those aren't her ideas
they're arthur c clarke's (a meeting with medusa) and arthur conan doyle's (the horror of the heights).
A British satellite expert reckons aliens will be enormous bewildering monsters ideal for depicting on telly science shows, the very sort of programme the government adviser is happy to front. Dr Maggie Aderin-Pocock said extraterrestrials could be football-field-size jellyfish with orange stomaches that float in the skies of …
On a topic of biology?
That's like asking your barber to defend you in court on a criminal matter. They might be a good at cutting hair, but they are not qualified to practice law.
Aderin-Pocock might be a decent person to discuss satellites, but she's fundamentally unqualified to discuss terrestrial biology, much less astrobiology.
Some people know a lot about things that they aren't professionally involved in. I don't think she's asking (or anyone else is asking on her behalf) that you should consider her argments based on her position. Nowhere does she say: "I'm right about aliens because I work with satellites." She's just putting forward some arguments that can be considered on their own merits. And in an interview where she was asked to do so as far as I can see. Is there anything wrong with what she's saying?
I think you'll find that almost anyone is well qualified to discuss astrobiology. Unless you know of any silicon based lifeform experts who can disprove her ramblings I'd just nod patronisingly and wait for some data to come along and add a small iota of science to the subject.
A I recall from my biochemistry (MANY moons ago) silicon analogs for DNA becomes more and more unstable the longer the chains become (if you try to replace carbon with silicon.) That restricts the versatility of silicon in extremely large molecules (but then the human DNA appears to have a large amount of redundancy built into it) so the biochemistry would have to be seen before we could explore it.
Carl Sagan's 'Cosmos' featured a painting of (and I have to use the word) blobominations in Jupiter's atmosphere, based on work by Sagan and a colleague from Cornell, Ernest Salpeter. They knew the planet's interior was rich in organic molecules and warm, so life wasn't out of the question.
And you're wrong.
A submarine uses compressed air to blow out water tanks, replacing water (heavy) with air (lighter).
What lighter stuff does the alien creature have? Compressed vacuum?
She could secrete water or condense it from the atmosphere. That could work.
But Miek is right. His comment shows how bad this thing is thought through.
Well it wouldn't necessarily need to change its boyancy. Not as long as the gradient in atmospheric density is gradual enough to be irrelevant. Birds are able to go up and down without having to change their density. They just need motive force in the appropriate direction. As birds are heavier than air, they need to provide it themselves to go up (and they just use gravity to go down). But a creature that had near-neutral boyancy in the atmosphere would just need to squirt some air upwards or downwards to descend or ascend. I mean sharks don't need to change their density to rise or fall in water, do they? And from the sounds of this, we're talking pretty dense atmospheres.
Not entirely true; The reletive mass of a submarine when dived is pretty much the same as the displaced water, and only minor changes in ballast are required at constant depth, usually as waste is discharged and food is consumed. To change a submarines depth, internal ballast tanks are used where the surrounding water is flooded in to increase the mass of the boat or pumped out by the ballast pump to decrease the mass of the boat, hence changing the depth.
The only other variable is that the volume of the submarine will change with depth due to the crush effect, thus becoming denser the deeper you wish to dive, therefore requiring de-ballasting on the way down.
I suppose the 'creature' in question would be internally less dense than the atmosphere around it, apart from it's onion shaped balls, which it would presumably blow only if it wanted to get really high!
If you inhale air from your top, and exhale air from your bottom*, you should be taking in lighter air and expelling heavier air. The difference may not be much, but if you're large enough and move enough air, plus have an internal mechanism to filter the heavier parts from the lighter parts, it might work.
* WHAT IS all that sniggering!? This is a serious scientific discussion!
The creature could turn nutrients into energy and heat the gas inside it, just like our hot air balloons. It could also get some energy from sunlight -if available in big enough amounts- and capture hot gas from rising convection currents; While on the convection current, it could absorb hot air, and that would give it buoyancy when it left the hot current.
If instead of a balloon-like structures it had some kind of hard carapace, it could also use some muscles to decrease its interior pressure. This last method could probably make sense in very dense atmospheres.
Silicon based life forms that are completely nonhuman, possibly insectoid? Gosh that will take some imagination! Or you could just get some 60 year old back issues of Fantasy & Science Fiction magazine...which is where I first saw this idea put forth. And, I might add, presented entirely from an alien point of view, which was quite awesome.
I say that if a scientist wants to talk about his neat theories for possible forms of alien life, he should learn to write a decent short story.
Beer, even though my work day is sadly far from over.
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