Astronomy / Physics Question

[Kilgore Trout]

Kind of an astronomy / physics question.

Let's say the earth just suddenly stopped rotating around the sun so that rotational speed around the sun was zero.
Would the earth fall directly into the sun over a couple of days or a couple of weeks or would something else happen.

Einstein taught us that gravity is really just bends and curves in the fabric of spacetime. Ie anything with heavy mass bends the fabric of space time toward itself as I understand it.
Since the earth is so far away from the sun (average distance 93 million miles) I'm wondering if maybe the gravity at that point is a bit weak and earth would just find a new slot to fall into and gradually build up speed and rotate around the sun in a different way from how current rotation is.

Or would the earth just tumble all the way in.

 

[blackrock13]

WOW, bored this morning were we?

 

[Ringworld]

There are two relevant forces acting on the Earth:

a) Because it's already moving, the earth has kinetic energy that wants to keep it moving at the same velocity at the same direction. The direction of this force is tangential to its circular path around the sun.

b) Gravitational force of the sun pulls the earth towards it.

The balance of these two forces keeps it in a circular path. If you remove the kinetic energy (a) by bring the earth to a dead stop, then the sun's gravity (b) would cause it to be pulled in.

I'm not bored, but I'm procrastinating.

 

[blackrock13]

There are two relevant forces acting on the Earth:

a) Because it's already moving, the earth has kinetic energy that wants to keep it moving at the same velocity at the same direction. The direction of this force is tangential to its circular path around the sun.

b) Gravitational force of the sun pulls the earth towards it.

The balance of these two forces keeps it in a circular path. If you remove the kinetic energy (a) by bring the earth to a dead stop, then the sun's gravity (b) would cause it to be pulled in.

I'm not bored, but I'm procrastinating.

I haven't even begun to procrastinate.

 

[George The Curious]

Straight in. Takes couple years.

 

[demien2k5]

Dunno. I been too worried about whether a tree falling in the woods without anyone there to see it makes any noise or not.

 

[Kilgore Trout]

Okay, thanks for all that.
I was thinking that maybe the rotation of the earth on its axis once every 24 hours would kind of create an effect like dropping a spinning top on the floor where the spinning action causes erratic twirling motion once it's on the floor.
In that way maybe the earth could tumble into a new slot or 'railroad track', say 61 million miles away from the sun, generate speed, and create new elliptical orbital position around the sun.

I was also speculating if maybe the fabric of spacetime itself is orbiting around the sun in a counter clockwise motion and, if this is so, maybe the earth would become like a ball tossed onto a spinning roulette wheel and therefore generate new counter clockwise rotational speed around the sun and fall into a new orbital position somehow that keeps it from falling all the way into the sun.

But I guess the earth is just too heavy for something like that to happen once orbital rotational speed is reduced to zero.

 

[bobistheowl]

There was a show on The Discovery Channel about this recently.

First, the Earth could not stop rotating immediately; it has too much momentum. It would take several years of slowing down first before it could stop rotating completely.

The first thing that would be noticeable if the Earth's rotation began to slow down would be with airplanes that use geosynchronous satellites for navigation. Within hours, the planes would be way off course, because the orbits of the satellites would not slow with the Earth's rotation. Until that happens, you have nothing to worry about. When it does, you'll have a year or so to complete your bucket list before everything REALLY starts to go to shit.

 

[Kilgore Trout]

Assuming the earth just stopped and then started falling in towards the sun, if you zero centripetal acceleration, it would take about three months for the earth to travel the 1 AU required.

And you're not taking about rotation, you're talking about revolution. The earth doesn't ROTATE around the sun, it REVOLVES around it. It ROTATES on its own axis.

Thanks for info on my imaginary cosmic catastrophy, ie centripetal acceleration of planet earth reduced to zero.
And thanks for distinction between revolves and rotates.

I guess once you know all the variables ie mass of the sun, mass of the earth, distance to sun you can calculate very precisely how long it would take to fall into the sun.

 

[Kilgore Trout]

Thanks for that.
I don't really know any of the math equations to calculate what would happen in various Astronomical / Physics scenarios. I'm just an amateur with curiosity.

By any chance, would you know: - if on its journey into the sun, by sheer coincidence, the earth flew by Venus at a distance of 5,000 km away, would Venus have enough gravity to capture the earth and become a kind of binary planet system revolving around the sun.
I imagine there is no chance this could happen since asteroids just fly by the earth when they come close and don't get captured by earth's gravity.

I imagine the only thing that could stop the earth from hitting the sun would be a direct or offset collision with Venus and perhaps a new planet would form in the annihilation that results from the collision of Earth and Venus.

 

[T.O.tourist]

Dunno. I been too worried about whether a tree falling in the woods without anyone there to see it makes any noise or not.

It does if a blind person is nearby.

 

[Kilgore Trout]

Thanks, arthurfonzerelli.

 

[George The Curious]

Thanks for that.
I don't really know any of the math equations to calculate what would happen in various Astronomical / Physics scenarios. I'm just an amateur with curiosity.

By any chance, would you know: - if on its journey into the sun, by sheer coincidence, the earth flew by Venus at a distance of 5,000 km away, would Venus have enough gravity to capture the earth and become a kind of binary planet system revolving around the sun.
I imagine there is no chance this could happen since asteroids just fly by the earth when they come close and don't get captured by earth's gravity.

I imagine the only thing that could stop the earth from hitting the sun would be a direct or offset collision with Venus and perhaps a new planet would form in the annihilation that results from the collision of Earth and Venus.

if earth comes real close to venus on route to Sun, then venus could pull earth off course and earth would fly off to space instead of colliding with Sun. It is impossible to become binary system though unless earth collide with venus and parts and pieces fly off then gets pulled back and start rotating together

 

[George The Curious]

No, almost certainly not. You have to picture the planets like little bullets flying through space - even when they pass VERY close together, they're just not close enough for long enough to significantly accelerate them.

I suppose so. But collision with venus or mercury is possible though extremely improbable.

 

[buttercup]

I was thinking that maybe the rotation of the earth on its axis once every 24 hours would kind of create an effect like dropping a spinning top on the floor where the spinning action causes erratic twirling motion once it's on the floor.
In that way maybe the earth could tumble into a new slot or 'railroad track', say 61 million miles away from the sun, generate speed, and create new elliptical orbital position around the sun.

Leaving aside the question of what could cause it to happen, if the earth were to suddenly stop in its orbit around the sun, then yes it would start to plummet towards the sun in a straight line. Whether it would actually crash into the sun is another querstion. Even a slight deviation from the straight path, and the earth would go into a new stable orbit around the sun, at a new (and smaller) radius - or more likely a new elliptical orbit.

One of the things that could cause a deviation from the straight path to hell is the rotation of the earth about its axis. As the earth falls, its natural rotation will lead to slight gyroscopic forces, and the earth will start to undergo rotations about other axes than its current one. That would set up major gyroscopic precessions, the effect of which would be highly unpredictable. (If you balance a pin on its point, you can predict that it will fall to on side, but whether it falls north south east or west is entirely unpredictable.) These variant precessions would deflect the earth from its straight drop, causing it to go into orbit, once again circling the sun.

I was also speculating if maybe the fabric of spacetime itself is orbiting around the sun in a counter clockwise motion and, if this is so, maybe the earth would become like a ball tossed onto a spinning roulette wheel and therefore generate new counter clockwise rotational speed around the sun and fall into a new orbital position somehow that keeps it from falling all the way into the sun.

The falling earth would be moving (and accelerating) through a rotating force field, caused by the gravity of the other planets (assuming them to be still rotating around the sun). Moving even at a constant speed through a rotating force field gives rise to coriolis forces and accelerations (try walking across a spinning roundabout/carousel). Again, these coriolis components would divert the earth from the straight path, and make it go into a new orbit rather than crash into the sun.

But I guess the earth is just too heavy for something like that to happen once orbital rotational speed is reduced to zero.

No, the earth is affected by forces generated by gravity and centrifugal forces, whatever its mass.


I will wager that, in the scenario you propose, depending as it does on gyroscopic precession and coriolis acceleration, the earth will not hit the sun, but will go into a new orbit.

As to the confidence level of this prediction, I'm as confident the earth will find a new orbit as I am that blackrock13 will resort to insult and derision in his very next post.

 

[Aardvark154]

There was a show on The Discovery Channel about this recently.

First, the Earth could not stop rotating immediately; it has too much momentum. It would take several years of slowing down first before it could stop rotating completely.

The first thing that would be noticeable if the Earth's rotation began to slow down would be with airplanes that use geosynchronous satellites for navigation. Within hours, the planes would be way off course, because the orbits of the satellites would not slow with the Earth's rotation. Until that happens, you have nothing to worry about. When it does, you'll have a year or so to complete your bucket list before everything REALLY starts to go to shit.

OP didn't really mean rotation he was writing of the earth orbiting the sun.

 

[seth gecko]

Anyone have any ideas on what might happen if an object gets too close to Uranus?

 

[slowandeasy]

Extremely improbable. But, hey, you've just stopped the Earth in its tracks - feel free to throw it at whatever celestial body you like!

Fonzie you have graduated from a 1960s mechanic, to a 21st century physicist. Glad to see you have been using your time wisely...

 

[slowandeasy]

Anyone have any ideas on what might happen if an object gets too close to Uranus?

Isnt' there a black hole by Uranus?

 

[David007]

This question has been answered for us. In the Bible, Judges 10, God gave Joshua an extra day by making the Sun and Moon stand still. So the evangelical apologists extrapolate that God froze the whole solar system so that Joshua could kill his enemies.

So there you go, historical proof!