NASA finds 'new earth'

You mean other then our rapidly growing population.

These types of things finding planets similar to ours are what make me mad that I wont ever see any of this stuff come to pass.

That's what i was getting at, yes.

That's not quite how gravity works.
By being 2.5 times bigger than the earth it might weigh 2.5 times more but because it's larger there's also a bigger increase in the radius and thus that makes the gravitation weaker.
Jupiter is like 318 times bigger than the earth and the gravity is only 2½ times stronger or so because of this.

You seem to have missed the assumption that the planet has similar density to Earth. Based on that assumption, he's entirely correct. Jupiter is a gas giant, and as we all know, gaseous entities are less dense than rocks.

We seem to be very casual with the terminologies here.

F_gravity = G * m1*m2/r^2
It matters how massive a body is, not how big nor how heavy. In fact, the larger a planet with the same mass is, the less surface gravity it has.

Just for clarification:
Heavy = how much something weighs, which is basically force due to gravity. It's erroneous to say a planet is heavy because it is more or less "floating" in space, and totally ignores its own gravity at any rate when one speaks of how heavy it is.
Big = volume. Indirectly portrayed as distance r in the formula.
Massive = how much mass something has.

Some interesting facts:
-- If a celestial object is the only object in existence, the force due to gravity would be zero at its center of mass. Yes, the core of Earth has zero gravity relative to Earth.
-- Gravity caused by a rocky planet is generally the strongest at the surface.

-- Gravity caused by a rocky planet is generally the strongest at the surface.

I don't quite grasp this. What's a "rocky planet"? Gravity should be strongest at infinitesimally close to the core, shouldn't it? Or am I interpreting it the other way, and it should be read "gravity caused by a rocky planet (as opposed to gaseous or liquidy ones) is generally the strongest when compared at the surface"?

I don't quite grasp this. What's a "rocky planet"? Gravity should be strongest at infinitesimally close to the core, shouldn't it? Or am I interpreting it the other way, and it should be read "gravity caused by a rocky planet (as opposed to gaseous or liquidy ones) is generally the strongest when compared at the surface"?

Think about it for a bit.

Ignoring all other matter, if planet A was really far away, it's a no-brainer to say that the direction of gravity from your perspective is towards planet A. Now throw planet B into the mix, which has the same mass and size (for simplicity's sake). If you were equidistant between these two planets, the net gravitational pull on you is zero. Throw planet C into the mix, which is just as far away from you, and all other planets are the same distance away from each other as well as being identical in mass and size. Net gravitational pull is still zero. We can keep on doing this for a however many planets.

Now imagine that you are in the center of a planet, ignoring all other matter. How will gravity pull at you? Because there's an equal amount of matter at any given distance away from you in all directions, the net gravitational pull is zero.

The thing about reality is, with the exception of black holes, it's not really accurate to treat bodies as a point mass. The way the educational system teaches it gets you "good enough" results (negligible difference) if you're sufficiently far away from something, just like how we don't factor in time distortion if we're moving at 200mph across Utah's salt flats.

x6 times the mass wouldn't mean x6 times the gravitational pull?

Isn't that like tuning your weight to x6 your current one? Bones are going to have some trouble there. Damn, someone sitting on you could break your legs.

Disregard, can't be bothered.

Think about it for a bit.

Ignoring all other matter, if planet A was really far away, it's a no-brainer to say that the direction of gravity from your perspective is towards planet A. Now throw planet B into the mix, which has the same mass and size (for simplicity's sake). If you were equidistant between these two planets, the net gravitational pull on you is zero. Throw planet C into the mix, which is just as far away from you, and all other planets are the same distance away from each other as well as being identical in mass and size. Net gravitational pull is still zero. We can keep on doing this for a however many planets.

Now imagine that you are in the center of a planet, ignoring all other matter. How will gravity pull at you? Because there's an equal amount of matter at any given distance away from you in all directions, the net gravitational pull is zero.

The thing about reality is, with the exception of black holes, it's not really accurate to treat bodies as a point mass. The way the educational system teaches it gets you "good enough" results (negligible difference) if you're sufficiently far away from something, just like how we don't factor in time distortion if we're moving at 200mph across Utah's salt flats.

Actually, not ENTIRELY true. Yes, you would assume that when you enter a planet the gravitational force gets greater because the radius shrinks, and what you said was correct, but not quite the true reason. If you go to the center of mass of an object (the core of the Earth, for instance), all of the mass of the object is pulling you equally. So, if you are for instance at the core, the north hemisphere is pulling you equally as strong as the south hemisphere. If you were on the surface, however, all of the Earth's mass is pulling you towards it (which happens to be towards the center). Pretty much a sum of all masses at different radii, or a triple integral.

Oh, point mass assumption. My bad, I was thinking of infinitesimal distance in the sense of two atoms.

Haven't read all the posts, because my english is bad when it comes to math and physics, but isn't this planet twise the size of earth, not 6 times?

Haven't read all the posts, because my english is bad when it comes to math and physics, but isn't this planet twise the size of earth, not 6 times?

Gravitational forces and accelerations are proportional to M/r^2 ,where M is the planet mass and r the planet radius so if it was 2.5 times the size, the planet would have to have around 6.25 as much mass to have the same Gravitational force acting on you.

Gravitational forces and accelerations are proportional to M/r^2 ,where M is the planet mass and r the planet radius so if it was 2.5 times the size, the planet would have to have around 6.25 as much mass to have the same Gravitational force acting on you.

Which would also equate to 40% of the density of Earth.

Every planet we colonize will essentially be given a greatly decreased lifespan. I'd trust an advanced robot over a human to make an important decision, at the very least. They will do what is most efficient for everything as a whole instead of simply going on some shady "gut feeling", lol.

Ok, time to go recruit Will Smith to an underground government facility so he can save us from I-Robot.

Edit: Just read this thread as I didn't notice we were on page 3. There are some intense physics and math discussions going on in here.

There are some intense physics and math discussions going on in here.

Not really. We're just discussing Newton's Law of Universal Gravitation, among other related things.

Not really. We're just discussing Newton's Law of Universal Gravitation, among other related things.

Compared to the rest of this forum, which at the most is fairly simple math for discussing skills or delay and such, I would say this could be classified as more intense discussion.

Compared to the rest of this forum, which at the most is fairly simple math for discussing skills or delay and such, I would say this could be classified as more intense discussion.

It's these types of discussions that gave southperry a "intelligent" image in the early days. It's not very uncommon, though it's becoming moreso in recent months.

A few ideas:
1) The closer you get to the speed of light, the slower time gets. So if humans could travel at (or near) the speed of light, then the "600 year journey" wouldn't take very long at all to the travelers. If we reached the speed of light, the journey should be instantaneous to the passengers.

etc.

1) That's not how relativity works, at all. A body travelling at the speed of light only goes so fast as the speed of light, it would still take that many years to cover those light-years. The only thing is that they when they finally arrived there many many more years would have passed for the people on earth and on their destination.

1) That's not how relativity works, at all. A body travelling at the speed of light only goes so fast as the speed of light, it would still take that many years to cover those light-years. The only thing is that they when they finally arrived there many many more years would have passed for the people on earth and on their destination.

It seems we're talking about three different time frames of reference here, first-person, third-person and objective frames. How would you, or relativity, distinguish them?

It seems we're talking about three different time frames of reference here, first-person, third-person and objective frames. How would you, or relativity, distinguish them?

The earth and the objective are stationary relative to the ship (well they are going very slowly), while the ship and its crew are going at near-c speeds. For the earth and the objective it will seem like an eternity has passed between the ship launch and arrival (though no one on earth will know of the ship's arrival since the information can't travel back all those light years).

It seems we're talking about three different time frames of reference here, first-person, third-person and objective frames. How would you, or relativity, distinguish them?

The earth and the objective are stationary relative to the ship (well they are going very slowly), while the ship and its crew are going at near-c speeds. For the earth and the objective it will seem like an eternity has passed between the ship launch and arrival (though no one on earth will know of the ship's arrival since the information can't travel back all those light years).

It seems we're talking about three different time frames of reference here, first-person, third-person and objective frames. How would you, or relativity, distinguish them?

The earth and the objective are "stationary" relative to the ship (well they are going very slowly compared to the ship), while the ship and its crew are going at near-c speeds. For the earth and the objective it will seem like an eternity has passed between the ship launch and arrival (though no one on earth will know of the ship's arrival since the information can't travel back all those light years).