The Oort Cloud Explained

[Foxhole87]

No, the Oort cloud is not a different solar system it is a made up zone.

I didn't say I was posting from the Oort cloud.

Would you believe that I was posting from a different solar system? Why or why not?

 

[dad]

Until someone has a better model that explains long-term comets,...

Better? It is purely a matter of preference. Godly or ungodly model. End of story.

 

[dad]

I didn't say I was posting from the Oort cloud.

Tell us about your cloud and other fantasies.

 

[Foxhole87]

It's not a conspiracy theory that the more scientists have to do with their religion the less the field wants to do with them.

Well, if a scientist is willing to simply throw his hands up and attribute any scientific mystery to God, they are a useless scientist.

 

[Foxhole87]

Better? It is purely a matter of preference. Godly or ungodly model. End of story.

"Better" as in "captures all of the available data" and therefore not simply a matter of preference.

 

[Goonie]

 

[Foxhole87]

Tell us about your cloud and other fantasies.

So, would you believe that I am actually posting from a different solar system? Why or why not?

 

[Crowns&Laurels]

Yea Christian in the U.S. are soooo persecuted. Just like the in crowd in High School is persecuted by not being allowed to do whatever they want to the outsiders.

Yeah, lord only knows the tyranny of having portrait of Jesus on a school wall. Makes you wonder what all those iron maidens and Judas cradles were even for.

Maybe they were just trying to one up the Muslims.

 

[Foxhole87]

Civility isn't really your thing, is it?
A thread about comets in space prompts you to post a depiction of decapitation by elephant?

 

[Crowns&Laurels]

Civility isn't really your thing, is it?
A thread about comets in space prompts you to post a depiction of decapitation by elephant?

Simply making a point in a brief side discussion.

 

[dad]

"Better" as in "captures all of the available data" and therefore not simply a matter of preference.

Absurd. It does not capture data, it hijacks it.

 

[Foxhole87]

Absurd. It does not capture data, it hijacks it.

How does the Oort cloud model hijack data?

Would you believe that I am actually posting from a different solar system? Why or why not?

 

[dad]

How does the Oort cloud model hijack data?

You see some actual comets and invent a magic cloud where they live.

Would you believe that I am actually posting from a different solar system? Why or why not?

\
No. I know the limits of science and the vacuous posting tendencies of same state past believers.

 

[Astrophile]

So a star brightens and dims on a regular basis. That all??!! So what?


Theoretically indeed. That says little but that you see something and try to make a formula.



?? You kidding? So some things go round other things in deep space...so?? That doesn't tell you how big the things are, all that they are made of (only the physical bits we can detect from a prism here on earth), how far away they are, or WHY they actually go round...etc.
Is this just me or does this sound somewhat circular to anyone else!?

But in any case times means time. The times are seen here where there IS time....

What about these? Are you still trying to establish the obvious that things go round other things in space??

Everett Interpretation wrote:

Hi Dad!
Do confirmed scientific predictions cut any ice with you?

You replied:

yes if they involve reality and this present state world. No if they involve the far future or past.

I am still trying to find out whether confirmed predictions of simple phenomena such as the changes in brightness of variable stars and the orbital motion of binary stars 'cut any ice with you' in Everett Interpretation's phrase. So far, you have evaded the question by asking about the physics of stellar light variation and other irrelevancies.
Let me try to re-phrase the question. Where astronomers have observed a periodic phenomenon in the past (e.g. light variations or orbital motion) and predict that this phenomenon will continue in the future, do you regard this sort of prediction as valid?

 

[dad]

Everett Interpretation wrote:

You replied:


I am still trying to find out whether confirmed predictions of simple phenomena such as the changes in brightness of variable stars and the orbital motion of binary stars 'cut any ice with you' in Everett Interpretation's phrase.

That depends if the predictions are based on just looking at a star brighten and dim or not. What is the basis for predicting the brightening?

So far, you have evaded the question by asking about the physics of stellar light variation and other irrelevancies.
Let me try to re-phrase the question. Where astronomers have observed a periodic phenomenon in the past (e.g. light variations or orbital motion) and predict that this phenomenon will continue in the future, do you regard this sort of prediction as valid?

That has nothing at all to do with science. They observe something and who cares if they 'predict' it will happen on cue as observed!!?? You kidding?

A prediction implies doing more than being a spectator.

 

[Astrophile]

Easy as pie. You think the orbital path "implies" something. That is your mistake. Tell us why that orbit implies that to you exactly, and we shall see.

Astronomers observe the movements of a comet against the frame of reference formed by the background of the 'fixed stars'. These cometary movements are used to calculate the comet's orbital elements, according to Newton's and Kepler's laws.

The calculated orbital elements are used to predict the motion of the comet while it is still visible. The agreement of the observed motion with this predicted motion confirms the accuracy of the orbital elements. Do you understand so far? To illustrate the point, I have observed many new comets, knowing where they are supposed to be from the orbital elements and ephemerides calculated from their motion shortly after their discoveries.

Now to come to the important point. The orbital elements of many comets, calculated, as I say, from their orbital motion, show that they have semi-major axes (a) of thousands of Astronomical Units, or even up to 20,000 AU. These comets must have orbital eccentricities (e) up to around 0.9995 in order for them to come within the Earth's orbit at perihelion. By Kepler's third law, they must have orbital periods (P) of tens of thousands or even millions of years.

If comets have P ~ 10,000 to >1,000,000 years and such comets appear frequently, there must be a sort of 'conveyor belt' containing millions of comets that are approaching the Sun but still too far away to be visible. If these comets are distributed evenly around their orbits, most of them must be near to aphelion, at distances up to about 40,000 AU. These comets form the Oort cloud.

Moreover, if the distribution of the orbital eccentricities of comets is uniform, there must be 20,000 comets with e < 0.9995 for every one with e > 0.9995. Given a population of millions of high-eccentricity comets on the 'conveyor belt' bringing them towards the Sun, we now have billions of comets with e < 0.9995 that never come near the Sun and that therefore remain invisible.

Please think about this before you reply. I have tried to explain the evidence that shows that the Oort reservoir of comets must exist. If you don't understand my explanation, let me know and I will try again.

 

[dcarrera]

I would think they'd be easier to document than planets around other stars.
Optically, they'd be huge compared to other planetary systems.
If there was such a cloud, I'd expect the stars to twinkle on their own.

Did you actually do a calculation to support this claim?

I find posts like this very depressing because you have just imagined something that makes some vague kind of intuitive sense to you and you asserted that it must be true without really making an effort to check it. To make this claim, you need to at least compute three things:

1) How often an Oort cloud object would cross the path of a star.
2) The duration of the crossing.
3) The amount of light blocked during the crossing.

Let's take the last one for example. A Jupiter-mass planet blocks about 1% of the light from a Sun-like star. The most photometrically precise instrument we have today is the Kepler spacecraft which can detect Earth-size planets, which block about 0.01% of the light from a Sun-like star. Let's compare this to (for example) an Oort cloud object around ~1km in size, orbiting at ~100,000 AU, and crossing a Sun-like star at 10pc (reasonable for a star you can see in the sky). The calculation is quite trivial:

(1 km / 100,000AU)^2 / (1 solar radius / 10 pc)^2 = 10^(-9) = 0.0000001%

Did you do that calculation? I suspect you didn't. But you boldly asserted that "Optically, they'd be huge compared to other planetary systems." The signal is completely undetectable by the most precise instrument we can build, but said you expected stars to twinkle on their own.

If you try any of the other calculations I suggested you will find them equally problematic for your claims. This is what I find depressing and scary. People in forums like this one do not check facts, do not do calculations, but confidently assert that things must be true or false based on nothing more solid than personal preference.

People! Please! Stop doing this! If you want to make a scientific claim, please take the trouble to do a reasonable calculation; and if you can't support your claim with a reasonable calculation, you should be suspicious of your claim.

 

[Astrophile]

That depends if the predictions are based on just looking at a star brighten and dim or not. What is the basis for predicting the brightening?

I have already explained that it is extrapolating into the future what has been observed in the past. The prediction of future light maxima or minima is based on the period obtained from past maxima and minima.

That has nothing at all to do with science. They observe something and who cares if they 'predict' it will happen on cue as observed!!?? You kidding?

No, I am not kidding. The behaviour of variable stars tells astronomers a lot about stellar structure and the physics of pulsation, and about mass transfer between binary stars.

A prediction implies doing more than being a spectator.

I am not sure what this means. Perhaps you mean that making a prediction requires analysis of observations or having an understanding of the physics governing the observed phenomenon, or both. If so, I agree with you.

 

[dcarrera]

It will lie mainly in the plane of the ecliptic, so any twinkling due to Oort bodies would be limited to the ecliptic.

No, the Oort cloud should be close to spherically symmetric. The real issue is this:

Also, although numerous, they'll be small and spread over a huge volume, so you probably wouldn't see any even if you passed through the cloud.

This is correct. Click here for a calculation.

 

[Foxhole87]

You see some actual comets and invent a magic cloud where they live.

Well, they must come from somewhere, and they must be going somewhere, what with Newtonian laws of motion and all.

No. I know the limits of science and the vacuous posting tendencies of same state past believers.

No, you believe that the world around you has the same limits it does everywhere else.

See, once you throw out the baby with the bathwater by rejecting Uniformitarianism, you must be ready to welcome in a whole slew of absurdities.