h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

For about the tenth time I can recall, the BBC has an article about Voyager 1 leaving the solar system. To me that means it should have passed through the Kuiper Belt and Oort Cloud and yet every description I've seen of them describes the Kuiper Belt as barely-understood and the Oort Cloud as hypothetical, extending perhaps as far as a light year away from the sun.

Aren't those two statements mutually contradictory? Surely if the Voyagers are well on their way to leaving the solar system, they must have passed through the Kuiper Belt and at least some of the Oort Cloud. Or am I missing something?

I think they're leaving the heliosphere, where the solar wind is. Once they pass through that, the (particle) radiation they experience will be that of interstellar space.

I think..

Well the truth it, as you allude, we just don't really know. Voyager is finding out.
BBC science articles have to search for a headline...Voyager *might* be leaving what we currently understand as the rather vaguely defined 'edge' of the solar system doesn't make for a very good headline

This is one of those things that points out our perceptual limitations.

Ignorant apes that we are, we persist in trying to draw lines - alive/not alive, a person/not a person, in the solar system/outside the solar system.

Sometimes (person/not a person) you HAVE to draw a line somewhere, so that it becomes illegal to have an abortion twenty minutes before you're due to give birth but it's legal to have one when it's only a month since you've conceived and the thing you've conceived is a barely visible clump of almost undifferentiated cells. Somewhere between those two extremes you must draw a line, and wherever you draw the line, you will be wrong, because there simply isn't a point at which you can say "this is not a person... still not a person... not yet... nearly... YES! now it's a person."

It's technically referred to as the Sorites Paradox, sorites being the Greek word for "heap". As in, if you have a single bean, you don't have a heap of beans. This is definitely true. If you don't have a heap of beans, adding one more bean won't make it so that you have a heap of beans. This is also obviously true. The logical conclusion one must draw from these two premises is that it is impossible to get a heap of beans. And yet this is obviously false.

If you keep on adding beans, sooner or later you incontrovertibly do actually have a heap of beans. But when?

It rests on the fuzzy edges of the meaning of the word "heap".

Similarly, the solar system has fuzzy edges. Time was the edge was fairly clearly defined as the orbit of the outermost planet, Neptune. But then we discovered another planet beyond that... but then we found that for some of the time that planet was actually closer to the sun than Neptune, which was odd... Then we decided that although it was clearly in the solar system, it wasn't a planet at all, then we discovered a bunch of other stuff that also was clearly in the system but not a planet and further away than Neptune, and now the boundary is anything but clear cut.

The only thing we can say with anything like certainty is that the solar system has a radius of less than 2.2 light years... because if you go that far in the right direction, you'll be closer to a different sun entirely. Beyond that, pick a definition.

Of course, somewhere between a single bean and a heap of beans is enough beans to make a very small casserole...

Ah, but do you know how many beans make five, or nine?

Some beans plus some beans makes..... four beans...

The scientists have reported that Voyager has entered a new zone where the solar wind is gone, but the galactic wind that they expected isn't there either.

So the question is, is this area of no wind caused by the sun's presence? Whether it's inside or outside the solar system is not really a big issue but it is the one latched onto by the headline writer, who hasn't necessarily understood or even read the content of the article.

My next question is will the Voyagers pass through the Kuiper Belt/Oort Cloud and would we be able to tell if/when they do?

I'm thinking that since this a cutting edge area of research - this is a bit like asking Christopher Columbus what Hispaniola was like before he landed

The Kuiper Belt/Oort cloud are spherical (maybe ellipsoid?) regions of space around the solar system - I guess it would be kind of hard to not pass through them if you're going to leave.
How you would tell I've no idea.

Rod: I know how many beans make five! My dad taught me that one when I was really little:

A bean and a half
A bean and a half
Half a bean and
A bean and a half.

Had never thought about a heap of beans (or heard about it) before. Busy revising the way I look at the world (again).

Mol

I thought the collective word for beans was 'a hill'.

Alternative - two beans a bean, a bean and a half and half a bean
(for some reason it seems more satisfying to finish off with 'half-a-bean' non?)

A hill of beans ... yep, think yer rite, G


>pass through the Kuiper Belt/Oort Cloud and would we be able to tell< ? : HI
well now, if the ship's systems have been wiped out, we'd have to listen out for the cessation of things banging against the hull trying to get in