PDA

View Full Version : In the spirit of the new Godzilla movie. How big can life get on other planets?



MVAgusta1078RR
2014-May-12, 09:36 PM
I don't think I've seen this answered by astrobiologists or biologists anywhere. I've seen quite a few documentaries about what life might look like or be on other planets. But I just thought of the question because of the new movie. We all know dinosaurs here on Earth got pretty big, up to 100 feet long. How big could they get on a planet with weaker gravity, or atmosphere pressure, more oxygen etc.

Movies always portray alien life being as big as people, Alien, Star Wars, Independence Day etc. But could something get 300 feet tall on some other planet somewhere?

Noclevername
2014-May-12, 09:39 PM
Life gets bigger that that on Earth (http://en.wikipedia.org/wiki/Sequoia_sempervirens).

MVAgusta1078RR
2014-May-12, 10:23 PM
I mean is there a physical limit to something that moves around and is not stationary like a tree. For instance, could dinosaurs have been bigger on a planet with more oxygen and weaker gravity? How big can something like an animal get physically in the universe?

Noclevername
2014-May-12, 10:42 PM
I mean is there a physical limit to something that moves around and is not stationary like a tree. For instance, could dinosaurs have been bigger on a planet with more oxygen and weaker gravity? How big can something like an animal get physically in the universe?

Without knowing anything about ET lifeforms or how they might function, we don't have any way to determine how big they might get.

MVAgusta1078RR
2014-May-12, 10:58 PM
When I say "life" I mean any life, such as carbon based life here on Earth but evolving on another planet with different gravity and atmosphere.

My question isn't what alien life might be like, my question is what we know about biology, how would gravity and atmosphere affect the limit on the size?

Barabino
2014-May-19, 07:48 AM
Without knowing anything about ET lifeforms or how they might function, we don't have any way to determine how big they might get.

We can only cite the illustrations by artist Wayne Barlowe ;-)

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

19539

19540

MVAgusta1078RR
2014-May-19, 08:45 AM
This is more a physics question than biology...

Do you know by chance? The definition of sextillion? And 70 Sextillion stars in the observable universe.

Cite my ***...Have you heard of probability and every roll of the dice too?

eburacum45
2014-May-20, 10:00 AM
On a planet with lower gravity it is conceivable that an anmal-like organism could get much taller than the tallest creature on Earth (which was probably Sauroposeidon at 18.5 metres or so, 60 feet high, mostly neck).

On Mars, with gravity at 0.376 gees, a creature might get to be 160 feet tall. But there is a problem; Mars has a very thin atmosphere, because of the low gravity- so a vast creature like this would have almost nothing to breathe.

What about Titan? This is a world with very low gravity but a very thick atmosphere. If gravity were the only consideration, we might expect to see creatures 428 feet tall on Titan. But this moon is very, very cold - so maybe the Titanic Titanosaurs of Titan would be very, very slow moving, as well as very tall. They might be mistaken for mountains, or at least respectably sized hills. Large animals of this kind would have a vast volume, and would exert great pressure on the icy surface of Titan - so much so that they would probably sink into the ice and become bogged down. Perhaps if they had myriads of very large feet this might be avoided, but this seems a difficult body-plan to work with.

kzb
2014-May-20, 11:36 AM
[QUOTE=MVAgusta1078RR;2213791]This is more a physics question than biology...

QUOTE]

According to physics, the big flying reptiles couldn't fly....

Barabino
2014-May-21, 07:10 AM
Physics/geometry tells me that an alien "man" twice as tall and big, does not weight double, but EIGHT times!!! (2^3=8)

So do your calculations... a slim (2 metres for 70 kg) man if 100 metres tall would weight... 70 kg *50 *50 *50= 8750 tonnes :-/

even considering a lower gravity (20%, 30%...), it's still hundreds of tonnes... no organic bones could support him!

(biggest elephants weigh up to 7 tonnes...)

DonM435
2014-May-21, 01:15 PM
[QUOTE=MVAgusta1078RR;2213791]This is more a physics question than biology...

QUOTE]

According to physics, the big flying reptiles couldn't fly....

Didn't some physicists once declare that the bumblebee couldn't fly?

(The bee didn't know this and just went on flying.)

kzb
2014-May-23, 04:14 PM
[QUOTE=kzb;2214074]

Didn't some physicists once declare that the bumblebee couldn't fly?

(The bee didn't know this and just went on flying.)


Exactly. Also the giant sauropods couldn't walk on land (there is even a theory that the air pressure must've been greater than on Venus to provide buoyancy for these reptiles).

The point is, biology often challenges physics. A physicist who thought a bumblebee was a conjectured alien spieces would've dismissed it as impossible. I think now the bumblebee flight is explained by physics, but it took the challenge of the bumblebee existence to make them do it.

kzb
2014-May-24, 05:06 PM
There is a Brian Aldiss (?) short story about what seems to be a six legged lizard type creature, thousands of miles in size. Basically it just landed on Earth one day. Everytime it moves (luckily not often) it causes major catastrophe of course. THAT is big, and also big enough to make it beleivable that human weapons would be powerless against it. Even H-bombs merely irritate it, and you don't want that.

Even a 100 metre creature would be easily dispatched with current weaponry, which makes these films a bit silly to me.

[added in edit] The story is called Heresies of the Huge God, and is indeed by Brian W Aldiss. The creature has eight legs (not six) and is 4,500 miles long, with each leg about 900 miles long. The story is a satire on religion of course, and full of black humour.

http://alfalib.com/site/download/id/103042

publiusr
2014-May-31, 06:38 PM
Bokrug is not pleased...

Colin Robinson
2014-Jun-01, 09:19 AM
On a planet with lower gravity it is conceivable that an anmal-like organism could get much taller than the tallest creature on Earth (which was probably Sauroposeidon at 18.5 metres or so, 60 feet high, mostly neck).

On Mars, with gravity at 0.376 gees, a creature might get to be 160 feet tall. But there is a problem; Mars has a very thin atmosphere, because of the low gravity- so a vast creature like this would have almost nothing to breathe.

What about Titan? This is a world with very low gravity but a very thick atmosphere.

Titan's atmosphere is thick yes. Also, it is not at chemical equilibrium, which means an organism could get energy by breathing it. ... However, the concentration of free hydrogen on Titan is a lot lower than the concentration of free oxygen on Earth, therefore energy is not as readily available there as here. This is why astrobiologists who have looked at the question of life on Titan think in terms of microbes (whose energy requirements are comparatively modest) rather than dinosaurs or people.


If gravity were the only consideration, we might expect to see creatures 428 feet tall on Titan. But this moon is very, very cold - so maybe the Titanic Titanosaurs of Titan would be very, very slow moving, as well as very tall. They might be mistaken for mountains, or at least respectably sized hills. Large animals of this kind would have a vast volume, and would exert great pressure on the icy surface of Titan - so much so that they would probably sink into the ice and become bogged down. Perhaps if they had myriads of very large feet this might be avoided, but this seems a difficult body-plan to work with.

I doubt they would sink into the ice, because water ice on the surface of Titan is not like water ice here... no tendency to melt (except perhaps in volcanic areas)... so it is really more like rock... a good stable surface for a Godzilla to walk on... if Godzilla has a solution to the just-mentioned energy problem...