Ask a physicist anything. (6)

[Chalnoth]

Why is that? And does that mean that it is known with reasonable certainty that some physical constants are variable and accidental? And is the probability distribution of this variation known?

With a reasonable degree of certainty, yes.

Basically, in the standard model of particle physics, some of the parameters are fixed completely randomly through spontaneous symmetry breaking. And in theories that go beyond the standard model, we get still more parameters that are fixed randomly, though at the same time we may discover that there are underlying relationships between some of the parameters in the theory as well. That is to say, right now only a couple of the fundamental constants are shown to be random, while there are a total of 26 dimensionless constants in existence. It is very likely that some of these 26 constants could be calculated, if we knew some more advanced theories, but it is highly unlikely that all of them can. It is also possible that as we learn more, we will discover yet more dimensionless constants.

 

[mzungu]

Finally: BBC News - IBM produces first 'brain chips'

 

[Cactus Jack]

If a nuclear weapon was detonated within Jupiter's or Saturn's atmospheres, would they ignite as suns? If so what effect would that have on the solar system?

 

[Chalnoth]

If a nuclear weapon was detonated within Jupiter's or Saturn's atmospheres, would they ignite as suns? If so what effect would that have on the solar system?

No, not even remotely. It would just be even less impressive than a nuclear explosion here on Earth, simply because these planets are so much bigger.

We know this for certain because asteroid and comet impacts can be far, far more energetic than any nuclear weapon we have ever built. See the Shoemaker-Levy comet impacts on Jupiter, for example:
Comet Shoemaker–Levy 9 - Wikipedia, the free encyclopedia

Over the next 6 days, 21 distinct impacts were observed, with the largest coming on July 18 at 07:33 UTC when fragment G struck Jupiter. This impact created a giant dark spot over 12,000 km across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT (600 times the world's nuclear arsenal). Two impacts 12 hours apart on July 19 created impact marks of similar size to that caused by fragment G, and impacts continued until July 22, when fragment W struck the planet.

Basically, the reason why stars burn nuclear fuel isn't because there was any especially energetic seed to the reaction, but because they have so much mass that the pressure and temperature near their centers is large enough to get nuclear fusion started. One way you might be able do it, however, would be the way the unknown aliens did it in 2010:
2010: Odyssey Two - Wikipedia, the free encyclopedia

The idea there was to convert a large fraction of Jupiter's mass to heavier elements. This doesn't increase the mass of Jupiter, mind you, but it does produce a large concentration of mass nearer the center of the planet, which, in turn, increases the surface gravity of this increasingly dense mass. Eventually that density can potentially become high enough that the hydrogen just outside the dense mass starts to fuse.

But in order to get nuclear fusion started without changing Jupiter's composition, you'd have to increase its mass by about a factor of eighty or so. Saturn, being much lighter, would need even more drastic changes.

 

[mzungu]

If a nuclear weapon was detonated within Jupiter's or Saturn's atmospheres, would they ignite as suns? If so what effect would that have on the solar system?

No. None of the Gas giants have the mass for fusion to occur. You would need at least 80 Jupiters to have enough mass to start a feeble red dwarf!

Star Size Comparison HD - YouTube

 

[mzungu]

Darn Chalnoth you beat me to it

 

[razeontherock]

No. None of the Gas giants have the mass for fusion to occur. You would need at least 80 Jupiters to have enough mass to start a feeble red dwarf!

Star Size Comparison HD - YouTube

I saw something similar a few years back, that also attempted to show relative distance between celestial bodies. Still awesome ...

 

[mzungu]

I saw something similar a few years back, that also attempted to show relative distance between celestial bodies. Still awesome ...

Just to show you how large the universe is; If you took every single grain of sand on the whole planet Earth and multiplied them by a factor of 1 million then that is how many stars (suns) there are. This is a staggering number. It matters not whether one is religious or not; The scales are astounding to say the least:

Size Of The Universe - YouTube

 

[razeontherock]

Just to show you how large the universe is; If you took every single grain of sand on the whole planet Earth and multiplied them by a factor of 1 million then that is how many stars (suns) there are.

Needs to be qualified by statements like, "estimate," and "known." And yes, words like staggering sort of don't do us justice here!

 

[mzungu]

Needs to be qualified by statements like, "estimate," and "known." And yes, words like staggering sort of don't do us justice here!

I agree with you; Perhaps the word "wondrous" is more apt? Whichever word we use; Our vocabulary is not capable of describing the vastness and wonderful albeit extremely hostile environment of the universe.

Excellent BBC documentary. This is the third part called staying alive. Enjoy:

Space with Sam Neill Staying Alive part 1 of 3 - YouTube

http://www.youtube.com/watch?v=TvR3xP0MI-g&feature=related

http://www.youtube.com/watch?v=6lQijaiNl5c&feature=related

 

[Cactus Jack]

What is the likelihood of life, intelligent or not, being present on any of the planets in our system?

 

[mzungu]

What is the likelihood of life, intelligent or not, being present on any of the planets in our system?

We have 2 strong contenders so far: Europa and Mars.

 

[Chalnoth]

What is the likelihood of life, intelligent or not, being present on any of the planets in our system?

Presumably you meant other planets

But I don't think anybody knows the answer, unfortunately. Possibilities for life other than Earth include Mars, Europa, and maybe Titan. Most everywhere else it is probably impossible.

 

[Wiccan_Child]

What is the likelihood of life, intelligent or not, being present on any of the planets in our system?

There are no overt signs of life on any planet but Earth, but Mars hints at having (or having had) some primitive life. Some moons, such as Europa or Titan, may also have more as much as complex ecosystems.

The odds are small, but not so small as to dismiss the possiblity outright.

 

[Chalnoth]

There are no overt signs of life on any planet but Earth, but Mars hints at having (or having had) some primitive life.

Well, those hints are so far entirely inconclusive.

 

[Wiccan_Child]

Well, those hints are so far entirely inconclusive.

Hence why they're just hints

 

[Chalnoth]

Hence why they're just hints

Yeah, just saying I thought your wording was a bit too optimistic for my tastes

 

[Tuddrussell]

If we could break down entire human corpses into a soylent green type foodstuff, would it supply all the essential nutrients we need?

If so, could a human society survive entirely off of processing and eating their dead?

Do enough people die a day to feed everybody, or is there a population that is small enough/big enough to be entirely sustained on its own dead?

Would the nutritional value of soylent green made out of people who have only ever eaten soylent green be less than the original soylent green made of people who have never eaten soylent green?

If so, could we supplement the soylent green with similarly processed non-human corpses? Such as horses, bison, and such?

Maybe a better idea would be to process anything edible that dies, and supplement it as needed. Like a big vat of slurry made of dead stuff, and it gets dehydrated into tasty snack cakes.

Everyone wins!

 

[Wiccan_Child]

If we could break down entire human corpses into a soylent green type foodstuff, would it supply all the essential nutrients we need?

We need a daily intake of nutrients, but all the atoms are there, so, given a sufficiently advanced method of resynthesising food from any source of atoms, sure.

If so, could a human society survive entirely off of processing and eating their dead?

It sounds awfully... circular The daily intake would require massive amounts of people to die per day to feed just a few. You would need massive human farms growing people for 18 years before slaughter - but as those farmed humans would need to be fed, watered, etc, the benefit of 'recycling the dead' is lost.

Do enough people die a day to feed everybody, or is there a population that is small enough/big enough to be entirely sustained on its own dead?

Would the nutritional value of soylent green made out of people who have only ever eaten soylent green be less than the original soylent green made of people who have never eaten soylent green?

That depends entirely on the makeup of soylent green. If you're just reconstituting meat, then they'll be far less healthy: diseases that are normally very rare will be concentrated and will spring up with more frequency, especially if you include brainmatter in the slurry. If you're atomising the carcass, then this would effectively sterilise the 'meat' (such that it is). But, if you can do that, you can use any sort of material you want, so long as it has hydrogen, oxygen, nitrogen, and carbon.

If so, could we supplement the soylent green with similarly processed non-human corpses? Such as horses, bison, and such?

I believe we already do - we call it beef, pork, KFC...

Maybe a better idea would be to process anything edible that dies, and supplement it as needed. Like a big vat of slurry made of dead stuff, and it gets dehydrated into tasty snack cakes.

Everyone wins!

*barf*

 

[Eudaimonist]

Have faith. Cthulhu will provide.


Iä! Iä!

Mark