About space junk and moon gravity....

I've been meaning to write a neutral thread, asking some questions that puzzle me. From the title it is obvious that two main questions that puzzle me are the subject of space junk and the subject of Moon's gravity.

This "analysis" will be purely amateurish, and I could be misunderstanding some the space mechanics involved. That's why I have you guys to point me in the right direction.

Moon's gravity

Let's throw in some numbers. So the Moon is 1/4 the size of Earth. Numbers say it's gravity is also far weaker, 83,3% weaker. So the Moon's gravity is around 16% of that of the Earth's. This is rather logical to my mind. Since today's paradigm revolves around gravity being the product of mass (in layman's terms). So more mass means stronger gravity. So far nothing out of the realm of unexpected.

Now, let sidetrack for a moment and check out what are tides:

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.

en.wikipedia.org...

I'm sure this is nothing new to educated men/women, but let's sit with that for a while. So the Moon, with it's 1/4 size and 16 % gravity of that of the earth's is influencing events on earth ? It would be safe to assume than that the earth's gravity is influencing the moon far more than vice versa. 3/4 larger and having far stronger gravity...it's a safe bet.

So how come the moon's orbit around the earth is getting bigger ?

Is moon moving away?

It's getting 3.8 centimeters longer per year. What this means is that it takes a moon 3.8 centimeters per year longer to go around the earth. Due to strong earth's gravity, should it really move away? I know there are many more orbital forces at work here, like "tidal friction", but those really don't logically explain the moving away part. Actually, tidal friction is slowing the moon down, so if anything the effects of earth's gravity should be even greater on the moon if it is slowing down. Please don't say the sun, 'cos there are no indications that it is moving towards the sun.


Eternally "hovering" space junk right above the strong gravitational pull

This is what I don't get. I'm sure you've all seen this pic:




And here is the excerpt from wiki junk page:

The vast majority of the estimated tens of millions of pieces of space debris are small particles, less than 1 centimetre (0.39 in). These include dust from solid rocket motors, surface degradation products such as paint flakes, and coolant released by RORSAT nuclear powered satellites. Impacts of these particles cause erosive damage, similar to sandblasting. This damage can be partly mitigated through the use of the "meteor bumper", which is widely used on spacecraft such as the International Space Station. However, not all parts of a spacecraft may be protected in this manner, e.g. solar panels and optical devices (such as telescopes, or star trackers), and these components are subject to constant wear by debris (and to a much lesser extent, micrometeoroids).

Continuing from the earlier supposition that earth exerts far stronger gravity than the moon...it still does not manage to attract all of the junk that circles around it on an altitude from 1-2 thousand miles. Yet moon is influencing objects pinned to the earth from a distance of around 356,400 km to 406,700, depending on the time of the year. What's keeping it up there for so long (besides the initial orbital velocity, which can not explain the long periods of junk staying up there) ? I red somewhere that the junk "life" cycle is around 50 years or something like that. 50 years of circling around the earth, as if...there is no attracting force. Or a very weak one.

Seeing how the moon is able to exert gravitational pull on Earth's water masses, how come the earth has space junk problems and our junk remains there...and it's even getting bigger.

We know that large orbital bodies, such as Sun, Saturn and Jupiter attract many asteroids that pass through our solar system, and thus saving the earth from them. The moon's face is bombarded with craters, compared to earth's relatively small number of craters. It is apparently known that the earth and the moon are almost of the same age. Shouldn't Earth attract far more space collisions than the moon ?


What my layman mind is seeing here, is that something is off here. Either the moon has far stronger gravity than we were told, or the Earth has a far weaker gravity than we think (but since we can measure it...it's not likely)....ooooor I understand very little about space and space objects.

-----------------------------------------------------

In conclusion, It will probably be apparent from this post that I'm a not even an apprentice when it comes to space science, and there is probably info I'm missing about these things. Perhaps this junk busyness is not all that strange...but something is off with our current knowledge of the moon's gravity. So much that I feel it's kicking me in the forehead with a baseball bat.


Anyway...knock yourselves out.

www.labspaces.net...

"Eternally "hovering" space junk right above the strong gravitational pull."

reply to post by de_Genova


Thanks, for putting it up. I still don't understand how some images show up on a post and some just as links. I always do the same thing.

Craters on the earth dont last as long, some are under oceans therefore you cant see them, atmosphere breaks up, burns up objects. Objects that hit earth become smaller than if they hit the moon, even if they were the same size.

Space junk...hehehehe.....to stay up there its moving very fast and falls around the earth, not to it. Theres no atmosphere to slow it down...

You ask some good questions though

Originally posted by phroziac
Craters on the earth dont last as long, some are under oceans therefore you cant see them, atmosphere breaks up, burns up objects. Objects that hit earth become smaller than if they hit the moon, even if they were the same size.

Space junk...hehehehe.....to stay up there its moving very fast and falls around the earth, not to it. Theres no atmosphere to slow it down...

You ask some good questions though

Your point on the craters stands. There would be more visible impacts and craters on the moon due to it having no atmosphere.


As for the space junk...hell...that sounds like a one hell of a perpetuum mobile...or damn near one. So we just go up there and shoot something around the earth and it will continue moving for 50 years? Without any continous propulsion? We should harness that great power. Imagine you had something on the earth that you can give an initial boost, and than watch it turn for 50 years. Now that's high yield if I ever saw one.

I wish I had a one line question, seems the post didnt ask me anything, just pondered a lot of things, which I cannot entertain.

Have no idea if it's related but..

Moon gravity is in itself. It, as a body, has gravity. Such as earth, but vastly less, as it's not anywhere near the size of earth.

Still has gravity tho.

Bit of metal flying about in space? They are caught in OUR gravity. they were sent to just above the earth, there they start, work, end and fail.

The moon has no influence on them, considering our gravity.

I'm old and this was what I knew in primary school.. what the hell are they teaching these days? Or is there an almost 90% increase on people leaving school before year 8?

Here's a great reference on how tides work. It's not just the moon gravity that causes them, but it's a combination of things, such as the earth spinning, etc.

home.hiwaay.net...

As for the space junk, the higher the orbit, and the less the mass/area of friction with the atmosphere, the longer it stays in orbit. Most space junk, as your link pointed out is very small. When the shuttle would launch, they would jettison the tank once in orbit, and it took a few hours for it to come down. There was a lot of mass, and a big area to interact with the atmosphere in orbit, so it slowed down much faster than something smaller and lighter.

The higher the altitude, the longer the orbital debris will typically remain in Earth orbit. Debris left in orbits below 600 km normally fall back to Earth within several years. At altitudes of 800 km, the time for orbital decay is often measured in decades. Above 1,000 km, orbital debris will normally continue circling the Earth for a century or more. Return to Top

orbitaldebris.jsc.nasa.gov...

I'm sure one of our space fanatics can explain things better than I can, but that's my basic understanding of things.

reply to post by winofiend


you missed the point...I never implied the moon should have any effects on pieces of metal flying around the earth. My point was, way those pieces don't fall down., as apparently everybody is saying that the junk is amassing, which escapes my logic.

reply to post by Zaphod58


thanks. As I said...this space junk thing doesn't bother me that much...although...I pointed on another thread. That looks almost like a perpetuum mobile. Let's just fire things up there and collect energy from it. Since it's flying around with no further propulsion needed.


Do you have any comments on the moon gravity thingy?

reply to post by Zaphod58

Here's a great reference on how tides work. It's not just the moon gravity that causes them, but it's a combination of things, such as the earth spinning, etc.

I realize that. I was merely commenting on it having any influence...on a body 4 times larger and having only 16 % of the earth's gravity. Yet, somehow it is able to overcome the "strong" earth's gravity for the water that lies on top of the strong source of gravity, and make it move toward the moon motion.

I know I am over simplifying things...but still...

reply to post by MarioOnTheFly


My understanding is that the moon isn't pulling on the water, it's pulling on the earth under the water, which causes a bulge, which causes tides.

Originally posted by MarioOnTheFly
reply to post by de_Genova

 

Thanks, for putting it up. I still don't understand how some images show up on a post and some just as links. I always do the same thing.

Got to the ATS toolbar at top of the "reply" window - click TOOLS - ATS uploads - Select image file - Click the file (from desktop? - re-sized to fit ATS window) - Click file thumb when it appears in the window - copy/paste the image address directly into the "Reply" window and the image appears.

reply to post by Zaphod58


Thanks for the reply...that's even worse
Pulling on the ground and displacing it... from a distance of 300,000 miles away

Coincidently - This image just appeared on Rense a few minutes ago.........

reply to post by MarioOnTheFly


The sun keeps planets in orbit from much father away.

reply to post by Zaphod58


Sure...but the gravity and size are incomparable.
The moon is a speck of dust compared to the Sun.


edit:

Now, in your view...don't you consider that to be strange...a body with such a weak gravity and so small?

reply to post by MarioOnTheFly


Well, the water isn't hurdling towards the moon right now, and that should answer all your questions.

reply to post by MarioOnTheFly


Not really. Have you ever really read up on gravity? It'll give you a headache.

Let me give it a shot:

The Earths gravity holds the atmosphere in place. You know this.
The atmosphere gets thinner with altitude. After about 300-500 miles or so the atmosphere is so thin it no longer affects orbiting sats. (slows them down) It's this slowing that causes sats to re-enter. The higher the orbit the less atmosphere the longer the orbit lasts. Otherwise they will orbit forever.

Why the Moons orbit gets bigger:
I has to do with the distortion of the Earth and the tide, both caused by the Moon. It's slinging the Moon ahead in it's orbit.

reply to post by MarioOnTheFly


Now, remember....the space junk does fall....eventually. but it gets replenished with new space missions. Have you looked at the propulsion systems on the space shuttle? The main engines have no fuel tank once its in orbit. Its using no energy to stay up there, except for very small guidance boosters to steer it. Same for the space station, and sattelites. Once youre up there youre up there. To get down typically requires a deorbiting burn. But its not because of a lack of gravity, its because youre far enough from earth and at a great enough speed that gravity makes you fall around the world and not to it. So, we are harnessing this great amount of energy when we go up there. But you cant harness that from the ground.

On missions that go into "deep space" (beyond earth orbit), such as apollo, voyager, ....gravity assists are used to gain incredible speeds. You go around the earth for a full orbit, til youre aimed at the moon, and do a burn at the right time, and now youre heading towards the moon at 35000 miles an hour or so. This is more important to get back to earth from the moon, as almost no fuel can be brought into space....

Voyager 1 used a once in a lifetime planetary alignment to go into orbit with multiple planets, and used gravity assists off each one to get to the next......

Its amazing what you can do without atmospheric drag....