Harvard babbles about planets; NASA launches mission to Pluto to take pics

[Blockzillahead]

it means the body is gravitationally dominant
http://en.wikipedia.org/wiki/Clearing_the_neighbourhood

i see
they shouldve said that instead

uh... what?

rotating velocity
thats what shapes the planet into a round shape is it not

yes! great point! everyone knows, if you meet only one of three requirements of being something, that means you are that something. good job!

pluto meets all those requirements but its not a planet so do i win a prize

You are not massive enough to have pulled yourself into a sphere.  Therefore you have not reached hydrostatic equilibrium.

so the greater the mass the greater the gravity and it pulls itself into a sphere sure
but what about velocity? if it was just the mass and gravity at play the planet would look like a deformed asteroid

[Ad Bot]

[Ipquarx]

It used to be that "nothing could escape black holes," but then we discovered Hawking radiation.

black holes do not exist

[Foxscotch]

yet they still can't send men to mars

yeah... that's totally comparable...

rotating velocity
thats what shapes the planet into a round shape is it not

no, it's not. gravity does that. rotation would be what makes it not a perfect sphere, and instead a kind of oval shape

pluto meets all those requirements but its not a planet so do i win a prize

it's not gravitationally dominant

[Xalos]

i see
they shouldve said that instead

It's a definition by scientists, for scientists.

pluto meets all those requirements but its not a planet so do i win a prize

It hasn't cleared its neighborhood of other objects.

but what about velocity? if it was just the mass and gravity at play the planet would look like a deformed asteroid

"If it was just the mass and gravity at play...", or in other words, if angular velocity = 0, then the planet would be disformed by its high angular velocity.  What?

Now, correcting for that blatantly wrong statement: No, high angular velocity would cause a planet to become an oblate spheroid - that is, still spherical.  The Earth itself is an oblate spheroid.

[WaterOre]

rotating velocity
thats what shapes the planet into a round shape is it not

Gravity pulls at around the same strength in a sphere from the center of mass, making rubble smooth out into a more or less spherical shape

pluto meets all those requirements but its not a planet so do i win a prize

See: Kuiper Belt, the location of pluto

so the greater the mass the greater the gravity and it pulls itself into a sphere sure
but what about velocity? if it was just the mass and gravity at play the planet would look like a deformed asteroid

Rotation causes stretching of a body
However, because most asteroids are potato shaped, most planets are deformed asteroids 

[Blockzillahead]

not gravitationally dominant

See: Kuiper Belt, the location of pluto

i see now

rotation would be what makes it not a perfect sphere, and instead a kind of oval shape

i still dont understand how gravity by itself would make it a sphere. dont you need to like... you know... rotate it at high speeds
if i took an asteroid as big as earth, gave it the same gravity but no motion in any way and waited a trillion years would it take the shape of a sphere?

[WaterOre]

if i took an asteroid as big as earth, gave it the same gravity but no motion in any way and waited a trillion years would it take the shape of a sphere?

yes, and it would barely even take 1000 years
the moon is thought to have coalesced in about a week from rubble

[Blockzillahead]

interesting

im now 1 step closer to becoming a professional astronomer

[Xalos]

i see now
i still dont understand how gravity by itself would make it a sphere. dont you need to like... you know... rotate it at high speeds
if i took an asteroid as big as earth, gave it the same gravity but no motion in any way and waited a trillion years would it take the shape of a sphere?

Centrifugal force (which is a real thing) causes mass to be forced outward from the center of rotation.  If centrifugal force were the only force involved, yet gravity somehow still worked, then mass would form into ragged mountains as everything attempted to roll upward away from the center of rotation.  This is why the Earth is flattened.  Gravity is the sphericalizing force - everything wants to have a lower potential energy, which means falling downward.  The closer to the center of mass you are, the less potential energy and the higher entropy you have.

Rotation makes planets not be spherical, gravity counteracts the usually-low speed of rotation to make planets stay spherical.

[Kearn]

yet they still can't send men to mars

actually just for the record this isnt a video game where you can scoop some poor idiot off the street and throw him in a cardboard box and have him be fine after a year with no food or water or oxygen or protection from stellar radiation

[Maxwell.]

interesting

im now 1 step closer to becoming a professional astronomer

I play kerbal space program so I obviously know more than you about this, you should feel bad

[Xphifre]

yet they still can't send men to mars

are you serious

[Blockzillahead]

I play kerbal space program so I obviously know more than you about this, you should feel bad

STOP

[Hiok1998]

There are 7 moons in our solar system that are larger than Pluto.

But to be fair, two of those are larger than Mercury.