Hypothetical scenario:
Assuming that humanity became aware *right this moment *(the year 2015) of an incoming killer asteroid - and assuming that most nations on Earth were willing to contribute as much funding as one could ask for, and share all the technology and know-how that they had, what is the minimum amount of notification time that would be required for humanity to be able to defeat an extinction-type asteroid? 8 months? Two years?
(That is, the minimum amount of time required to gather the engineers and scientists, get the project started, get the assembly facilities going, get the committees talking, design a rocket and assemble the nuclear warhead, and train the astronauts, or, build the solar foil, and the guidance system, and the detonation system, or the steering motor, or whatever method that humanity decides to come up with to try to defeat the incoming asteroid. The total amount of time for the massive engineering project and the mission launch and mission execution and completion, from start to finish. Starting from “Hey, there’s an incoming asteroid!” to the moment that the nuke or other device actually goes off on the asteroid. This has to be done with the technology of today, the year 2015.)
At what point would the notification time be too little to save humanity from extinction? 6 months?
Probably a decade, at least. It would also depend on the path of the asteroid.
A nuclear warhead is a movie solution, i.e. the absolute worst thing you could do in real life. Search for other threads of deflecting asteroids. The real world solution is to push it slightly off course. Changing the orbit takes time, and the particulars would vary for each individual case so there’s no good way to give a timeline for a hypothetical. Just keep telling yourself that Bruce Willis will not be involved.
I keep hearing that, I guess because of the fear that a nuclear warhead will just break one large asteroid into a bunch of smaller ones. But what if we try to use a nuke to vaporize the asteroid? What’s the largest body that we could vaporize, leaving only some non-threatening dust behind?
It looks like Wikipedia has a good discussion on the nuclear topic and it doesn’t seem like an automatic terrible solution.
Couldn’t a well placed nuclear warhead change the asteroid’s course so it no longer threatens the earth?
You can blow up an asteroid into dust, but that doesn’t magically make the dust non-threatening. What makes asteroids dangerous is the kinetic energy, and you’re not losing any of that by blowing it up.
Define “defeat”, though. We’ve had the technology to survive a dino-killer asteroid for thousands of years, if we have warning against it. Just spend seven years of plenty stockpiling food (and seeds), and start over once the climate returns to normal.
If small enough, though, the particles could vaporize in atmospheric reentry.
Note that this would add the same amount of energy to the upper atmosphere as if it was all in one lump. The difference is that it would be spread out over a larger area, and the lump wouldn’t impact the ground.
What people misunderstand is this. Use a nuke and the asteroid will break up into multiple pieces. What people think that means is now they have multiple asteroids to deal with and thsts true. The caveat is that, the energy of all the pieces combined will equal that of the original asteroid. Each individual one will much smaller.
In real life, after the hit the pieces will behave in different ways. Some (hopefully most?) will be put on a trajectory which makes them miss the earth, others will have to deal with the Planetary Protection System (aka the atmosphere). Some will bounce off and others will burn up. It will be the rest we have to worry about. Even then, it’s not like their is a shortage of nukes on earth and there still might be time to engage larger dangerous pieces before they hit with further strikes.
Of course this is dependant on the size of the asteroid. If its a Thea sized object, we are well and truly fucked.
I don’t think any of the answers here really addresses the magnitude of the problem. A “humanity killer” is not a pissy little 1 km asteroid, it’s one 10 km or larger in diameter like the one that caused the Chicxulub Crater. A 10 km asteroid is estimated to weigh 1.31 trillion tons (1.31 × 10^15 kilograms). The wiki page on impact avoidance includes the quote from Edward Teller that a 1 Gigaton nuclear device would be needed to divert the course of a 10 km extinction level asteroid. That’s 20 times bigger than the Tsar bomba, and although it seems some theoretical research has been done on multi stage bombs that could reach that size, we have no idea if they would work in practise.
In short I don’t believe that even with 10 years we could do anything about a 10 km plus asteroid short of stock piling bunkers for the 1 percent of humanity that might survive.
refs:
Now, if a 10km wide asteroid slammed into Earth, could everyone on Earth *feel *the impact? (Prior to dying.)
One of the links I give above states that a 10km impactor on the ocean produces a magnitude 12.4 earthquake, a 1.2 km high Tsunami 100 km from the impact site and a 100 meter high tsunami 10,000 km from the impact site.
I’ll let someone else do the math on if the whole planet could feel a 12.4 magnitude earthquake.
Just as a matter of practical interest. Even though the Near Earth Object (NEO) project has been running for quite a few years now, we don’t actually know what is out there. The really big planet-busting asteroids are tracked because they are big enough to find.
However there are thousands of smaller rocks which could demolish a city or worse and we only know about possibly 30%.
Consider the Chelyabinsk meteor which caused a 500 kiloton explosion over Russia in 2013 and was estimated to be around 20 metres in diameter. Nobody saw it coming.
Incidentally, detecting NEOs is a task which we can thank amateur astronomers for. Around the world every night there are telescopes looking for a momentary twinkle in space, the sign that an object has for a few seconds reflected sunlight. The information is entered onto a website and other astronomers watch the location. Over days or months eventually an object is confirmed.
Even if we have a 10 year window and any solution is in the hands of the UN or Congress, bend over and kiss your ass goodbye.
Whoops wrong thread
Not if you use it Orion-style (i.e. not just one big nuke)