The Universe

[captain kirk]

ASTEROID SIZE OF CUBA ON TARGET TO ANNIHILATE HUMAN RACE (IN YEAR 3063)

Good news we can stop worring about global warming then.

[Hedgecutter]

http://www.rememberthe13th.com/

"NASA has made a historic discovery that will shake the entire planet. This announcement will be released to the media on November 13th, 2013. It will be a day to remember and One for the history books."

So, what we thinking?

So Purple Ninja is the new Black Matter then, huh.

[Boomtown Boy]

ASTEROID SIZE OF CUBA ON TARGET TO ANNIHILATE HUMAN RACE (IN YEAR 3063)Eta: Site claims that the news has been brought forward to 6th October. Two days until global panic and widespread looting.

Have they made this announcement yet?

[Hedgecutter]

Have they made this announcement yet?

See my last post above. They announced the big news yesterday.

[DAFC]

Has anyone suggested the idea that maybe the Universe is on a loop and the space inside it expands and contracts again?

Horrible to think that everything just expands then dies.

[Ludo*1]

As I'm about to prove with this question, I'm not the brightest on the subject. We define 'life on mars' as life that could only live on earth so in that sense it needs a mixture of key ingredients such as water/oxygen or whatever. So who is to say that the likes of Jupiter isn't beaming with life forms that breath gas and don't need water for survival?

[Hedgecutter]

As I'm about to prove with this question, I'm not the brightest on the subject. We define 'life on mars' as life that could only live on earth so in that sense it needs a mixture of key ingredients such as water/oxygen or whatever. So who is to say that the likes of Jupiter isn't beaming with life forms that breath gas and don't need water for survival?

The distinct lack of land on the gas giant Jupiter could be a factor. Maybe getting crushed to a pulp under the enormous gravitational forces too. However, I have also wondered why people base water as being a requirement for life. Why couldn't life in some far flung place have evolved to use some other substance rather than water?

[grumswall]

It could have, we only search for life based on our own experience of what life needs to flourish. As we have seen on this planet life flourishes under all different scenarios but they all have the same or similar requirements to ourselves.

[grumswall]

Wont let me edit. Not the best way of putting it but you should get the gist.

[Hedgecutter]

They have the same or similar requirements to ourselves.

Not that surprising considering most things (if not everything?) have evolved from the same algae / bacteria on a small planet for 3 billion or so years.

[captain kirk]

Horrible to think that everything just expands then dies.

Sounds like the life of your average rangers fan.

[DAFC]

Waistline and football team, so sad.

[dorlomin]

Edinburgh based scientist wins the physics Nobel.

http://en.wikipedia.org/wiki/Peter_Higgs

Awesome!

[renton]

As I'm about to prove with this question, I'm not the brightest on the subject. We define 'life on mars' as life that could only live on earth so in that sense it needs a mixture of key ingredients such as water/oxygen or whatever. So who is to say that the likes of Jupiter isn't beaming with life forms that breath gas and don't need water for survival?

Water really is just very useful for the job. Neutral pH allows it to dissolve metallic and non metallic ions equally, the fact organic molecules (more on that in a minute) can be both hydrophobic and hydrophilic with respect to H2O means that you can create specific water enclosing membranes - i.e. you can start to use simple organic molecules to create structures like cells. Another thing going for it is the fact that it's small molecule size would mean it would ordinarily be a gas, but for the polar nature of the molecule, this hydrogen bonding holds it into a liquid state - it's very easy to get energy in and out of the system, so that any water environment is thermodynamically quite stable, which allows for quite a quiescent enviroment for life to flourish.

Carbon, is the other big one. Carbon has a flexiblity in forming compounds that is virtually unmatched aside form silicon, it can form long covalent bonds with hydrogen and oxygen to form organic polarisable molecules that become the building blocks of proteins and then to DNA. The reason that is important is that we can consider any instance of life in terms of information storage and transmission, what you are can be reduced to the map of your genomes, each repeating instance of certain proteins in sequence, like a bitstream of data. Life, at it's most basic is the ordering of information in unique forms which are then repeated, spliced, overwritten and re-ordered. Why carbon is important is that it allows for the construciton of a great many different base molecules ot form the proteins that become the DNA sequence. Other base elements would not be able to form the variety of molecules Carbon does, and thus would limit the number of more complex structures that could be formed. That limitation would inevitably restrict the amount of information that could pass from generation of life to the next and would stunt the growth of any evolutionary tree. Carbon,then, represents an optimal state of formation of information carrying molecules.

So, yeah, we look for those elements, carbon, hydrogen, nitrogen and oxygen, as these are the elements that allow the formation of complex molecules and further into more complex biochemical structures. That's not to say they ar ethe only ones. Ammonia could easily replace water, as a cradle for life to form, and silicon could conceivably form the base of long complex covalent chains, as carbon does - but it has the disadvantage of not forming double or triple bonds as easily as carbon, also, unlike carbon it has a strong association with oxygen, oxidised silicon forms a solid, oxidised carbon forms a gas. Think of that in terms od respiratory systems. We breathe out carbon based gas - imagine trying to cough up silicon oxide (or sand, as it's more commonly known). Now, that might be thinking too anthropomorphic and respiration might not be based on oxygen elsewhere, but there is no doubt that the exchange of energy between carbon and oxygen is an optimal reaction in comparison to most others. Silicon also lacks chirality: carbon based molecules form left and right handed mirrors of each other in sugars and proteins, important in allowing for the replication of DNA. Finally, there is a far greater percentage of Carbon than silicon in the universe. Making life based on carbon, a higher probability.

Again, there is nothing to say that life could form without using DNA, it is probable, however, that in terms of reordering and replicating information, you require to build complex molecules, and while alien life might not exhibit what we'd recognise as a double helix DNA strucure, it's not a bad assumption that it would be based on chiral carbon chains. So, we go looking for environments that would support the formation (or at the very least, survival) of such molecules (I say survive becuase it's possible that these chains originated in comets that then crashed to earth, all life, may be extra terrestrial!) water, we know is a fantadtically benign environment for life to originate in - but it's not just water, being a rocky and volcanically active place, there has always been oases of energy that allowed complex carbon chains to form without being too volatile that they were destroyed. This in term enables the formation of life. Could life originate on Jupiter? the gas giant possibly could, but without a relatively constant energy source, could life arise, maybe in the upper atmosphere? the problem there is that as soon as your carbon atom is heavier than the hydrogen that makes up the majority of Jupiter's mass, so it sinks down towards the core, where, under immense pressure and heat, it strips any attempt at a complex molecule back to it's base elements. Places like Europa are of interest, as we are fairly sure it has an acitve geothermal core and a nice big ocean: energy, a thermodynamically benign environment to regulate the energy and carbon.

Finally, we cannot escape the basic anthropomorthism of the search, we look for water and carbon and oxygen becuase we know it works. It could work with ammonia and/or silicon but we don't know how and all oour chemistry suggests it would be a less than optimal set of circumstances. That's not to say it couldn't happen though.

Edited October 8, 2013 by renton

[King Joffrey]

Quite.

[Ludo*1]

That is a sensational answer and told me exactly what I wanted to know! I'll get you dotted as soon as I'm on a computer. Thanks very much.

[renton]

That is a sensational answer and told me exactly what I wanted to know! I'll get you dotted as soon as I'm on a computer. Thanks very much.

Might all be bullshit mind. I know some carbon chemistry and a lot of silicon chemistry as part of my job (work in semiconductor device design), but I'm no biologist.

[Confidemus]

Might all be bullshit mind. I know some carbon chemistry and a lot of silicon chemistry as part of my job (work in semiconductor device design), but I'm no biologist.

Would you classify yourself as a boffin?

[renton]

Would you classify yourself as a boffin?

I have my moments....

[JustOneCornetto]

http://buff.ly/15Ptyoc