- or to use your term, an opinion.

Yes, what I wrote here was an opinion, just as what you wrote here. Scientific theories, Relativity, Continental Drift, Inherited traits, they are all just opinions. Intelligent people evaluate scientific opinions by how well thought out they are, and how well they are backed up.

Your dismissal of my opinion, without making any attempt to offer a refutation? How seriously should anyone take it?

Small meteors do burn up before they hit the ground. But we aren't talking about a single small meteor, or even dozens, or hundreds, or millions of small meteors.

Single small meteors burn up in the atmosphere, but that doesn't mean that their kinetic energy simply disappears. Some of the kinetic energy heats up and ionizes the air they pass through. Some of their kinetic energy is transferred to the air they pass through.

The 2008 TC3 event, and the 2014 AA event, were the first two times the arrival of meteors were predicted, before they struck. They were both only a few metres in diameter, and each weighed something like 80 tons. https://en.wikipedia.org/wiki/2008_TC3, https://en.wikipedia.org/wiki/2014_AA Tunguska was 60 to 190 metres in diameter. Volume is proportional to the cube of the dimensions, so, using the 190 metre diameter, Tunguska would outmass 2008TC3 and 2014AA by a factor of over 100,000 - over 8 million tons.

How large are the meteors we remember watching during a meteor shower, that appear about the brightness of a background star, for half a second or so? I frankly don't know, but I am going to suggest we pick between 100 grams and 10 kilograms. I suggest we call it 1 kilogram. Tunguska, broken up into a cloud of small meteors, would contain 8 million tons of 1 kg meteors, 8 million 1 kg meteors. In my post above you first challenged, I asked readers to consider a strike by a 10x Tunguska.

80 million meteors, striking essentially at the same time, would not be harmless, no matter what enthusiastic fans of the Armageddon movie might want to believe.

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[–] Sluggr-3 8 years ago

It is simple Newtonian mechanics but on a grand scale.

FF'd through Helios and from what I gather it is an asteroid, hence a rock and not a dirty snowball like a comet (which is why comets leave trails). Outgassing would happen with a comet where low pressure ice is rapidly transformed to high pressure steam and the resulting acceleration from the comet will cause an equal and opposite movement of the comet. X-rays actually do have mass when the photon becomes a particle, so there is a transfer of beam energy into momentum in a purely physical sense, and there may also be a heating aspect which causes the solid rock to evaporate into particles which thus impart a momentum like the phase change of ice to steam.

Now, as to when they do it. First, they have to screw around with the development of civilization to ensure that all the components for the laser and the power source are here at the right time.

Then they have to make sure that the asteroid is far enough away so that an extremely minute shift in its course translates into a sufficient deflection to miss the planet. But the further away it is the harder it is to hit as a target. So they need to work in a window where it is neither too close nor too far, ditto for energy requirements, since the coherent laser beam should not lose too much energy over distance, but the further away it is the less energy needed to deflect it sufficiently to miss the earth.

Blowing it up somehow risks a Shoemaker-Levy type multiple impact scenario which could be worse than one big impact.

Of course, all the changes which the travelers have made in human history may in fact cause more harm to the planet than if the asteroid hit. Think of how changes in technology could have led to overpopulation and depletion of resources which are ultimately worse. Not sure of how much the impact would affect the orbit of the earth, but it could be that avoiding an impact in 2017 causes us to remain in an orbit which makes the Earth a target for an impact in the 22nd century. Talking to the most recent traveler who says things are worse suggests that defeating the initial threat may have been the wrong move.

As for selecting the recipient brains, it is assumed that once dead those people won't contribute much to history, and we hope that the travelers don't use their advanced knowledge to create harm (like the junkie did by trying to save children) to the future. But who is to say that one of them has children or by not dying changes their family dynamic so that someone close to them who was depressed by the death instead is never affected and goes on to alter history in a significant way. Losts of things to nit pick, but this is one heck of an undertaking, both the show and the premise of the show.

My Chimp DNA seems to have lost its password temporarily. Sluggr-2

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[–] chrisjdel 8 years ago

In theory the laser would vaporize a small section of the surface which would then outgas and give the asteroid a push. Large holes or craters would make the best targets, since they'd channel the escaping gas into a more or less directional stream like the exhaust nozzle of a rocket engine. Exactly how much energy an x-ray beam would need to deflect a rock of mass m through a given angle wouldn't be simple to calculate because the terrain is such an important factor.

You'd expect things in the future to change a little every time you did something in the present. For people in the future to remember the asteroid impact after it was prevented (and other similar events) they'd need to update their systems using history files from their agents in the past who still remembered the old timeline. Which means they'd accumulate historical records from many different timelines, making them progressively better at deciding which things to alter. That's basically the idea behind all this. You're tinkering with the past until you get a satisfactory present. It's going to be partly a matter of steering large events, and partly a million stupid little things you change by accident (or like Philip, not by accident). That's the unpredictable part of the formula. Which is why I think they don't go ballistic and relieve travelers of duty whenever they deviate from plan. They need some of those little deviations, there's just no way to know ahead of time which ones - if phrases like "ahead of time" have any real meaning in the context of time travel.

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[–] chrisjdel 8 years ago

You seem to be implying there is a meaningful distinction between outgassing, the term I used, and vaporizing.

Vaporizing is what happens when the solid material on the rock's surface is shock heated into vapor form. The (initially plasma) cloud then expands rapidly into the surrounding space. That's the outgassing, which provides the push.

In the event of a nuclear war, primary targets are ringed with a series of half to full megaton explosions rather than one really big nuke right in the center. The blast waves converge and overlap in the middle and cause catastrophic damage to a greater distance. Getting the same effect with a single detonation would require ten or fifteen megatons. Yes, the conditions at ground zero with a bigger nuke get even more extreme, reach higher temperatures and pressures, but let's face it. Destroyed is destroyed. Dead is dead. Spreading ten megatons out with ten separate charges instead of one big one lets you devastate a larger area. This is why both the US and USSR employed this targeting strategy (which we thankfully never got to see demonstrated for real).

Multiple asteroid fragments carry the same amount of kinetic energy as the original body, but spreading it out will destroy more cities and cause more immediate fatalities than a single large impact. That 91 million figure they gave on the show probably referred to prompt, day zero deaths. The real killer would be climate disruption leading to multi-year crop failures and major food shortages. Starvation, disease, and wars (even between former allies) over remaining resources.

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[–] Sluggr-3 8 years ago

We do see it in a limited basis with fuel air munitions which create a large area of lethal overpressure vs a central zone of extreme overpressure that diminishes by inverse square. They are also more effective pound for pound since the oxidizer is already in place and doesn't need to be carried.

I am still curious about the length and extent that the travelers have been affecting human civilization. How much of the infrastructure to make the laser was naturally in place without their interference (by interference I mean any effect which was sourced from the future)?

We are also assuming that the traveler numbers refer to an actual transport. Blue (117) might have been an early member of the program who has now only gone back once. During Apollo I believe their were 20 people in the program for every astronaut who went up in a rocket. I suspect Brad Wright has mapped a pretty elaborate storyboard to keep it going much like the original Stargate.

My Chimp DNA seems to have lost its password temporarily. Sluggr-2

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[–] gswan 8 years ago

At the end of the episode, when the laser is deployed, McLaren suggests that if the mission succeeded they would have wiped out the existence of the Directorate.
If they had, (1) they might have to "go native", as they never receive any more missions; (2) they too might disappear from 2016.

They don't disappear. New travelers continue to arrive. New missions are assigned.

Trevor explained to Grace Day that there were no "do-overs". Once the Directorate started sending Travelers back they became restricted. They could no longer send anyone to a time earlier than the most recent traveler they sent back.

This might mean the laser failed.

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[–] Sluggr-3 8 years ago

DIRECTOR!

My Chimp DNA seems to have lost its password temporarily. Sluggr-2

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[–] chrisjdel 8 years ago

This might mean the laser failed.

Phillip said that the asteroid's path had definitely been altered and the impact avoided. It just didn't have the sweeping effect on the future they were expecting.

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