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CA Distance Nominal (LD | au) The most likely (Nominal) close-approach distance (Earth center to NEO center), in LD (Lunar Distance) and au. CA Distance Minimum (LD | au)
The minimum possible close-approach distance (Earth center to NEO center), in LD (Lunar Distance) and au. The minimum possible distance is based on the 3-sigma Earth target-plane error ellipse.
originally posted by: EmmanuelGoldstein
It's a good thing we live under a protective dome then
originally posted by: dragonridr
a reply to: MissSmartypants
Those readings are based off AU. An astronomical unit is the distance between the earth and the sun. Not the earth and the moon. Re do your calculations based off 93 million miles or 150 million kilometers. It will miss us with room to spare.
Did the math the moon is 0.002566882112227 AU from earth. So these won even get close.
You can "if" all you want but a lunar distance is measured just the way I said.
originally posted by: Vroomfondel
a reply to: MissSmartypants
Very interesting, however, I respectfully question the validity of the research.
As you stated, one LD is the distance from the center of Earth to the center of the Moon. Subtracting the radii of these bodies accomplishes nothing other than providing a distance from two points tangent to the surfaces of the bodies. This information is meaningless unless the impact is measured in LD from the surface - not the center.
If the impact area is measured in LD from the center of Earth then the point of impact is 2386.06 miles from center Earth, or, a point on a line tangent to a plane 1573 miles below the surface of the Earth at the deepest point on that plane. Subtracting the radii of the Earth and the Moon, 3959 and 1079 respectively, from that figure creates a miss by 2652 miles or .011145 LD.
Standard units of measurement have set dimensions. Perhaps there is a scientific term for the distance from the SURFACE of the earth to the SURFACE of the moon but that scientific term is not Lunar Distance ....because, a Lunar Distance is the distance from the CENTER of the earth to the CENTER of the moon. Look it up.
originally posted by: roadgravel
Wouldn't it be 3959 - 2386 = 1573
Could they have already made allowance for the Earth diameter in the approach distance?
originally posted by: MissSmartypants
You can "if" all you want but a lunar distance is measured just the way I said.
originally posted by: Vroomfondel
a reply to: MissSmartypants
Very interesting, however, I respectfully question the validity of the research.
As you stated, one LD is the distance from the center of Earth to the center of the Moon. Subtracting the radii of these bodies accomplishes nothing other than providing a distance from two points tangent to the surfaces of the bodies. This information is meaningless unless the impact is measured in LD from the surface - not the center.
If the impact area is measured in LD from the center of Earth then the point of impact is 2386.06 miles from center Earth, or, a point on a line tangent to a plane 1573 miles below the surface of the Earth at the deepest point on that plane. Subtracting the radii of the Earth and the Moon, 3959 and 1079 respectively, from that figure creates a miss by 2652 miles or .011145 LD.
Did you just sick Phage on me? If I weren't right I'd be intimidated right now. Phage is my hero.
originally posted by: Trueman
a reply to: MissSmartypants
I'll go bed now. When I wake up I want to see Phage debunking you.
originally posted by: MissSmartypants
Standard units of measurement have set dimensions. Perhaps there is a scientific term for the distance from the SURFACE of the earth to the SURFACE of the moon but that scientific term is not Lunar Distance ....because, a Lunar Distance is the distance from the CENTER of the earth to the CENTER of the moon. Look it up.
originally posted by: roadgravel
Wouldn't it be 3959 - 2386 = 1573
Could they have already made allowance for the Earth diameter in the approach distance?
Sigh...1)Of course not a threat to earth. Even the massive meteor that killed off the dinosaurs was no threat to the planet...just the life on it. The meteor that exploded over Russia a few years ago was only 20 meters in diameter and injured 1500 people and damaged numerous buildings.
originally posted by: eriktheawful
a reply to: MissSmartypants
Sorry, but you've misunderstood a few things:
1) Any body less than 140 meters wide is not considered a real threat to our planet. Neither of those objects are even close to 140 meters wide.
2) While a LD (Lunar Distance) is the average distance from the center of the Earth to the Moon (238,856 miles), it is a unit of measurement only. When it says that it will pass 0.00262 LD, it means that it will pass about 625 miles from the surface of the Earth.. The LD is a unit of measurement only. When distances are expressed in LD or AU, the objects closest distance is from the surface of our world.....not it's center.
Thank you, rickymouse. As I was busy telling everyone how right I was I was secretly hoping no one would call me out on the distance between the earth and moon fluctuating. But yeah...like you I think they use a standardized number as well. Great minds and all that.
originally posted by: rickymouse
originally posted by: MissSmartypants
Standard units of measurement have set dimensions. Perhaps there is a scientific term for the distance from the SURFACE of the earth to the SURFACE of the moon but that scientific term is not Lunar Distance ....because, a Lunar Distance is the distance from the CENTER of the earth to the CENTER of the moon. Look it up.
originally posted by: roadgravel
Wouldn't it be 3959 - 2386 = 1573
Could they have already made allowance for the Earth diameter in the approach distance?
LD is center of earth to center of moon. That actually can vary though, because the distance from the moon to the earth varies depending on the orbit of the moon. But I think they use a standardized number, and it always is from center to center. I have never seen it any other way.
Oh I get it now...you're trying to be funny. Good one.
originally posted by: eriktheawful
a reply to: MissSmartypants
You're still not understanding.
LD is a unit of measurement.
It is 238,856 miles. It's the distance of the center of the Earth to the center of the Moon. That's ALL that it is.
When we measure the distance of a asteroid to the Earth, we do not measure it from the center of the asteroid to the center of the Earth. We measure it from the asteroid to the surface of the Earth. One of the units of measurement that can be used is the LD.
For example: let's say I measure the northern tip of Greenland to it's southern most tip, and all that many miles 1 GD (Greenland Distance). It is now a "unit of measurement".
I then measure how many miles it is from New York to London, and tell you how many GD units it is.
Notice how we used a unit of measurement, but we didn't start in Greenland to make that measurement.
Get it?
We see the asteroid and measure how close it will come from it, to the surface of the Earth. Why? Why because if it were to hit the surface of the Earth, that's where it would stop.
Just like the AU.......sorry, but no astronomers are standing inside the core of the Earth and looking at the other planets in our solar system and measuring how far away they are. They are standing on the surface of the Earth and using the AU as a unit of measurement.
The starting point of where you measure does not have to be the center of the Earth. It's just that to explain how long that unit of measurement is, astronomers decided to measure it from core to core is all.
Like an apple sitting on a table in front of you. Do you shove the tape measure deep into the apple and then yourself to measure the distance from you? No. No you do not.