Naked Science Forum
General Discussion & Feedback => Just Chat! => Topic started by: Eternal Student on 25/07/2021 23:40:10
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Candidate 1: "Science Time" . Overall impression 4/10.
Not sure If we can really talk about good videos we would recommend. That might be unfair advertsing.
However, I'm fairly sure we can talk about YT videos we wouldn't recommend.
"Science Time" keeps coming up in the automatic recommendations of my YT experiences.
I've seen only a couple of these. They "claim" to be discussing a topic "with a famous scientist" but they always seem to be talking about a topic and then mixing in some pre-recorded speech from that scientist. I've never seen the scientist in the video only ever heard their voice. Sometimes the audio quality is very poor and not at all indicative that the scientist went to a sound studio to record this for Science Time
To complement their audio, Science Time show a collection of images on the screen which really are very pretty but often have very little to do with the conversation.
They choose topics that are obviously interesting to the general public but after wasting 12 minutes of your life, you will leave feeling that you have barely learnt anything and spend the rest of day trying to remember where you heard that speech or presentation before.
Somehow they have 190k+ subscribers.
Am I missing something here? Is Science Time just as interesting as the stuff they call "musak" and play in the lift ("lift" = "elevator" in some countries)?
Comments welcome. Has anyone watched more of their videos and do they get better?
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Other side of the coin:
I was once interviewed for a Swedish radio program. Unlike several previous UK presenters, the interviewer had clearly done a lot of homework and it became a friendly interrogation bordering on a viva exam, running exactly 10 minutes. I asked if I could hear the broadcast. She said there wasn't much point as they didn't edit these packages, and it would be embedded in a Swedish language music and chat show (think Radio 2), but at midday every day they broadcast a 10 minute interview with a scientist "always in English, because people want to hear scientists speaking for themselves".
Now that's what I call a culture!
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Candidate 2: "Why are there giant concrete tunnels in the desert?" - by Physics Girl. Overall impression: 7/10
In this video Physics girl was talking about the LIGO experiments and the detection of gravitational waves. Physics girl is usually a great channel. There is so much here that we could categorise as being exceptionally good. However, sometimes errors creep into the videos. This is made much worse when elaborate animations and descriptions are added so that we end up having something explained to us in a way that seems so reasonable and official but it is actually just fundamentally wrong.
Sadly, there is one such error in this video. Physics girl explains gravitational waves by using the example of the sudden disappearance of the sun and how long this will take to affect the orbit of earth.
This is a pet hate of mine and featured in one of the first threads I ever started in this forum. I'll only summarise the problem here: The sun can't just disappear in General Relativity, the local conservation of energy-momentum ( ∇μTμν = 0 ) will not allow it. As a consequence the Einstein Field Equations cannot sensibly be used - they would just be inconsistent. Hence, there is no way to know if a gravitational wave would emanate from where the sun was previously located or if the entire metric must change throughout all of space instantly. There is no correct answer, the situation is just fundamentally inconsistent with General Relativity.
Perhaps one of the best things about Physics girl is that she is very human and very enthusiastic. It's a good thing to see some mistakes being made sometimes. How accurate does an edu-tainment video need to be in order to be useful and worthwhile? I'd say that at least 90% accuracy is desirable. If more than 1 thing in 10 we are told (or shown) is significantly wrong then the video becomes more harmful than useful. I don't know but please feel free to comment... or comment on some other video you've seen recently... or something. There's no point in my talking to myself. Also, please recall that this thread was originally established to discuss problems or videos that are "not so good". There is no point advertising your own video here but equally let's remember how hard it is to create videos and be reasonable with your criticism and/or emphasise that there are some good bits.
Thanks and best wishes.
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In general, it is a bad idea to cite lots of bad videos.
Links to a video "promote" it on search engines...
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At the risk of being cited for spam, I've just learned that "Eating ourselves to extinction" is on cinema release today. Not sure if they used it in the final edit, but part of the argument was based on my calculation of agricultural carbon dioxide emissions.
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Hi all.
My pet hate on YT are the videos which claim that gravity is caused by GTD!?
Ok I'll have a look at the PBS Space Tie video later. I can already guess how or why GTD gets associated with the cause of gravity. There is a need (or wish) to show that gravity is just a consequence of the curvature of spacetime. I mean that is the basic message from General relativity. It's just that around an object like planet earth, most of that curvature is shown in the time component of the metric describing spacetime around the earth and not in the spatial components of the metric.
It's not especially fair or accurate to say that GTD causes the gravity we experience on earth, it could just as easily be considered as an effect of the unusual curvature of spacetime.
In general, it is a bad idea to cite lots of bad videos.
Links to a video "promote" it on search engines...
Agreed. I've been careful to avoid active hyperlinks. I appreciate that some of the search engines will still know who we are talking about.
I don't know which way to go on that issue. I'd like to talk about some of the problems with videos sometimes and I can't help it if some search engines do whatever they do. I can't talk about the good ones too much because that would be advertising plain and simple. I'll probably leave this thread alone but every now and again there may be a video that I just can't ignore and feel the need to moan about it (sorry).
but part of the argument was based on my calculation of agricultural carbon dioxide emissions.
Well done. "At the risk of being cited for spam" but still, well done and congrats.
Best Wishes to everyone.
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Hi.
My pet hate on YT are the videos which claim that gravity is caused by GTD!?
Gravitational Time Dilation. I dismissed them, as nonsense, until the PBS Space Time's one. "Wot"!?
Please have a look and comment upon them.
I can only find one video of what claims to be a two-part discussion on the topic. It seems the second part has not been released yet.
It seems a slightly clumsy way to explain gravity and so far fails to apply to photons (until part 2 appears). The creator has directly mentioned that there are other interpretations. It's probably unfair to comment until that second part is released but at the moment it seems like "Matt" (I think that's his name) is proposing a novel way to visualise or explain something from General Relativity: That particles travel along geodesics through spacetime, which could also be described another way - particles move in such a way that their velocity vector is parallel transported through spacetime.
I'm not convinced that one thing he mentioned is actually correct. He implies that individual particles (in a teapot for example) want to try and keep moving straight through time and not "leak" some of that speed into a velocity through space. The different flow rates of time at different altitudes force the overall 4-velocity of the teapot to turn and this seems to be a result of interactions (forces) acting between those particles to keep the whole object together. This is shown elsewhere in the video by two canoes connected by a rod and in a river with different flow rates near the centre and edges of the river. If this was correct then we should observe a compression force between particles of a bound object like a teapot moving along a trajectory close to a massive object like the earth (the particles at higher altitude must push the particles at lower altitude). However, the way we think gravity applies is that the particles at lower altitude would actually naturally tend to have their path bent more than the particles at higher altitude. So they would tend to pull the particles at higher altitude and we would observe a tension (not a compression) in the object.
It seems to have been 6 months since the second part was promised, maybe Matt is having a re-think.
Best Wishes.
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The sun can't just disappear in General Relativity, the local conservation of energy-momentum ( ∇μTμν = 0 ) will not allow it. As a consequence the Einstein Field Equations cannot sensibly be used - they would just be inconsistent. Hence, there is no way to know if a gravitational wave would emanate from where the sun was previously located or if the entire metric must change throughout all of space instantly. There is no correct answer, the situation is just fundamentally inconsistent with General Relativity.
But we do have instances of small masses evaporating into massless photons, with absolute conservation of energy and momentum, so what happens to the gravitational field of the electron-positron pair?
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And where does the gravitational field come from when a single photon produces a positronium pair?
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Hi everyone.
But we do have instances of small masses evaporating into massless photons, with absolute conservation of energy and momentum, so what happens to the gravitational field of the electron-positron pair?
We've had similar discussions before, Alancalverd.
I think this is the thread:
Problems with PopSci articles in GR. Should we stop using one example? - started by Eternal Student 19/05/21
https://www.thenakedscientists.com/forum/index.php?topic=82317.msg640621#msg640621
I'll try to keep my reply brief rather than repeating the previous discussion.
Where matter annihilates to form photons, those photons have energy and momentum. As you (Alancalverd) stated they have exactly the same energy and momentum as the original matter. As far as general relativity is concerned, those photons will be a perfectly good source of gravitation. Since there is precisely the same energy and momentum at the same places, the metric field (or the gravitational field) doesn't change at all. (Well, it will change in a progressive way as the photons travel and move away but it won't be the "instant" change that was shown in the video and is generally implied whenever people talk about the sun suddenly disappearing).
Anyway, "the gravitational field" that was caused by a positron and electron doesn't just disappear when the particles annihilate, it's still there but now seemingly caused by the photons rather than the massive particles.
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That's exactly what Prof.Brainy Greene/horn/e said, in his 2011 The Hidden Reality book in a footnote on p34?
But what does it really mean? Even at the surface of the Sun, GTD is practically nothing!
What does it mean? I suspect that referring you to the first couple of chapters in a textbook on General Relativity would be better than assuming I can explain it in some better and shorter way here. (I'm really not that good at explaining stuff). There's a lecture series by Prof. Leonard Susskind that I watched first before reading Sean Carroll's book.
I don't know your initial level of experience in this, all I can say is that it could take a few weeks before it makes sense (sorry).
Personally, I don't think it's fair to say that the time component of the metric explains the motion we observe here on earth in what we consider as our gravitational field. It's the assumption that objects naturally move along geodesics that is pivotal. I'm probably arguing over abstract notions that make little sense to you anyway. You need both things to make sense of the movement of objects in the gravitational field around planet earth (and a few weeks to study it all).
I don't know if it helps but there are dozens of questions I still have about General Relativity. For example, why should objects tend to move along geodesics? It relates to another thread in this forum about Lagrangian mechanics and a least action principle but I don't suppose it's worth explaining the connection here. Anyway, timelike geodesics are paths taken by objects with mass. These paths maximise the proper time experienced by the object given that it was required to move from an initial event to a final event. So we could answer your (curious cat) question about why GTD is important to explain motion in the presence of gravitational field in this way: An object moves along a path so as to maximise the proper time that it experiences. It will naturally tend to move into a region with a greater time dilation to take advantage of this and maximise the proper time it experiences. Don't get me wrong, it's not a very satisfying answer and it just deflects the key question from one thing to another. We can now see why time dilation is important and why an object tends to fall into a gravitational well to experience time dilation but we have another queston to answer: Why does Nature care about maximising or minimising something? It might be best to start learning about GR with the attitude of "shut up and calculate" similar to Quantum Mechanics. Don't ask why things move along geodesics, just accept that they do. Do the calculations and you will see that the time component of the metric around planet earth is what's important and explains most of the motion that we observe for projectiles launched from earth.
Best Wishes.
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So let's consider a universe in which there is only a positronium pair P and a single, neutral lepton L. Clearly the gravitational field of P will attract L which accelerates towards P (it works for apples, and we assume so for all particles). Then P disintegrates into two photons which, in my simple universe, fly off at right angles to the track of L. Does L continue to accelerate towards where P was?
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Hi.
Does L continue to accelerate towards where P was?
Yes, more or less. This is more complicated than you might have realised. It's also too late for me to find the references I would have wanted. I'll try to add them later if you wanted more information or more proof that things can be this weird.
Anyway, here we go with the answer:
At the instant of annihilation, yes.
On the very short term, just after the annihilation of the positronium, something slightly interesting happens - the acceleration of the lepton should continue to be towards where the positronium would have gone (i.e. as if the positronium had continued along it's trajectory with the same velocity and hadn't annihilated). This is slightly different from pointing to where the positronium was..... it's as if the Lepton thinks not only that the positronium is still there but that it has also continued to move.
After that there should be a smooth and progressive change. The general idea is that the pair of photons will become a source of gravitation equivalent in magnitude to the original positronium. As the photons move away, the metric field will change. It's the photons that will be the new source of gravitation and the gravitational attraction will be towards the photons (wherever they may go). You've given us a pair of photons, so we have two accelerations and need to do a vector sum to find the net acceleration - but it's not too difficult.
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U may care to check out my reply to Halc in How close are we from building a virtual universe?
It may shed some light on your Lagrangian Mechanics - Why is Nature lazy?
Thanks. I have read it and will try to keep an eye on further developments.
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I'm tired, bye for now and best wishes to everyone.
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So let's consider a universe in which there is only a positronium pair P and a single, neutral lepton L. Clearly the gravitational field of P will attract L which accelerates towards P (it works for apples, and we assume so for all particles). Then P disintegrates into two photons which, in my simple universe, fly off at right angles to the track of L. Does L continue to accelerate towards where P was?
Those photons will still have a gravitational field. Rest mass isn't needed for that. Energy will do it too.
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Hi.
What do U, guys, think of all those physics videos, on YT?
There's lots of them. Some of them are quite informative others are just entertainment or "info-tainment" as they are sometimes called. Many of them are awfull. Money and payment for getting views has become a huge part of YouTube.
I don't think I can discuss the good ones in this thread. The thread could quickly be taken over by people just advertising their own videos and/or those of friends. The forum has a policy on advertising (try not to do it). All links should be relevant to the discussion at hand, if they were more relevant to boosting your own (or your friends) profile or bank balance then they they really don't need to go in the posts.
This thread was originally set up to discuss the problems in YT videos, in the hope that no one would want to put their own video in here anyway.
There are many times when I would like to see, listen and even talk to someone, rather than just read something in a book. YT videos are one of the few places where you can get something like this if you are unable to physically attend a University or similar place. Forums can also be useful for this.
Best Wishes.
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Hi All.
🙋
I found a few vids on Utube on the Topic :- Breatharianism.
I've been relentlessly Reporting them as Spam, Misleading, Dangerous & Harmful Acts.
But to no avail.
👎
Ps - With all due Respect, Utube Mods SucK!
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Hi @Zer0
Thanks for the warning. I've no idea what that is and very little desire to find out.
oh... and I guess you mean the moderators by "UTube Mods". On first reading I thought you meant some kind of browser extension or downloadable app for Youtube.
I'm not sure Youtube have many "moderators". Whatever regulations they have it seems limited to keeping things legal. They would argue that it's not their job to curtail creativity of any kind. Videos don't have to be factually correct to be entertaining etc. For example, most famous politicians probably didn't really deliver their speeches in the style of a rap or dub-step track - but these sorts of videos are still very popular and successful as far as Youtube are concerned.
Best Wishes.
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Hi Eternal!
I completely understand your point of view.
Sorry for creating the confusion, Yes i meant YouTube Moderators.
E_S I'm in a personal dilemma of sorts...
I keep Reporting all such crappy videos, and after 3months, i see Action being taken.
But i wonder, what if they never surfaced on Utube...
Then they would keep spreading silently like a plague..
Perhaps it's Good for Evil to rise up n show it's head, so that it can be chopped off rightfully.
Secondly, I'm loosing my mental & emotional Balance.
My levels of Tolerance towards Believers & people of Faith is drastically dropping.
I find it Extremely Difficult now to just " Live & Let Live ".
I Just Cannot take this BS Anymore!
I feel like I'm turning into a Science Extremist & Fact Fanatic.
These Morons spit & shame on my logical reasoning.
They demean & insult my ability of critical thinking.
I Consider this as a Personal Attack on my " Freedom to Think for Myself ".
Ps - i Do Not wish to promote this following video which debunks soo called " Art of Breatharianism ".
But it Deserves a Spot in this OP.
Thanks a Million, All Rights & Credits, and Alot of Respect to - That's Inappropriate Channel/YouTube.
(This Lady Deserves All the Praise & Accolades for Standing up for what is Logically Correct.)
I Sincerely Wish someday, someone, will Sue YouTube for serving Unethical, Immoral, Suicidal content to the Innocent, Ignorant, Gullible masses.
& I can Only Hope noone has lost their precious life(as yet) by being misled by YouTube.
(Please Do Not Misunderstand Mee!
I Like Utube, I don't want it to be Banned, i just wish for it to Change for the greater good)
✌️
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Hi again!
😊
I've found a plethora of " Conspiracy Theories " & " Time Travel Evidence " videos on YouTube.
Ps - I've got the free version of Utube.
Now mostly there are 2 back to back skippable ADs before almost every video.
I do Not mind Adverts, i understand the financial implications...but a few ADs instigate physical pleasures & quite frankly cannot be watched around or with family.
(Utube is going from Order towards Chaos real fast)
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Ummm...i wasn't Aware that Oprah Winfrey had soo many shows based on " Past Life " Experiences.
WooW!
& She was able to get hold of All these " Reincarnated People " & convince them to come onto the TV Show.
WooW!
Ps - Is " Parapsychology " a Real Subject one could take up in a University?
Do Departments Of Parapsychology Exist? Still Exist?
(No Kidding eh)
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MODS...Eternal would perhaps be away for awhile.
Should i still keep posting in this Thread?
Bcoz of Utube Content, i feel i could keep doing this for a very long time.
Loads of BaD stuff out there.
Or should i just give this a pause Now?
Ps - H...Advise?
🤔