

900 foot-wide asteroid to make close approach to Earth today - drucken
http://www.independent.ie/world-news/900-footwide-asteroid-to-make-close-approach-to-earth-tomorrow-scientists-3347065.html

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brianchu
Let's be clear, the probability of Apophis colliding with the Earth in the
next 100 years is extremely small: 7.4e-06 [1]. And even then it wouldn't be
an extinction event. To me this is a non-issue - the odds of a massive
pandemic or nuclear war with greater destructive potential in the next 100
years are arguably higher.

There _is_ some level of uncertainty with the estimates because the asteroid's
orbit will change in 2029. But even if the estimates are off by a couple
orders of magnitude in the worst case, we are still looking at a very small
probability.

[1] <http://neo.jpl.nasa.gov/risk/a99942.html>

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robryan
With asteroid close approaches I find it helpful to compare it to the earth to
moon distance. In this case 9 million miles seems to be 37 times the earth to
moon distance.

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yread
The 2029 event should be pretty cool to see (literally, magnitude 3.4 which is
visible(sort-of) for a naked eye) if it really comes as close as 30 000 km.
Geostationary satellites are 36 000 km...

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pkorzeniewski
News like this always reminds me how vulnerable our small planet is and
despite all the technological development, we can be wiped out from the
universe in a second and there is little we can do about it.

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laumars
the terrifying thing is how hard they are to detect (basically spotting a
black speck against the black of space).

But at least, if detected early enough, an asteroids path can be changed. If a
star goes supernova within a few million light years of Earth, we'd all be
fried.

Despite how mind boggling big space is, world extinction events are worryingly
easy.

/me is pretty sure he'll have nightmares tonight...

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CapitalistCartr
"If a star goes supernova within a few million light years of Earth, we'd all
be fried." Within a few light years, perhaps. The entire Milky Way galaxy is
only a little over 100,000 light years across. A few million light years would
be outside of the Local Group.

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laumars
A few million light years could still be within our local group (depending on
the exact value of "a few"), but you're right about my error. I'm not really
sure where I pulled that epic brain-fart of a figure from...

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typpo
Apophis isn't getting closer than 9 million miles today. If you're interested
in close passes, you may look forward to February 15th, when 2012 DA14 will
pass only about 21,000 miles away, within the orbits of the moon and
geosynchronous satellites. [1]

[1] [http://earthsky.org/space/asteroid-2012-da14-will-pass-
very-...](http://earthsky.org/space/asteroid-2012-da14-will-pass-very-close-
to-earth-in-2013)

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darkarmani
What are the chances of it wiping out our (artificial) satellites in 2029?
It's pretty crowded up there, right?

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Tuna-Fish
If your definition for crowded is "mean distances between satellites is more
than 1000km."

Space is big. The geostationary orbit has a diameter of 265000km, and there
are something like 200 satellites up there.

The lower orbits have a lot of gunk on them, but this asteroid will only cross
the geostationary orbit. It's pretty damn unlikely it will hit anything.

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mdc
I think you mean the circumference of geostationary orbit is 265000km.
Diameter is about 36000km.

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paigalhaes
just to help getting the scale in meters... 900 foot = 274.32 meters

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phragg
Redirect it using electromagnetism?

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laumars
The current preferred method is essentially firing painballs at one side of
the asteroid.

[http://web.mit.edu/newsoffice/2012/deflecting-an-asteroid-
wi...](http://web.mit.edu/newsoffice/2012/deflecting-an-asteroid-with-
paintballs-1026.html)

~~~
phragg
Hmm very interesting. So this would make it much more reflective, causing suns
photons to bounce off and push it off orbit.

In order to further understand this, and forgive me here if it sounds strange,
would a flat black car essentially be 'faster' than a gloss white car due to
lack of reflection?

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sp332
Photon radiation pressure is almost immeasurably tiny. It takes years to make
a smallish deflection, and that's exposed to hard radiation.

A larger, related effect is visible with this desk toy:
<https://en.wikipedia.org/wiki/Crookes_radiometer>

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rikacomet
hmm, what if it doesn't hit earth, and hits venus, to which it is also on a
collision course, and sets off a chain of events that unbalance our SS.

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dangerlibrary
It would just bump Venus's orbit a bit - probably not even enough to notice. A
single asteroid doesn't have the potential energy to destabilize a planetary
orbit.

see: the pockmarked surface of the moon, which still has a stable orbit.

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rikacomet
but what if it sets of some sort of chemical reaction, Venus does not have a
atmosphere like earth, so he asteroid would hit its bare face, perhaps setting
off some sort of volcanic reaction? Just saying, as I don't want us to be on
the blind side of the fence.

Clearly, the whole system is our domain, and we should be know events like
this are not to be ignored, as they are way bigger than your average
metropolitan housing millions of you and me.

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rmc
Venus does have an athmosphere, it's just not made of the same gasses as the
Earth's athmosphere. There is no "bare face".

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rikacomet
thanks a lot, I got to know about slooh from this!

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darkhorn
Foot? Doesn't make any sense.

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maeon3
<http://en.wikipedia.org/wiki/99942_Apophis>

It's Level 1 on the Torino impact hazard scale.

The close approach in 2029 will substantially alter the object's orbit, making
predictions uncertain without more data.

If it hits Earth, then it's 500 megatons of TNT going off.

If it passes through a half mile "keyhole" which is unlikely, it will hit
Earth in 2036.

Apophis broke the record for the highest level on the Torino Scale, being, for
only a short time, a level 4, before it was lowered.

So worst case scenario: it hits the half mile keyhole and in 2036 the
equivalent of a nuclear weapon (10 tsar bomba's at once) goes off on a certain
city. But there is a plot twist. There will be weeks of warning, and the risk
area where it will hit will be narrowed to the size of half the earth, or if
we use the science, maybe a whole continent.

So it'll be like a hurricane evacuation, but instead of one state, it will be
quarter of the earth's surface. Imagine the logistical nightmare if that
happened near India/china. The prospect of relocating 5 billion people within
2 weeks notice with all of their junk and to do it sustainably? Plot for a
cool sci fi movie there.

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wyuenho
I wonder what kind of weaponry and energy is required to push it away from
Earth's orbit or just simply shatter it into much smaller piece so they'll
burn up in the atmosphere.

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xhrpost
If asteroid mining becomes a reality, I wonder if we could simply mine the
thing down to nothing before impact.

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pavel_lishin
Sure, but when you mine stuff, where does the stuff go?

Instead of deflecting the whole asteroid, you're suggesting chipping it into a
bunch of pieces and deflecting those somewhere. Same problem.

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will_work4tears
We'd bring what we mined to earth or the moon, wherever the processing plants
are. Mine != blow up and leave alone.

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dredmorbius
Changing the orbit of an asteroid is a function of its mass and orbit (net
momentum).

De-aggregating the asteroid via mining does nothing to the net momentum of the
asteroid. It would take just as much energy to re-orbit 1000 or 1,000,000
chunks of an asteroid as it would to re-orbit one. The energy transferred by
multiple chunks of asteroid to the Earth is the same whether it arrives in one
chunk or thousands.

The only thing that would possibly make sense would be to drive two parts of
the asteroid in different orbits. The net momentum hasn't changed, but the two
pieces would split the difference and pass to either side of earth, possibly
missing crucial "keyhole" orbits which would dictate a subsequent impact,
though you could likely accomplish the same thing by exerting a small thrust
against the entire mass over a long time.

Mining doesn't change the fundamental orbital mechanics or energy costs.

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xhrpost
Very valid point. However, wouldn't this be true for all asteroid mining?
Meaning if mining becomes a reality, it's something that will have to be
accounted for. I'm guessing though that even by 2036 we won't be mining
asteroids this big .

