How many planets?

[Karlos]

@Dandy

I studied chemistry to postgraduate level so phase diagrams are no stranger :-)

I think you are thinking of Helium. Hydrogen's melting point is at 14K and the solid phase is well characterised. Helium, under 1 atmosphere pressure is still liquid as close as anybody has ever gotten to absolute zero (a temperature which is basically impossible to achieve in reality). Helium will solidify under 1.5K if you subject it to at least 26 atmospheres. Below about 4K at normal pressure, Helium (at least He4) switches to it's superfluid phase, which is a highly interesting state where the viscosity of the liquid effectively vanishes and the thermal conductivity becomes immense. It'll creep over any surface and find it's own level within any enclosed space, regardless of the topology. The thermal conductivity means you can't boil it, for example, the heat is dispersed so quickly through it that it simply evaporates to a gas phase.

Crazy stuff.

Going back to hydrogen, under enough pressure and temperature it becomes metallic, and may even be superconducting.

[Hyperspeed]

Would Hydrogen retain it's metallic form after the conversion process? Could we all be wearing hydrogen rings in the future that could power our house?

:-D

I saw liquid Helium on Sky TV years ago, if you take the lid off the container it screams like a falling bomb and tries to do a runner!

In my opinion to be a planet the object must be perfectly spherical. A designation would be mathematical. Can non-spherical objects retain an atmosphere?

Interesting is the fictional 'world' of Halo... a weapon/planet who's entire surface is the inner track of a giant ring. Maybe we should start thinking of more designations when technology allows us to make our own worlds or discover things that don't fit the mould!

[Tigger]

Hyperspeed wrote:

Interesting is the fictional 'world' of Halo... a weapon/planet who's entire surface is the inner track of a giant ring. Maybe we should start thinking of more designations when technology allows us to make our own worlds or discover things that don't fit the mould!

Thats a steal from Niven's Ringworld, which is a sub idea of Freeman Dyson's shell or as its more commonly known today, a Dyson Sphere.
   -Tig

[Dandy]

Karlos wrote:
@Dandy
...
I think you are thinking of Helium. Hydrogen's melting point is at 14K and the solid phase is well characterised.
...

No, no - I was thinking of hydrogen.
I thought I was taught that the boiling point of hydrogen is at 0 K.

But now that I read about hydrogen at wicki, I was rather astonished to read that the boiling point was not at 0 K, but at 20,4 K (= -252,8 °C) and that there even is a melting point at 14,025 K (-259,125 °C).

Hmmmmm - eigther I mixed it up after all those years or my teachers tought me BS...

But nevertheless:
(Quote from wicki)
"Many Experiments are continuing in the production of metallic hydrogen in laboratory conditions. Arthur Ruoff and Chandrabhas Narayana from Cornell University in 1998, and later Paul Loubeyre and René LeToullec from Commissariat à l'Énergie Atomique, France in 2002, have shown that at pressures close to those at the center of the Earth (3.2 to 3.4 million atmospheres), and temperatures of 100 K–300 K, hydrogen is still not an alkali metal. The quest to see metallic hydrogen in the laboratory continues, well beyond 70 years after its existence was predicted."

So I assume that all this talk about metallic hydrogen is just theoretical/hypothtical?

Karlos wrote:
Crazy stuff.

Indeed...

Karlos wrote:
Going back to hydrogen, under enough pressure and temperature it becomes metallic, and may even be superconducting.

Yes, in theorie - as I understood it, up to now no one  successfully produced metallic hydrogene...

[Karlos]

@Dandy

As far as I understood, they did make it, over the duration of the compression experiment (250ns).

Putting it in a jar, however is an entirely different proposition. The pressure required to keep it metallic is far beyond current material sciences' ability to produce a container for.

[Agafaster]

Arthur C Clarke predicts that the core of Jupiter could be an enourmous diamond - a piece of this is found on the now melting moon Europa, in his books 2010/2061.

[Hyperspeed]

Arthur C Clarke - a diamond geezer!

On this subject though how will world economics evolve over the next few centuries when asteroids, moons and planets are discovered with gold, uranium, diamonds etc. on them?

The UK had to sell off a lot of it's gold reserves a few years ago due to the falling prices... imagine the impact on a country's economy if it's reserves of some mineral were superseded by a mine on the moon!

I read a year or two back that a few scientists think that viruses come from space... that millions of tonnes of organisms live high up in the atmosphere and that they suggested viruses were literally raining down from the sky. Freaky.

[Karlos]

I don't expect a large diamond to exist in jupiter's core. A very large mass of heavily compressed iron, surrounded by a rock mantle up to several earth radii, then atmosphere all the way out, proceeding from metallic hydrogen (sustaining immense electric currents that power the magnetosphere) through a normal liquid phase and eventually gaseous, without any well defined boundaries between each.

[Hyperspeed]

Do diamonds have electrical properties, like Quartz oscillates a current?

Such a perfect lattice should be capable of something extraordinary besides being very hard and twinkly!

:-D

I saw an astronomy program once where it described billions of volts arcing from Jupiter to one of it's moons, constantly. They also say that Jupiter is effectively Earth's guardian angel - absorbing all the asteroids.

What I have been thinking lately is that for planets like Neptune to orbit the Sun there must be some physical thing grabbing hold of them and keeping them in this ring of motion.

Now I've never studied physics academically but surely gravity must be a form of matter to have an effect on anything?

I couldn't make head nor tail of Steven Hawkings' nut book but I don't agree that time is interwoven with gravity. I believe the vacuum of space is in fact a solid entity filled completely with quantum particles and that the planets behave exactly like electrons around a nucleus.

Can anyone educate me or even propose wackier ideas?

EDIT:
And while I'm off on a tangent here - can anyone explain if our moon, if artificially provided with one, could retain a very thin atmosphere (enough for humans to be able to breathe)?

It was suggested that atom bombs could be used to melt the ice on Mars to speedily provide the planet with an atmosphere - how long would artificial atmosphere generation take using today's technology and could it be applied to Ozone regeneration on our own planet?

[Karlos]

Trust me, if you believe in quantum mechanics at all, electron 'orbits' within atoms are about as different from planetary orbits as it is possible to get ;-) You simply cant apply macroscopic scale physics to the microscopic (as in atom scale) world, it simply breaks. It has been said that macroscopic physics is an approximation of quantum mechanics for where the 'uncertainty' limit is zero, rather than [d]h[/d]/2PI...

There's no real mystery about planetary orbts. Gravity is holding neptune in orbit. The sun's gravitational influence extends a hell of a lot further than that, too. Gravity as 'matter' is an explored idea, do a search for 'graviton' particles.

Regarding diamond, it's a very poor conductor. However, if you dope it with boron, nitrogen or similar atoms you can make semiconductors from it. Diamond has very good thermal conductivity, making it a very good future substrate, though it's expensive to make at the moment.

Having said that, carbon under billions of atmospheres of pressure and at tens of thousands of degrees kelvin, who knows what properties it would have?

[Karlos]

Hyperspeed wrote:

And while I'm off on a tangent here - can anyone explain if our moon, if artificially provided with one, could retain a very thin atmosphere (enough for humans to be able to breathe)?

No. First of all, RMS speed of gaseous nitrogen/oxygen molecules at standard temperatures are above the moon's escape velocity. Secondly theres' no decent magnetic field around the moon which means it takes the full brunt of the solar wind which would rapidly strip away any atmosphere it managed to keep hold of.

It was suggested that atom bombs could be used to melt the ice on Mars to speedily provide the planet with an atmosphere - how long would artificial atmosphere generation take using today's technology and could it be applied to Ozone regeneration on our own planet?

No. The idea on mars is to release the frozen CO2 in the caps, thickening the atmosphere, which is mostly CO2. As much as 1/3 of the atmosphere freezes out into the caps during Mars' winter.

Dropping nukes all over our ice caps would do nothing but make our planet even more screwed up than we managed so far. I suspect if it had any effect on ozone at all, it would deplete it.

[Hyperspeed]

by Karlos:
No. First of all, RMS speed of gaseous nitrogen/oxygen molecules at standard temperatures are above the moon's escape velocity. Secondly theres' no decent magnetic field around the moon which means it takes the full brunt of the solar wind which would rapidly strip away any atmosphere it managed to keep hold of.

I see...but why do some moons have atmospheres? Doesn't Titan have one, or is this because it's big enough to hold one down?

by Karlos:
No. The idea on mars is to release the frozen CO2 in the caps, thickening the atmosphere, which is mostly CO2. As much as 1/3 of the atmosphere freezes out into the caps during Mars' winter.

Dropping nukes all over our ice caps would do nothing but make our planet even more screwed up than we managed so far. I suspect if it had any effect on ozone at all, it would deplete it.

I'm sure the idea was to create an accelerated form of global warming on Mars. Why this was suggested I don't know - especially if the ice caps are CO². If the planet got warmer would any plants be able to live on CO² alone (they breathe oxygen during the night don't they?).

Imagine a plant that would breathe only CO² and emit oxygen, you could plant your own atmosphere generators! Hey, maybe even microbes could be engineered to survive the martian environment and generate oxygen or fuel.

With the nukes I didn't mean nuking our own ice caps. I did see some satellite style device on TV once that generated ozone but the estimated time of repair would have been 10,000 years with this basic gizmo.

This new idea of storing carbon dioxide underground though is a really bad one. One earthquake and you could release years worth of CO².

[Karlos]

Hyperspeed wrote:

by Karlos:
No. First of all, RMS speed of gaseous nitrogen/oxygen molecules at standard temperatures are above the moon's escape velocity. Secondly theres' no decent magnetic field around the moon which means it takes the full brunt of the solar wind which would rapidly strip away any atmosphere it managed to keep hold of.

I see...but why do some moons have atmospheres? Doesn't Titan have one, or is this because it's big enough to hold one down?

The hint was in the word 'temperature'. Gas molecules statistically start to move faster as the temperature rises.  If you look up the Kinetic Theory of Gases, you will see a proof for

v(rms) = sqrt(3kT / M)

where v is the RMS speed of the gas molecules, T is the temperature in Kelvin, M the molecular mass of the molecule and k is Boltzmans Constant.

Two things you will observe about Titan (which has a dense atmopshere) and Triton (which has some atmosphere) is that they are both very, very cold. So much so that the bulk of the gases in their atmospheres are safely below their gravitational escape velocity. They are also quite large (Titan especially) but they aren't that dense so their gravitational pull is not as strong as their size might imply.

The second thing about these moons is that they are also sufficiently far from the sun to receive a much reduced solar wind flux, although theres still enough to erode an atmosphere as loosely held as they are. However, these moons are protected to a degree by their parent planet's magnetospheres. Even then, Titan bleeds gases into orbit around Saturn, though I recall there was evidence to suggest the lost gases are recaptured as they don't escape Saturn orbit and are within the protection of the magnetosphere.

Regarding Ozone, the stuff will naturally break down in darkness. You actually need UV light dissociating normal molecular oxygen to produce ozone ;-)

One thing about the hole in the ozone layer that always puzzled me. Most of the human population (therefore the CFC production with it) live in the northern hemisphere, yet the largest hole is in the southern one. At the altitudes involved, I don't envisage you'd get a large crossover (I could be wrong about that, however), so why isn't the larger hole in the northern one?

[Hyperspeed]

Karlos: That was an excellent response - my mind is nourished.

:-D

Makes you appreciate how delicate our planet's life support system is.

With the ozone layer though, don't they say that farting cows are mostly to blame? And paddy fields... there's a lot of them in the far east.

You don't think like Aurora Borealis/Australis that the Earth's magnetic field and solar radiation has anything to do with the holes? Why are the holes... at the poles!?

;-)

[iamaboringperson]

Vincent wrote:

Cymric wrote:
being used to the familiar chant Mercury-Venus-Earth-Mars-Jupiter-Saturn-Uranus-Neptune-Pluto

I thought it was:

Mercury-Venus-Earth-Mars-Jupiter-Saturn-Uranus*snigger*-Neptune-Pluto

:-D

I was alway taught that it was 9 planets at school. It will always be 9 planets!  :-P

[cecilia]

get with the times, buddy.
it's 8 planets! :roll: