This is, to put it bluntly but simply, complete bullshit.
Anyone with actual astronomy experience will literally laugh at that paper. It is about 65% irrelevant padding that provides nothing towards their thesis and is there to look intimidating and impressive.
Thermonuclear bombs run off deuterium fusion - proton-proton reactions have such a low cross-section and rate that you really can't get it to happen at their temperatures. And the thermonuclear explosion itself only uses up some of its TIGHTLY PACKED SOLID fuel right next to a fission explosion before it rarifies to the point that it just can't keep reacting. To fuse protons you need gravitational confinement, not inertial confinement.
Stars are well within a range of conditions where they exhibit negative feedback. That is, if they heat up, they expand and the adiabatic expansion cools them to a point that they produce less energy.
On top of that, even if you accelerated the rate of fusion temporarily in part of a star... so what? The heat produced per unit volume of the sun's core is less than that of a compost heap and orders of magnitude less than human flesh. At the heat capacity of over a ton of hydrogen plasma per cubic meter, a temporary increase in heat output of a small region isn't destablizing anything.
On top of that, the last two points refer to the core. They are talking about mucking with the surface. If you heated up part of a star not normally hot enough to cause fusion, even if you managed to heat up it would just expand away and mix.
On top of that, far more energetic events than nuclear explosions happen to stars all the time. Magnetic events on the surface of the sun regularly relase more energy than all of Earth's nuclear arsenals at once. There are stars with gigatons per second of gas pulled off a puffed-up companion star falling onto a small spot on their surface at 800 km/s, where that spot glows X-ray hot and outshines the rest of the star. There are sun-sized stars that we can tell by their lithium content (which is burned up by nuclear reactions at much lower temperatures than other elements throughout the stellar volume) ate entire gas giants that fell into them at hundreds of kilometers per second within the last 50 million years.
And they compare the approach of a solid object across millions of kilometers in which the blackbody temperature exceeds 2500 C and gas at millions of degrees streams past, and at the surface falling at 600 km/s through 5800K gas, to the galilleo probe which fell through regular gas for 70 seconds at 60 km/s (and burned away more than half its mass in the process)?
I don't care if this was authored by Isaac Newton, it's utter bullshit and the idea of someone taking it seriously confuses me.
I don't care if this was authored by Isaac Newton, it's utter bullshit and the idea of someone taking it seriously confuses me.
That is because you don't grasp, on a gut level, that most other people know less physics than you. (Philosophy major here, I didn't know what to think of this paper until this thread.)
On top of that, even if you accelerated the rate of fusion temporarily in part of a star... so what? The heat produced per unit volume of the sun's core is less than that of a compost heap and orders of magnitude less than human flesh.
Really? Fascinating. I kind of expected it to be more than that. But then I suppose that would mean it would inevitably burn up in less than billions of years so that makes sense.
I don't care if this was authored by Isaic Newton, it's utter bullshit and the idea of someone taking it seriously confuses me.
He did author some bullshit, now that you mention it.
I suppose that would mean it would inevitably burn up in less than billions of years so that makes sense.
Yeah. The sun is just so hot due to its huge mass to surface area ratio - so much volume per square meter of emitting area. The total heat energy inside the sun at any given moment is also equal to several hundred thousand years worth of its fusion output. You could somehow shut down the fusion and never have anyone else in the solar system notice a thing for kiloyears unless they had a neutrino detector, until it starts to slooooooooowly shrink and redden, taking millions of years...
The only way to increase the fusion rate is to increase the temperature or pressure (or both at the same time which is more likely). But the heat contributed to a volume by fusion is so ridiculously tiny over any timescale that anything could inject heat into it over that once the heat being used to increase the fusion rate went away the fusion would never be able to sustain the higher temperature that was causing it. The gas would expand under the increased temperature and pressure, and undo whatever was being done to it.
There are variable stars that pulsate on human timescales, but those don't happen due to pulsations in the fusion rate. Instead they are mostly old red giants with puffed up cool outer atmospheres where some ions can actually hold onto a few electrons. The outer atmosphere expands outwards and cools, the ions grab a few electrons and become more transparent due to fewer charged particles to intercept photons, the atmosphere then loses energy it cant intercept and shrinks, it heats up from adiabatic contraction, re-ionizes, becomes more opaque, heats up more and expands, rinse, repeat. Only the outer layers, a tiny fraction of the mass, are affected. Other stars pulsate via other mechanisms too but thats the most common.
The only times that fusion changes on human timescales are in red giants that have a kernel of degenerate matter at the center, held up only by electron degeneracy (AKA the pauli exclusion principle). That is because in that case, pressure is a constant rather than being a function of temperature and the negative feedback I mentioned cannot operate because as the core heats up it fails to expand. This is what gives you 'helium flashes' in red giants where they suddenly put out a few hundred thousand years worth of output in ten seconds... at the center of a solar mass or more of gas that already contained nearly that much heat energy to start with, such that it takes hundreds of thousands of years for the doubled heat energy content to work its way out to the surface and bleed out into space.
He did author some bullshit, now that you mention it.
I can't wait until 2060 (if I survive that long). We can have the "Newton was WRONG?!" party, and then start planning the April 5th, 2063 "Vulcans Welcome" party.
Also the author cites a criterion named after himself and cites himself more often than all other sources put together; these are both major crackpot flags.
I would expect far more intense explosions within the Sun all the time, like solar flares, and I would expect more energetic infalls of comets (though I suppose their energy might be discharged gradually into the surrounding medium). Does not pass anything remotely like a smell test.
I am not a nuclear physicist and I haven't read the paper, but given that there were no observations of sun-like stars going Nova and that anything humans can do can also probably occur naturally just by chance, the odds of this being workable given the current technology are too low to worry about. Though maybe a bit higher than of the LHC creating an earth-swallowing black hole. But still at the Pascal's mugger level.
An obvious rejoinder to this is that while a Boeing 747 could assemble itself naturally by chance, the fact that we don't see any 747's occurring naturally isn't evidence for their impossibility. Therefore doesn't your point about no sun-like stars going nova only carry weight if we assume that there is other intelligent life in the observable universe?
As a side note, I read somewhere that John von Neumann once had an epiphany in which he imagined that supernovas were the final acts of civilizations that had learned to harness the power of nuclear fusion. We could even imagine von Neumann probes being constructed with this purpose, destroying every star in their forward causal cone. You have to admit, it would be a funny old universe if it turned out that such a thing were possible!
The absence of 747s spontaneously assembling is evidence for their impossibility. Its just that evidence is completely overwhelmed by all the additional evidence we have indicating that it is possible - evidence which appears lacking from this particular case.
Or nuclear bombs. Why could we apply the same argument here? "We never see any nuclear explosions on earth, either during human history or in the form of radioactive craters, therefore it is very implausible that if we combine specially crafted and refined substances we will get something like that."
This seems extremely unlikely. We don't see stars doing this naturally, and stars are very big objects so the chance of this happening by sheer chance shouldn't be that low if it can happen with anything like marginally plausible technology. Similarly, from a Great Filter standpoint, we don't see a lot of sun-like stars going boom, so this can't be a substantial fraction of the Great Filter.
It is also extremely unclear how one would go about setting this off even if it were possible. You'd need to somehow get a large, specifically engineered nuclear weapon deep into the sun without it being damaged or destroyed in the process. Overall, I'm not terribly worried.
There's already a huge boundary layer where high pressure hydrogen in the sun is exposed to the fusion of the inner core and not fusing. The only possibility for the sun going boom is that there is another, higher, self-sustaining fusion rate (or at least, taking into account pressure changes once you start fusing), that has never been accessed by, e.g. proto-planets falling into the sun.
This has not been adequately demonstrated by the paper you cite (they make big approximations and don't demonstrate that they get back multiple possible fusion rates), though I can't rule it out from what I know.
The mechanism there seems to be slightly different. Turchin is looking at detonating objects with unusually high deuterium density in otherwise stable objects with temperatures much lower than the sun. This paper in contrast seems to be talking about primarily detonating regular hydrogen in the sun.
Edit: Now having skimmed Turchin, his scenario is much more plausible and mildly disturbing. The destruction of such an event would be very large scale, but might not be easily visible on an astronomical scale, so one can't a priori rule it out as a Great Filter consideration.
Thank you for listing my article. Bolonkin clearly is not right because Sun's hydrogen can't detonate.
Only deuterium and lithium on cold gas planet is good for detonation. Or you should go as far as Sirius B which is white dwarf and could theoretically be detonated. Or as close as Earth where lithium deposits or uranium mines could be regarded as possible candidates for detonation.
But it does not mean that we can't do something to the Sun. If Sun would be hit by a comet with 100 km diameter - which is rare but much-much more often than such hit for Earth - the energy of the impact would be 1000 times more than Sun's output in a second, which means that for a few seconds the Sun will became hundreds times brighter and this could cause fires everywhere. And also it could provoke strong magnetic event and some nuclear reactions in the moment of the impact, the main risk from which is not energy boost but radioactive contamination of space and Earth.
The large comet could be relatively easy disturbed in Oort cloud as orbital velocities there are very small and even a small incoming impactor would be enough to put a comet body in a free fall towards the Sun - which will take hundreds of years.
Some large stellar flares on Sun-like stars could be explained by this mechanism. Such flares were recently discovered and their origin is no so clear.
'Superflares' erupt on some Sun-like stars http://www.nature.com/news/superflares-erupt-on-some-sun-like-stars-1.10653
If Sun would be hit by a comet with 100 km diameter [...] the energy of the impact would be 1000 times more than Sun's output in a second, which means that for a few seconds the Sun will became hundreds times brighter and this could cause fires everywhere. And also it could provoke strong magnetic event and some nuclear reactions in the moment of the impact, the main risk from which is not energy boost but radioactive contamination of space and Earth.
That all sounds very very wrong. The impact introduces kinetic energy, which presumably manifests as some sort of temporary turbulence at the impact site in the outer layer of the sun. It's not going to turn into radiative energy. Similarly, there is no reason for the impact to produce nuclear reactions - the spread-out substance of the vaporized comet would just become a minor contaminant of the mostly-hydrogen sun, spectroscopically detectable for some years. Maybe the impact would make a small coronal hole, but giant ones happen naturally anyway.
Impact speed would be 600 km/sek which is equal to temprary rise of temperature to around 500 million C in the place of impact. On this temperature some nulear reactions are possible but their enegry will not dominate impact energy. Also a lot of light will be emited by impact place on this temperature.
I thought about it more... We have a giant rock - a small world in itself, but still just a pebble to the sun - dropping like an anvil into a ball of superheated gas. It has been falling through space for years and by the time it arrives it's moving like a super-bullet.
From the comet's perspective, each particle in its path arrives at its surface like a cosmic ray. So as it gets closer to the sun, it experiences a rain of particles, and the rain gets heavier and heavier. This "rain" will kick up a plasma on the surface of the comet, as the particles smash into the atoms of the comet's surface and splash them apart. As this surface plasma builds, increasingly the solar particles are colliding with the plasma and not directly with the comet surface. The cometary plasma is a shock wave travelling just in front of the comet as it approaches the surface of the sun. Some of the plasma will stream across the comet's face and out of its path, but the shock wave will grow as the density of arriving particles increases.
Eventually the comet and its shock wave will fall as far as the sun itself. If the comet is big and hard enough, I see no reason why it couldn't sink all the way to the core, where it might just drift around, melting and shrinking until it had boiled away completely, like an aspirin pill in a bathtub of boiling water. So I think the question is, what is the history of the shock wave of plasma that accompanies the comet as it falls into the sun? Does some zone form inside it, where the collisions are intense enough that fusion occurs, and if so, how large is it and how long does it last? Is it just a burst or is it a sustained burning that consumes a significant part of the comet's leading face? Or alternatively, does turbulence in the shock wave damp the force of its collision with the solar atmosphere, enough to mostly avoid fusion?
So now I believe it could happen. Though I would want to understand that shock wave, to really decide... Where did you get the estimate of "1000 times more than Sun's energy output in a second"?
It is important in my idea that it is a comet - that is large chunk of not connected ice, not a hard rock. As we know from examples of Tunguska event 1908 and Chelabinsk event this year, such bodieas tend to desintegrate on high altitude in large explosion because they quickly fall apart. Chelabinsk flash video. https://www.youtube.com/watch?v=OPSzpnHHwos
Estmation of the energy is based on the speed of imact, that is 600 000 meters per second (second cosmic speed on the Sun surface), mass of the object - that is 10++18 kg (based on water density and size of a cube with 100 km rib) and formula for kinetic energy, that gives us enegry of impact 3.6x10xx29 J.
Energy output the Sun is 10x26 J per second. So, total energy of impact would be 3600 times more than Sun's output. Not all energy will go in radiation so 1000 times seems to be good estimate.
In fact I started from the question «What is the size of the body, which could cause harm to the Earth if it fall on Sun?" And find that 1 km will not be even visable, but 100 km is dangerous.
Now I need estimation of the frequency of such impacts.
First correction, the Sun's luminosity is ~3.827E+26 W, so the falling ice-cube would have a kinetic energy of ~1,000 seconds of solar output. However an object falling into the Sun - such as a 100 km ice-cube - would only release its kinetic energy in such a burst if it was brought to a sudden halt. At 600 km/s the object is a solid surface moving through a fairly diffuse gas - the outer layers of the Sun are thin, hot plasma. A good estimate of the braking effect would be Newtonian Flat Plate drag - i.e. the stuff of the Sun immediately in front of the object is ramming into it, causing drag, with essentially no flow around the object. At 600 km/s the dynamic pressure on the front face is 360 GPa times the plasma density - enough to decelerate the ice-cube (with 100,000 tonnes per square metre areal density) at 3600 m/s^2 if the plasma density was just ~1 kg/m^3. Of course the object won't decelerate until the gas drag is greater than the Sun's gravity - equivalent to ~28 GPa pressure on the front face, which is achieved about 4,000 km below the Photosphere. The dynamic pressures would obliterate the mass eventually, but sound in ice only travels at ~3 km/s, so the main mass should travel for about ~30 seconds before starting to fragment as pressure waves travel from the front to the back of the 100 km block. But if it ablates, then it may travel some distance after that. Seems likely to be a rather protracted process, which might produce a flash, but the only hazard to Earth would be if it was in the line of sight of the impact, I suspect.
I think that the comet would desintegrate quicker than with speed of sound, and more like with the speed of incoming gases that is 600 km/sec, so it would be destroed in less than 1 second. Comet is not asteroid - it is very fragile and it will start to desinegrate even before the impact bacuse of gravitational forces - it will be inside Roshe limit of Sun and tidal forses will start to elongate it.
The mass of whatever the impactor is has to be brought to a halt and for a 100 km chunk massing as much as you've computed, that's not happening in an instant in the photosphere of the Sun. Computing exactly how long is a non trivial task and at that speed is more like the injection of a supersonic fluid through a much lower density medium since the internal strength, heat capacity and even the ionization energy of the object is trivial against the kinetic energy it is dissipating.
I recall reading (but cannot find at the moment) a different study looking at sunlike stars with known exoplanets that did not involve the kepler data. It found that there was a preponderance of super-flare prone stars amongst sunlike stars with hot-jupiter-style large close in exoplanets, adding fuel to the idea that magnetic interactions cause a subset of them. Might not account for all of course even though the Kepler data would only actually see a tiny fraction of the hot jupiters that exist in its field of view.
Stars as gravitational sinks that allow strong energy release just from objects falling onto them is an interesting concept. I presume that what makes such an event extremely rare is the very small amount of angular momentum you need to actually hit one and the fact that light pressure and sublimation will tend to destroy or deflect most objects long before they come close to anything like an impact?
Sun has large size ans small comets hit it every year. But I would like to know how often it is hit by 100 km size body. My uncalibrated idea is one in 1 million years. I will try to ask on Bad astromomy forum or serch for more extimates and will post resul here.
a more practical consideration is that launching big things even into earth orbit is EXPENSIVE. I don't think launching a precisely targeted mega-nuke at the sun is feasible for most governments and feasible to hide for even fewer.
Barring changes of type, such as a successful orbital elevator or a similar change to a technique where fuel is not part of the payload, pretty likely. The technical costs of space flight have decreased, but the costs of fuel and materials haven't changed that dramatically.
And that understates the energy costs involved when you're talking about the sun, specifically. There's a huge amount of delta-v involved in a straight shot -- the Earth orbits the sun at 30 kilometers per second, compared to the 8-10 km/s that a space ship needs to orbit the Earth, where the cost of delta-v increases exponentially -- and not many good targets for gravitational slingshotting to reduce that.
Your statement would be a safe bet based on the past 50 years. 50 years ago, or 1963, was 4 years before the Saturn V first launched. Using modern figures of 3.3 billion/launch, including R&D costs, that comes to approximately $28,000 per Kg to low earth orbit. The same math says that the Space Shuttle cost about $61,000 per Kg.
(I'm lumping in the total cost of the entire program in both cases divided by the number of launches. There's problems with this method, but it means that costs can't be hidden by accounting tricks as easily)
With that said, there are scads of methods that would lower this cost, at least for unmanned payloads, and there is also the realistic possibility that automated manufacturing could build the rockets for a fraction of what they currently cost. There's videos taken at the SpaceX plant showing automated lathes, and direct metal 3d printers can apparently make parts that meet spec. It seems at least possible that over the next 50 years the entire end to end process could be automated to take minimal human labor.
it depends: Manufacturing and space delivery will become cheaper and easier but surveillance and data gathering will also. I don't know what will prove more important but I feel comfortable not planning for this disaster 50 years from now when we'll definitely have more knowledge about it in 15 years or whatever.
Bolonkin & Friedlander (2013) argues that it might be possible for "a dying dictator" to blow up the Sun, and thus destroy all life on Earth:
The Sun contains ~74% hydrogen by weight. The isotope hydrogen-1 (99.985% of hydrogen in nature) is a usable fuel for fusion thermonuclear reactions. This reaction runs slowly within the Sun because its temperature is low (relative to the needs of nuclear reactions). If we create higher temperature and density in a limited region of the solar interior, we may be able to produce self-supporting detonation thermonuclear reactions that spread to the full solar volume. This is analogous to the triggering mechanisms in a thermonuclear bomb. Conditions within the bomb can be optimized in a small area to initiate ignition, then spread to a larger area, allowing producing a hydrogen bomb of any power. In the case of the Sun certain targeting practices may greatly increase the chances of an artificial explosion of the Sun. This explosion would annihilate the Earth and the Solar System, as we know them today. The reader naturally asks: Why even contemplate such a horrible scenario? It is necessary because as thermonuclear and space technology spreads to even the least powerful nations in the centuries ahead, a dying dictator having thermonuclear missile weapons can [produce] (with some considerable mobilization of his military/industrial complex)—an artificial explosion of the Sun and take into his grave the whole of humanity. It might take tens of thousands of people to make and launch the hardware, but only a very few need know the final targeting data of what might be otherwise a weapon purely thought of (within the dictator’s defense industry) as being built for peaceful, deterrent use. Those concerned about Man’s future must know about this possibility and create some protective system—or ascertain on theoretical grounds that it is entirely [impossible]. Humanity has fears, justified to greater or lesser degrees, about asteroids, warming of Earthly climate, extinctions, etc. which have very small probability. But all these would leave survivors—nobody thinks that the terrible annihilation of the Solar System would leave a single person alive. That explosion appears possible at the present time. In this paper is derived the “AB-Criterion” which shows conditions wherein the artificial explosion of Sun is possible. The author urges detailed investigation and proving or disproving of this rather horrifying possibility, so that it may be dismissed from mind—or defended against.
Warning: the paper is published in an obscure journal by publisher #206 on Beall’s List of Predatory Publishers 2013, and I was unable to find confirmation of the authors' claimed credentials from any reputable sources with 5 minutes of Googling. It also has two spelling errors in the abstract. (It has no citations on Google scholar, but I wouldn't expect it to have any since it was only released in July 2013.)
I haven't read the paper, and I'd love to see someone fluent in astrophysics comment on its contents.
My guess is that this is not a risk at all or, as with proposed high-energy physics disasters, the risk is extremely low-probability but physically conceivable (though perhaps not by methods imagined by Bolonkin & Friedlander).