Colliding Planets

Right now no two orbits come close to each other. Our solar system is in a pretty stable middle age rut right now. The closest thing to that is the x-planet called Pluto, which has a perihelion that takes it inside the planet Neptune's orbit, but Pluto's orbit is inclined about 17 degrees from the ecliptic and there really isn't any way the two planets can intersect. Simply put, they run two different race tracks.

But then there was the Chaos Theory just to put a spanner in the works. What ever happened to the fifth planet.(Planet V) Just a bunch of rubble now.

Quoting geomech: "What ever happened to the fifth planet.(Planet V) Just a bunch of rubble now"

Yep, and there is a fair chance that one of those pieces of rubble might plow into Earth in the not too distant future!

Further, one good theory of how the Moon originated is of a Mars-sized planet that collided with Earth not long after original formation of our solar system.

There will always be a degree of chaos in the planetery orbits due to the non-infinite speed of gravity waves (this worried Newton) but as there are not many planets there is little chance of major disturbance before the Sun swells up and destroys the lot.

I have a similar question about the topic:

I recall from my primary class lectures that in the early mornings and sunsets you could see Venus and maybe Jupiter with naked eye. Venus even has a special name "Morning Star" in Turkish.

I now think that these planets have their own year periods, and it is quite unlikely for these planets to come close enough to be observed.

I don't know if the planets lie on the same horizontal plane, but why would they? If they don't, it should be even more scarce, since most of the time they would fall far apart from each other.

How come we can see Venus so often when there is the Sun in between most of the year?

Venus would only be between the Earth and the Sun for long periods if their years (time to orbit the sun) were perfectly equal and Venus lied on a line between the Sun and the Earth. Anything different would means that Venus would be visual (as is the case).

You may want to revisualize what you are thinking.

Cameo, you asked: "I now think that these planets have their own year periods, and it is quite unlikely for these planets to come close enough to be observed."

Venus, being the closest planet to Earth, passes on the 'inside' of Earth every 18 months or so, if I remember correctly. Whatever the relative timing, it is visible from Earth for much more than half of that period, sometimes in the early mornings and sometimes in the early evenings.

Twice during a passing cycle, Venus becomes naked-eye visible in broad daylight, when it is around 30° on either side of the Sun, having the best distance-illuminated area ratio from our vantage point.

Jupiter is only rarely in a position favourable for being a naked-eye daylight object, I think! The amateur astronomers should correct me on this one!

I have heard that the future positions of the planets are very predictable, but that if you go far enough ahead we can't even predict what side of the sun Pluto is going to be. ??????????

PlbMak, you wrote: "I have heard that the future positions of the planets are very predictable, but that if you go far enough ahead we can't even predict what side of the sun Pluto is going to be. ???????"

True! Poster #3 said it all: "...then chaos theory took over", or something to that effect. We simply cannot solve (or even write down) an analytical equation for all the planets, asteroids, comets, etc. for all time. So..., we do it by successive approximation or numerical integration. After a suitably long time, that's not accurate enough and things simply diverge...

I think it is Einstein who said: "God rules empirically. He does not care about mathematical difficulties!"

Venus is completely covered in a thick reflecting carbon dioxide atmosphere which is part of the reason it is so bright. It also is the closest planet to the Earth, coming at times within 42 million miles of the Earth. At certain times, Venus can reach a magnitude of up to -4.5, which is bright enough to appear during the day, but only when the sun is close to the horizon (when daytime is dimmer).

Venus is called the Morning Star or the Evening Star. This is because, depending upon it's location in its orbit relative to the Earth, it appears right after sunset or right before dawn. The reason is because it's orbit is inside that of the Earth's and so always appears close to the sun to us. As the surface of the Earth turns away from the sun (nightime), or turns toward it (daytime), it turns away from or torwards Venus as well.

As for Jupiter, I don't think it's possible to view it by eye during daylight hours. I don't think it's bright enough, but I could be wrong.

Just because we're talking about Venus and it's fun to see the surface of other planets, here's an image of the surface of Venus taken by Venera and cleaned up a bit;

I have often seen Venus after the sun has risen it is easy to find , I have never seen Jupiter but no doubt with careful calculation of its position with good seeing conditions it could be done.

Total eclipse of the Sun and if the position of Jupiter is right you should get a chance.

Hero said: "Total eclipse of the Sun and if the position of Jupiter is right you should get a chance."

My astronomy friends tell me that if Jupiter is at it's best and it happens to be near the Moon in daylight, people with keen eyesight easily spot it! The Moon's daytime image gives the eyes the opportunity to focus at infinity, something that does not happen easily if you just look up into a featureless blue sky.

I was planning on googling this but since there are a lot of knowledgeable people in CR4, I'll ask it here.

Why are the planets in the same plane, more or less? Is this just chance or is it natural for planets around a star to eventually settle on the same plane?

Solar cops. They are brutal.

Well, digging back to my childhood teaching of astronomy, the creation of the solar system began with what is called an accretion disk of gasses and dust that slowly over time started to form clumps and later proto-planets as the cloud condensed around our newly formed star, the Sun.

The accretion disk lay on the ecliptic of the Sun, so as proto-planets formed they formed more or less within the same plane about the Sun. Since the early solar childhood was full of clumping rubbish, some perturbations and collisions caused some eccentricities and deviations from the plane, but not by much.

The accretion disk theory also explains why all the planets orbit the Sun in the same direction.

In space there is almost no friction at all, which means that if you are spinning, you tend to stay spinning. On Earth, if you spin a top, it will stand on it's tip. If you try to tip it over it will right itself. That's because Angular momentum is perpendicular to spin. In the same way, the planets rotate about the Sun and have an angular momentum as well and will resist being tipped out of the plane that is perpendicular to their rotation about the Sun.

As for why they are spinning about the sun in the first place, I think Hero's comment answered that well.

Are we truly in the eliptic ? does not Jupiter which is the majority of orbital energy in the solar system define the eliptic, how does the the rotation of the sun in as much as it can be determined fit in

Hi syhprum, if Roger will pardon me for barging in, you surely mean the ecliptic and not the eliptic!

The ecliptic is a convention, defined to be the plane of the orbit of the Earth relative to the Sun. So we are "truly in the eliptic" by definition!

I just thought of something. The reason why the planets wind up on the same plane is because of gravity! The planets attract each other enough that they eventually have to end up on the same plane.

If the solar system started out as a dust cloud and planets were formed out of dust particles sticking together, their distribution must have been more or less even around the sun. When a planet gets closer to its neighbor, it gets nudged out of its original path and over billions of years they eventually end up on the same plane because that's where the gravititional forces are at its maximum.

'Not a new idea I bet.

Vulcan, you said: "The planets attract each other enough that they eventually have to end up on the same plane."

There may be an element of truth in what you say, but I think the disk is formed mainly due to the fact that contracting masses always pick up spin in some or other plane (somewhat like the spin of water exiting a bathtub).

As I understand it, the spin causes centrifugal forces that flatten the sphere more and more into a disk, where the density of gas and dust then becomes higher than in the spherical part. This is where proto-planets are most likely to form. Our Galaxy's disk was presumably formed in a similar way, but there are also halo stars that are not part of the disk.

This also initially causes all the planets and moons to orbit and spin in the same direction. Later collisions upset this initial uniformity a bit, so there are some spinners in the opposite direction.

Now, I get it.

The dust cloud starts to spin and, since the maximum force is at the widest part of the spinning mass, the ball or cloud starts to flatten out, much like the Earth is wider at the equator. Eventually, the cloud forms larger particles which become planets. The planets then start to spin in one direction because the side nearest the center of the cloud has more resistance, maybe because the cloud's density is higher near the center.

Okay, you got me. I believe one or two planets, however, spin differently from the rest (Venus and Uranus, I think). That must mean that they came to the solar system later and were captured by the Sun's gravity. Still, they ended up on the same plane so my gravity theory must have some merit.

Hi Vulcan, your: "The planets then start to spin in one direction because the side nearest the center of the cloud has more resistance, maybe because the cloud's density is higher near the center." is not quite the right idea, I think.

As the planets contract due to the gravity of a local dense spot, they already have an angular momentum in the general direction of the rotation of the disc. So in an ideal situation, planets will continue to rotate in the same direction as the disc.

The odd-one's-out is thought to be the result of collisions within the disc or collisions with intruders from 'outside'.

Read an article on the interesting spacing of our planets on my website.

As always, great explanations Jorrie.

Thanks Roger! Coming from a great 'teacher of engineers', it's much appreciated.

Colliding Planets dam we cant get too missile to hit one another never mind all the time and money spent !! ack !two car's collide at at walmart is faster haa ! dam where my wife ! here a note went to get bread dam !!