distant planets

[Vaskez]

Originally posted by krunchyfrogg: quote: Originally posted by Vaskez: What's the point in having a discussion if no one reads what you write? This is ****in pointless! As far as I'm concerned the issue you raise has been addressed Gouldum [img]tongue.gif[/img]

[/QUOTE]Been here much longer than you [img]tongue.gif[/img]

[Marant]

Refering back to the whole "life must be carbon based" thing it's not necessarily true. You can work things along pretty far substituting sulphur for carbon and ammonia for water. It just doesn't work so well in an oxygen atmosphere. In fact a while ago they thought they'd found sulphur based life forms here on earth, around volcanic vents on the ocean bed - so called black smokers. Silicon life forms are not impossible either..

try http://www.daviddarling.info/encyclo...monialife.html

or http://www.daviddarling.info/encyclo...liconlife.html

I'm not sure of the scientific validity of this site as I haven't read it all through. So consider this a disclaimer of any hoki bunkum that you may find.

I don't think that you will have to go all that far to find life - the best chance is right here in our own solar system on Europa, one of the moons of [jupiter?]. Whilst the surface is frozen over, there is strong evidence of liquid water under the surface, indicating that the moon has an internal source of heat. If there are black smokers there like there are on earth, then the warm, rich chemical soups they pump out may be ideal for the formation of life. It's considered that life first evolved on earth around these vents. Unlike as is frequently supposed, light is not necessary for life.

[Thoran]

There have been several recent discoveries that have moved the drake equation towards increasing probability of life.

There's the work being done on Mars that hints that it may have once had an environment hospitable to our version of life. There's the discoveries by Cassini/Huygens that Titan HAS the constituents of life... if it was warmer who knows... it might have had life on it by now.

We've got a number of bodies in our tiny backwater solar system that have pieces of the "habitable planet" puzzle... and then we add to that the discoveries that many stars have planetary systems (I believe it likely that virtually ALL stars over a certain age have planetary systems, but that's still debatable) and you end up with a whole lot of potential sites for a earth-like planet to develop. Perhaps the close in gas giants are a problem and perhaps they're not, but they're finding gas giants at jupiter/saturn distances now... so they no longer think that the close in gas giant is the norm. IMO in our little Galexy alone there are likely MILLIONS of star systems with configurations that leave a rocky planet in a temperature zone amenable to a liquid water presence. Hell we almost have two such planets in this system alone.

The only question that I feel is relatively unanswered is what is the probability of life developing on a liquid water planet. I think that's not a question we're going to answer anytime soon, because even if we find microbial life in Mars or another non-terran site, it would be quite possible that it would represent earth contamination not an independantly evolved life. We need to find extra-solar proof of life before we can get a handle on the life part of the equation.

Personally I believe the probability of extra-terran life is very close to 100% (99.999... and a lot more 9's), and the probability of intelligent extra-terran life is also very high. (better than 99%)

[Vaskez]

This whole discussion can get the scientific-religious mind in a twist Some believe that God really only needed to interfere twice in the history of life. Once when amino acids first formed life and once when intelligent life evolved from primates. This then leaves the question (if you believe in this) would He interfere on other planets as well? [img]smile.gif[/img]

[Iron Greasel]

I would answer that, Vazzy, but it would be too much like religious discussion. [img]tongue.gif[/img]


Shamrock, how can we see light bend around the space-time as we are parts of it? We can see the bending of two-dimensional bedsheet through the third dimension, but the Posiible two-dimensional life forms shouldn't be able to. In my opinion. If light travels through all the bumps and twists in space, it moves in straight lines from its own point of view. And as we get most of our imformation of the universe via light or light-like thingies, we see the light as moving in straight lines. It would all make sense if light ignored the spatial bumps and holes and knots and moved in what four-dimensional beings would perceive as straihgt lines.

Of course this is just what I have thought with my own brains. For some reason they don't teach multidimensional physics on 9th grade.

[shamrock_uk]

Well, observationally, when the sun is covered by the moon (as in an eclipse) we observe that the position of certain stars are actually shifted. This is completely from memory so it may be slightly innacurate, but basically we're able to see stars that should be 'behind' the Sun from our perspective. In other words their actual position is slightly behind the edge of the disk of the Sun, yet somehow we can see them. Like this:
(the .'s are needed to stop the forum from screwing up my diagrams! they just represent empty space)

....x = Star
....|
....|
....|
....|
..O.|
OOO| = Sun
..O.|
....|
....|
....E = Earth

The |'s represent the path the light takes - we would expect that the light from these stars would be blocked by the Sun - Einstein told us that we should expect to see the path of the light distorted and could therefore observe stars that we shouldn't be able to. This was shown experimentally for the first time approx 1919 (around that time anyway [img]tongue.gif[/img] )

The reason we have to wait until an eclipse is that only the Sun has a large enough mass for us to easily observe this phenomenon and usually its too bright to see any stars near to it. The only way we can see stars near it is during an eclipse when it's nice and dark.

The answer to your question about how we can see it bend when we always see light travel in a straight line is that we can't of course [img]smile.gif[/img] It looks like this:

......x = Star
......|
......|
......|
......|
..O..|
OOO| = Sun
..O..|
......|
......|
......E = Earth

Except we know from observing this star normally (ie. at night) that it's over to the left as in the first diagramme. It's only during an eclipse that we see it in the wrong place. It still looks like the light is travelling in a straight line, but we know better [img]smile.gif[/img]

Interestingly, this phenomenon has now been observed on a much larger scale in a process called gravitational lensing. It's a bit different, but the end result is similar - instead of the sun, imagine an entire galaxy or other massive object in the way. Sometimes we're able to see galaxies from really really far away and usually gravitational lensing is the culprit. It's slightly different because the distant object also gets magnified, but it's another example of how distorted space-time can be observed.

If you google for Hubble and Gravitational Lensing you'll probably find some nice pictures of it.


Edits to sort out my diagrams. grr...hang on, this will take a minute
Aah, that's better. You'd be amazed how much the forum software mangles straight lines like that.

Incidentally, if you're only in the 9th grade yet able to realise that it wouldn't be possible to see light travelling on a curved path then I suggest you think about a career in physics! That's remarkably perceptive!

[ 04-11-2005, 01:46 PM: Message edited by: shamrock_uk ]

[Iron Greasel]

Ah, I get it! curled-up space doesn't bend light, gravity does. The heavy thing acts just like a magnifying glass.

[shamrock_uk]

Yes, but you can't leave the curled-up space completely out of the equation - gravity 'bends' space which in turn changes the path the light travels.

[Vaskez]

Interesting post shammy and nice diagrams

So why DOES light get effected like that? This sounds like a stupid question but since light is an electromagnetic wave (the light-like "thingies" Greasy) why does it have mass, which it must do to be affected by gravity? Well I suppose there's the whole wave-partical duality thing. Do photons have mass? I thought they were just "energy packets" - changes in space in the amount of energy at that location...

[shamrock_uk]

The light doesn't get affected directly at all. It's just travelling on its own merry way, runs into the curve in space caused by the gravity and follows that.

Let me think of another analogy...

Ok, you're travelling slowly along a narrow river in a boat (which represents our beam of light) and there's a weir to the right hand side. The presence of the weir has absolutely no direct effect on your boat whatsoever (ie. there's no force from the weir that is pulling your boat) - it's just keeping going forward.

However the weir is moving the water that your boat is floating on and therefore your boat will veer to the right.The weir isn't affecting your boat itself though, just the water it travels on.


As for photons having mass and other such nasty questions. A physics textbook will tell you they have negligable mass (same as electrons and things like that). Now, bear in mind that negligable doesn't actually mean zilch, just really really tiny.

Another of Einstein's famous equations E=mc^2 tells us that anything with energy and velocity will have a mass of sorts, even if it is ridiculously tiny.

I was visiting Cern and got to watch this visitor telling the particle physicist that electrons didn't have mass. Well, the response was that it did have a mass. For normal people its so ridiculously tiny it doesn't really matter, but for these guys I guess it starts to be a bit more important.

Once again though, the fact it has even a token mass has nothing to do with it appearing to be bent by gravity - the gravity is affecting the space it travels in, not the light itself.

[ 04-11-2005, 03:52 PM: Message edited by: shamrock_uk ]