RSS iconTwitter iconFacebook icon

The Trek BBS title image

The Trek BBS statistics

Threads: 140,927
Posts: 5,478,778
Members: 25,054
Currently online: 517
Newest member: DRayTrekkie

TrekToday headlines

Trek Shirt And Hoodie
By: T'Bonz on Nov 27

A Klingon Christmas Carol’s Last Season
By: T'Bonz on Nov 27

Attack Wing Wave 10 Expansion Pack
By: T'Bonz on Nov 27

New Star Trek Funko Pop! Vinyl Figures
By: T'Bonz on Nov 26

QMx Mini Phaser Ornament
By: T'Bonz on Nov 26

Stewart as Neo-Nazi Skinhead
By: T'Bonz on Nov 26

Klingon Bloodwine To Debut
By: T'Bonz on Nov 25

Trek Actors In War Of The Worlds Fundraiser
By: T'Bonz on Nov 25

Star Trek: The Next Generation Gag Reel Tease
By: T'Bonz on Nov 24

Shatner In Haven
By: T'Bonz on Nov 24


Welcome! The Trek BBS is the number one place to chat about Star Trek with like-minded fans. Please login to see our full range of forums as well as the ability to send and receive private messages, track your favourite topics and of course join in the discussions.

If you are a new visitor, join us for free. If you are an existing member please login below. Note: for members who joined under our old messageboard system, please login with your display name not your login name.


Go Back   The Trek BBS > Misc. Star Trek > Trek Tech

Trek Tech Pass me the quantum flux regulator, will you?

Reply
 
Thread Tools
Old March 9 2010, 05:49 AM   #1
The Borgified Corpse
Admiral
 
The Borgified Corpse's Avatar
 
Location: Ouch! Forgotten already? You were just down there 20 minutes ago.
Simple gravity question

I'm collaborating with some other writers on a sci-fi webseries. It's set on a heavy gravity prison planet. My question is, how heavy can the gravity get before a normal, Earth-bred human is rendered incapable of functioning normally?

One draft mentions that the planet is 7 times the size of Earth. If we're talking 7 times Earth's mass, thus 7 times its gravity, that sounds rediculous to me. Am I wrong?
__________________
Kegg: "You're a Trekkie. The capacity to quibble over the minutiae of space opera films is your birthright."
The Borgified Corpse is offline   Reply With Quote
Old March 9 2010, 07:56 AM   #2
psCargile
Ensign
 
Location: GA
Send a message via Yahoo to psCargile
Re: Simple gravity question

You are right.

Seven gees is exceptionally high. A 200 lb person would weigh 1400 lbs. Even at 2 g that's 400 lbs. I would think that if you aren't able to support twice (or more) your weight for a long period of time, you'll be incapacitated rather quick. The heart is going to have a hard time pumping blood. The best analogy is what combat pilots can endure. Do a search for that for better explanations than what I can give.

Is there a reason why the prison planet needs to be a high gravity world? If it were just to make it exotic, I'd drop the whole notion. But if you need it, anything over 1 to 2 gees will be suitably uncomfortable until a person acclimates. 3 gees might be pushing it. At 7 to 9 gees, its not so much a prison planet as a means of execution.
psCargile is offline   Reply With Quote
Old March 9 2010, 08:20 AM   #3
The Borgified Corpse
Admiral
 
The Borgified Corpse's Avatar
 
Location: Ouch! Forgotten already? You were just down there 20 minutes ago.
Re: Simple gravity question

^Honestly, I think they're just trying to make it exotic. Certainly, making the gravity slightly heavier would add to the hostile nature of the planet. But I'm thinking 1.25 gees would probably be sufficient. 2 gees is probably as far as I would go. Any further and it would also start interfering with some of the cool martial arts fighting & such.

I'm just trying to make it a scant more plausible. The central conceit of the series is such strange fantasy to begin with, we probably don't want to compound it with crap science.
__________________
Kegg: "You're a Trekkie. The capacity to quibble over the minutiae of space opera films is your birthright."
The Borgified Corpse is offline   Reply With Quote
Old March 9 2010, 08:23 AM   #4
The Borgified Corpse
Admiral
 
The Borgified Corpse's Avatar
 
Location: Ouch! Forgotten already? You were just down there 20 minutes ago.
Re: Simple gravity question

BTW, the dialogue in the draft merely says the planet is 7 times the "size" of Earth. I suppose that could be referring to something else, like surface area, not mass. What's the likelihood of a planet with an Earth-like mass but 7 times the surface area?
__________________
Kegg: "You're a Trekkie. The capacity to quibble over the minutiae of space opera films is your birthright."
The Borgified Corpse is offline   Reply With Quote
Old March 9 2010, 03:14 PM   #5
Chaos Descending
Vice Admiral
 
Chaos Descending's Avatar
 
Location: Grand Canyon State
Re: Simple gravity question

Earth-like mass but 7 times the surface area would mean a planet with a much greater radius, and therefore a much lower surface gravity.

Also, in regards to original post, 7 times the mass would not equate to 7 times the gravity unless the volume (and therefore the radius) of the planet was exactly the same as Earth. The force of gravity is proportional to the mass but inversely proportional to the square of the radius.
__________________
"Romanes eunt domus"
- Brian
Chaos Descending is offline   Reply With Quote
Old March 9 2010, 03:37 PM   #6
Deks
Rear Admiral
 
Re: Simple gravity question

How much of a time frame would be needed for a Human to adapt from a 1 G environment to 3 G for example?
If/And once the individual in question adapts ... can you then try to put the 3G adapted human into a 4, or 5 G environment and see if they can adapt with sufficient amount of time?
__________________
We are who we choose to be but also have predefined aspects of our personalities we are born with, and make art that defines us.
Deks is offline   Reply With Quote
Old March 9 2010, 05:35 PM   #7
Chaos Descending
Vice Admiral
 
Chaos Descending's Avatar
 
Location: Grand Canyon State
Re: Simple gravity question

I don't know that a human being could EVER adjust to a 3g+ environment. A 200 pound man would have to get used to weighing 600 pounds. I just don't think that our knees, back, etc. are designed to withstand that sort of load.
__________________
"Romanes eunt domus"
- Brian
Chaos Descending is offline   Reply With Quote
Old March 9 2010, 08:05 PM   #8
Ronald Held
Rear Admiral
 
Location: On the USS Sovereign
Re: Simple gravity question

Why don't you be vague about the planetary physcial parameters and just state what the acceleration is in gees.
Ronald Held is offline   Reply With Quote
Old March 9 2010, 08:28 PM   #9
sojourner
Admiral
 
sojourner's Avatar
 
Location: I'm at WKRP
Re: Simple gravity question

Just a note, this thread would be better in science and technology than trektech. With that out of the way.

Don't forget about how a high gravity world is going to effect your martial arts. You would see very few throws, jumping manuevers, high kicks, etc. Most of it would be grapples, sweeps, etc.
__________________
Baby, you and me were never meant to be, just maybe think of me once in a while...
sojourner is offline   Reply With Quote
Old March 10 2010, 02:11 AM   #10
The Borgified Corpse
Admiral
 
The Borgified Corpse's Avatar
 
Location: Ouch! Forgotten already? You were just down there 20 minutes ago.
Re: Simple gravity question

Chaos Descending wrote: View Post
Earth-like mass but 7 times the surface area would mean a planet with a much greater radius, and therefore a much lower surface gravity.

Also, in regards to original post, 7 times the mass would not equate to 7 times the gravity unless the volume (and therefore the radius) of the planet was exactly the same as Earth. The force of gravity is proportional to the mass but inversely proportional to the square of the radius.
OK, so, because I'm not always a math whiz, what would be the approximate surface gravity of a planet of Earth-like density with 7 times Earth's mass & 7 times Earth's volume?
__________________
Kegg: "You're a Trekkie. The capacity to quibble over the minutiae of space opera films is your birthright."
The Borgified Corpse is offline   Reply With Quote
Old March 10 2010, 02:24 AM   #11
sojourner
Admiral
 
sojourner's Avatar
 
Location: I'm at WKRP
Re: Simple gravity question

I am probably wrong, but I am guessing 1g.
__________________
Baby, you and me were never meant to be, just maybe think of me once in a while...
sojourner is offline   Reply With Quote
Old March 10 2010, 04:42 AM   #12
T'Girl
Vice Admiral
 
T'Girl's Avatar
 
Location: comfortably residing in the meat packing district
Re: Simple gravity question

If the world had seven times the volume of Earth the diameter would be 32,970 miles, with a total surface area of 3,414,976,873.7 sq. miles, that's 17.34 times the area of Earth. If this world had Earth's mass the gravity at sea level would be 0.5665 gee.

If the world had Earth's density the gravity would be 2.87 gees.
__________________
.
TOS, TNG and VGR never mentioned a "Federation President."

Last edited by T'Girl; March 10 2010 at 05:15 AM.
T'Girl is offline   Reply With Quote
Old March 10 2010, 07:44 AM   #13
SpyOne
Commander
 
Re: Simple gravity question

The effect of high gravity on people for extended times is largely guesswork: we haven't spent a lot of time having test subjects living in centrifuges to see what happens.
IIRC, 1970s scifi had human colonies on worlds up to 2.5g on a regular basis. By the late 80s, scifi games were predicting that above 1.2g would interfere with your ability to sleep.

In the 1970s, scientists at the University of California at Davis raised some chickens in centrifuges specifically to see if the predictions were accurate. After living in 2.5g for months, chickens were 3 times stronger, had low body fat, had improved endurance, and their hearts were moving much greater volumes of blood.

I also should point out that a world much larger and more massive than the Earth will probably also be denser than the Earth: the gravity and the weight of the rock and stuff that makes up the planet will be squishing the stuff at the center much more than the Earth does. So a planet as described above (seven times the volume of Earth, at least as dense as Earth) would likely be even denser than Earth, and thus have higher gravity.
SpyOne is offline   Reply With Quote
Old March 11 2010, 01:04 AM   #14
psCargile
Ensign
 
Location: GA
Send a message via Yahoo to psCargile
Re: Simple gravity question

Borgified Corpse (neat name LOL) I have a calculating spreadsheet at home (at work as I post) that I created for determining planetary attributes based on size and mass. This is something I made for my own fiction and creating solar systems in Celestria. I can email this to you if you want.

Does a planet with 7 times the amount of mass as Earth have 7 times the pull of gravity, no matter it's radius? Let's find out:

g= G*(m1/r^2) where by G is the gravitational constant 6.6742x10^-11, m1 is the mass of the Earth in kilograms, 5.9736X10^24, and r is the Earth's radius in meters, 6.37101X10^6.

For 1g that equals 9.822 meters per second per second acceleration.

7 times the Earth's mass is 4.18152x10^25, which gives, 68.757. Divide that by 9.822 and you get 7.

7 times the Earth mass and 7 times the Earth radius gives 1.403 m pers s squared, or .143 g. This would be a planet a lot less dense than Earth.

7 times the mass of the Earth and 2.4 times the radius would give you 1.21 g.


http://en.wikipedia.org/wiki/Earth%27s_gravity for the formula. Plug that into a spreadsheet and play.
psCargile is offline   Reply With Quote
Old March 11 2010, 02:47 PM   #15
Christopher
Writer
 
Christopher's Avatar
 
Re: Simple gravity question

It depends on the density. The density of a planet can vary widely depending on its composition. Looking at my worldbuilding spreadsheet:

A pure silicate world with no significant metals and a mass of 7 M(Earth) would have a radius of 1.81, a density of 1.18, and a surface gravity of 2.14, all relative to Earth. A 7-Earth-mass world with an Earthlike composition (an iron core making up about 32.5% of its mass) would have a radius of 1.68, a density of 1.48, and a gravity of 2.48. A 7-Earth-mass world with a Mercury-like composition (iron core making up 70% of its mass) would have a radius of 1.49, a density of 2.12, and a gravity of 3.15. These are idealized cases, especially the first one, but they should give you ideas of the range of possibilities.

Or let's say you make it an ice planet with the composition of some of Saturn's moons, about 50% ice and 50% rock and metal. In that case, at 7 Earth masses, the radius would be about 2.33 of Earth's, the density only about 56% of Earth's, and the gravity only 1.29 gees. (Well, actually what I have in the spreadsheet is about 53% rock and metal and 47% ice by mass, but you get the idea.)


As for the ability to perform in high gravity, it would be extremely difficult at first, but if you trained properly and avoided injury, you could get strong enough to cope with it, just like any other kind of physical training. However, if you did strain or injure yourself early on, it might be hard to heal properly and the effects could be crippling. Also, in the long term it would put more strain on the circulatory system, but again, I think that's a question of training. I've read stories postulating that people on high-gee worlds had more heart failures and shorter lives, but I'm not so sure that's accurate. The heart is a muscle, so the more use it gets, the stronger it gets (again, assuming excessive strain and injury are avoided). So I'd think that, as with the rest of your muscles, it's a question of whether you train it properly, whether you get to start out slow and build up your strength and endurance. However, if you're suddenly dropped into a prison planet with 2-3 times your accustomed gravity and have to start fighting or struggling right away, that's more likely to lead to overstrain and injury and make it difficult to function. Although if you're already very physically fit to begin with, your chances would be better. (Needless to say, your cardiovascular fitness could be negatively impacted by factors in the prison environment such as stress or tobacco and drug use. Clean living is your best bet, but if you lived clean, why would be on a prison planet?)

Of course, all this is assuming normal, unaugmented humans. If you bring genetic and technological enhancements into the mix, all bets are off. People sent to live on high-gee worlds could have their joints reinforced or replaced with superior artificial versions, could possibly have their muscles augmented by nanofiber cables that contract with much greater force than human muscle, could have their heart and organs similarly augmented, etc. Or they could just wear the kind of strength-enhancing armature that's already being developed for military and medical uses.
__________________
Christopher L. Bennett Homepage -- Site update 11/16/14 including annotations for "The Caress of a Butterfly's Wing" and overview for DTI: The Collectors

Written Worlds -- My blog
Christopher is offline   Reply With Quote
Reply

Bookmarks

Tags
gravity

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 04:09 AM.

Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
FireFox 2+ or Internet Explorer 7+ highly recommended.