"Shocking" video of comet ISON causes "panic"?!?

[SamBridge]

You missed my point. Just because we know the trajectory doesn't mean we can reach it. The delta-V needed to merely intercept an incoming comet would most likely be beyond today's technology. You mentioned nuclear technology. That requires landing on or moving with the comet. That adds even more delta-V (an unattainably high amount) to that already unattainable intercept delta-V.

Any asteroid traveling at speeds less than a 100th the speed of light we can definitely "reach", the questions is "will we do it in time?". Explosives only require a landing if the rock is loose like with many comets and would otherwise not transfer much of a shockwave throughout the whole comet. If it is one solid piece of rock you can just launch a dozen missiles at it and hopefully vaporize enough of it or steer it off course.

 

 

Thousands will be needed, all in a very short time window. It's not possible.

Which is more or less what I was saying before, if it is too close or will be too close in too short of an amount of time there's not much we can do, but even with that, it is "possible" to still use explosives on it, it's just that using 1000 or even 100 nukes less than a million miles from Earth will probably damage the atmosphere or sterilize a lot of life or just in general cause a lot of radiation sickness. But if we know the trajectory enough in advanced, it's a pretty simple principle that we can just shift the angle of it's direction by even half a degree and it will barely avoid Earth.

Edited June 11, 2013 by SamBridge

[Moontanman]

Do we have the ability to shoot missiles out of Earth orbit? ICBMs cannot leave Earth orbit, so where do you get the missiles to hit the comet?

[SamBridge]

Do we have the ability to shoot missiles out of Earth orbit? ICBMs cannot leave Earth orbit, so where do you get the missiles to hit the comet?

Well we can launch probes that carry explosives in them which are designed to detonate when the probe experiences an amount of force greater than a preset value. Actually what we can do is launch a probe which then launches another thing like a weight or explosive which is then what hits an asteroid, or in most recent cases, planets.

[D H]

Any asteroid traveling at speeds less than a 100th the speed of light we can definitely "reach", the questions is "will we do it in time?".

 

That "will we do it in time" is a crucial part of "can we reach it". We have to reach in time or we haven't reached it. Reaching where it would be 200+ years in the future is not an option. The comet no longer exists; it collided with the Earth 200 years earlier. We have to hit it early enough so that our limited ability to impart a Δv on the comet will have the desired goal of diverting it from a collision.

 

Suppose some astronomer discovers a small 1 km diameter comet and find that it will collide with the Earth eighteen months later. Note very well: I'm already invoking magic technology here. The technology to do this does not exist yet. We still don't know the size of C/2012 S1 (ISON), and the initial guesses at a comet's orbit are just that, initial guesses.

 

You have eighteen months to save the world.

 

Invoking more magic technology, you find that there's a magical nuclear device that has a mass of but 2500 kg and that can impart a Δv of up to 5 meters/second on this comet if blown up at just the right spot. The comet will still collide if you apply this small Δv a few months before impact. Suppose you find that you need to apply this Δv at least 9 months prior to impact to divert the comet from a collision.

 

You have now have but nine months to save the world.

 

Let's ignore all the bureaucratic problems with launching a nuclear weapon into space. Let's ignore all the logistics problems with getting everything together. Suppose that you could launch tomorrow if that would do the trick. You find that that won't do the trick. You run into a trajectory optimization problem.

 

The problem is that for a given launch time and a given intersect time there is an optimal trajectories that minimizes the amount of energy needed to launch at that launch time and intersect the comet at that intersect time. Since neither the launch time nor the intersect time is fixed; you can optimize over these as well. Suppose that the very best trajectory that you can find has a C₃ of 400 km²/s². So you look for a launch vehicle that can supply that amount of energy. Well, there is none. The Delta IV Heavy has a C₃ of 60 km²/s²for a 2500 kg payload. Is that C₃ of 400 km²/s² out of line? The answer is yes. It is unreasonably low for a comet intercept. Values in excess of 1000 are more in line with reality.

 

You have now zero months to save the Earth. Comet deflection is something that cannot be done using present technology, or even with present technology plus magic.

 

 

But if we know the trajectory enough in advanced, it's a pretty simple principle that we can just shift the angle of it's direction by even half a degree and it will barely avoid Earth.

 

It's even easier with a simple wave of the magical wand.

 

Sans that magical wand, deflecting comets is a problem for some future generation. Deflecting asteroids is something our generation can solve.

[SamBridge]

 

That "will we do it in time" is a crucial part of "can we reach it". We have to reach in time or we haven't reached it. Reaching where it would be 200+ years in the future is not an option. The comet no longer exists; it collided with the Earth 200 years earlier. We have to hit it early enough so that our limited ability to impart a Δv on the comet will have the desired goal of diverting it from a collision.

 

Which is what I was saying before, the developed countries of the world are looking into the best technology for this.

 

 

 

That "will we do it in time" is a crucial part of "can we reach it". We have to reach in time or we haven't reached it. Reaching where it would be 200+ years in the future is not an option. The comet no longer exists; it collided with the Earth 200 years earlier. We have to hit it early enough so that our limited ability to impart a Δv on the comet will have the desired goal of diverting it from a collision.

 

Suppose some astronomer discovers a small 1 km diameter comet and find that it will collide with the Earth eighteen months later. Note very well: I'm already invoking magic technology here. The technology to do this does not exist yet. We still don't know the size of C/2012 S1 (ISON), and the initial guesses at a comet's orbit are just that, initial guesses.

 

You have eighteen months to save the world.

 

Invoking more magic technology, you find that there's a magical nuclear device that has a mass of but 2500 kg and that can impart a Δv of up to 5 meters/second on this comet if blown up at just the right spot. The comet will still collide if you apply this small Δv a few months before impact. Suppose you find that you need to apply this Δv at least 9 months prior to impact to divert the comet from a collision.

 

You have now have but nine months to save the world.

 

Let's ignore all the bureaucratic problems with launching a nuclear weapon into space. Let's ignore all the logistics problems with getting everything together. Suppose that you could launch tomorrow if that would do the trick. You find that that won't do the trick. You run into a trajectory optimization problem.

 

The problem is that for a given launch time and a given intersect time there is an optimal trajectories that minimizes the amount of energy needed to launch at that launch time and intersect the comet at that intersect time. Since neither the launch time nor the intersect time is fixed; you can optimize over these as well. Suppose that the very best trajectory that you can find has a C₃ of 400 km²/s². So you look for a launch vehicle that can supply that amount of energy. Well, there is none. The Delta IV Heavy has a C₃ of 60 km²/s²for a 2500 kg payload. Is that C₃ of 400 km²/s² out of line? The answer is yes. It is unreasonably low for a comet intercept. Values in excess of 1000 are more in line with reality.

 

You have now zero months to save the Earth. Comet deflection is something that cannot be done using present technology, or even with present technology plus magic.

 

 

 

It's even easier with a simple wave of the magical wand.

 

Sans that magical wand, deflecting comets is a problem for some future generation. Deflecting asteroids is something our generation can solve.

I'm not sure why you think magic is involved, we have complex computers. If we know the angle it's at and the speed it's going, in other words a single vector, since we already have the capability of tracking the location of other planets and therefore their interference, we merely project where it will go in that direction based on the increasing gravitation strength it experiences from the sun or any planets it may go near, which Isaac Newton could do without a computer even. We've also sent 20 ton rockets into space already during the cold war, the mass of single explosive devices isn't a problem, we can send a group of many small explosives if the mass is too much for any particular one to reach a particular speed. But for a simple deflection we would send a weight, a single 2 ton weight or a 20 ton weight. Have you ever heard of railguns too? A single individual helium nuclei traveling near the speed of light has the force of a baseball bat traveling 90mph, and a few militaries have been working on that technology for a while and making them better.

People knew about meteor threats for a while now, for hundreds of years even if you consider ancient prophecies. We've been researching with various technologies and it seems we're less than a century away from being able to deal with any asteroids 20km or less. With our current technology, we at least have some kind of chance, though hopefully the countries of the world will continue working together to develop better technology.

Edited June 12, 2013 by SamBridge

[D H]

Come off it. You should switch from reading sci fi and astrology to learning some engineering and astronomy instead.

[SamBridge]

Come off it. You should switch from reading sci fi and astrology to learning some engineering and astronomy instead.

And you should talk to actual astronomers like those I met at the University of Illinois Observatory and Washburn Observatory in Madison or engineers I talked to at the Fermilab in Illinois. I'm not saying it would be easy or guaranteed with today's technology, but we have more than a 0% chance for sure, given that we have a month or two in advanced or more.

Edited June 12, 2013 by SamBridge

[Ophiolite]

And you should talk to actual astronomers like those I met at the University of Illinois Observatory and Washburn Observatory in Madison or engineers I talked to at the Fermilab in Illinois. I'm not saying it would be easy or guaranteed with today's technology, but we have more than a 0% chance for sure, given that we have a month or two in advanced or more.

And you might want to check into DH's background.

 

Here are some other points:

1. No one is denying that we are investigating ways of deflecting bolides. We are simply saying those technologies are all speculative at present and could not be implemented in the available time frame.

2. You blithely continue to ignore the difficulty of detecting comets until they are quite close in to the sun. While larger comets are easier to detect they are also much more difficult to deflect.

3. In terms of trajectory calculation you have completely ignored the fact that as a consequence of assymetric degassing comet's orbits change unpredicatably. (Now one day we may land robot craft on comets to induce selective degassing to effect the change in trajectory - but not today, and not in eighteen months.

4. You still seem to have zero grasp of the importance of delta-V in this problem. We would find it practically impossible to get 'a device' to the comet in the time frame required. Do the maths.

 

Your ideas on this are ill informed. If you continue to ignore the detailed explanations other posters are giving you then your ideas become silly.

[John Cuthber]

I seem to be missing a couple of things.

Why is DH assuming that we would only send one device?

And it might be helpful to explain the problem with getting a missile to the comet; after all, if we wait the comet comes to us.

It might be difficult to get one to the comet before it's too late but that's surely a matter of how early we could detect it.

[Moontanman]

I seem to be missing a couple of things.

Why is DH assuming that we would only send one device?

And it might be helpful to explain the problem with getting a missile to the comet; after all, if we wait the comet comes to us.

It might be difficult to get one to the comet before it's too late but that's surely a matter of how early we could detect it.

 

The main problem as i see it is that we don't exactly have a huge stockpile of missiles capable of leaving Earth orbit.

[D H]

Which is what I was saying before, the developed countries of the world are looking into the best technology for this.

 

Asteroid deflection? Yes. Comet deflection? No.

 

Asteroids represent about 99% of the impactors, they can be detected far, far in advance (far, far = multiple decades) of collision, and they are reachable by current technology. Comets are a problem left to some future generation. Current technology means we won't even see them until a year or two prior to impact, even a big one. Current technology also means the comet is most likely unreachable. As both Ophiolite and I keep saying, you are ignoring the delta-V problem.

 

 

I'm not sure why you think magic is involved, we have complex computers. If we know the angle it's at and the speed it's going, in other words a single vector, since we already have the capability of tracking the location of other planets and therefore their interference, we merely project where it will go in that direction based on the increasing gravitation strength it experiences from the sun or any planets it may go near, which Isaac Newton could do without a computer even.

 

This is completely wrong. Newton's second law is a second order differential equation. Seven parameters are needed to describe an orbit: An epoch time, a position vector at that epoch time, and a velocity vector at that epoch time. (Alternatively, an epoch time plus six orbital elements will do. Either way, the magic number is seven.) The epoch time is easy: Just pick one. That reduces the problem to six degrees of freedom. A single sighting yields but three parameters: Time, hour angle, and right ascension. In fact, a single sighting says nothing. Multiple sightings are needed so as to distinguish that comet from the background stars. These readings are inherently inaccurate; every measurement is inherently inaccurate. It takes a number of sightings, preferably from multiple sites, to overcome these inherent inaccuracies.

 

Orbit determination is a complex problem. You can specialize in just this one problem area as an aerospace engineer graduate student. Orbit determination is particularly problematic for comets. Astronomers have very good planetary ephemerides in part because we have thousands of years of observations for the six classical planets, in part because we have lots of high precision observations spanning decades for all the planets (plus Pluto). A newly sighted comet: We have but a few months of reduced fidelity observations.

 

 

Have you ever heard of railguns too? A single individual helium nuclei traveling near the speed of light has the force of a baseball bat traveling 90mph, and a few militaries have been working on that technology for a while and making them better.

 

Like I said, stop reading science fiction. A rail gun is going to be useless against deflection asteroids or comets, even one straight out of science fiction.

 

 

With our current technology, we at least have some kind of chance, though hopefully the countries of the world will continue working together to develop better technology.

 

Against asteroids? Yes. Against comets? No.

 

 

I seem to be missing a couple of things.

Why is DH assuming that we would only send one device?

 

I didn't assume that. Here's what I wrote:

One nuke won't do it for our medium sized, 10 km diameter comet. Thousands will be needed, all in a very short time window. It's not possible.

 

That, by the way, was ridiculously optimistic. I should have said tens of thousands. That's more rocket launches in a hundred days or so than we have launched, ever. That is impossible with our current technology and our current logistics trains.

 

 

And it might be helpful to explain the problem with getting a missile to the comet; after all, if we wait the comet comes to us.

It might be difficult to get one to the comet before it's too late but that's surely a matter of how early we could detect it.

 

Let's split the problem into two parts depending on whether the comet will hit the Earth while inbound or outbound.

 

The former isn't a problem for some future generation to solve. It's a problem for a far future generation to solve. We are triply screwed with regard to deflecting a comet that will hit us inbound. The detection problem is greatly magnified. We detect comets because we see them moving with respect to the background stars. That cross-track motion is drastically reduced for comets that will hit us while still inbound. We might not see the object as a comet until it starts outgassing. Another problem is that these inbound colliders will hit us months sooner compared to those that will hit us outbound. The final problem is that perihelion passage greatly magnifies any small delta-V that we can impart to a comet. We're just screwed if the comet is going to hit us while inbound.

 

Suppose we wait for a comet that is going to hit us while outbound until after perihelion passage. Going back to my fly changing the trajectory of a bowling ball analogy, this is akin to a fly trying to turn a strike into a gutter ball where the bowler gets to release the ball a meter from the headpin. We have to hit the comet while it's still inbound.

 

There are two ways to do this, the long way around and the short way. Going the long way around means launching toward the Sun. That means a C₃ of at least 1000 km²/s². We can't do that with current technology. We can't even come close. Going the short way around almost always requires an unattainably high C_3. There's a brand new problem in the very, very few cases where a short way around intercept is feasible. Have you ever gone duck hunting? Shooting a duck that's coming straight at you is a lot easier than shooting one whose flight path is orthogonal to the line between you and the duck. Hitting a duck that's moving 50 km/hour across your line of sight is very hard.

 

Now try to imagine the difficulty of hitting a duck that has a cross-track velocity of 50 km/second. That 50 km/second duck is our comet.

 

[SamBridge]

 

Asteroid deflection? Yes. Comet deflection? No.

 

Asteroids represent about 99% of the impactors, they can be detected far, far in advance (far, far = multiple decades) of collision, and they are reachable by current technology. Comets are a problem left to some future generation. Current technology means we won't even see them until a year or two prior to impact, even a big one. Current technology also means the comet is most likely unreachable. As both Ophiolite and I keep saying, you are ignoring the delta-V problem.

We've cataloged literally over 4000 comets and many of them take years and years to make a complete orbit. The icy trail makes them more visible compared to distant stars so I'm not sure what your point is. I must have missed your delta v problem because we can literally produce enough energy to destroy the world a few times over, if we put all of our energy and resources into it, which the world definitely would if there was a confirmed collision heading our way, we could accelerate something fast enough the possibly intercept most rocky objects in the solar system. We can definitely "reach" it even at 100km/s, but if it's oubound there's a good chance we won't be able to intercept it at a great distance due to its increased speed, but your fly analogy also makes little sense because as you probably know, people get shoved back and die from bullets, which typically have less than 1/1000th of the mass of an average person.

 

 

 

Asteroid deflection? Yes. Comet deflection? No.

 

Against asteroids? Yes. Against comets? No.

Asteroids in this system typically have the same size range as comet nuclei which are usually a maximum of 40km, I don't see what your problem is with this comparison. The composition of ice and snow would make the harder to handle with a single explosion, but it takes less energy to vaporize the water-ammonia-CO2 ice holding the comet together as a trade off. Weights wouldn't necessarily work, they may just get absorbed or somewhat pass through, but we can simply put a time counter on an explosives we launch that explodes at the time we think it will be near the comet's surface if the impact would not be hard enough. I agree it would be harder to deal with comets as opposed to a solid piece of rock, but as I said before people have known about the threats of extraterrestrial bodies for a while now, and as someone who's talked to actual astronomers about meteors and comet impacts, unless they were for some reason lying about having a chance, we have more than a 0 percent chance of dealing with inbound comets, and even outbound comets, though I would agree is less likely to deal outbound comets without some kind of damage happening.

Outbound comets, if they're already on there way here and we can't intercept them fast enough, our only chance would be to vaporize it with many explosives with the risk of damaging life on Earth, no guarantee we would be unharmed but if we're going to die anyway, we might as well see if we can get rid of it almost completely which we can definitely for sure attempt.

Edited June 12, 2013 by SamBridge

[Ophiolite]

We've cataloged literally over 4000 comets and many of them take years and years to make a complete orbit.

And every year we identify many new comets that have never been seen before and are never seen again. The problem is not the comets we know about, it is the comets we don't know about.

 

The icy trail makes them more visible compared to distant stars so I'm not sure what your point is.

The point is that the tail does not appear until the comet is relatively close to the sun. It is coming in from the Oort cloud, where its temperature is close to absolute zero. Have you considered what the temperature is out at, say, the orbit of Jupiter? So, by the time we can identify the comet it is already well into the inner reaches of the solar system and accelerating.

 

I must have missed your delta v problem because we can literally produce enough energy to destroy the world a few times over, if we put all of our energy and resources into it, which the world definitely would if there was a confirmed collision heading our way, we could accelerate something fast enough the possibly intercept most rocky objects in the solar system.

How are you going to get a suitable missile into space, supplied with sufficient fuel, which you also have to get into space, and directed towards where the comet will be, and supplied with even more fuel to allow you make the necessary change of velocity to change orbit and accelerate so that it reaches its target soon enough to make a difference?

 

Where is the technology coming from to produce such a missile. Check out how long it took us to get the Messenger probe into orbit around Mercury. It could have been done a lost faster, but only at the cost of massive fuel requirements. (And all the time I am saying fuel, you need to think fuel and oxidiser.)

 

You need a rocket that will deploy the warhead. You need rockets that will serves to carry fuel into orbit. You need a system for transfering that fuel in orbit. That's not going to be robotic, so you need humans. Where is NASA's manned delivery system?

 

And you have to do this not once, but many times.

 

We can definitely "reach" it even at 100km/s,

Seriously, calculate what mass of payload you have to deliver to the comet. Decide where it is going to be when we intercept it. Figure out how much fuel you need to attain the appropriate delta V to get there. (I really hope you are not one of those people who think it is easy to 'fall towards the sun'.) Now show me that you have rocket that we can place in space, with operable engines and a fuel tank capacity that will let us achieve the goal. DH knows way more about this than I, but I am pretty damn sure that we have nothing that would allow us to do this today, or on the horizon that could be reached in the time frame we would have. Feel free to prove me wrong with the math.

 

 

but your fly analogy also makes little sense because as you probably know, people get shoved back and die from bullets, which typically have less than 1/1000th of the mass of an average person.

Please calculate the mass of a typical comet and review whether you want to retain that opinion.

 

Asteroids in this system typically have the same size range as comets which are usually a maximum of 40km, I don't see what your problem is with this comparison.

This is a seriously flawed observation. The asteroids we are concerned with, those which are at some risk of impacting the Earth, are measured in tens, or at most, hundreds of metres. Comets are measured in kilomteres.

 

someone who's talked to actual astronomers about meteors and comet impacts, unless they were for some reason lying about having a chance

You have created a false dichotomy: you suggest either the astronomers are telling the truth and there is a risk, or they are lying. You have not considered the possibility that you misunderstood their comments and explanations.

 

 

 

 

 

[SamBridge]

Please calculate the mass of a typical comet and review whether you want to retain that opinion.

Consider that you get pushed back and killed by a piece of metal with less than 1/1000th of your mass. This scenario is only a problem if the rock is loose and the impact will either fragment clearly such that the components keep their original momentum or not transfer enough force to the whole rock.

 

 

This is a seriously flawed observation. The asteroids we are concerned with, those which are at some risk of impacting the Earth, are measured in tens, or at most, hundreds of metres. Comets are measured in kilomteres.

No I'm pretty 200% sure we've cataloged many asteroids more than a few kilometers large, http://en.wikipedia.org/wiki/298_Baptistina, http://en.wikipedia.org/wiki/951_Gaspra to name a couple.

 

 

You have created a false dichotomy: you suggest either the astronomers are telling the truth and there is a risk, or they are lying. You have not considered the possibility that you misunderstood their comments and explanations.

How many ways are there to interpret "at least some kind of chance"?.

 

How are you going to get a suitable missile into space, supplied with sufficient fuel, which you also have to get into space, and directed towards where the comet will be, and supplied with even more fuel to allow you make the necessary change of velocity to change orbit and accelerate so that it reaches its target soon enough to make a difference?

 

Where is the technology coming from to produce such a missile. Check out how long it took us to get the Messenger probe into orbit around Mercury. It could have been done a lost faster, but only at the cost of massive fuel requirements. (And all the time I am saying fuel, you need to think fuel and oxidiser.)

 

You need a rocket that will deploy the warhead. You need rockets that will serves to carry fuel into orbit. You need a system for transfering that fuel in orbit. That's not going to be robotic, so you need humans. Where is NASA's manned delivery system?

 

And you have to do this not once, but many times.

We can use many smaller devices which individually do not require as much fuel but together may vaporize enough material of the comet, other than that the main problem isn't in space, we can use an ion drive to give the probe a high specific impulse when it is close enough to the comet, and use chemical fuel to accelerate out of the atmosphere as well as being applied to the probe in space, which will accelerate at an increasing rate due to the fact that the mass is decreasing from the chemical fuel being used up.

If we have less than a couple months, we've hit asteroids before https://en.wikipedia.org/wiki/Deep_Impact_(spacecraft) but the only thing we'd be able to do is launch explosives. Because of the shorter distance we'd need the explosives to travel in this scenario they would perhaps not need as much fuel or energy, but within a few moon-orbits of Earth, detonating a thousand warheads nearly at once could damage life or the atmosphere, but we certainly do have the actual material to release enough energy to vaporize the entire comet completely, the way thermal nuclear devices act in space may be different enough without an atmospheric shockwave that it isn't much different than a very small gamma-ray burst which is the only reason why we'd need so many.

Edited June 13, 2013 by SamBridge

[D H]

If we have less than a couple months, we've hit asteroids before https://en.wikipedia.org/wiki/Deep_Impact_(spacecraft) but the only thing we'd be able to do is launch explosives. Because of the shorter distance we'd need the explosives to travel in this scenario they would perhaps not need as much fuel or energy, but within a few moon-orbits of Earth, detonating a thousand warheads nearly at once could damage life or the atmosphere, but we certainly do have the actual material to release enough energy to vaporize the entire comet completely, the way thermal nuclear devices act in space may be different enough without an atmospheric shockwave that it isn't much different than a very small gamma-ray burst which is the only reason why we'd need so many.

 

That's nonsense, Sam. If we have less than a couple of months, the only thing we can do for a large (but not too large) impactor is to figure out what part of the Earth will suffer damage from the impact and evacuate them. A couple of months is a reasonable amount of time to evacuate everyone from the affected areas. It is far too little time to prevent the catastrophe from happening.

 

If we don't see it until it's within a few lunar orbits of us we don't even have time to do that. The collision will occur in a few hours in the case of a comet.

[SamBridge]

That's nonsense, Sam. If we have less than a couple of months, the only thing we can do for a large (but not too large) impactor is to figure out what part of the Earth will suffer damage from the impact and evacuate them. A couple of months is a reasonable amount of time to evacuate everyone from the affected areas. It is far too little time to prevent the catastrophe from happening.

 

If we don't see it until it's within a few lunar orbits of us we don't even have time to do that. The collision will occur in a few hours in the case of a comet.

I don't think you correctly interpreted what I was saying. I implied that when we sent the missiles, they would explode within a few moon orbits because they meet the comet there which was already traveling for 2 months. If we would have detected the comet as just becoming outbound and had a couple months, we would have time to send explosives to meet the comet at the distance of at least few moon-orbits from Earth. Otherwise, it wouldn't be a bad precaution to use some kind of giant underground facility and evacuate.

Edited June 13, 2013 by SamBridge

[D H]

I don't think you correctly interpreted what I was saying. I implied that when we sent the missiles, they would explode within a few moon orbits because they meet the comet there which was already traveling for 2 months.

This doesn't make sense. Try typing this again. Within a few moon orbits of what?

 

If we would have detected the comet as just becoming outbound and had a couple months, we would have time to send explosives to meet the comet at the distance of at least few moon-orbits from Earth.

If this is what you were writing about, I understood exactly what you typed. This is nonsense. A long period comet such as C/2012 S1 (ISON) will have a closing velocity well in excess of 50 km/second with respect to the Earth. The people of the Earth have eight hours or less to live life as they know it if nothing is done until the comet reaches four lunar orbit radii from Earth. The only reasonable action at this late hour is to bend over and kiss one's rear end goodbye. Sans some magical teleportation device that could move the comet from here to there, there is *no* avoiding the collision. It is inevitable.

[SamBridge]

 

This doesn't make sense. Try typing this again. Within a few moon orbits of what?

I sincerely hope that is a joke, I'm talking about the distance of the moon from the only planet we know of inhabited in this solar system with a single object in orbit around it that we call "the moon", there is no reason why you should assume otherwise, we have been talking about comets hitting Earth this entire time, the fact that you misinterpreted such a basic, easily understandable part of my post must suggest you aren't reading what I am saying very seriously, which would explain previous misconceptions you had that I pointed out.

 

 

 

If this is what you were writing about, I understood exactly what you typed. This is nonsense. A long period comet such as C/2012 S1 (ISON) will have a closing velocity well in excess of 50 km/second with respect to the Earth. The people of the Earth have eight hours or less to live life as they know it if nothing is done until the comet reaches four lunar orbit radii from Earth. The only reasonable action at this late hour is to bend over and kiss one's rear end goodbye. Sans some magical teleportation device that could move the comet from here to there, there is *no* avoiding the collision. It is inevitable.

As I said before, I didn't guarantee anything, all I know is it is certainly possible to launch many explosives to intercept the comet, I pointed out they would not act as much more than small gamma-ray bursts, but as I also said before, we are not incapable of attempting. Any energy we put into reducing the mass or velocity will reduce the damage it does, but if we can't use explosives far away enough they may damage Earth in some way.

Edited June 14, 2013 by SamBridge

[D H]

 

This doesn't make sense. Try typing this again. Within a few moon orbits of what?

I sincerely hope that is a joke, I'm talking about the distance of the moon from the only planet we know of inhabited in this solar system with a single object in orbit around it that we call "the moon", there is no reason why you should assume otherwise, we have been talking about comets hitting Earth this entire time, the fact that you misinterpreted such a basic, easily understandable part of my post must suggest you aren't reading what I am saying very seriously, which would explain previous misconceptions you had that I pointed out.

 

No, Sam, it wasn't a joke. Look at that huge run-on sentence you just wrote. Parse it, please.

 

To forestall criticism that I too am guilty of writing huge run-on sentences: Yes, I am. However, I'm quite aware of the fact that I sometimes do write long Germanic-style sentences. I'll rewrite it when someone tells me that what I wrote doesn't parse.

 

The reason I asked for the rewrite was because I did not know whether you were writing two sentences about a single scenario or two sentences about two separate scenarios. So which is it? I think the second sentence was the addressing a scenario in which the comet is hit with nukes when it has closed to within a few lunar radii of the Earth. I couldn't tell whether the first sentence was a prelude to that or was talking about something completely different. That other interpretation involves hitting the comet with nukes when it is well removed from the Earth, but having the nukes explode at a distance of a few lunar radii of the comet.

 

So which is it, one scenario or two distinct ones?

 

 

As I said before, I didn't guarantee anything, all I know is it is certainly possible to launch many explosives to intercept the comet, I pointed out they would not act as much more than small gamma-ray bursts, but as I also said before, we are not incapable of attempting. Any energy we put into reducing the mass or velocity will reduce the damage it does, but if we can't use explosives far away enough they may damage Earth in some way.

 

Waiting to do something to a comet on a collision course with the Earth until the comet is within a few lunar radii of the Earth is useless. It is equivalent to bringing coal to Newcastle, owls to Athens, tea to China, ice to Eskimos, sand to the beach. The collision is inevitable and won't reduce the damage one iota. Using nukes is worse than useless. It gives a brand new meaning to the term "dirty snowball".

Edited June 14, 2013 by D H

[jfy1966]

I teach 8th grade physical science. Many of my students get really....freaked out...when these types of events occur. It's a good learning opportunity for them, though.

My experience is that many of the parents of my students have similar reactions so a lot of misconceptions are passed down before my students enter the classroom.

 

Are there any teachers out there with similar experiences? How do you approach misconceptions in science? What works and what doesn't?

 

Thanks!

[sevenseas]

The observatory of Lisbon has leaked important information about comet ison.

 

They claim that fragments of Comet ison will hit earth in december, this based in emulations performed using supercomputer 'Tiger 2' and a propietary model.

 

They claim that the when the comet enter the atmosphere of the sun the ice will change state abruptely, turning into a propellant, changing the trajectory of the comet.

 

They claim that the fragments of the comet will spread in the shape of a cone with a base diameter of 300.000 kms , that is the distance of from the earth to the moon.

 

they claim that the comet after crossing the sun will be higly fragmented, fragments ranging from a football to the size of a ship.

 

they say that the propulsion of the ice will change the trajectory of the fragments, causing a shower of cometary fragments that will hit Earth in december.

 

 

Trajectory calculated by Nasa without considereng the rocket effect of ice

 

 

Comet ison requires only a change of 2 degrees to hit Earth

https://www.youtube.com/watch?v=07gtLKEXAQw

 

 

How can ice turn into rocket fuel?

https://www.youtube.com/watch?v=WJYtvOt00MM

 

 

 

 

They have leaked this in several forums, they also say that they will speak openly in about a month, after the comet passes a callibration point to verify their calculations.

 

 

Is important to note that the trajectory of ison is perpendicular to the plane of the planets, two planes intersecting perpendicularly.

 

 

 

 

 

 

 

They say that the path of the fragments is very similar to the path of Coronal Mass ejection from the sun.

 

https://www.youtube.com/watch?v=zHxPbC5Wu2o

 

 

For more information here

 

http://third-secret.pro-forum.co.uk/h51-comet-ison

Edited July 20, 2013 by sevenseas

[John Cuthber]

Here's their webpage

http://oal.ul.pt/

Where's the story?

 

Also, do you realise that " a proprietary model."

means an untestable one?

[Janus]

Even if one accepts that it would only take a 2° change in trajectory, this change would have to take place at perihelion. Perihelion for comet Ison is 1.86 million km at which point it will be moving at a speed of 378717 m/s.

 

To deflect it by 2° would require a delta v of 13217 m/s.

 

The highest exhaust velocities achieved by steam rockets specifically designed to be efficient as possible is 1911 m/s.

 

So, assuming perfect conditions, we can use the rocket equation to determine just how much of the comet would have to be converted to steam and ejected in order to generate the needed delta v.

 

 

That equation is

 

[tex] M/m = e^{\frac{\Delta v}{v_e}} -1[/tex]

 

Ve is the steam exhaust speed.

 

This gives an answer of M/m = 1008

 

Meaning that Comet Ison would have to convert ~99.9% of it mass to steam in order to deflect the remaining 0.1% the required 2°.

 

Keep in mind, that this assumes a properly designed pressure chamber and nozzle. In the case of a comet, such would have be formed from the comet substance itself, which means the comet would break up and the rocket action would cease after it had only generated a small fraction of the needed delta v.

 

Considering how easy it was to debunk this part of the argument, I calling bogus on the idea that this claim originated from an actual scientific institution.

[swansont]

!

Moderator Note

Threads merged. sevenseas, do not open more threads on this same silly topic. Furthermore, "soapboxing" is against the rules. Posting and repeating points without response to critique is against the rules.

[DeathRayBob]

I hope this won't adversely impact (chuckled a little right there) the stock market. I hate it when the price of fuel goes up.