[meteorite-list] Geometry and velocity trump gravity

[Rob Matson via Meteorite-list]

Hi E.P.,

Doug's reply pretty much covers it, but I wanted to give you an example so
that you can see how your intuition is failing you on this problem. Let's take
the case of a slower-than-average asteroid closing velocity encounter of
20 km/sec. And let's say that in the absence of any gravitational attraction
from the earth or the Moon, the asteroid would come no closer than the
altitude of geosynchronous satellites -- 35786 km. (This is a rather close
encounter, I'm sure you'd agree. Any trajectory with a more distant
point of closest approach would obviously experience less trajectory
bending than this case.) If we "turn on" earth's gravity, how much will
the trajectory be diverted toward the earth's center? Without getting into
the calculus of actually solving the problem, let's make some simplifying
assumptions that are very ~generous~ in the amount of gravitational
acceleration we're going to apply.

The acceleration due to gravity at the height of geosync satellites is
around 0.224 m/sec^2. Let's assume that that amount of acceleration is
applied during the entire encounter, and that it is always directed
perpendicular to the asteroid's original velocity vector. Define the start
of the encounter as being when the earth is 45 degrees to the left
of the velocity vector (at range 59629 km -- the square root of 2 times
the distance to the earth's center). The midpoint is when the earth
is 90 degrees to the left of the velocity vector (point of minimum
range to the earth center), and the end is when the earth is 135 degrees
to the left of the velocity vector. To first order, the distance travelled
is 2*42164 km = 84328 km. How long would it take in the absence of
gravity?  84328 km / (20 km/sec) = 4216 seconds -- a little over 70 minutes.
Recall your basic distance equation under constant acceleration:
X = 1/2 * A * T^2. Here we've generously allowed A to be 0.224 m/sec^2
for the entire encounter (when in fact A at the start is only half that).
What does X work out to?

X = 0.5 * 0.224 * (4216)^2 = 1.99 million meters or 1990 km.

Compare that to the 35768 km altitude of the GEO belt, and you see
that the amount of diversion is rather small. So the take-away from
all this is that the outcome is dominated by simple geometry. Yes,
very close encounters with the earth will bend a trajectory -- perhaps
quite significantly, but post-encounter the new trajectory is just as
likely to be diverted toward the Moon as away from it.  --Rob

-Original Message-
From: Meteorite-list [mailto:meteorite-list-boun...@meteoritecentral.com] On
Behalf Of E.P. Grondine via Meteorite-list
Sent: Sunday, June 26, 2016 9:11 AM
To: meteorite-list@meteoritecentral.com
Subject: [meteorite-list] What killed off megafauna?

Hi Rob, Doug - 

(Glad to hear that you're doing okay, Doug)  

What both of you need to do is to take the perspective of a potential impactor
passing through the inner solar system,
as seen in the first few seconds of this video:
https://www.youtube.com/watch?v=GDrBIKOR01c

The basic geometry of the problem is set out here:
https://www.youtube.com/watch?v=qTDcfI2dabk

If it makes it easier,
think of the Earth-Moon system as a pair of girls at a darkly lit party, 
and yourself as a young man.
(A variant of the famous mathematical problem of the drunk's walk at the frat
party.)
While you may be attracted to the "prettier" (in terms of gravity/area) Moon,
you are far more likely to run into her much larger "wingman", the Earth.
Sorry, but that is just the way it is.

At first, you're getting a warm fuzzy feeling (gravity) from the combined
Earth/Moon system.
That warm fuzzy feeling varies by the cubes of the radius of each of the two
bodies, 
and is located somewhere amongst them.

On your approach to the Earth/Moon system, you see your landing area (for only
part of the month, see second video) 
in terms of area, which varies by the square of the radius. 
But of course gravity also varies by distance, 
so as you get close to theses two 
you're getting far more of that warm fuzzy feeling from the Earth,rather than
the Moon. 
You head that way. 

You can use any computer language you prefer to model this system, 
and run it on any machine you like.
But as a check on your computer model, you have to rely on the data.
In this case, compare the data on smaller impactors from the Moon, 
(Apollo seismic and optical astronomy)
with the data from the reconnaissance systems which have been operating 
on the Earth since the 1950's, 
and "alarming" the "stuff" out of those looking at the data from them.

If there is a difference between your model's results and the data, then your
model is defective.
 
(An entertaining video on phonetic loading,
the diameters of lunar craters,
typing monkeys, and other natural phenomena:
https://www.youtube.com/watch?v=fCn8zs912OE)

good hunting, 
E.P.

PS - Will NEOcam make meteorite hunting far easier?
Will the increased supply drive down prices even further? 

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[Rob Wesel via Meteorite-list]

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www.facebook.com/Nakhla.Dog.Meteorites
www.facebook.com/Rob.Wesel

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Re: [meteorite-list] What killed off megafauna?

[MexicoDoug via Meteorite-list]

Hi Ed and thanks for spirited discussion,

I already covered most of what's wrong with your caricature of the Earth-Moon 
system when I discussed cosmic velocities in my original post.  In science 
terms, the kinetic energy swamps the Earth's gravitational potential you are 
relying upon to protect the Moon from impact.

Unfortunately the media continue to characterize the Earth and Moon as if they 
were these massive objects a whisper apart.  It is as bad a caricature as it 
gets.  Your first link to the Cassini image is confusing you and not 
representative of the relatives sizes and distances of Earth's and the Moon's 
disks.  You are looking a images of light closer to the limit of the resolution 
from Saturn, which for all I know as well were taken at that precise moment to 
capture a Moonrise ... when the moon emerges from being eclipsed, an aesthetic 
planetary imaging target.  You are then saying this is what at impactor sees.  
Saturn is around a billion miles away!  That I assure you is not what an 
impactor sees!

Your second video is a joke.  Here is the video I ask you watch in reply to 
your bad geometry/astronomy lessons. as it pertains to impact shielding, and to 
give you a better visualization of how big space is and how insignificant our 
little planet is, even in the scheme of the Moon.  Try to imagine how few 
objects approach the Moon after grazing Earth, or how few would reach it if not 
impacting Earth:

https://www.youtube.com/watch?v=Bz9D6xba9Og

As far as adjusting our models, lol, that would be Newton's department, not 
mine, though Rob might enjoy tweaking Newton ;-).  The apple reputedly impacted 
his head and was not sucked into the trunk of the of the massive apple tree 
that had him daydreaming.  Had it been otherwise, Newton's law of gravity might 
have been different and the gravitational constant might have allowed the Earth 
to protect the Moon from impacts with some practical significance.  You do not 
provide a reference for your claim about significant impact protection of the 
Moon by Earth I won't reply on that one.  It requires digging through your 
notions of why Rob and I may have defective understandings.   There may be some 
interesting discussion there as to your notions and interpretations, but the 
other references you gave don't convince me to be a grunt at the moment ;-)

Back to the concept of cosmic velocity (and the related law of conservation of 
momentum).  If you take Newton's law of gravity between Earth and a would-be 
impactor coming in, and set it equal to the kinetic energy at the top of 
Earth's atmosphere it would need to be captured, you will see that the velocity 
relative to Earth must be less than 11.1 km/sec.  That is an awfully slow 
moving rock.  That speed is known as an escape velocity.  Notice I said at the 
top of our atmosphere (100 km high).  The speed drops off.  Geosynchronous 
satellites have an escape velocity of just 4.3 km/sec.  Cosmic velocities can 
well over 10 times that.  The orbits can be bent, but unless they are on a very 
precise path to impact long before entering the Earth Moon system, they simply 
would fly right on by if they are moving faster than this velocity but not 
already headed for impact. As a matter of fact, beyond a geosynchronous orbit, 
I believe the Sun's gravitational pull is greater than Earth's.  That'
 s a cool fact to know, considering Earth and the Moon are still pockmarked 
regularly.

This is the hard part of space exploration.  Impact or orbital insertion can be 
much more precision maneuvers than uncontrolled flybys.  If you think 
differently, I recommend taking up golf, maybe putting is easier than they say!

Kindest wishes
Doug



-Original Message-
From: E.P. Grondine via Meteorite-list 
To: meteorite-list 
Sent: Sun, Jun 26, 2016 12:11 pm
Subject: [meteorite-list] What killed off megafauna?

Hi Rob, Doug - 

(Glad to hear that you're doing okay, Doug)  

What both of you need to do is to take the perspective of a potential impactor 
passing through the inner solar system,
as seen in the first few seconds of this video:
https://www.youtube.com/watch?v=GDrBIKOR01c

The basic geometry of the problem is set out here:
https://www.youtube.com/watch?v=qTDcfI2dabk

If it makes it easier,
think of the Earth-Moon system as a pair of girls at a darkly lit party, 
and yourself as a young man.
(A variant of the famous mathematical problem of the drunk's walk at the frat 
party.)
While you may be attracted to the "prettier" (in terms of gravity/area) Moon,
you are far more likely to run into her much larger "wingman", the Earth.
Sorry, but that is just the way it is.

At first, you're getting a warm fuzzy feeling (gravity) from the combined 
Earth/Moon system.
That warm fuzzy feeling varies by the cubes of the radius of each of the two 
bodies, 
and is located somewhere amongst them.

On your approach to the 

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[Peter Marmet via Meteorite-list]

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Thank you,
Peter

Peter Marmet - IMCA #2747
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http://www.marmet-meteorites.com
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[meteorite-list] What killed off megafauna?

[E.P. Grondine via Meteorite-list]

Hi Rob, Doug - 

(Glad to hear that you're doing okay, Doug)  

What both of you need to do is to take the perspective of a potential impactor 
passing through the inner solar system,
as seen in the first few seconds of this video:
https://www.youtube.com/watch?v=GDrBIKOR01c

The basic geometry of the problem is set out here:
https://www.youtube.com/watch?v=qTDcfI2dabk

If it makes it easier,
think of the Earth-Moon system as a pair of girls at a darkly lit party, 
and yourself as a young man.
(A variant of the famous mathematical problem of the drunk's walk at the frat 
party.)
While you may be attracted to the "prettier" (in terms of gravity/area) Moon,
you are far more likely to run into her much larger "wingman", the Earth.
Sorry, but that is just the way it is.

At first, you're getting a warm fuzzy feeling (gravity) from the combined 
Earth/Moon system.
That warm fuzzy feeling varies by the cubes of the radius of each of the two 
bodies, 
and is located somewhere amongst them.

On your approach to the Earth/Moon system, you see your landing area (for only 
part of the month, see second video) 
in terms of area, which varies by the square of the radius. 
But of course gravity also varies by distance, 
so as you get close to theses two 
you're getting far more of that warm fuzzy feeling from the Earth,rather than 
the Moon. 
You head that way. 

You can use any computer language you prefer to model this system, 
and run it on any machine you like.
But as a check on your computer model, you have to rely on the data.
In this case, compare the data on smaller impactors from the Moon, 
(Apollo seismic and optical astronomy)
with the data from the reconnaissance systems which have been operating 
on the Earth since the 1950's, 
and "alarming" the "stuff" out of those looking at the data from them.

If there is a difference between your model's results and the data, then your 
model is defective.
 
(An entertaining video on phonetic loading,
the diameters of lunar craters,
typing monkeys, and other natural phenomena:
https://www.youtube.com/watch?v=fCn8zs912OE)

good hunting, 
E.P.

PS - Will NEOcam make meteorite hunting far easier?
Will the increased supply drive down prices even further? 

__

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Re: [meteorite-list] Block this eBay bidder

[Ruben Garcia via Meteorite-list]

It's because he immediately changed his user I.D. to light887  -
probably because I turned him in -
but it was edupert last night


so block eBay user light887 now!

On Sun, Jun 26, 2016 at 8:11 AM, Daniel Noyes via Meteorite-list
 wrote:
> Hello Ruben,
>
> eBay said that is not a valid id (edupert) when I tried adding it to my
> blocked bidder list...?
>
> Best,
> Daniel
>
> Daniel Noyes
> Genuine Moon & Mars Meteorite Rocks
> i...@moonmarsrocks.com
> www.moonmarsrocks.com
>
>
>
>  Original Message 
>
>
> --
>
> Message: 5
> Date: Sat, 25 Jun 2016 19:10:30 -0700
> From: Ruben Garcia 
> To: "Meteorite-list@meteoritecentral.com"
>  
> Subject: [meteorite-list] Block this eBay bidder
> Message-ID:
>  
> Content-Type: text/plain; charset=UTF-8
>
> Block eBay bidder edupert - Trust me, you'll be glad you did!
>
>
>
>
>
>
> Rock On!
>
> Ruben Garcia
> http://www.MrMeteorite.com
>
>
> --
>
> Subject: Digest Footer
>
> ___
> Visit our Facebook page:
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-- 
Rock On!

Ruben Garcia
http://www.MrMeteorite.com
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Re: [meteorite-list] Block this eBay bidder

[Daniel Noyes via Meteorite-list]

Hello Ruben,

eBay said that is not a valid id (edupert) when I tried adding it to my
blocked bidder list...?

Best,
Daniel

Daniel Noyes
Genuine Moon & Mars Meteorite Rocks
i...@moonmarsrocks.com
www.moonmarsrocks.com



 Original Message 


--

Message: 5
Date: Sat, 25 Jun 2016 19:10:30 -0700
From: Ruben Garcia 
To: "Meteorite-list@meteoritecentral.com"
 
Subject: [meteorite-list] Block this eBay bidder
Message-ID:
 
Content-Type: text/plain; charset=UTF-8

Block eBay bidder edupert - Trust me, you'll be glad you did!






Rock On!

Ruben Garcia
http://www.MrMeteorite.com


--

Subject: Digest Footer

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Re: [meteorite-list] Block this eBay bidder

[Tommy via Meteorite-list]

He's got nothing for sale it seems.


Tom



On 06/26/2016 10:12 AM, Ruben Garcia via Meteorite-list wrote:

I received many emails saying this user I.D is invalid.

It's because he immediately changed his user I.D. to light887  -
probably because I turned him in -
but it was edupert last night

so block eBay user light887 now!

On Sat, Jun 25, 2016 at 7:10 PM, Ruben Garcia
 wrote:

Block eBay bidder edupert  -   Trust me, you'll be glad you did!






Rock On!

Ruben Garcia
http://www.MrMeteorite.com





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Re: [meteorite-list] Block this eBay bidder

[Ruben Garcia via Meteorite-list]

I received many emails saying this user I.D is invalid.

It's because he immediately changed his user I.D. to light887  -
probably because I turned him in -
but it was edupert last night

so block eBay user light887 now!

On Sat, Jun 25, 2016 at 7:10 PM, Ruben Garcia
 wrote:
> Block eBay bidder edupert  -   Trust me, you'll be glad you did!
>
>
>
>
>
>
> Rock On!
>
> Ruben Garcia
> http://www.MrMeteorite.com



-- 
Rock On!

Ruben Garcia
http://www.MrMeteorite.com
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[meteorite-list] Meteorite Picture of the Day

[Paul Swartz via Meteorite-list]

Today's Meteorite Picture of the Day: Laguna Manantiales

Contributed by: Paul Swartz

http://www.tucsonmeteorites.com/mpodmain.asp?DD=06/26/2016
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