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andrew s

Science in Astronomy Now

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Not withstanding contributions from esteemed SGL members I find the accuracy of the science in Astronomy Now to be wanting. Given the October editions editorial on "Fake New" this is especially disappointing. I have sent emails to the editor before pointing out significant errors but have never had a reply.

A classic this month is the following from page 102 "ASK Astronomy Now"

"If a person were to fall into a black hole, time would come to a halt for them at the event horizon, so photons would not even reach their eyes"

This statement is completely wrong. An observer crossing the event horizon would not know they had done so.  They could see in and out (i.e. photon could reach them from all directions. How long this would last would depend on the mass of the black hole as eventually the curvature of space-time would start to manifest itself by tidal forces and what they could observe from different directions.

An observer at infinity however, would see the observer who crossed the horizon appear to get stuck there forever.

Regards Andrew 

Edited by andrew s
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I am by no means an expert on relativity, but I have recently read Kevin Brown's Reflections on Relativity, and how you describe falling into a suitable black hole it is exactly as he describes it.

Magnus

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Would not person falling into black hole suffer from increased gamma ray radiation from surrounding light sources - visible light would first be shifted towards UV, then x-rays and eventually high energy gamma.

External observer would actually see person falling "slow down" but also fade out of view as light shifts towards IR and radio. But if external observer tried to illuminate person falling in - they would in fact "incinerate" them with high energy rays.

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16 minutes ago, andrew s said:

As you cross the event horizon nothing changes in any dramatic way. As I said before in all probability they probably would not notice. As they progress toward the singularity then the release of gravitational energy from all concurrently in falling light and matter to which they are causally connected will "toast" them if there is still a them to toast as the increasing tidal forces rips them apart.

How dramatic all this is depends of the scale and hence mass of the black hole. 

 

Not sure what you mean by "slow down" but they will appear to stop at the event horizon for a distant observer.  Any clock they had will slow down due to the red-shift you describe. 

Regards Andrew

I'm not even sure that distant observer would be able to see them at all as they approach event horizon - any light reflected off subject will be progressively red shifted and one would need larger and larger aperture to resolve "clock" and verify that it is actually slowing down. I would think that any subject approaching event horizon would "fade away" from view of distant observer.

What would actual speed of subject be when crossing event horizon? Let's suppose we have "free fall" subject and they have been falling from enough far away - gravitational acceleration will speed them up considerably in relation to "rest of the universe". I suspect that subject will indeed experience all sorts of weirdness associated with such speed - things will start to look distorted, colors would start shifting - due to different red / blue shift of light due to increased speed and gravity curvature. Not sure if I can even imagine what it would look like even before they enter zone of significant gravity tidal forces.

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1 minute ago, vlaiv said:

I'm not even sure that distant observer would be able to see them at all as they approach event horizon - any light reflected off subject will be progressively red shifted and one would need larger and larger aperture to resolve "clock" and verify that it is actually slowing down. I would think that any subject approaching event horizon would "fade away" from view of distant observer.

What would actual speed of subject be when crossing event horizon? Let's suppose we have "free fall" subject and they have been falling from enough far away - gravitational acceleration will speed them up considerably in relation to "rest of the universe". I suspect that subject will indeed experience all sorts of weirdness associated with such speed - things will start to look distorted, colors would start shifting - due to different red / blue shift of light due to increased speed and gravity curvature. Not sure if I can even imagine what it would look like even before they enter zone of significant gravity tidal forces.

Valiv - I edited my post while you were replying. The link there is to an interpretation by a respected Physicist rather than my somewhat inaccurate ramblings. 

Regards Andrew

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2 hours ago, vlaiv said:

Would not person falling into black hole suffer from increased gamma ray radiation from surrounding light sources - visible light would first be shifted towards UV, then x-rays and eventually high energy gamma.

 

For an observer who freely falls from rest from a great distance, light received from a star that is directly overhead is redshifted, not blueshifted. At the event horizon, the redshift factor is 2, and as the singularity is approached, the redshift factor approaches infinity.

Roughly, Doppler redshift between source (star) and receiver trumps gravitational blueshift.

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Mercifully my own contributions are simply those of a jobbing astrophotographer so I dodge this dart!

It might be a moment to remember the late Alan Longstaff, whom I'm privileged to be able to name as a personal friend. It used to be 'Ask Alan,' and, to the best of my knowledge, he was picked up only once for an error (about which he was mortified, I can tell you, but it was a minor one since he'd located the right formula.)

Olly

PS It's still a great magazine. I mean, check out that front cover image of M31! :D

Edited by ollypenrice
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No darts aimed at you or Alan Longstaff Olly. It has gone down hill of late.

Yes the images are good but the science is often poor even from a popular science perspective.

Regards Andrew 

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I'd like to simplify it all by suggesting that the observer approaching the event horizon of a black hole probably won't see anything on account of being smeared all over spacetime making it tricky to keep their eyes open.

I could be wrong though.  If someone wants to try it and see, please do let me know how it goes.

James

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I'll number the arguments, please tell me where it goes wrong. They may all be wrong. The astronaut I have in mind is especially hardened.

1. the escape velocity of a black hole is the speed of light, so any astronaut who falls in will arrive at the event horizon with the speed of light.
2. an outside observer sees the clock of the infalling astronaut slow down and eventually come to a halt as his speed increases. The astronaut appears to flatten and freeze on the event horizon.
3. The infalling astronaut notices nothing wrong with his own clock, but instead sees the outside universe speed up, the universe running through the entire course of its existence in the time that the astronaut needs to reach the event horizon.
4. as the universe ages, eventually all black holes 'evaporate' due to Hawking radiation. This also happens to the black hole that the astronaut us in the process of entering. He will evaporate off his spot on the event horizon before he full and well enters.

There's a problem with 2. How can the astronaut freeze in place because he falls in with the speed of light (or at least asymptotically so). That sounds like "his speed becomes near zero because it is near the speed of light". It's awfully confusing.

 

 

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I am confused, if it takes infinity for an astronaut to cross the event horizon of a black hole how to they grow or even exist?

Alan

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12 hours ago, andrew s said:

No darts aimed at you or Alan Longstaff Olly. It has gone down hill of late.

Yes the images are good but the science is often poor even from a popular science perspective.

As a magazine editor myself I can say it's not easy to find someone with the skills to edit a magazine and a universal knowledge of their subject matter. This is particularly true of technical publications; I know I learn several new things with every issue.

These days the economics of magazine production mean you have a very light team and tight deadlines. Proof readers are not likely to have expert knowledge and editors can't be expected to fact-check everything that appears.

Ultimately the quality of a magazine depends on two things. In the short term it's the quality of the material submitted and in the long term it's the editors ability to cultivate the right sort of submissions and guide contributors in the right direction. Although you can change the appearance of a magazine overnight (rarely a good idea!) changing the feel and 'culture' of a magazine takes time and great sensitivity to the readers.

I would hesitate before criticising the editor of any magazine these days. The huge diversity of online publications has fragmented the market and made it much more competitive. Special interest magazines can't support the teams of staff writers and assistant editors they had in the past and are mostly the work of a small group of freelancers. It's likely that Astronomy Now's current editor has far more to keep tabs on with less support than those of the past.

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10 hours ago, Ruud said:

I

 

There's a problem with 2. How can the astronaut freeze in place because he falls in with the speed of light (or at least asymptotically so). That sounds like "his speed becomes near zero because it is near the speed of light". It's awfully confusing.

 

 

There is one big apparent paradox. Time flows at different speeds and from any point looking out at the 'observable universe' doesn't shows you reality as it is, just a perspective on what different bits were at different times. Overlaid on this appears to be the arrow of time - causality - which can't be broken. So how can everything, everywhere happen in the 'right sequence' if what I saw in my past is still in your future, just because you are elsewhere? The solution to this is the idea that spacetime is curved rather than broken.

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53 minutes ago, Stub Mandrel said:

It's likely that Astronomy Now's current editor has far more to keep tabs on with less support than those of the past.

Neil, I accept the difficulties but in an issue that lambasts "Fake News" science it is incumbent on the editor to at at least acknowledge and correct an error when they have been pointed out - something not done in the past when I pointed out an issue with their description on the size of the observable universe. I will point this error out to him via email and report back if I get a response.

Regards Andrew

 

Edited by andrew s

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The best way to pass on corrections is to do so in a way that doesn't criticise the contributor who made the error, but instead offers a clarification. Well written,  such notes often make for useful 'postbag' content.

 

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I sense I'm a bit forgiving about stuff? And I do think one should
always STRIVE for as much *scientific correctness* as possible. ?
(I also acknowledge I've forgotten [never knew] re. lots of stuff!)

I am the (lucky) co-author of many *collaborative* papers, but I
would not like to account for the exact TRUTH in many of them.
Some I KNOW contain errors due to *analysis program* bugs. ?

One that I wrote *completely* myself, had a *humdinger* of a
mistake in the theory! My Thesis "forgot"... significant details... ?
I am grateful that the author I cited in the former was GENTLE
is his criticism and that my Viva Examiners were "generous"! lol

For me, the "Joy of Science" is:  It gets folks to think (question)?
It is not about strict correctness ALL the time? And I don't see
science (sic) having a duty to battle "fake news" (or nobbers)? ?

I suspect part of the "answer" to this lies in the following...
https://en.wikipedia.org/wiki/Spaghettification
I might be right / wrong / irrelevant! ?

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37 minutes ago, Stub Mandrel said:

The best way to pass on corrections is to do so in a way that doesn't criticise the contributor who made the error, but instead offers a clarification. Well written,  such notes often make for useful 'postbag' content.

 

Blown that then. It is difficult to provide clarification on something so totally wrong.

Regards Andrew 

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43 minutes ago, Macavity said:

For me, the "Joy of Science" is:  It gets folks to think (question)?
It is not about strict correctness ALL the time?

For me the joy is in knowing how things work or at least our best models of how they do as science is never about strick correctness.

We all make mistakes which is why I removed one of my post and provided a link to a clear discussion on the topic.

Be that as it may I seem to be alone in expecting a popular science publication to at least acknowledge and correct errors when they are pointed out. Contary to Neil's view, I don't see it as my job to write the correction for them. I have never seen such a correction in AN except for minor mislabeling of images or diagrams. I will vote with my wallet and stop buying it even if it means missing Olly's contributions.

Regards Andrew

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31 minutes ago, andrew s said:

Blown that then. It is difficult to provide clarification on something so totally wrong.

Regards Andrew 

I would say that the article has an error of perspective; it stated what an observer would see, rather than what the person falling into the black hole would experience themselves, which is...

Just saying 'your article is totally wrong' may be satisfying but it doesn't make interesting copy for other readers.

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1 hour ago, andrew s said:

For me the joy is in knowing how things work or at least our best models of how they do as science is never about strick correctness.

We all make mistakes which is why I removed one of my post and provided a link to a clear discussion on the topic.

Be that as it may I seem to be alone in expecting a popular science publication to at least acknowledge and correct errors when they are pointed out. Contary to Neil's view, I don't see it as my job to write the correction for them. I have never seen such a correction in AN except for minor mislabeling of images or diagrams. I will vote with my wallet and stop buying it even if it means missing Olly's contributions.

Regards Andrew

I'm with Andrew on this one.  Science, specifically publication of science should be about being  correct unless the author is making it clear that what has been written contains some margin of error. In those cases the author should clearly state the nature and range of  the likely error or "unknown".  A case in point that sticks in my mind is the fiasco surrounding uptake of the MMR vaccination.  Ill founded and misinterpreted research together with selected reporting caused real damage to what should have been a success story .  As most will know,  the strength of a vaccination lies in achieving so called "herd immunity" which in turn relies upon uptake.  Once the media got hold of the corrupted science the protection that MMR offered, against what are seriously debilitating diseases, was fatally undermined.  If you are going to report on anything, and above all on a matters of understood science,  then you have a duty to get it right. 

Jim 

Edited by saac

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11 minutes ago, andrew s said:

Be that as it may I seem to be alone in expecting a popular science publication to at least acknowledge and correct errors when they are pointed out.

Not alone Andrew. If professional journalism in any form is to survive it needs to demonstrate clearly why it should exist in a world awash with "free" alternatives by at least being factually accurate.  (Actually this is one area where internet publishing as opposed to print has an advantage. If the article had appeared as a blog style post on the internet, the error would soon have been spotted and pointed out in the comments)

Robin

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4 minutes ago, Stub Mandrel said:

I would say that the article has an error of perspective; it stated what an observer would see, rather than what the person falling into the black hole would experience themselves, which is...

I never said the article was totally wrong - if I did please show me where I did. I just commented on the quote 

"If a person were to fall into a black hole, time would come to a halt for them at the event horizon, so photons would not even reach their eyes"

and while my English is not my strong suit, this is clearly referring to the one who fell in.

This is how I referenced the quote in my email to the AN editor

"This is incorrect even for a popular science exposition. The response seems to be confusing and mixing up what the person approaching the horizon would see with that of a distant observer. "

I also sent the link I posted here to provide the explanation.

16 minutes ago, Stub Mandrel said:

Just saying 'your article is totally wrong' may be satisfying but it doesn't make interesting copy for other readers

I don't understand what you are trying to say. I am doing it for my satisfaction? 

Regards Andrew

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26 minutes ago, andrew s said:

I don't understand what you are trying to say. I am doing it for my satisfaction?

No, I think you are doing it out of understandable irritation or frustration; but any magazine editor will make mistakes; I doubt any issue of any magazine has ever been published without an error of some sort.

When there's a fairly significant error like the one you've highlighted appears to be (and I haven't seen the article) if I spot it or it simply gets mentioned, I'll print a correction. If someone writes me a decent email or letter on the subject, I'll publish it and that almost certainly gets the 'correct' information to more people. It also helps build a 'positive culture' around the magazine; where corrections get ignored or just blamed on 'someone else' it really undermines readers' faith in the integrity of the publication. This is evident from your own reaction.

I once calculated that by publication I will have normally read an article at least seven times. With the greatest care in the world this does mean that sometimes you see/read what you expect, not what is actually written. A good recent example was where temperature signified by a superscript zero instead of a degree symbol got multiplied by ten when set and the writer's formatting was removed. When proofing I just saw big numbers where I expected big numbers (bear in mind people often write 100 C, for example, so the absence of the symbol wasn't obvious). Boy, that gave me a big postbag and a couple of discussion threads on our forum! The letter I printed included several other constructive observations on the article, adding to its usefulness as well as correcting the error.

Making it easy for a publication that isn't particularly good at correcting itself to do so may help with improving it to the benefit of all readers; as I said at the start, bear in mind that no-one publishes such errors deliberately. A constructive correction is more likely to be seen as helpful and acted on rather than one perceived as an attack on someone's capability or knowledge.

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25 minutes ago, Stub Mandrel said:

No, I think you are doing it out of understandable irritation or frustration; but any magazine editor will make mistakes; I doubt any issue of any magazine has ever been published without an error of some sort.

I fully agree with you that magazines will make mistakes. 

You seem to respond as if I am criticising your publication but I don't even know which one it is. Your description of how you would respond seems totally satisfactory.

However, AN did not respond at all, not even a thank you for you letter, when I wrote pointing out an error in an article which included the statement to the effect that:

" the size of the observable universe is limited to the point where the recession velocity of galaxies etc equals c"

I wrote what I felt was a sensible comment saying that this was not true and that we had already observed objects with higher recessional velocity v ~3c plus some other information including that the CMB is currently the furthest we could see back with z ~ 1000. 

There was no correction or comment in AN as far as I can tell. That's why I highlight AN in this regard. Have you ever seen such a correction in AN? The only ones I have seen are when they mislabeled a diagram or image.

I am sure you are a fine editor if you let me know what your magazine is I will give it a try.

Regards Andrew

 

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