Sciencemadness Discussion Board - 1908 siberia explosion

1908 siberia explosion

xxxxx - 13-6-2006 at 11:58

there have been speculations that the 1908 siberia explosion was caused by a chunk of antimatter. the problem i have with this idea is that space is not entirely empty. i was wondering how far a piece of antimatter one meter in diameter and specific gravity of 1.00 could travel through interstellar space before it was completly neutralized by the miniscule quantities of hydrogen present in interstellar space, but i don't have the information to calculate the variables.

unionised - 13-6-2006 at 12:39

If it were antimatter there would still be leftover radioactivity. There isn't so it wasn't.

If you had a lump of antimater flying through space the energy released by destroying less than a thousandth of it would spread the rest out into a vapour cloud with a bigger area. This would then hit even more normal matter...

vulture - 13-6-2006 at 12:53

IIRC, it was a small comet that collided with earths atmosphere under a shallow angle.

The explosion has been the subject of numerous conspiracy theories though, the Tesla experiment is one of them.

neutrino - 13-6-2006 at 19:14

>If you had a lump of antimater flying through space the energy released by destroying less than a thousandth of it would spread the rest out into a vapour cloud with a bigger area. This would then hit even more normal matter...

Outer space is a very high vacuum. Slow heating due to matter / antimatter collisions would probably reach an equilibrium of sorts with blackbody radiation. Granted, near the Earth's atmosphere it would probably fly apart, but in the vacuum of interstellar space I imagine it would be quite stable.

edit: Now I can't stop thinking about how the math of this works out...

I'm sure I'll have something tomorrow.

Chemistry ... astronomy ... physics ... calculus ... brain overload...

[Edited on 14-6-2006 by neutrino]

unionised - 14-6-2006 at 11:00

Typically the amount of heat needed to vaporise something is very small compared to the heat released by anihilation.

So, on a long time scale the heat would destroy it unless the heat is radiated away.

At the exact location where the mass was destroyed there would be a couple of gammas produced. Statistically, one of these will plough into the rest of the antimatter. I guess it's possible that this energy would get a chance to be lost before it built up enough to boil the stuff, but some stuff will be spalled off into space.
Of course, because it's in a ludicrously high vacuum, the boiling point would be a lot lower than normal too.

(OK, I don't know what happens with proton + antiproton reactions but it won't be any more gentle)
How good is the vacuum in interstellar space? (and how does anyone know?)

JohnWW - 14-6-2006 at 14:26

As I recall, it happened on 22 May 1908, in a very remote and uninhabited area of Sibera in imperial Russia. It flattened trees for 50 or more miles around, the direction of the fallen trees (many of which still remain, due to the cold climate) indicating the epicenter of impact, although there was no impact crater. Rivers in the area (which were still partly frozen at that time of year near their Arctic Ocean mouths, which frequently causes flooding upstream) burst their banks. I read somewhere that eyewitnesses who saw the object just before it exploded said it was "shuttle-shaped", i.e. a long cylinder. For days after the explosion, the sky was luminous at night in northern Europe and Asia and North America. I have also read that explorers who found and examined the epicenter of the explosion years afterwards found that the pattern of fallen trees indicated a shallow-angle path for the object, and that small spherules of metal (unspecified) were found in the area. An explosion of an alien UFO is one of the other postulated causes.

lordmagnus - 14-6-2006 at 20:29

Explosion of a UFO is where the anti-matter idea came from, the ships power core containment failed as it broke up in our atmosphere (think of the COLUMBIA when the plasma infiltrated the inner hull). There has also been some theories of alien ship remains in that area, I think FATE magazine once had article about local indians exploring the area after the explosion, and the found odd mechaincal remains, after sleeping the night there many developed rashes, and burns on their skin (radiation exposure), the soviets supposedly tested some nuclear warheads in that area as well, and the explosive yeild was way more tahn it should have been, (secondary fission, something fissionable was exposed to fast nuetrons {soviet warhead} and had an additional effect on the test). Then there is the BPRD's stance on it, it was the obolisk that the OGDRU'Jihad sent to earth for HELLBOY to unlock (with the right hand of doom), so they could be freed from their crystal prison.

IrC - 15-6-2006 at 00:47

Antimatter is never going to be used for star travel. Any race smart enough to travel the stars will not be stupid enough to run out of gas around the galactic core. No antimatter gas stations anywhere. If such races existed or in general if any race contemplated star travel, I have no doubt the energy source for multi parsec distance trips is going to be fundamentally different than any science we know or have conceived of, except possibly for some kind of zero point generator. In short anyone smart enough to build such a ship is going to be smart enough to use an energy supply that does not need a refill anywhere in the universe unless there is always a reserve to make it from one point to a source of a fill up. What if the antimatter containment hit a rock while 4 wheeling? Even if the hole was patched they would still likely run out of gas, unless of course the leaking antimatter blew up the ship.

The entire concept of antimatter power in a starship is nothing more than a leftover mindset of the 60's from the Star Trek fame. Just as in the 40's and 50's atomic rockets were the dream. In effect the theories always reflect current science and therefore never work. Anyone remember the klystron modulator to call home to earth from Altair in the 1956 "Forbidden Planet"? Clearly in 1956 the idea of a klystron seemed futuristic to writers and so was the device of choice at this timeframe in our history. In the face of sheer distance, interstellar travel is not possible for us since our science is crap. We cannot even build a battery worth shit. Since zero point energy would be available anywhere in creation it makes sense to use it, no need for fuel stops anywhere. I did not even bring up the energy needs to maintain life support, an even bigger problem minus an inexaustable power source.

Any science capable of interstellar flight is going to include somthing like zero point energy as well as gravity neutralization, meaning the ship could just descend or hover or whatever. Just the sheer logic of my statements here negates the possibility of an antimatter explosion from an alien craft.

I tend to think something more along the lines of nature itself took place (some physical law or fact of nature as yet unknown to us?). Since we really do not know all about black holes (or even if they really exist?) there could be physical properties to say a mini black hole which would allow it to explode when striking the earth. Antimatter is quite simply impossible (as stated no radiation was around to give evidence either), the moment a chunk of it hit a few molecules several hundred miles up, sheer radiation pressure from the anhilating matter would vaporize the whole chunk hundreds of miles up, long before even the lower atmosphere was reached a huge explosion would have taken place leaving nothing to fall even as low as the bottom of the ionosphere. In short I vote for a quantum black hole explosion, either above ground or at impact (one coated with debris from interstellar flight which temporarily shielded it upon re-entry?).

Whether the mini hole was the engine core of a Romulan ship remains to be seen. As for me I love Star Trek but do not buy into it so I am for the physical reality explanation meaning some new to us quirk of nature was the cause.

lordmagnus - 15-6-2006 at 14:23

Oh yeah, I forgot about the quantum black hole theory of the tunguska blast. Quantum black holes (singulariies) held in a containment field would be a source of incredible power, as matter in anhilated near the event horizon, phenomenal ammounts of energy are released as x-rays and gamma ray emmisions. As for zero point energy, it is the ultimate power source that we can currently conceive of. A zero-point device would completely eliminate fission, fusion, antimatter power sources, in theory it would quickly eleminate all world wide energy problems, and pollution problems, every country would be free from the other as for energy needs. but with that much potential power some nut would probably try to use a zero point device to power a particle beam weapon, or the godz only know what else with it for relgiious or other terrorist agendas.

IrC - 15-6-2006 at 16:00

My first use of zero point energy would be a weapon no doubt. It is called survival. Everyone involved in the global energy market would be out to kill me and supress the invention if I invented a true free power source with endless potential. Therefore whoever does invent a working model is a fool if they do not first build an ultimate weapon before they tell anyone about the free energy.

lordmagnus - 15-6-2006 at 20:01

Good point, it's the ol' the best defense is an ultimate offense

12AX7 - 15-6-2006 at 20:03

So what happens when you fill all the zero points with energy?

lordmagnus - 15-6-2006 at 20:17

One of the many theories is that the Zero Point device will slowly reach a point at wich it just quits working, at this point the device can be scrapped for parts, and rebuilt anew. There are allot of ideas about zero point, the first original one is that a single 100 watt light buld has enough potential energy in the vacuum contained in it to boil off all the earths oceans. So far no one has figured aaway to tap this power, although there have been rumors of some very minor success with klein bottles, etc inside an ultravacuum, and so on, and so forth..

Odyssèus - 15-6-2006 at 21:12

I dont know much about zero point energy, but extracting useful work out of it looks to me like trying to run a heat engine without a cold sink.

You could say a block of ice has enough heat energy to boil off an amount of liquid water almost three times its mass... but how would you go about doing that?

Just my two cents. Dunno if comparing it to heat is accurate, though.

lordmagnus - 15-6-2006 at 21:21

Actually you can extract heat from near freezing water (HEAT PUMP based climate control), I know a guy who's mothers house sits on a parcelof land that has a very deep, ice cold water well on it, he uses a well pump to transfer the cold water up and into the house and through a heat exchanger, I don't grasp the whole concept, I need to study heat pump system design more, but in winter he can still get a certain ammount of heat out of the system to heat the house as well.

Odyssèus - 15-6-2006 at 21:40

A heat pump is sort of the opposite of a heat engine... one that takes mechanical energy and uses it to move heat from a cold sink to a hot sink, I think.

You might be able to move zero-point energy out of a vacuum using energy and create sort of a zero-point battery which does work by moving zero-point energy back in. Like the heat pump/engine it doesnt sound like you'll actually be able to extract energy from the zero-point energy itself.

But then, things are... funny at the quantum level, you never know.

woelen - 15-6-2006 at 22:48

Quote:

In short I vote for a quantum black hole explosion, either above ground or at impact (one coated with debris from interstellar flight which temporarily shielded it upon re-entry?).

Why in need of such a weird explanation. I just believe it was a ball of ice/stone, maybe remains of a small comet, which (almost) completely vaporized in the atmosphere, with a trememdous blast of energy quite close to the surface. This explains why there is no creater, while at the same time, a center of explosion can be derived (because of all these trees, bent in a radial way).

A black hole, interacting with earth, would leave more traces. In that case, there also would be a lot of radioactivity. Atoms are broken apart, when falling towards a black hole and a lot of radiation and all kinds of funny exotic particles would be spewn out, contaminating the area with all kinds of radioactive matter. There are no traces of such things.

neutrino - 16-6-2006 at 06:03

Someone a few posts up mentioned the object's shape from eyewitness accounts. I have to doubt these descriptions for two reasons.

First, an object entering the Earth's atmosphere usually comes in at such a high speed that it travels through the entire troposphere in a matter of seconds. That means that it would only be visible to someone not looking at it with a powerful telescope for only a tiny fraction of a second. How anyone could make out the shape of a small object in a few milliseconds I don't know.

Second, how could anyone have gotten close enough to this thing to see the object clearly and live to tell about it? Anyone close enough would probably have been killed instantly by the massive explosion.

My two cents.

vulture - 16-6-2006 at 13:01

Quote:

Second, how could anyone have gotten close enough to this thing to see the object clearly and live to tell about it? Anyone close enough would probably have been killed instantly by the massive explosion.

Exactly. The very few eyewitnesses, as it is an extremely remote area and we're talking 1908, were killed. Only earwitnesses were left. Ofcourse some of them were probably deaf afterwards

/pun

Antimatter/whatever would have left radiation traces and should have left clear evidence on the trees.

As for bizarre metal tools...Meteors are known to contain fair amounts of both Nickel and Iron. Metal getting vaporized instantly usually gives funny shapes after cooling.

lordmagnus - 16-6-2006 at 16:31

Humm,

Well, adn of the following would leave traces; ANTIMATTER, FUSION explosion, FISSION explosion, QUANTUM SINGULARITY, etc. They would all leave some forms of radioactivity, and evidence of atomic transmutation as well.

IrC - 17-6-2006 at 01:16

"So what happens when you fill all the zero points with energy?"

You get $200 for passing go.

I remember reading once that the normal traces of Ir and Ni among other elements was not there which suggested it was not rock. Woelen's ice ball is likely the culprit but the esoteric weird black hole/alien explanations are more interesting to talk about. Ice is boring.

vulture - 17-6-2006 at 13:32

Ice is not boring in interstellar space. I wonder how rapidly it sublimes in stellar vacuum.

franklyn - 12-7-2007 at 14:43

http://www.sciencemadness.org/talk/viewthread.php?tid=8741&a...

.

Waffles - 15-7-2007 at 13:07

From everything I've heard, the only two reasonable explanations for the Tunguska event are a small meteorite/large comet vaporizing or the small black hole theory. Given the huge explosion and shockwave, no trace of radioactivity, and no crater or ejecta whatsoever, these are the only non-conspiracy theory explanations.

Nerro - 15-7-2007 at 13:28

If a ball of matter completely evaporates in the earths atmosphere before it hits the ground it can cause a violent explosion. Probably violent enough to cause the trees to fall over. The greatest mistake a scientist can make is to look for explanations that are more complex than is required.

indigofuzzy - 15-7-2007 at 18:49

Shaving cometray ice with Occam's Razor? :cool:

Wasn't it Jesus fighting with Allah, Santa Claus stepped in apparently

Panache - 16-2-2008 at 00:05

Actually if i wrote Jesus was fucking Allah (or visa versa) that would offend more irrationals however as this is not my priority i retract it and apologise to everyone.
If you are offended by the Australian spelling of 'apologise' i aoplogise for this also.

Did you know Indigenous Australians only got the vote some 40 years ago, when did Native americans get the vote, for that matter African Americans. Australian women (not the indigenous ones) got the vote in 1907, why the fuck it took us another 60 years to figure out aborigines where just as important, relevant and the what who knows.

That Mr Stevens is getting to me again....
'..saturday night and I ain't got nobody..'
except i think Allah gave him a new name

Anyway thats my Dawkins-esc tirade over with and concerning the little event in Siberia 100 years ago. There will never be enough information to say definitively, never ever ever, but i think my Jesus explanation is more likely than an advanced races', anti-matter tank's fuel gauge being faulty.
Wow that last sentence was difficult to punctuate.
8)

Sauron - 16-2-2008 at 00:34

I firmy believe it was one of the Great Old Ones, perhaps Yog-Sothoth, or Azathoth, stopping by to see to his pet shoggoths.

A Cthulhu mythos explanation is as valid as any of the utter rubbish being kicked about in this thread.

From my perspective, this century old event has generated little in the way of scientific data and way too much in the way of Fortean bald bullshit, which for a hundred years has been embellished and embroidered by every crackpot psudoscience writer out there, and they are legion, until the seperation of fact from half-fact and outright fabrication is well nigh impossible. Even Chris Carter's writers at The X Files had a go at it.

Idle speculation about antimatter, FTL drives, UFOs, cosmic anomalies etc. may be amusing but they are generally meaningless exercises in futility. Engaging in such flights of fancy is not amateur science. This forum is about amateur science. Not flying saucers or close encounters. Go join area51.com or something.

[Edited on 16-2-2008 by Sauron]

microcosmicus - 16-2-2008 at 09:15

Wading through the nebula of deritus which has accreted upon the nucleus of this
thread, one gets to an original question which had scientific merit, namely how
far could a chunk of antimatter travel through interstellar space before being annihilated
by matter it met along the way. Time to do a back-of the-envelope estimate.

As our lump of antimatter, let's take an anti-meteor which consists of a mole of
anti-iron. Now, such an object weighs 56 grams and occupies a volume of 7 cc,
for simplicity, we may envision it as a cube 1.9 cm on each side. A cubic
centimeter of interstellar space will contain somewhere between 10^2 and 10^6
atoms of hydrogen, i.e between 1.7E-22 and 1.7E-18 moles. As a round average figure.
let us take something near the geometric mean, say 1E-20 moles.

Assume that each time our anti-meteorite encounters a hydrogen atom in it path,
the proton collides with a proton in an anti-Fe nucleus and that the energy liberated
wrecks that nucleus. (A reasonable assumption, because a(n anti-)proton weighs
a GeV, which is about twice the binding energy of an (anti-)Fe nucleus). Then we
can estimate that the distance which our anti-meteor travels before being
completely annihilated by the interstellar medium is such that the volume it
sweeps out is such as to contain a mole of the medium. Now, volume equals
base times height, so the ratio of the volume of the meteor to the volume it
sweeps is the ratio of the height of the meteor to the distance it travelled.
Thus, in order to run into a mole of interstellar medium it needs to travel
10^20 times its height, or 2E20 cm, which works out to around 2000 light-years.

not_important - 16-2-2008 at 10:51

Even though a proton/anti-proton annihilation releases enough energy to fully disrupt the nucleus, that doesn't make all that (anti) mass. You've eliminated one anti-proton, but most of the nucleus is still there. From what I've read the annihilation kicks out 3 or 4 pions carrying 145 MeV each, on the average. At least in the case of heavier nuclei, the nucleus remains mostly intact or fissions in the case of very heavy nuclei.

This means that a single collision is only going to reduce that mass by a (anti)proton mass, at least until most of the nuclei are reduced light ones. And even light ones that are buried deep enough would yield hydrogen or helium trapped in the lump.

So it would seem that you need to interact with closer to 50 grams of hydrogen/protons, pushing your range out to 100 K light-years or about the diameter of the galaxy.

len1 - 17-2-2008 at 02:36

Quote:

Originally posted by not_important
Even though a proton/anti-proton annihilation releases enough energy to fully disrupt the nucleus, that doesn't make all that (anti) mass. You've eliminated one anti-proton, but most of the nucleus is still there. From what I've read the annihilation kicks out 3 or 4 pions carrying 145 MeV each, on the average. At least in the case of heavier nuclei, the nucleus remains mostly intact or fissions in the case of very heavy nuclei.

This means that a single collision is only going to reduce that mass by a (anti)proton mass, at least until most of the nuclei are reduced light ones. And even light ones that are buried deep enough would yield hydrogen or helium trapped in the lump.

So it would seem that you need to interact with closer to 50 grams of hydrogen/protons, pushing your range out to 100 K light-years or about the diameter of the galaxy.

I would argue against this factor of 50 on the grounds that the cross section for ppbar scattering gives tiny penetration depths into the target. The energy release is nuclear decay is far in excess of the binding energy - thus the constant bombardment will make the outer surface of the meteorite peal much faster than even the first approx suggests by disrupting the binding forces. Also the 10^2 - 10^6 H2/cm^3 is much too high, 10^6 is about 10^-15 down on the suns density, we would have to be about 5 orbits of pluto out from the sun to recreate the suns mass - that would be a substantial correction to the orbit of pluto say. The figure for deep intestellar space is generally accepted at about 1 H2/cm^3

We also have baryon number conservation:

sum(antiprotons+antineutrons-protons-neutrons) = constant

That means unless the proton backward scatters out of the antimatter it must ultimately lead to the decay of at least one antimatter atom, it can not equilibrate using pions.

[Edited on 17-2-2008 by len1]

JohnWW - 17-2-2008 at 13:07

I understand that many small iron spherules, which must once have been molten then widely dispersed by an explosion above ground, have been found in and around the epicenter of the 1908 Siberian explosion. This would favor the meteorite theory, although what made it explode before hitting the ground (no crater was found, only large numbers of trees blown oveer and pointing away from the epicenter) is unclear. It may have been an unusual comet, consisting of a mixture of pieces of meteoritic iron (which also contains cobalt, nickel, and other heavy metals including platinum group metals), and volatile compounds which vaporized due to atmospheric friction, thereby providing the propellants needed for the explosion.

microcosmicus - 17-2-2008 at 17:02

What I did was simply a crude first estimate to get the ball out of the
gutter and rolling again so I am glad you fellows are pointing out the
weak spots and making improvements. For my data on density, I simply
did a quick UTFSE and went with the figures which showed up, so
no big surprise if they're off

Continuing in this direction, here are some
more remarks.

Let's remember that proton-antiproton annihiliation is a strong process
and that the strong force is also what keeps nuclei together, hence it
should be easy for the energy released to be absorbed into the nucleus.
Consider the situation in more detail. If the proton and antiproton
were colliding in a vacuum, the energy released would be carried
away as kinetic energy of the outgoing pions. However, since the
proton happens to be part of a nucleus, one can expect recoil. The
exact amount will depend on the kinematics, but I would expect this
to be on the order of MeV's. Given that the chemical bonds holding
the nucleus in place are on the order of eV's. I would expect that, even
if all that happens is that a single nucleon gets removed. the remaining
nucleus would be knocked right out of its place in the crystal lattice.
This would produce defects, weakening the meteor.

Furthermore, what about those pions? Since they are emitted inside
a nucleus, I expect that many of them would interact with nucleons.
inelastic scattering of 140 MeV pion with a nucleon would knock it
out of the nucleus. Elastic scattering could destroy another nucleon
and make more mesons. Thus, the damage to to collision with
the hydrogen atom should be more substantial than just removing
a single nucleon.

len1 - 17-2-2008 at 18:26

proton antiproton anihilation, as primarily an electromagnetic process, and not strong contrary to appearances. The primary vertex is

p pbar -> virtual photon -> anything

if the collision is of high enough energy to individuate the quarks its still an EM process

q qbar -> virtual photon

with spectator strong interactions. The interacting atom must change its identity leading to decay in almost all cases due to baryon number conservation

microcosmicus - 17-2-2008 at 19:35

I primarily had in mind the spectator processes which rearrange the remaining quarks in mind
when I used the term "strong". Your point is well-taken, the choice of wording was not good,
what I was primarily getting at was that the result of a proton reacting with an antinucleus
would involve significant, quite energetic, disruption which would break up the meteor faster than
if each collision with a proton simply remove a single nucleon and not do much else. The main
point here is that pions interact with nucleons (after all, one can explain nuclear binding in terms
of virtual pion exchange) so I wouldn't expect 145 MeV pions produced in a nucleus to simply
carry away energy like neutrinos or photons.

len1 - 17-2-2008 at 19:56

I agree, the meteor will disintegrate faster than single nucleon destruction, that was also my point.

regarding the pions, its unimportant because, as I keep saying, unless an antiparticle backscatters the total number of nucleons will decrease by 1. It follows almost 100% that an atomic decay must occur.

microcosmicus - 17-2-2008 at 21:47

I agree with what you say about the pions and baryon number. The only role in which I
consider the pions important is as a means of transferring the energy
coming from annihilation towards disintegrating the meteor.

So, back to the main question. If we use a density of 1 atom / cc for deep space, then
our meteor would need to travel 200000 ly to have encountered a mole of H2. While
this would mean that only 1/56 th of the baryons would have annihilated, the meteor
would be in bad shape, falling into pieces. Now, breaking an object into pieces increases
the surface area, hence the annihilation and disintegration goes faster. Moreover,
once the thing goes to pieces, the pieces are going to drift their separate ways so,
after another light-year, we are going to have a diffuse cloud of disintegrating
meteorites and gas instead of a meteor. Thus, I think it reasonable to conclude that an
antimatter meteor which made it to Earth would have originated within our Galaxy
or, at any rate, the local group of galaxies.

Leaving aside the aliens and conspiracies, the only origin I can think of for macroscopic
quantities of antimatter would have been back in the early history of the universe when charge
conjugation symmetry broke. Given what we said above, primordial
antimatter would have no chance of surviving for cosmological times
in a matter-dominated galaxy. I highly doubt that the Andromeda
galaxy or other neighboring galaxies are made of antimatter either
or that dark matter and halos inbetween them are actually dark
antimatter (how would it stay dark?) so that pretty much rules out
possible places of origins, so I agree with xxxxx that an antimatter
meteor making it to Earth sounds implausible.

[Edited on 18-2-2008 by microcosmicus]

chemoleo - 18-2-2008 at 18:03

Just wondered - as antimatter-matter annihilations are extremely energetic, shouldn't this leave a noticeable identifiable residue in the cosmic background radiation, even though it is red-shifted due to the universe expansion? I assume these annihilations occurred mainly during the early times of the universe. Therefore, any annihilations in recent universe history, particularly in our galaxy, should be quite noticeable, right?

On the matter of meteorite impact at the 1918 tunguska explosion - I seem to have read very recently that apparently asteroids much smaller than anticipated previously should also be capable of causing the devastation seen.
Plus, I think they have found a lake in the area which is roughly elliptical, and shows a bottom profile that would resemble a meteorite/asteroid impact.
If you want I can dig the info out.

len1 - 18-2-2008 at 22:50

That is indeed so. All sorts of energetic processes contrinuted to the energy we see now as the microwave background. Less than a microsecond after the universe formed we had a quark gluon plasma, mean kinetic energy exceeded the binding energy in nuclei - matter-antimatter annihilation was just part of all proceses contributing to interactions at that stage. As the universe cooled the quarks combined into nuclei and we had a nucleon - electron - photon plasma - some residual smoothing out of matter-antimatter fluctuations continued here. Later as the mean thermal energy dropped below the ionisation energy of atoms the photons decoupled from matter and parted company, but there was plenty of time for the firball to equilibrate, that is why the micerowave background is (too) uniform

[Edited on 19-2-2008 by len1]

microcosmicus - 18-2-2008 at 23:32

Quote:

Just wondered - as antimatter-matter annihilations are extremely energetic, shouldn't this leave a noticeable identifiable residue in the cosmic background radiation, even though it is red-shifted due to the universe expansion?

The microwave background is what is left of the photon gas pretty much as it was when atoms formed.
At that time, the density of the radiation outweighed that of the matter (hence "radiation dominated
era") so the effect of annihilations would not be quite as drastic as today in the sense that
turning matter and anti-matter into radiation would increase the energy density locally by a
moderate factor. Offhand, I wouldn't remember exactly what the ratio of matter (and antimatter) energy
density to radiation energy density was at the time of decoupling and it is too late to look that up
now so I will have to come up with the numerical value of that factor later. Morever, to some
extent the inhomogeneity would have diffused out. Depending on the values, the effect may
or may not turn out to be all that noticable.

Quote:

Therefore, any annihilations in recent universe history, particularly in our galaxy, should be quite noticeable, right?

This was something I thought about as I imagined what a meteor gradually disintegrating from
colliding with interstellar medium would do. One tell-tale sign would be 511 MeV photons
coming from e+ e- annihilation. As for the hadrons, initially they make pions but these
decay; at the end of the day, one is left with more photons, neutrinos, electrons, and positrons.
The positrons will annihilate electrons from hydrogen atoms; between the widowed H+'s and
the e-'s from the decay, one would have a "smoke trail" of ionized interstellar medium.

Of course, a direct collision between an astronomical object made of antimatter with one
made of matter would be a much more dramatic event.

Quote:

Plus, I think they have found a lake in the area which is roughly elliptical, and shows a bottom profile
that would resemble a meteorite/asteroid impact. If you want I can dig the info out.

If it's not too much trouble, post some of that information or a reference. Then maybe we
can dump some of the deritus about aliens and X-files in the bottom of the lake and move
on

At any rate, speculating about the fate of a lump of antimatter has certainly been
a fun excursion into astronomy and particle physics.

len1 - 18-2-2008 at 23:46

The temperature at which the photons decoupled from matter was of the order of the ionisation energy, 10000K, this is much less than the proton annihilation energy, several GeV, hence matter-antimatter annihilation was very significant and rare at that stage

tumadre - 19-2-2008 at 11:35

http://www.space.com/scienceastronomy/070626_st_tunguska_cra...

The first expedition did not occur until 1926, giving plenty of time for this lake Cheko to be filled with water and overlooked.

Arguments against this lake as the impact site include the 1961 expedition which found "meters thick silt" and concluded that the lake was 5000 years old. It is also 8 kilometers north-north west of the supposed center.

chemoleo - 19-2-2008 at 14:54

There's also more info, pics here (but article is in German which you can translate with babelfish)
http://www.spiegel.de/wissenschaft/natur/0,1518,490518,00.ht...

Cant find the article on the higher than anticipated impact of small asteroids, but it has been all over the news.

len1 - 7-3-2008 at 06:53

Quote:

Originally posted by chemoleo
Just wondered - as antimatter-matter annihilations are extremely energetic, shouldn't this leave a noticeable identifiable residue in the cosmic background radiation, even though it is red-shifted due to the universe expansion? I assume these annihilations occurred mainly during the early times of the universe. Therefore, any annihilations in recent universe history, particularly in our galaxy, should be quite noticeable, right?

While the Siberian explosion is reasonably understadable and so not so interesting, the above quote has more to be said, in a way that can be understood by people here, and hopefully give the a useful insight.

As I said before matter-antimatter annihilation was much more common in the early universe. Now that it has cooled it can not be frequent as else it would severly distort the mwave background to which chemoleo refers. Indeed it places a limit on the inhomogeneity of matter/antimatter regions - they must be separated by at least 3-10kpc - the radius of the milky way.

The ratio

number barions + antibarions in universe now
/
number barions + antibarions in universe at big bang

gives the effectiveness to which mass has annihilated.

This equals roughly

number barions + antibarions now / number photons now.

Number photons we know from Stefans Law - for 2.7K mwave background it is 410 cm-3. Number barions we know from Hubbles expansion - how fast galaxies are receeding from us. When this is measured it directly determines R(t) in the simplest metric

ds^2 = dt^2 - R^2(t) dr^2

when this metric is put into Einsteins equations, whose essence is to relate metric to particle density, we get the matter density - 10^-7 cm-3.

So the ratio of baryons to photons is about 10^-10 which is much larger than simple cosmological models can explain. One of the problems in cosmology.

[Edited on 8-3-2008 by len1]

pyrochemix - 19-3-2008 at 11:11

nuclear explosion releases bout .7% of the nucleo-chemical energy stored in an atom through fission, when antimatter and matter collide they release 100%, therefore (bomb dropped on hiroshima was about a square foot or so i think of uranium) therefore the same amount of antimatter would have destroyed the lower center part of russia.

A small sample

franklyn - 15-2-2013 at 08:25

www.reuters.com/article/2013/02/15/us-russia-meteorite-idUSB...

Approach => www.youtube.com/watch?v=90Omh7_I8vI

Shockwave => www.youtube.com/watch?v=Np_mpGYSBSA

.

bfesser - 15-2-2013 at 08:27

Beat you to it.

<a href="viewthread.php?tid=23380">New Thread</a>

Traveller - 15-2-2013 at 12:16

I thought they were only called meteorites after they landed .

IrC - 15-2-2013 at 17:26

Stop it. You are using Occam's razor to ruin perfectly good conspiracy theories.

zenosx - 18-2-2013 at 18:24

Quote: Originally posted by neutrino

Someone a few posts up mentioned the object's shape from eyewitness accounts. I have to doubt these descriptions for two reasons.

First, an object entering the Earth's atmosphere usually comes in at such a high speed that it travels through the entire troposphere in a matter of seconds. That means that it would only be visible to someone not looking at it with a powerful telescope for only a tiny fraction of a second. How anyone could make out the shape of a small object in a few milliseconds I don't know.

Second, how could anyone have gotten close enough to this thing to see the object clearly and live to tell about it? Anyone close enough would probably have been killed instantly by the massive explosion.

My two cents.

I have to disagree with this statement based on personal experience.

It's been a few years ago, but I personally witnessed a meteor streak across the sky to eventually impact with a VERY large flash bright enough to make midnight look like noon for about a second. Like a lightning flash.

The meteor itself was very visible and at least towards the surface, while travelling very fast, was still visible.

Where I do agree however is that this item, and others look like long tubes from the ionized gas flowing behind the object from friction. Even a spherical object will look long and tube-like in this regard. They could not have seen the actual object because of this gas/fire, only the bright blaze.

I am not sure about the exact specifics, but at least as far as smaller meteors go (like this one), the atmosphere creates enough resistance to reduce the object to terminal or slightly over velocity. Only meteors of very large size (I know more than 10 mi. width count here) have absolutely NO interaction with the atmosphere for all intents and purposes and smacks the planet as if there was no atmosphere.

They hypothesize this type of impact was what wiped out the dinosaurs (perhaps with century long volcanic eruptions in the Asia sector), and it hit around the ocean/Columbia interface if I remember correctly. Sorry off topic a bit there.

franklyn - 27-3-2013 at 09:18

Story of the meteor on the Public Broadcasting Service PBS program NOVA
www.pbs.org/wgbh/nova/earth/meteor-strike.html

Tonight at 9:00 pm eastern time - check local area listings - www.pbs.org/wgbh/nova/airdates.html

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IrC - 27-3-2013 at 10:04

After years of wondering about this topic I think the idea of a comet (one not too large or too small) exploding above the ground makes the most sense. Big bang plus shock wave, but not too many rocks (or rock dust) as evidence. Some, but not as much material as an asteroid that large would leave.