Post by: neilep on 19/02/2008 02:38:54
An awe inspiring event with devastating consequences too...
mushroom_cloud.jpg (13.64 kB . 300x376 - viewed 7351 times)Why does a big explosion make a cloud this shape ?......what's going on ?
Post by: another_someone on 19/02/2008 02:55:01
Post by: Karen W. on 19/02/2008 03:00:44
You know those mushroom clouds are not exclusive to Nuclear explosions.
You can see them upon other larger explosions like volcano's etc.
It can happen happen like when something slams into the ground to. it causes this hot gas to get down near the ground and the gas rises up quickly making kind of an overflowing funnel that curls over the top forming the mushroom look there, but at the same time it draws smoke, dust and other debris and particles up to make what looks like the stem. The stuff from the top falls out . that is what we know as fallout! Like when Mt St Helen erupted! the ash from her cloud came clear here in California it was crazy how far it went!
Post by: Karen W. on 19/02/2008 03:01:16
Post by: DoctorBeaver on 19/02/2008 08:36:21
Post by: lyner on 19/02/2008 09:52:55
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you have a partial vacuum pulling up dust and debris,Naughty boy!!!!
You aren't allowed to talk in terms of 'sucking' these days. Pressure only works 'downhill'. Air cannot pull anything; the attractive force between adjacent molecules is far too small.
The official line, now, is that.
1. The initial explosion raises the temperature of the air, locally.
2. It expands against the surrounding air and the density decreases. (The initial shock wave / blast are outwards from the explosion).
3. Once the initial expansion has finished, the more dense surrounding air produces upthrust and the 'hot air rises'. The hot gases keep expanding as they ascend.
4. The movement is so violent that the speed of the incoming colder air is enough to sweep objects along with it - inwards and upwards.
5. The inflow of air at the bottom constricts the flow so you have a stalk for the mushroom.
6. At a certain height, the vertical speed and inward pressure reduce and the cloud continues to expand, giving the mushroom head.
7. The energy starts of run out; the edges of the cloud start to droop and you then get doughnut-shaped convection currents.
Much the same thing happens with a normal bonfire; it's just not as impressive.
Post by: another_someone on 19/02/2008 09:57:25
Ah You beat me George!
You know I'm not a violent bloke - I would never beat a lady!
Post by: DoctorBeaver on 19/02/2008 10:00:42
Ah You beat me George!
You know I'm not a violent bloke - I would never beat a lady!
Lady?
Post by: lyner on 20/02/2008 09:51:39
Post by: DoctorBeaver on 20/02/2008 09:53:10
Post by: lyner on 20/02/2008 19:56:24
Post by: Karen W. on 20/02/2008 20:26:26
Ah You beat me George!
You know I'm not a violent bloke - I would never beat a lady!
LOL.. Yes I do know that! Your funny George! [:)]
Post by: Karen W. on 20/02/2008 20:28:13
Ah You beat me George!
You know I'm not a violent bloke - I would never beat a lady!
Lady?
Who says I am not a lady??? You scoundrel YOU!! [;)] [:)]
Post by: Karen W. on 20/02/2008 20:32:33
But of course. Innocent until proved guilty.
Why Thank you!!
Sorry I posted in your post instead of hitting the quote.. all fixed and My apologies!
Post by: Karen W. on 20/02/2008 20:35:36
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fscared%2F6.gif&hash=08a81c8fc1d1120807dff38e5469cced)
LOL...Yeah yeah....Good thing I don't bite! LOL! [;D]
Post by: Andrew K Fletcher on 22/02/2008 08:14:38
The density changes in the air current would not cause the flow and return without gravity (my argument for fluid transport in trees uses the same density changes to show how fluids circulate because of gravity. The same goes for gas and even rocks in giant density flow and return recycling movement.
Andrew K Fletcher
Post by: lyner on 22/02/2008 22:12:40
Post by: Andrew K Fletcher on 26/02/2008 10:34:47
The explosion on Earth shoots up because it is suppressed by the surface of the Earth. Density changes in gas and debris are affected upon by gravity, which provides the climate for this observation. No gravity = no mushroom cloud!
If so “do you” have any supporting Maths and quantitative evidence for this view?
Post by: lyner on 26/02/2008 14:51:48
Of course, in space the explosion would be more or less symmetrical. There would be no atmosphere and no convection effects. The blast would just consist of the parts of the bomb case and these would keep going 'for ever'. The mass of the bomb is negligible so there are no significant gravitational forces out there.
But I would disagree with your comment about gravity suppressing the explosion directly on Earth or anywhere. The actual velocity of the parts of the bomb would be well in excess of the Earth's escape velocity. What limits the distance that the bits of bomb and the immediately surrounding air can travel is the damping by the rest of the atmosphere. It's not linear under those conditions but if you consider the work done in expanding a spherical shell of a few km diameter against atmospheric pressure by just a few metres, it's huge. Effectively, the initial Kinetic Energy of the explosion is transferred to the internal (thermal) energy of the surrounding atmosphere.
I think my 'noddy' description of what happens, in my earlier post is reasonable. I have used common terms like convection and pressure wave which don't really need further clarification. The whole situation on the Earth's surface is a result of the presence of gravity, of course.
BTW
I have just looked at your movie of the water circulation which, of course, works because the column of salt solution on one side is more dense than the column of freshwater on the other. The energy for the demonstration / experiment comes from the work done in lifting the salt solution to the top of the loop. Once the salt is all flushed through the system (fallen to the bottom), the circulation will stop; the gravitational potential energy source will have run out.
I notice you refer to 'negative tension' which is not an established term. Are you referring to 'pressure difference" perhaps?
Post by: Andrew K Fletcher on 26/02/2008 16:43:00
The damping caused by the atmosphere is a direct result of the presence of gravity, no gravity = no atmosphere
Well in excess of the Earth’s escape velocity, yet unable to escape from the Earth’s influence proves my point really.
As for the tubular water experiment, 1 grain of salt or sugar can induce the flow when it is added above ground level to either side of the water filled column, and if added at the top of the loop of tubing at 24 metres, then as it falls it creates a dragging effect on each of the water molecules causing the entire water filled column to rotate as the less dense fluid is pulled up to replace the denser water flowing down. 1 grain of salt or sugar can induce this flow. And more than 1 grain of salt or sugar are present in the leaves and fluid at the canopy of a tree. All that is required to induce this flow is to concentrate the fluids in the downward flow slightly more than in the upward return flow and we have induced a powerful yet hitherto overlooked non living physical force which must take place due to the massive concentrating of fluids as they flow from leaf to leaf evaporating 99% of all the water drawn through the roots.
Post by: lyner on 26/02/2008 18:25:03
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Well in excess of the Earth’s escape velocity, yet unable to escape from the Earth’s influence proves my point really.But Science usually likes a bit more of a nuts and bolts explanation. Of course the presence of the Earth is relevant. The details of 'how' are what makes Science interesting, surely.
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then as it falls it creates a dragging effect on each of the water molecules???? The force is due to PRESSURE difference. Atmospheric pressure acts on the surface of each of the reservoirs. It is this pressure that supports the column of water. This was discovered by Torricelli, yonks ago.
http://en.wikipedia.org/wiki/Evangelista_Torricelli (http://en.wikipedia.org/wiki/Evangelista_Torricelli)
One atmosphere will support about 10m of water at sea level.
When you introduce even a small amount of more dense liquid on one side of your tubes the pressure is a tiny bit greater at the bottom of that tube. The pressure at the top of the tube will consequently be a bit less than at the top of the other tube and water will flow to equalise the pressure. If, instead of two shallow troughs at the bottom, you had two deep jars, the situation would balance out with a slightly higher level in the jar at the bottom of the tube with the solution in it.
By injecting salt into the top of the system you are introducing more energy into the system - the energy coming from your muscles. There is nothing magical or unknown about this. You are not getting any 'free' gravitational energy.
The effect of fresh water flowing onto the top of salt water is seen at the sea locks at the ends of the Panama Canal; the gates swing open (equal hydrostatic pressures each side) when the fresh side is still higher than the salt side and fresh water pours out into the sea. This is what is happening at the top of your loop.
Yours is a pretty demo but doesn't demonstrate anything new to Science. remember, there is very little actual ENERGY transfer involved. It has not been 'hitherto overlooked', it hasn't been utilised because it doesn't actually supply any appreciable amount of energy.
As you imply, when plants do this, the energy source is probably from the evaporation (transpiration) of the water from the leaves. This produces a change in concentration of salts in the sap which achieves what the plant needs.
Post by: Andrew K Fletcher on 27/02/2008 07:46:41
This topic has been covered in depth here and might answer your questions better than beginning again.
Post by: lyner on 27/02/2008 16:52:57
First, I have to say that using the words 'suction' or 'tension' where bulk liquid is concerned goes against established Scientific ideas. Nothing wrong with that, of course, if the 'heretical' words are the only ones which will explain what's going on. Surface tension is much too weak a force to be considered as a candidate.
The simple inverted loop model can be explained perfectly well in terms of Pressure (a good, healthy, concept which works everywhere else). You just can't have 'tension' or 'suction' in fluids. It's always excess pressure on one side which makes liquids flow. I needn't repeat my explanation.
The problem seems to be how to explain lifting higher than the 10m limit. It strikes me that the complex structure of the Xylem is capable of combining both hydrostatic lift and osmotic pressure (which works horizontally as well as vertically) in a distributed mechanism. Water which has been pushed to a reasonable height by hydrostatic pressure in one u tube can then be moved sideways to another inverted u tube by osmosis. This starts the process again and the final height is not limited by to 30m. You can either visualise it as a set of small, discrete vertical then horizontal motions. The energy comes from the overall loss of latent heat of evaporation when the leaves transpire.
If you can devise an experiment which demonstrates, unequivocally, the presence of your 'tension' in water and cannot be explained in terms of conventional hydrostatic pressure then I would be very interested to hear of it.
Post by: Andrew K Fletcher on 06/03/2008 16:43:28
Any other likely explanation to offer?
Have read all of the other explanations and not a single mention of gravity among them. Odd how we take gravity for granted ain't it ?
Post by: lyner on 06/03/2008 23:22:02
Post by: Andrew K Fletcher on 09/03/2008 08:35:50
To ignore gravity as the force that provides us with the shape of the mushroom cloud could lead many people into believing that gravity is a weak force, when in fact if gravity was a more weaker force than the powerful explosion of a nuclear weapon, we might expect to see far more spectacular results from a detonation. When what we do see is a blast that is far weaker than a volcanic eruption, which of course, any such eruption is a direct result of the immense power of gravity providing us with instability at times and thankfully some stability on the Earth’s surface!
We cannot talk about the atmosphere providing us with the suppressing blanket over a nuclear explosion without first considering that it is gravity that provides us with every single event that occurs here on Earth, in space and on every single solar system out there! When we split the atom to cause the explosion we break the atoms away from the force of gravity, and as we can see this is fortunately but a temporary situation as the status quo is rapidly returned in the wake of the explosion. And as we can see by the shape of the cloud that forms we are presented with a spectacular example of how powerful gravity really is!
Without gravity the people that create the bomb would not even exist to begin with! Without gravity there would not be a nuclear force because there would be no atoms to split! There would be no minerals, chemicals, metals, machines, or even thoughts on how to build a nuclear weapon. Without gravity there is not even nothing!
Andrew K Fletcher
Post by: CZARCAR on 18/05/2011 17:47:10