The Ocean, gravity and tides......

Not a lot to say at present, but I had a very, very vivid dream last night. The second of such. Where I was looking up at the sky across some land and shoreline. The sky was swirling like a strange rainbow, with the odd black patch with jagged outlines appearing and disappearing just as quickly. In my dream I distinctly knew this was a global event and not just local. I also knew it was natural.

I then noticed the tide was out but could visibly seeing it coming in, not rapidly in a wave like a tsunami, but like the regular tide just much faster.

End of dream....

When I awoke a question popped into my head immediately . And it was ...

What if something caused the ocean to lose it pressure and swell. Because unlike, say oil that cannot be pressurized, water does compress. So if the earth somehow lost a % of it gravity, wouldn't the oceans swell.

Not that I believe in the Bible, but I do remember being told when young by a Minister, the great flood came from below, in a mist. Not heavy rain like some believe. Or could this be the real reason for our oceans growing at present. But whatever is influencing it is not full strength yet.

I could not shake the feeling that what I was seeing was some kind of "super tide"


Any thoughts peoples...?





[edit on 11/19/09 by thedeadtruth]

Yes, water does compress, so as the gravitational pull weakens then the ocean would expand.

If I remember correctly, if all the saltwater in the ocean became 'unconpressed' the sea level would rise by about 35-40 meters! (I don't have any sources but if you look into it I think this is about right).

So if we lost gravitational pull here on earth somehow, then It would be logical to suppose that the pull from the sun and moon would have a stronger effect.

Never thought of it like that though!

Takes a dream I guess!

[edit on 3-6-2010 by vagabondrobb]

reply to post by vagabondrobb


I think you're confusing a few things, here. A google search can make learning fun...

Yes, water does compress...

Well...given enough force, then yes...but a LOT of force is required, and there is a limited result. Of course, in a sense, ALL matter is just empty space, (the space between the electrons and nucleus of atoms, for instance).... but that's more of a question for theoretical particle physics, not 'natural' physics, and materials science.

Still, in the conditions being discussed?? You should consider water to be mostly uncompressible ... or so little as to be hard to measure.

...so as the gravitational pull weakens then the ocean would expand.

I'd want to check that one, however.

WHICH gravitational pull? Earth's? Or the Moon's?

IF the Moon's influence were to be suddenly removed, the oceans would not 'expand'....the tidal actions woudl cease, eventually. That's about it.

If Earth's gravititational force were to suddenly 'weaken' (an impossibility, but just a thought experiment for now)...there would also be minimal change. Even if it dropped by half, the oceans would look about the same...

Temperature changes can influence solids, and liquids, making them shrink...but, as we all know (or should) water is somewhat special when it freezes...it actually EXPANDS when ice crystals form, as the H2O molecules link up into the crystal matrix.....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I think the concept here is, IF earth's gravity weakened, then the very, very deep water, under "compression" near the bottoms of the oceans, would somehow 'swell' up?

My instincitve, gut feeling says 'No' to that idea....it doesn't seem rational, from what I understand about physics.

There are calculators, online, that I saw after a search...someone could do the math, I suppose.

But, anyway...the Earth's gravity isn't going to change that much, not in our lifetimes. Nor, has it any time in the past (barring. of course, the time of earliest planetary formation events....)



[edit on 3 June 2010 by weedwhacker]

reply to post by weedwhacker


Hi,

Thanks for the detail!

Well...given enough force, then yes...but a LOT of force is required, and there is a limited result. Of course, in a sense, ALL matter is just empty space, (the space between the electrons and nucleus of atoms, for instance).... but that's more of a question for theoretical particle physics, not 'natural' physics, and materials science. Still, in the conditions being discussed?? You should consider water to be mostly uncompressible ... or so little as to be hard to measure.

There is incredible forces involved when we are considering the vast depths of the sea- remember, we're talking up to 10km deep!

Water density also depends on the amount of pressure, since pressure compresses water slightly, making it heavier. For studying how sound reflects off deep water layers, the pressure effect is relevant, but not for water circulation. The table on right shows how salt water compresses with depth. It is interesting to note that the ocean (average depth 4000m) would stand 36m higher if water were truly incompressible. (at 4000m, water is compressed by about 1.8%, averaging 0.9% for the whole water column, or about 36m.)

www.seafriends.org.nz...

I agree that compression is extremely slight, even at extreme depths, but when you consider the sheer volume of water involved, relative to our environment (surface of earth is 70% ocean) then the visible effects of any considerable 'decompression' might be quite noticeable and certainly measurable.

IF the Moon's influence were to be suddenly removed, the oceans would not 'expand'....the tidal actions woudl cease, eventually.

Yes you are quite right, I was thinking in the wrong direction here, thanks for pointing that out!

However I would certainly disagree that half the earths gravitational pull dissapearing would have no noticeable effect on sea level, that doesn't seem logical to me, not that I'm an expert and I don't mind being proven wrong on this!

I'm not talking 30 meters here, but certainly a little.

reply to post by vagabondrobb


Good thinking points.

I went to your link, and pull this out:

Seawater density from compression
Depth .... Density
0 m .... 1.02813
1000 .... 1.03285
2000 ... 1.03747
4000 ... 1.04640
6000 ... 1.05495
8000 ... 1.06315
10000 .. 1.07104

Now, just rough back-of-the-envelope brainstorming....

I get, from surface, to 10km depth, a change in compressibility factor of about 0.042% (If I put the math numbers in the right slots....)

Of course, it is a range, because the ocean is not universally 10km deep, nor does the compressiblity say the same at all depths -- increasing, naturally, with increasing depth.

SO, it's a very complicated (and maybe unsolveable) math problem..at least for my limited abilities.

But, for a round figure, I suppose one could estimate the entire volume of the oceans, use a value of, (on average?) about 0.025 to 0.030% 'expansion' (IF all gravity were removed!) and calculate how that would 'spread' out, over the entire surface area of all the waters....

But, when I see less than one-tenth of one percent...? I tend to think it'd be minimal.

Fun exercise, though!