Planets...

[Piece]

Asteroids are likely to be broken up planets.
Actually there is no such thing as a round or spherical planet in any sense. That only exists in mathematics.
There are 2 big theories of physcics. Classical and quantum where the latter is more reliable.
Planets are believed to be the debris after the birth of a star. In time they will settle into their own orbits, but only after bombardments have occurred.
Gravitational pull does not exist. There is no attraction between a rocky planet like Earth and a distant helium factory like the Sun. Earth has simply found its own path through curved space.
The miracle of the Earth is that it has found a place within the "Goldilock's Zone". A place not too hot or cold.
Comets have their base outside the solar system in the Oort Belt, but they can be deflected inwards by a passing star.
Apart from Mercury all planets, asteroids and comets follow a flat elliptical orbit caused by all the objects interfering with curved space.

No force, no attraction between two large masses? Pure luck that the Earth, other planets, and all the other planets in the universe have simply found their own path by traversing a space/time "orbit" around a larger mass? Binary stars? Perhaps you didn't mean to say what you said.

 

[backwoodsman]

Going back to the original OP question, the simple answer is that planets are round by definition. If it ain't round, it ain't a planet. One part of the definition is that the body has sufficient mass such that self gravity allows it to attain hydrostatic equilibrium - a round or nearly round shape. Smaller lumps - asteroids etc - dont have the mass to do that. Stefanovic can argue that gravity doesn't exist, but I'm happy to accept the view of the IAU on the matter. And NASA. And plenty of others.
SILH's point about JuMBO's raises the argument of whether the definition needs revising - but for the time being, JuMBO's aren't planets.

 

[stefanovic]

If it ain't round, it ain't a planet.

Planets are not round by definition.
They are spheroids, which means they are flattened at the poles.
A pendulum will swing differently at the poles and equator.
There are at least 2 double planets in our solar system.
Earth-Moon and Pluto-Charon have mutual tidal locking, which means they show the same face to each other as they move through space.

No force, no attraction between two large masses

There isn't. Einstein proved it by General Relativity.
He also proved that space is curved.
Earth merely follows as straight a path as it can through curved space.
Just think, how is the Earth suspended in space?
Leads to wonderful revelations about why it exists at all.

 

[TimShady]

Planets are not round by definition.
They are spheroids, which means they are flattened at the poles.
A pendulum will swing differently at the poles and equator.
There are at least 2 double planets in our solar system.
Earth-Moon and Pluto-Charon have mutual tidal locking, which means they show the same face to each other as they move through space.


There isn't. Einstein proved it by General Relativity.
He also proved that space is curved.
Earth merely follows as straight a path as it can through curved space.

The Earth and moon aren’t double planets. The barycentre of our orbit with the moon lies within the body of our planet, thus it is colloquially described as orbiting us and is our satellite.

It feels like you’re trying to impress people with word salad.

 

[stefanovic]

Does then the Moon orbit the Earth or the Earth orbit the Moon.
They are in orbit around each other.

"Pick a flower and you move the furthest star". Attr. to Paul Dirac.

 

[TimShady]

Does then the Moon orbit the Earth or the Earth orbit the Moon.
They are in orbit around each other.

"Pick a flower and you move the furthest star". Attr. to Paul Dirac.

Yes, we orbit each other but as the barycentre lies within the bounds of Earth, convention states that the moon orbits us.

 

[cliveb]

Yes, we orbit each other but as the barycentre lies within the bounds of Earth, convention states that the moon orbits us.

Does this mean that Jupiter doesn't orbit the Sun?

 

[TimShady]

Does this mean that Jupiter doesn't orbit the Sun?

They orbit each other technically.

 

[stefanovic]

If gravity is a force which keeps the planets in orbit around the sun, then explain:

What exactly is gravity?
A: Gravity is just a convenient metaphor to describe the warping of space-time in the presence of a large object.
Technically it can be the smallest object.

If gravity is a force of attraction then why doesn't the Earth crash into the Sun, or the Moon crash into the Earth?
A: They follow the path of least resistance.

Why does Mercury have a wobbling type of orbit?
A: Being so close to the Sun it's in a very strong "gravitational" field.

If you have better answers, let's hear them.

A mention of rogue planets.

| EarthSky

earthsky.org

 

[backwoodsman]

Planets are not round by definition.
They are spheroids, which means they are flattened at the poles.
A pendulum will swing differently at the poles and equator.
There are at least 2 double planets in our solar system.
Earth-Moon and Pluto-Charon have mutual tidal locking, which means they show the same face to each other as they move through space.


There isn't. Einstein proved it by General Relativity.
He also proved that space is curved.
Earth merely follows as straight a path as it can through curved space.
Just think, how is the Earth suspended in space?
Leads to wonderful revelations about why it exists at all.

You can choose to be pedantic if you like - but I did actually use the correct phrase of hydrostatic equilibrium in my post. And that means the body attains a shape of 'round or nearly round' - a phrase I also used. And if I'm not wrong, a spheroid quite neatly fits the bill of 'nearly round'. You also need to bone up on the (current) definition of a planet. None of the Moon, Pluto, and Charon are planets. Maybe they should be, or maybe not. But at the moment, by definition, they aren't. You, and others - including respected physicists, astronomers, planetary geologists etc- can choose to ignore the current definition. But that's your look-out not mine
.

 

[bobmac]

You can choose to be pedantic if you like - but I did actually use the correct phrase of hydrostatic equilibrium in my post. And that means the body attains a shape of 'round or nearly round' - a phrase I also used. And if I'm not wrong, a spheroid quite neatly fits the bill of 'nearly round'. You also need to bone up on the (current) definition of a planet. None of the Moon, Pluto, and Charon are planets. Maybe they should be, or maybe not. But at the moment, by definition, they aren't. You, and others - including respected physicists, astronomers, planetary geologists etc- can choose to ignore the current definition. But that's your look-out not mine
.

Which moon?

 

[TimShady]

Which moon?

Capital M means it’s our moon.

 

[Bunkermagnet]

Wish I hadn't bothered asking now it's turned into a Thesaurus and Dictionary competition.
No one is impressed BTW.

 

[bobmac]

Capital M means it’s our moon.

You haven't watched QI then

 

[TimShady]

You haven't watched QI then

A show which has often been called out for being wrong. And if they don’t think our moon is called The Moon, they got it wrong again.

 

[TimShady]

Wish I hadn't bothered asking now it's turned into a Thesaurus and Dictionary competition.
No one is impressed BTW.

So you asked about a highly complicated issue involving scientific concepts but want it explained in layman’s terms?

 

[bobmac]

A show which has often been called out for being wrong. And if they don’t think our moon is called The Moon, they got it wrong again.

Can someone else explain it to him, I can't be bothered.
Note to self......never attempt humour again on this forum

 

[Tashyboy]

Can someone else explain it to him, I can't be bothered.
Note to self......never attempt humour again on this forum

Your attempt at not being numerous tickled me

 

[Lord Tyrion]

So you asked about a highly complicated issue involving scientific concepts but want it explained in layman’s terms?

Yes, I think that was the point.

 

[TimShady]

Yes, I think that was the point.

Then post five was the one to close the thread.