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Some days ago I had a discussion with a friend about possible alien life forms.

He was stating that there anywhere could be lifeforms that do interplanetary or even interstellar travel by jumping of from the planetarys velocity.

I tried to counter argue, while I had ideas in mind like it couldn't be because:

  • How a species should develop this way? What benefit would a species with its origin on a planet gain that requires it to jump into space, without which it wouldn't survive? And how should this mutate?

  • Gravity?! When thinking about the forces required for escaping earths velocity, assuming at what ever low scale the gravity of that planet may be, the energy consumption of such a being that it in theory could develop this jump trait would be so enormous, that it couldn't be provided with enough resources by such a planet, that there a whole set of species could evolve from a what ever state to a state where it is able to do this kind of jumps, before the planets resources in that way, useful for such a being would be completely harvested.

But actually I wasn't able to bring it to a point that would have been convincing, since both are sciences I'm not that much sued to.

So could one complete my assumptions with scientifically backed data, or if my arguments are wrong how can it be disproved?

Of course, in case I was wrong and this COULD actually happen, I would like to hear this as well.

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  • $\begingroup$ You do realize the implications of tagging this question [hard-science], don't you? (I'm not saying you don't want to use that tag, I just want to make sure you realize what it means in terms of what answers you might get.) I did otherwise edit the tags somewhat to try to better categorize your question. $\endgroup$ – a CVn Apr 19 '16 at 11:13
  • $\begingroup$ Take a look at Michael Crichton's classic The Andromeda Strain. en.wikipedia.org/wiki/The_Andromeda_Strain If you have a life-form that does not need an atmosphere to live and that can convert energy to matter, then you would have something that can live on low gravity bodies - like asteroids and planetary ring fragments - and that spreads whenever something collides with their "home". $\endgroup$ – MichaelK Apr 19 '16 at 11:23
  • $\begingroup$ @MichaelKjörling: Maybe I don't, but what I wanted to implicate by tagging it as this, was, I want a scientific disprove of such beeings could be existing (if there is) or on the other hand, if I was wrong, I want to see an proven (by available scientific data) theory that would at least support the idea of those beings could exist. If thats not what the hard-science tag is for, feel free to elt me know or just edit in the science-based tag isntead (or what ever would be fitting) $\endgroup$ – Zaibis Apr 19 '16 at 11:23
  • $\begingroup$ @MichaelKarnerfors: interesting read, but I actually can't judge about how much of it would scientifc be possible and how much is just scifi. $\endgroup$ – Zaibis Apr 19 '16 at 11:25
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    $\begingroup$ The Andromeda Strain doesn't "jump", it's more like a bacteria or virus spreading through accidental contacts. $\endgroup$ – Tim B Apr 19 '16 at 12:23
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Did the question specify naturally evolved? If so I missed it.

So what are the limits to artificially engineered life? I cannot think of a fundamental reason why something like Larry Niven's stage trees could not be caused to exist. They were once ICBM rockets that grew instead of being built. They outlasted the war.

My favorite fictional interstellar life form are the titans in John Varley's Gaea trilogy. They were originally engineered as cyborg seeds which would grow on large asteroids and small moons, then launch themselves and develop into space habitats. They are sentient beings. They have been modifying their own design over many millions of years and seeding neighbouring star systems. They can't remember what happened to their creators (or so Gaea says; she is a most unreliable source).

Its a wonderful vision and the only thing in the fiction that I'm almost sure is impossible is oddly one that I'm now sure the author did not need to invent. Computers have come so far that an AI no longer needs a McGuffin as it's underlying hardware to be plausible!

I'd agree that natural evolution on planets with atmospheres does not offer a means for life to get off-planet. Whether some other sort of life can evolve in space, we do not know. It hasn't here, as far as we know.

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  • $\begingroup$ Hm, nice one. I didn|t specifz it because I didn|t think about it. We both when discussing were not thinking about it. But in point of said discusson this probabblz would have been valid :) nice one. $\endgroup$ – Zaibis Apr 19 '16 at 19:00
  • $\begingroup$ There are also the aliens of Robert L. Forward's Camelot 30K. Although they know nothing of their origins they must have been created as there's no way they could have evolved. Again, the spread is only in reproduction, the aliens themselves never leave their world. $\endgroup$ – Loren Pechtel Apr 20 '16 at 0:41
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The simple answer is, no. Not on earth-like planets anyway.

Escape velocity of earth is 11.2km/s. But we're not in a vacuum, you have a huge amount of atmospheric drag as you rise.

You should read this article: https://en.wikipedia.org/wiki/Space_gun

It has been conjectured that space guns could place satellites into Earth's orbit (although after-launch propulsion of the satellite would be necessary to achieve a stable orbit), and could also launch spacecraft beyond Earth's gravitational pull and into other parts of the Solar System by exceeding Earth's escape velocity of about 11.2 km/s or 40,320 km/h (25,050 mph). However, these speeds are too far into the hypersonic range for most practical propulsion systems and also would cause most objects to burn up due to aerodynamic heating or be torn apart by aerodynamic drag. Therefore, a more likely future use of space guns would be to launch objects into near Earth orbit, from where attached rockets could be fired or the objects could be "collected" by maneuverable orbiting satellites.

There is no feasible organic creature that is capable of doing anything resembling a jump at 25 thousand miles per hour. Even if it could then it would get ripped apart or super-heated by passing through the atmosphere, and even if it survived that then it actually needed to jump faster to compensate for that drag.

And that's just getting into space, nothing about getting anywhere once you are in space!

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  • $\begingroup$ While I agree with the point made, strictly speaking to get into space you only need a velocity of about 8 km/s along the correct vector. At escape velocity you leave the graviational influence of the planet never to return; a nonpropulsive object at escape velocity will approach but never reach a standstill relative to the origin body. Of course, for "interplanetary travel" escape velocity is more in line with what you'd need than is orbital velocities. For interstellar travel you need even more to break free of the Sun's gravity. $\endgroup$ – a CVn Apr 19 '16 at 13:26
  • $\begingroup$ The US had a project back in the 60s that used a cannon to fire test probes out of the atmosphere. The highest altitude reached was about 110 miles, but the project never came close to launching something into orbit. (en.wikipedia.org/wiki/Project_HARP) $\endgroup$ – Howard Miller Apr 19 '16 at 14:35
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Given the problem exactly as stated the answer is a clear no. The issue is energy density. There is no chemical reaction energetic enough to lift it's components to orbit. Thus, quite apart from the already-mentioned issues of passage through the atmosphere you're simply not going to get there.

To reach orbit of an Earth-sized body requires leaving a lot of mass behind. You either leave your power source behind (supergun, launch loop or space elevator) or you discard spent reaction materials as you go (rockets).

Do I hear "nuclear" from the peanut gallery?? Nuclear energy has the density required, a chunk of U-235 has plenty of energy to lift the creature. The problem here is one of energy flow. How do you convert that nuclear power into a jump? And how do you avoid vaporizing however that muscle is attached to the body?

Now, I could conceive of a nuclear-powered creature capable of getting into space but it would be an Orion drive, not jumping.

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A species can develop any way imaginable (and a few more) by developing technology that allows them to create new species or change existing species.

The jumping might involve a pretty generous definition of "jump", and have various requirements for the launch planet's atmosphere.

Mandatory reading material:

https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

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