OJBs Web Site: Blog Page

Note: You are currently viewing my old web site. There is a new version with most of this content at OJB.NZ.
The new site is being updated, uses modern techniques, has higher quality media, and has a mobile-friendly version.
This old site will stay on-line for a while, but maybe not indefinitely. Please update your bookmarks. Thanks.

Add a Comment (Go Up to OJB's Blog Page)

Gell-Mann Revisited

Entry 2121, on 2021-04-19 at 21:19:44 (Rating 2, Science)

I talked about the Gell-Mann Amnesia effect in a previous post titled "Gell-Mann Amnesia", from 2019-06-18. If you haven't heard of it before, here is a brief description: people notice errors in news items and articles on subjects they know a lot about, but when reading articles on other topics from the same source they forget these problems and assume the other material is accurate.

For example, I might read an article in my local paper about computing which might make a statement I know is false, because I know more than most about computers. But then I might read another article about something I am not an expert on, let's say embroidery, and assume that is accurate. But why should I? I only realised the computer article was wrong because I know enough to notice. I don't know enough about embroidery to know how accurate that is, but based on the stuff I do know about, which the media often get wrong, shouldn't I assume the other stuff is just as inaccurate?

I have made no secret of my overall contempt for mainstream media today, primarily because they seem to be more interested in virtue signalling or supporting their favourite political movement than reporting actual news. I often say that poor performance in institutions like the news media could be the result of two deficiencies: incompetence and corruption. By "corruption" here I mean moral corruption (deliberate lying, for example) rather than the financial or legal variety.

I would assume that most of the biased and inaccurate political reporting is caused by corruption, but there are plenty of examples of inaccuracy where there is no discernable reason for being deliberately misleading, so maybe incompetence is also rife.

Here are a few examples of inaccurate, and just plain wrong, statements I have come across in mainstream media recently...

An expert appearing on an item on computer malware stated that ransomware attacks are a big problem because they spread across networks.

While many attacks of this type do spread over networks, so do many other forms of malware, and that isn't the main reason ransomware is a problem. The real problem is that the technique is used by relatively skilled attackers for the specific purpose of extracting money (the ransom) from the target organisation or individual by encrypting their data and making it unavailable until the ransom is paid.

Here's another one: an "expert" on astronomy stated that Mars is the closest planet to the Earth. While this is a more interesting and complex question than you might think (more on that later) there is no way that Mars can be the correct answer.

In the same interview it was stated that Mars is 227 million kilometers from Earth.

Again, this is almost always untrue. Mars is approximately that distance from the Sun, but the Earth is 150 million kilometers from the Sun. Because the Earth and Mars orbit the Sun with different periods (365 days for the Earth, 687 days for Mars) the distance between them constantly changes from a minimum of about 77 million kilometers (227-150) to a maximum of about 377 million kilometers (227+150).

In fact, it's more complicated than that, because the planets don't orbit the Sun in perfect circles, so their distance from the Sun varies by millions of kilometers. Because of this, the closest approach possible (based on current distances, and remember that over billions of years these numbers do change) is 54.6 million kilometers.

There are times when the distance from Earth to Mars is 227 million kilometers, as the person stated, but the same applies to any number between the minimum and maximum I gave above, and it is definitely not the answer anyone who knew what they were talking about would give.

So what about that question concerning the closest planet to Earth? Well, if you interpret this as the closest possible at the optimum time in their orbits, the answer is Venus. That planet is 108 million kilometers from the Sun (on average, because its orbit isn't circular either). This means that the closes distance is 42 million kilometers (150-108) but it can be as close as 38 million kilometers (when Venus is at its greatest distance from the Sun and Earth is at it least and the two planets are lined up on the same side of the Sun).

Just to make things even more complex, the orbits are also tilted a bit above and below the plane that the planets roughly lie on!

But clearly Venus can get closer to Earth than Mars, but is it the closest?

That depends on the exact question. If we ask about the minimum possible distance the answer is Venus, with Mars being second. But if you ask about the average distance, in other words, the distance if you averaged all the distances between Earth and other planets over their entire orbit, the correct answer is (perhaps surprisingly) Mercury.

So the closest planets to Earth (in million of kilometers) on average are: Mercury 156, Venus 170, Mars 254. Note that all of these are greater than the Earth-Sun distance, indicating that all of the planets spend more time further from the Earth than Earth is from the Sun, an obvious point when you look at the geometry.

A further consequence of this is that Mercury is the closest planet, on average, to every other planet in the Solar System, even Neptune and Pluto (if you want to call it a planet) away out on the edge, billions of kilometers away from Mercury which is closest to the Sun.

There is one other point here, that I just thought of. If I chose a random point in time, which planet is most likely to be closest? Well, I haven't done the calculations, because they are really complex, but intuitively I would say the say the chance of being closest would be Mercury, then Venus, then Mars again. None of the other planets get closer than Mercury at its greatest distance.

So that silly mistake made on RNZ is actually the source of some interesting conclusions when the real numbers are calculated. And this also indicates how difficult it is to answer many questions when the question is stated using simple English. What exactly do we mean by "the closest planet"? Whatever it is, Mars is not the best answer!

Comment 3 (6544) by Ken Spall on 2021-04-20 at 14:54:59: (view earlier comments)

500 words or not it's still worthy of discussion and a good read.
cheers
Ken

Comment 4 (6545) by Anonymous on 2021-04-20 at 15:55:25:

There are two issues here:

(1) Is the topic worthy of discussion - probably, if that floats your boat.
(2) Maybe it's not entirely fair to criticise somebody for giving a simple answer when not everybody wants the 500 word answer that is still ambiguous...

Comment 5 (6546) by Ken Spall on 2021-04-20 at 18:16:30:

No criticism intended, just wanted to make a comment.
cheers
Ken

Comment 6 (6547) by OJB on 2021-04-20 at 19:04:41:

I often write these blog posts intending to comment on one issue then find myself taking a slight diversion into other areas. In this case I wanted to highlight the inaccuracy of the original comment, but then remembered an interesting discussion on Quora about how to define the closest planet.

Note that the original statement I was criticising was just wrong, and wanting to simplify the answer or state it quickly is no excuse.

And I love ambiguity. Yes and no answers are so boring. It is far more interesting to live with both nuance and doubt!

Comment 7 (6548) by OJB on 2021-04-20 at 21:18:35:

What is my 5 word answer to "How far away is Mars"? How about "At its closest, 55,000,000 kilometers" or "As little as 55,000,000 ks" or "Varies from 55 to 380 million ks" (OK, 7 words there).

You can leave comments about this entry using this form.

To add a comment: enter a name and email (both optional), type the number shown above, enter a comment, then click Add.
Note that you can leave the name blank if you want to remain anonymous.
Enter your email address to receive notifications of replies and updates to this entry.
The comment should appear immediately because the authorisation system is currently inactive.