gravity

[Chiropteran]

The effect of gravity is said to be identical to that of acceleration. This is why when you are in free fall, you have a feeling of weightlessness and don't feel gravity- the acceleration of falling exactly counters the "acceleration" effect of gravity.

This means we don't feel the gravity of the sun. We are in free fall, with the entire planet earth, in orbit around the sun, so we don't feel the effects of the sun's gravity. Also, because of our distance from the sun, even if we did feel the effects of it's gravity it wouldn't be very noticeable, according to a quick google search the sun's gravity on earth is about 0.0006 times the strength of the earth's gravity, seems barely noticeable.

However, the closer you get the stronger the force of gravity. Also, some other systems have much more massive stars, more compact stars, and some that are both. The obvious extreme is a black hole. But before you reach the level of a black hole, at some point you reach the threshold where the gravity is strong enough to kill a human.

This would, in some ways, be worse than passing the even horizon of a black hole. There would still be theoretical capability for a spaceship or craft to escape from the gravity at that point, but in doing so the force of acceleration would crush the occupants to death. I don't see any way around it. You either live in free fall for the rest of your time, or you try to fly away and get crushed by the force of gravity.

Now imagine if there was a solar system with such a massive/dense star that it's gravity was beyond the human limit of survival, but yet it had a hospitable planet within that limit. You could land there and live the rest of your life, but you could never escape. As long as you are in free fall around the star you would be fine and you wouldn't feel it's incredible gravity, but if you tried to fly away the only way to do so would be to accelerate beyond crushing speeds. Is this even possible, could a star with a gravity so strong have a planet in it's orbit, or would the orbit just decay too quickly?

tl;dr: I can't summarize this, maybe someone else will.

 

[So]

Er, can't you just accelerate really slowly from freefall and "climb" up the orbits until you're clear?

 

[So]

Like this: MS PAINT T3H HORROR

 

[So]

Oh, and: http://en.wikipedia.org/wiki/Hohmann_transfer_orbit

 

[YOyoYOhowsDAjello]

That's the first thing I thought of, So

 

[DrawninwarD]

Originally posted by: Chiropteran
The effect of gravity is said to be identical to that of acceleration. This is why when you are in free fall, you have a feeling of weightlessness and don't feel gravity- the acceleration of falling exactly counters the "acceleration" effect of gravity.

This means we don't feel the gravity of the sun. We are in free fall, with the entire planet earth, in orbit around the sun, so we don't feel the effects of the sun's gravity. Also, because of our distance from the sun, even if we did feel the effects of it's gravity it wouldn't be very noticeable, according to a quick google search the sun's gravity on earth is about 0.0006 times the strength of the earth's gravity, seems barely noticeable.

However, the closer you get the stronger the force of gravity. Also, some other systems have much more massive stars, more compact stars, and some that are both. The obvious extreme is a black hole. But before you reach the level of a black hole, at some point you reach the threshold where the gravity is strong enough to kill a human.

This would, in some ways, be worse than passing the even horizon of a black hole. There would still be theoretical capability for a spaceship or craft to escape from the gravity at that point, but in doing so the force of acceleration would crush the occupants to death. I don't see any way around it. You either live in free fall for the rest of your time, or you try to fly away and get crushed by the force of gravity.

Now imagine if there was a solar system with such a massive/dense star that it's gravity was beyond the human limit of survival, but yet it had a hospitable planet within that limit. You could land there and live the rest of your life, but you could never escape. As long as you are in free fall around the star you would be fine and you wouldn't feel it's incredible gravity, but if you tried to fly away the only way to do so would be to accelerate beyond crushing speeds. Is this even possible, could a star with a gravity so strong have a planet in it's orbit, or would the orbit just decay too quickly?

tl;dr: I can't summarize this, maybe someone else will.

WTF?

Okay suppose that star has such a strong gravitational pull that it would kill you if you were to be in the solar system. Then it's impossible for there to be a freaking hospitable planet. You'd DIE ANYWHERE in the solar system. You can't dupe gravity like that.

And if gravity was so strong from a star, I really don't think you'd have a hospitable chunk of rock anywhere close by.

 

[So]

Originally posted by: YOyoYOhowsDAjello
That's the first thing I thought of, So

:beer: Problem solved.

 

[JTsyo]

That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

 

[So]

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

True. http://en.wikipedia.org/wiki/Roche_limit

 

[Cuda1447]

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

What if you were a midget then?

 

[destrekor]

Originally posted by: So

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

True. http://en.wikipedia.org/wiki/Roche_limit

And you know what's really weird about gravity, in terms of the combined force of multiple bodies exerting gravity? The existence of Lagrangian points/orbits.
Lagrangian Points

The James Webb Space Telescope, the successor for the Hubble Space Telescope, will be placed at the L2 point, with the Earth's shadow forever blocking the radiation from the sun from interfering with the image quality/electronics of the telescope (main reason is to keep that bastard super cold, or else it won't function properly).

That such points exist, just due to the interacting gravitational pull of two orbiting bodies, is pretty crazy. And neat. A tidally locked and completely stationary orbit for a body that exists at that point, completely mimicking the Earth. It's only going to take extremely minimal thruster use to keep it in step, instead of it taking a good deal longer than an Earth year, and insane thruster use to balance that out. So it'll have the same elliptical orbit of Earth, which not all the planets have the same exact orbit, and it'll take barely any external effort to keep it at the same exact 1-year orbital period. Nuts.

And it's about 1/100th AU further out into space than our orbit at any given moment, a pretty significant distance out there, though not extremely significant in terms of orbits in comparison to our nearest neighbors. Mars is like 1.5 AU on average, aphelion and perihelion having a difference of about 0.2 AU, but takes 1.8 years to orbit - Venus is roughly 0.7 AU, it's aphelion and perihelion far from as significantly different compared to Mars, and takes about 0.6 years to complete its orbit. Venus varies by about 0.01 AU, Earth by about 0.03 AU.

None of that really has anything to do with anything of this topic. I am simply fascinated by just about everything regarding space.

 

[So]

Originally posted by: destrekor

Originally posted by: So

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

True. http://en.wikipedia.org/wiki/Roche_limit

And you know what's really weird about gravity, in terms of the combined force of multiple bodies exerting gravity? The existence of Lagrangian points/orbits.
Lagrangian Points

The James Webb Space Telescope, the successor for the Hubble Space Telescope, will be placed at the L2 point, with the Earth's shadow forever blocking the radiation from the sun from interfering with the image quality/electronics of the telescope (main reason is to keep that bastard super cold, or else it won't function properly).

That such points exist, just due to the interacting gravitational pull of two orbiting bodies, is pretty crazy. And neat. A tidally locked and completely stationary orbit for a body that exists at that point, completely mimicking the Earth. It's only going to take extremely minimal thruster use to keep it in step, instead of it taking a good deal longer than an Earth year, and insane thruster use to balance that out. So it'll have the same elliptical orbit of Earth, which not all the planets have the same exact orbit, and it'll take barely any external effort to keep it at the same exact 1-year orbital period. Nuts.

And it's about 1/100th AU further out into space than our orbit at any given moment, a pretty significant distance out there, though not extremely significant in terms of orbits in comparison to our nearest neighbors. Mars is like 1.5 AU on average, aphelion and perihelion having a difference of about 0.2 AU, but takes 1.8 years to orbit - Venus is roughly 0.7 AU, it's aphelion and perihelion far from as significantly different compared to Mars, and takes about 0.6 years to complete its orbit. Venus varies by about 0.01 AU, Earth by about 0.03 AU.

None of that really has anything to do with anything of this topic. I am simply fascinated by just about everything regarding space.

Put some O'neill cylinders at the Lagrange points!

 

[Chiropteran]

Originally posted by: JTsyo


Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

I understand that, but can we be certain that this occurs before reaching the point where the gravity is fatal to humans? Also, you could replace planet with an orbiting space station, or a larger ship, or whatever, if the only issue is that a large planet would get ripped apart.

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

It's more complicated than you make it sound. If gravity is pulling you down at 9.8 m/s^2 and you accelerate up with force sufficient to accelerate 9.8 m/s^2, you will feel 1g and you will not be moving because the two forces exactly cancel each other. To move upwards, you need a little tiny bit more acceleration- you aren't forced to endure 2g.

e: spelling is complicated

 

[Fritzo]

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

This.

It's called gravitational shearing, and it's what created the rings around Saturn and the asteroid belt.

Large, solid objects tend to get ripped appart near strong gravitational fields because of differences in gravitational attraction.

 

[Inferno0032]

Originally posted by: Chiropteran
If gravity is pulling you down at 9.8 m/s^2 and you accelerate up with force sufficient to accelerate 9.8 m/s^2, you will feel 1g and you will not be moving because the two forces exactly cancel each other.

No no no, you are comparing forces and accelerations, they are different. In order to accelerate and equal but opposite direction, you will need twice the force, and experience your 2G pull.

 

[Chiropteran]

Originally posted by: Inferno0032

Originally posted by: Chiropteran
If gravity is pulling you down at 9.8 m/s^2 and you accelerate up with force sufficient to accelerate 9.8 m/s^2, you will feel 1g and you will not be moving because the two forces exactly cancel each other.

No no no, you are comparing forces and accelerations, they are different. In order to accelerate and equal but opposite direction, you will need twice the force, and experience your 2G pull.

Who ever said anything about accelerating away at the same force as gravity? It's not needed. As long as you exceed the force of gravity by some amount, you will be able to escape the orbit eventually. There is no need to make it exactly double the force.

 

[destrekor]

Originally posted by: So

Originally posted by: destrekor

Originally posted by: So

Originally posted by: JTsyo
That's not how gravity works. If the planet is pulling you down at 9.8 m/s^2 and you accelerate up at 9.8 m/s^2, you feel 2gs on you.

Also large bodies can't survive near large gravity fields due to the difference in gravity across its diameter. Since gravity decreases with r^2, one side of the body will accelerating faster than other and the body will be torn apart.

True. http://en.wikipedia.org/wiki/Roche_limit

And you know what's really weird about gravity, in terms of the combined force of multiple bodies exerting gravity? The existence of Lagrangian points/orbits.
Lagrangian Points

The James Webb Space Telescope, the successor for the Hubble Space Telescope, will be placed at the L2 point, with the Earth's shadow forever blocking the radiation from the sun from interfering with the image quality/electronics of the telescope (main reason is to keep that bastard super cold, or else it won't function properly).

That such points exist, just due to the interacting gravitational pull of two orbiting bodies, is pretty crazy. And neat. A tidally locked and completely stationary orbit for a body that exists at that point, completely mimicking the Earth. It's only going to take extremely minimal thruster use to keep it in step, instead of it taking a good deal longer than an Earth year, and insane thruster use to balance that out. So it'll have the same elliptical orbit of Earth, which not all the planets have the same exact orbit, and it'll take barely any external effort to keep it at the same exact 1-year orbital period. Nuts.

And it's about 1/100th AU further out into space than our orbit at any given moment, a pretty significant distance out there, though not extremely significant in terms of orbits in comparison to our nearest neighbors. Mars is like 1.5 AU on average, aphelion and perihelion having a difference of about 0.2 AU, but takes 1.8 years to orbit - Venus is roughly 0.7 AU, it's aphelion and perihelion far from as significantly different compared to Mars, and takes about 0.6 years to complete its orbit. Venus varies by about 0.01 AU, Earth by about 0.03 AU.

None of that really has anything to do with anything of this topic. I am simply fascinated by just about everything regarding space.

Put some O'neill cylinders at the Lagrange points!

I had to look that up. And my reaction? Hell yes!
It'd be perfect, though we'll have to wait until we have more efficient means of transport from Earth to space. But we should definitely establish a Moon Base of sorts, a mini-colony meant to serve as a hopping point between space colonies and Earth, and for mining/engineering purposes.

Space colonies is exactly what we need soon, but not until either the UN can step up to be more of a unified global governing body, or something steps into that place. At least, that's how I look at it. I don't think space colonies should just be a tourist place, but rather something akin to a jurisdiction of sorts, and how that is handled needs to be carefully planned.

 

[Chiropteran]

Originally posted by: destrekor
I don't think space colonies should just be a tourist place, but rather something akin to a jurisdiction of sorts, and how that is handled needs to be carefully planned.

If tourists want to pay to visit the moon, why stop them? You'd rather force tax payers to foot the bill?

 

[destrekor]

Originally posted by: Chiropteran

Originally posted by: destrekor
I don't think space colonies should just be a tourist place, but rather something akin to a jurisdiction of sorts, and how that is handled needs to be carefully planned.

If tourists want to pay to visit the moon, why stop them? You'd rather force tax payers to foot the bill?

No, no - not at all.

Tourists go to other countries.

I simply think things like space colonies, should be true colonies, of course featuring a tourism industry (helps keep colonies in float, for lacking other things to base an economy around).
However, I think these colonies would need representation. Globally.

It's all part of the plan I'd like to see carried out, in which the world becomes more unified, and we start spreading out into space. These people in space, if the total populations of colonies are large enough (space colonies, moon colony/colonies), should also be recognized as a separate entity of sorts. How we define that, incorporate that into the world... is beyond my guess, unless we move closer to a global governing body.