• We have updated the guidelines regarding posting political content: please see the stickied thread on Website Issues.

Ocean Question

hunck

hunck

Antediluvian
Joined
Jul 13, 2011
Messages
9,512
Location
Hobbs End
A question for forumers: How long would it take in minutes for a marble dropped from the surface to reach the floor of the lowest trench in the ocean - around 11 kilometers?

No looking it up on the internet. If you get within 10 minutes I'll be awarding points, & points mean prizes. I'll give it a couple of days to run.

An additional question for someone more scientifically knowledgeable than me - would the marble sink at a uniform rate throughout it's descent? The pressure rises the deeper you go but would higher pressure, which gets immense at depth, slow descent or have no effect?
 
I'm deleting my answer as I did look to see how fast a marble travels in water.. And that is a violation after reading rules again, I think!
It is sometimes warmer at surface of ocean, cooler deeper -this would affect rate of travel through water because of density.
 
Last edited:
feinman said:
I'm deleting my answer as I did look to see how fast a marble travels in water.. And that is a violation after reading rules again, I think!
It is sometimes warmer at surface of ocean, cooler deeper -this would affect rate of travel through water because of density.
Click to expand...

You can still give your answer. If the sinking is not uniform due to temperature/density it'll be harder to estimate.
 
That's the Marianas Trench? Although I find the name a bit like bananna in that I attempt to add in letters all the time...

I don't know. I'm going for an hour because it's a nice round number. My back-up answer is 144 minutes because 144 is a nice number to play with! :rollingw:
 
I say that a regular sized and waited marble would probably just get swept around by ocean currents and not end up at the bottom of the trench.

But if it did sink to the bottom, 7 minutes 30 seconds.

And the rate of decent would slow as it got nearer the bottom.
 
hunck said:
You can still give your answer. If the sinking is not uniform due to temperature/density it'll be harder to estimate.
Click to expand...
I wish I could, but I looked further when I though I was disqualified and my math was wrong. It was and I just forgot to divide things again or it would have been correct. D'oh! I am happy to watch others struggle now. :cool:
 
Frideswide said:
That's the Marianas Trench? Although I find the name a bit like bananna in that I attempt to add in letters all the time...

I don't know. I'm going for an hour because it's a nice round number. My back-up answer is 144 minutes because 144 is a nice number to play with! :rollingw:
Click to expand...
I'm going with Frideswide's guess!
 
I would guess that even though the marble's wouldn't, the water's density would get greater. Can't rightly fathom (hah!) what that would end up like though.
 
hunck said:
A question for forumers: How long would it take in minutes for a marble dropped from the surface to reach the floor of the lowest trench in the ocean - around 11 kilometers?

No looking it up on the internet. If you get within 10 minutes I'll be awarding points, & points mean prizes. I'll give it a couple of days to run.

An additional question for someone more scientifically knowledgeable than me - would the marble sink at a uniform rate throughout it's descent? The pressure rises the deeper you go but would higher pressure, which gets immense at depth, slow descent or have no effect?
Click to expand...
An African marble, or European? If I remember my physics GCSE, gravity accelerates a falling body at 10m per second per second until you reach terminal velocity courtesy of air pressure (not to mention, eventually, land pressure, which I imagine would tend to emphasise the terminality of proceedings...)

But we're not talking about air. Do we know the relative density of the marble and the water? Does the water density remain constant regardless of depth? Intuitively, water density increases proportionally with depth, but if that were actually the case, at one depth or another water would turn solid.

Anyway, I'm going to guess an average descent speed of 1m per second. That equates to 11 thousand seconds to plumb 11 vertical kilometres, or a smidgen under 3 hours 6 minutes.
 
Krepostnoi said:
Intuitively, water density increases proportionally with depth, but if that were actually the case, at one depth or another water would turn solid.
Click to expand...

Actually, water is one of the very few things that is less dense when solid, although I realise that you weren't really thinking about ice.

To answer the main question, I reckon that (ignoring currents) it could be around 10 hours.
 
Last edited:
Hmm... In the article I found online which prompted the question, seemed to be from a reputable source & showed the various layers/pressure of ocean it would go through, the answer given was 6 hours or 360 minutes. Of course I now can't find the article again.

On looking up various other sources, I'm now not convinced - depends on size & density of the object - the more dense the object, the quicker it sinks. Drag co-efficiency also involved. Looking for spherical objects:

According to Naked Scientists a shotput would take about 36 minutes.

BBC Science Focus says just over an hour for a pebble but doesn't show workings.

Quora gives 74 minutes for a 16lb cannon ball.

Water pressure it seems may play a part, but not much.

On this basis I think Frideswide wins the prize of free drinks for a month at the Trolls Head.
 
Yes, the difference in bouancy would mean they would descend at a different rate. Also the glass one might shatter from the pressure.
 
Xanatic* said:
Yes, the difference in bouancy would mean they would descend at a different rate. Also the glass one might shatter from the pressure.
Click to expand...
I too was curious about the marble cracking so i looked it up, this is the best i could find

If I were to drop a glass marble into an infinitely deep body of water, would it eventually crack or continue to be compressed indefinitely?

Well...at some depth of your infinite water, the water would start undergoing nuclear fusion, (if you substitute "infinite body of water" for "extremely large hydrogen gas cloud", this is what leads to star formation).

It would not be like in a roadrunner cartoon where the marble just gets compressed into an infinitely flat pancake. On its way down the pool, the marble would

(EDIT: someone pointed out that it likely will not crack from pressure induced stress due to the minute change across the marble and the high YM of borosilicate glass would not fracture it before it hit an ICE IV barrier and stopped moving. I maintain that there would be no Ice IV barrier due to the heat from the fusion of water far far below, (remember that this is an infite ocean, infinite depth, area and constant gravity), and provide an explanation, below. We are still discussing it.),

https://www.reddit.com/r/askscience/comments/14tcxz
 
You must log in or register to reply here.
Back
Top