Cosmos - With Neil deGrasse Tyson

[Christopher]

Well sure, you're "technically" correct, but you missed my point. What I was actually referring to is the process by which that information is transmitted via radio.

The transmitter itself is broadcasting at a certain frequency on the electromagnetic spectrum, say between 87 and 108 MHz. You pick one of those frequencies, and generate an electromagnetic wave at that frequency. That frequency is then "modulated", meaning instead of a nice sinusoidal waveform, you actually have a jagged-edge waveform that resembles a sine wave, using superposition. (AM radio does the same thing, however it is modulating the amplitude and not the frequency).

The receiver (your radio) then takes that jagged-edge waveform, and subtracts the original sinusoidal waveform from it, leaving you with only the energy levels of the audio portion. This is what is translated to vibrations in the speaker.

Ah, okay, you're talking about the carrier wave vs. the modulations that convey the actual data.

If we wanted to, we could send audio through a modulated light wave (say for example, a laser), but you run into issues such as the wavelength being extremely short, whereas radio waves have much longer wavelengths and can go through walls and stuff like that. Not to mention laser lights are extremely focused and radio can radiate in all directions.

They do use lasers as surveillance mikes -- reflect the beam off a window, and its vibrations from the sounds inside create interference patterns in the beam which can be deciphered to reconstruct the sounds.


As for climate-change deniers, I think that, if they really wish to be honest and consistent in their beliefs, they should cancel all their insurance policies. You don't absolutely know for a fact that your car will be in an accident or your house will burn down, but you're willing to invest money in taking precautions against such eventualities because the stakes are high enough that it's worth erring on the side of caution. And we have far more certainty that dangerous climate change is happening -- it may not be absolutely 100 percent inevitable, but the likelihood that we're wrong is extremely small. So if anyone insists that we need absolute, 100 percent certainty of a risk to the planet before making any effort to guard against, then they prove themselves hypocrites if they're willing to spend money on any kind of insurance. So my challenge to climate-change deniers is to put their money where their mouths are and cancel all their insurance policies -- or else admit that their arguments are invalid and it's worth taking precautions against potential risks.

(Rhetorically speaking, of course, since people in the US are required by law to have auto insurance if they drive, and are now required to have some form of medical insurance. I don't wish to exhort anyone to break the law. But I hope the point is made.)

 

[Awesome Possum]

And the whole past temperature reconstruction debate is itself a meaningless distraction, because the climate swings back and forth all the time, almost completely unrelated to mans' historic development of the scientific method. We've been advancing through all those ups and downs of climate, and where we happened to pop up on the curve (with our new mental tools) is essentially random.

No one denies that the climate swings back and forth. But to pretend that CO2 levels haven't risen dramatically in the last 100 years, at a faster rate than ever before recorded (and coinciding with when we started pumping so much of into the atmosphere), just seems silly. And there's a lot more evidence to rely on for that that just some tree rings.

Sure some of the gloom and doom is probably a bit overblown, and the Earth will likely recover no matter what we do to it, but in the meantime we do still have to live here.

Don't bother. He's just trolling, I doubt he believes a fraction of what he says. You'll notice that every single post he has made is an attempt to hijack it away from discussing the show.

He's switched to being a climate change denier because he knows that anyone will a basic knowledge of science accepts as fact and there isn't any evidence to oppose it. It's nothing more than cherry picking data, confusion over the weather vs climate and character assassination (note his comments on Sagan and Gore).

He needs a new act, this one was old when he got kicked out of TNZ years ago.


As for the episode, absolutely amazing.

 

[gturner]

Okay, I'll take your challenge, but instead I'm going to sell you a climate insurance policy for $100 bucks a month. Make your checks payable to me, here.

But first I need to know where you live to assess the risks. For example, if you live in Southern Virginia there's a small chance that your property could become as warm as northern North Carolina within a hundred years, as indicated by the predictions of the IPCC working groups. I suppose maybe your roses would bloom a few days earlier, but I don't think I'd have to pay out on that.

You might claim, contrary to the IPCC and climate science, that you'd be subject to more severe or more frequent extreme weather events, but you're not going to have any statistics to back it up, so I won't have to pay out on that, either. In fact, we've been breaking record lows for tornado activity, and Obama is the first full-term President who hasn't faced a major hurricane landfall,

Overall, worldwide wind speeds have been dropping as temperatures increased, quite contrary to the idea that more energy in the atmosphere should produce more extreme weather. Going back through the records, it's interesting that the worst hurricanes occured during the 1700's, when the Earth was in the grip of the Little Ice Age.

Scientists still can't account for the phenomenon, and they were very surprised to find out that winds on Neptune reach supersonic velocities even though it receives only a trickle of energy from the sun. That adds to a general observation that wind speeds increase the further you get away from the sun. Venus has extremely slow winds, Mars has freakishly fast winds, and Jupiter, Saturn, Uranus, and Neptune are even worse.

One theory was that maybe really cold air somehow doesn't form eddy's very well, and thus its friction is greatly reduced. I would note that PV=nRT means that for a given delta T, the delta V per V (or the change in density per volume) is an inverse function of absolute temperature. A one degree rise in a 1000 K atmosphere produces a change in volume of 0.1%, but a one degree rise in a 100K atmosphere produces a volume or density change ten times larger, and changes in density (and thus pressure at a given altitude) drives wind. The strongest winds on Earth aren't in the tropics, they're in the Antarctic and Greenland.

Also, going back to the precautionary principle, there's a small chance you have testicular cancer. I'll loan you some garden shears if you really want to be safe about it.

 

[Greylock Crescent]

^ Rubbish.

As for the episode, it was one of the most satisfying for me, from start to finish. I loved the use of "light" as a topic of science, and as a metaphor for the scientific process. Everything, from the topic to the music to the visuals to Tyson's enthusiastic presentation worked in harmony - to me, anyway.

Beautiful.

Regarding the absorption lines, I vividly remember a Earth Science lab from 8th grade where we looked at various neon lights (which used different elements) and looked at the different "black lines" in the spectrum.

Really, very cool (and powerful) stuff.

 

[Allyn Gibson]

The dark lines in the spectrum were what surprised me. I had never thought about it, I had never heard about the reasons behind the dark lines in the spectrum. I didn't know such reasons existed! This was another excellent episode.

I learned about the absorption lines, probably around the age of 10, through an article or book on finding extraterrestrial intelligences.

The author of the piece suggested that we check stars for the absorption lines of technetium. As a radioactive element that doesn't occur naturally, an alien species could make technetium in large quantities and dump it into the star as a way of saying, "Here we are!"

It turns out, which I learned later, that stars can, in fact, produce technetium, generally red giants. It hasn't been found in K or G-class stars, however.

 

[gturner]

Don't bother. He's just trolling, I doubt he believes a fraction of what he says. You'll notice that every single post he has made is an attempt to hijack it away from discussing the show.

He's switched to being a climate change denier because he knows that anyone will a basic knowledge of science accepts as fact and there isn't any evidence to oppose it. It's nothing more than cherry picking data, confusion over the weather vs climate and character assassination (note his comments on Sagan and Gore).

He needs a new act, this one was old when he got kicked out of TNZ years ago.

I guess anyone like the chair of the department of climate science at Georgia Tech (who routinely testifies on climate issues before Congress and who was recently asked by the American Association for the Advancement of Science to skeptically review their position on climate change), doesn't understand anything about climate science.

The IPCC is backing away from their earlier reports, lowering their estimates of climate sensitivity, and many climate scientists are backing away from earlier positions in light of new data (science does that). This is making alarmists more and more vicious, calling for the jailing of anyone who doubts their Truth, etc. In the annals of science history, they won't be portrayed as the scientists, they'll be portrayed as the mindless defenders of religious dogma and supporters of the inquisition.

Also, I can go back to TNZ anytime I become willing to support Obama. (It's probably the weirdest ban in TrekBBS history).

 

[Amaris]

^ Rubbish.

As for the episode, it was one of the most satisfying for me, from start to finish. I loved the use of "light" as a topic of science, and as a metaphor for the scientific process. Everything, from the topic to the music to the visuals to Tyson's enthusiastic presentation worked in harmony - to me, anyway.

Beautiful.

Regarding the absorption lines, I vividly remember a Earth Science lab from 8th grade where we looked at various neon lights (which used different elements) and looked at the different "black lines" in the spectrum.

Really, very cool (and powerful) stuff.

The dark lines in the spectrum were what surprised me. I had never thought about it, I had never heard about the reasons behind the dark lines in the spectrum. I didn't know such reasons existed! This was another excellent episode.

I learned about the absorption lines, probably around the age of 10, through an article or book on finding extraterrestrial intelligences.

The author of the piece suggested that we check stars for the absorption lines of technetium. As a radioactive element that doesn't occur naturally, an alien species could make technetium in large quantities and dump it into the star as a way of saying, "Here we are!"

It turns out, which I learned later, that stars can, in fact, produce technetium, generally red giants. It hasn't been found in K or G-class stars, however.

You guys must have attended good schools. My science teacher was too busy flirting with the cheerleaders, and talking about sports.

Seriously, though, I never actually thought about it until Neil explained that the black lines actually meant something. Once he revealed what they meant, my mind just went *poof*.

 

[Awesome Possum]

Don't bother. He's just trolling, I doubt he believes a fraction of what he says. You'll notice that every single post he has made is an attempt to hijack it away from discussing the show.

He's switched to being a climate change denier because he knows that anyone will a basic knowledge of science accepts as fact and there isn't any evidence to oppose it. It's nothing more than cherry picking data, confusion over the weather vs climate and character assassination (note his comments on Sagan and Gore).

He needs a new act, this one was old when he got kicked out of TNZ years ago.

I guess anyone like the chair of the department of climate science at Georgia Tech (who routinely testifies on climate issues before Congress and who was recently asked by the American Association for the Advancement of Science to skeptically review their position on climate change), doesn't understand anything about climate science.

The IPCC is backing away from their earlier reports, lowering their estimates of climate sensitivity, and many climate scientists are backing away from earlier positions in light of new data (science does that). This is making alarmists more and more vicious, calling for the jailing of anyone who doubts their Truth, etc. In the annals of science history, they won't be portrayed as the scientists, they'll be portrayed as the mindless defenders of religious dogma and supporters of the inquisition.

Says the man who has no evidence to back a single claim. Even your claims are similar to those of Holocaust deniers, 9/11 Truthers and Creationists. You have "proof" but science/government/other vague boogeyman are covering it up for nefarious reasons. The whole thing is a joke, I'm shocked you're even wasting your time pretending to believe it.

Also, I can go back to TNZ anytime I become willing to support Obama. (It's probably the weirdest ban in TrekBBS history).

Is that what got you banned? Because I remember you posting racist pictures after just serving a temporary ban for similar behavior. But whatever delusion gets you through the night is alright.

Seriously, though, I never actually thought about it until Neil explained that the black lines actually meant something. Once he revealed what they meant, my mind just went *poof*.

That just blew me away. I'm glad they explained that, I had no idea how they were able to determine what stars are made of by only viewing them.

 

[gturner]

Says the man who has no evidence to back a single claim.

I see you still rely on argument from ignorance in every comment.

Even your claims are similar to those of Holocaust deniers, 9/11 Truthers and Creationists.

Um, no. Those would be pretty much the same claims that the IPCC itself makes, along with numerous top tier climate scientists who testify before Congress and consult with the American Association for the Advancement of Science. You are just unwilling to put aside dogma and hatred to accept science and knowledge.

You have "proof" but science/government/other vague boogeyman are covering it up for nefarious reasons. The whole thing is a joke, I'm shocked you're even wasting your time pretending to believe it.

Um, no. It's not being covered up, it's being widely reported and has been for decades now. From the BBC to the Economist, they're doing a big walk-back. In fact, one of my friends will soon face Michael Mann in court. Michael Mann is doomed, as he's lied repeatedly to the court in his filings, wrongly claiming to be a Nobel Prize winner and wrongly claiming to have been exonerated by investigative bodies that didn't even look at him, and one of whom he attacked for pointing out that his methods were deeply flawed, angrily demanding an apology from someone who he claims vindicated his work.

Most respectable climate scientists are about fed up with his antics, as he's done more to fuel skepticism than anything the Koch brothers could conceivably dream up, and he routinely sends legions of his mindless minions to harass any climate scientist who dares to question his hockey stick, which isn't supported by any regional temperature reconstruction that isn't done by his team. In the Climate-gate e-mails, even his fellow team members said it was trash.

Also, I can go back to TNZ anytime I become willing to support Obama. (It's probably the weirdest ban in TrekBBS history).

Is that what got you banned? Because I remember you posting racist pictures after just serving a temporary ban for similar behavior. But whatever delusion gets you through the night is alright.

I'm pretty sure that making up racist charges about TNZ in other forums will get you banned.

 

[Awesome Possum]

Says the man who has no evidence to back a single claim.

I see you still rely on argument from ignorance in every comment.

Post proof or retract all your claims.

Even your claims are similar to those of Holocaust deniers, 9/11 Truthers and Creationists.

Um, no. Those would be pretty much the same claims that the IPCC itself makes, along with numerous top tier climate scientists who testify before Congress and consult with the American Association for the Advancement of Science. You are just unwilling to put aside dogma and hatred to accept science and knowledge.



Um, no. It's not being covered up, it's being widely reported and has been for decades now. From the BBC to the Economist, they're doing a big walk-back. In fact, one of my friends will soon face Michael Mann in court. Michael Mann is doomed, as he's lied repeatedly to the court in his filings, wrongly claiming to be a Nobel Prize winner and wrongly claiming to have been exonerated by investigative bodies that didn't even look at him, and one of whom he attacked for pointing out that his methods were deeply flawed, angrily demanding an apology from someone who he claims vindicated his work.

Most respectable climate scientists are about fed up with his antics, as he's done more to fuel skepticism than anything the Koch brothers could conceivably dream up, and he routinely sends legions of his mindless minions to harass any climate scientist who dares to question his hockey stick, which isn't supported by any regional temperature reconstruction that isn't done by his team. In the Climate-gate e-mails, even his fellow team members said it was trash.

It's nothing more than cherry picking data, confusion over the weather vs climate and character assassination (note his comments on Sagan and Gore).

You should try being original. Being a hack climate change denier isn't working for you.

Also, I can go back to TNZ anytime I become willing to support Obama. (It's probably the weirdest ban in TrekBBS history).

Is that what got you banned? Because I remember you posting racist pictures after just serving a temporary ban for similar behavior. But whatever delusion gets you through the night is alright.

I'm pretty sure that making up racist charges about TNZ in other forums will get you banned.

Pointing out that you got banned for posting a picture of President Obama as a witch doctor with a bone through his nose (this is after we told you to lay off it if you wanted to stay in TNZ) makes me racist? You poor baby. It isn't fair that you got punished for such an innocent act.

 

[Christopher]

Anyway, am I the only one who's bewildered by the idea that the ancients ever seriously believed that we saw things because of beams emanated from our eyes? I mean, if that were the case, why can't we see things at night or in a darkened room? It's overwhelmingly obvious that we see when there is a light source such as the sun or a flame, and don't see things in the absence of a light source. It's also pretty obvious that the side of a thing that's facing the sun or a flame is easier to see than the side that's facing away from it.

So I have to wonder if the claim that the ancients used to believe that about vision is even true. Maybe it's a myth like the "People used to think the Earth was flat" meme. Educated and well-traveled people always knew the Earth was round; the myth that they thought it was flat was invented by Enlightenment-era writers like Washington Irving as a way of ridiculing the old social institutions by portraying them as too stupid to grasp the obvious. And yet generations of textbooks have reported it as fact because they didn't realize it was propaganda. So maybe the "people used to think we shot rays out of our eyes" thing is more of the same. I just can't believe people could've overlooked something so obvious for so long.

 

[Awesome Possum]

People can believe some pretty weird stuff. I wonder if that's where the idea of a "watched pot never boils" came from. Our eye beams caused the water to not boil.

 

[gturner]

Says the man who has no evidence to back a single claim.

I see you still rely on argument from ignorance in every comment.

Post proof or retract all your claims.

How many thousands of links would you like? Please list them in order by subject so I can spam the thread with them.

You should try being original. Being a hack climate change denier isn't working for you.

You should try arguing the science instead of using every argumentative fallacy known to man.

Pointing out that you got banned for posting a picture of President Obama as a witch doctor with a bone through his nose (this is after we told you to lay off it if you wanted to stay in TNZ) makes me racist? You poor baby. It isn't fair that you got punished for such an innocent act.

Would you like me to post the PM's from the Mod, who freely admitted that I was trying to help the other side in the debate (they were flailing around for an example of what they were attacking), but that I was perma-banned anyway because I kept disparaging Obama's health care plan, and would remain so until I support him. It's still sitting in my inbox. It might upset some people.

Anyway, you're a sterling example of a typical global warming alarmist. You don't know any of the science and hatefully attack anyone who points it out, defending dogma and personally attacking anyone who dares speak science against the mob's apocalyptic prophesies ladled out by their priesthood.

That, and that Carl Sagan first stoked the mobs with his scientifically incorrect climate models, makes this the perfect thread to raise such behavioral issues. Not everyone who held that the Earth rotated around the sun was an agent of Satan, and not everyone who points out that the climate alarm is a bit daffy and a lot of it is based on bad science is being paid off by Jewish bankers. But once he unleashed the good versus evil, mythological version of science, bad things for science were sure to follow.

I find it somewhat ironic that people can watch Cosmos with their pitchfork handy, ready to lynch anyone who actually says that science doesn't really indicate that the apocalypse is coming any day now, even after the 17-year delay in the prophesied end times, probably just after having watched an episode about that same behavior.

Now it is considered normal conduct to viciously attack any scientist who disagrees with the worst of the alarmism, including an IPCC lead author who is under strong assualt for noting that the AR5 summary for policymakers hyped the alarm compared to the more in-depth chapters of the report. Science didn't used to work that way, and that it does now has alarmed many throughout the scientific community, who have been writing very deep posts about the philosophy of science and where things went off the rails.

Climate science used to be an obscure, boring field, and until recently no one even called themselves a climate scientist. Prior to the money pouring in, they all called themselves atmospheric scientists, geologists, oceanographers, and other terms, and they labored in obscurity to try and unlock some fundamental bit of how the climate, ocean, and atmosphere worked. Then came the alarmism and the modeling and the fame and money.

Many climatologists say the modeling wasted decades of scientific effort on a futile endeavor. Without the fundamental and much deeper understanding of climate, the inputs and relations in the models are just guesses, and the model output is whatever someone wants it to be. That's why none of the models can be validated, and at this point many in the modeling community, including the IPCC itself, are giving up on the notion that they just needed more computing power to get things right. (That's in AR5) The models have proved largely useless for anything other than generating press releases and research grants. They've failed at all other applications.

And oddly enough, when Carl Sagan first estimated the temperature of Venus, his calculation for a nitrogen atmosphere was hundreds of degrees hotter than for a carbon dioxide atmosphere. But that didn't make him famous, the "runaway greenhouse effect" did, even though Venus doesn't have a runaway greenhouse effect, it has a very thick atmosphere whose temperature is determined by the radiative equilibrium at the top of the cloud layer and the adiabatic lapse rate below that, just as Sagan had correctly used to calculate the surface temperature for the nitrogen and CO2 cases. At the layers of Venus' atmosphere at Earth's sea-level pressure (about 53 km up), we could walk outside in T-shirts and be perfectly comfortable (except for a wee bit of sulfuric acid). Venus's problem is that the ground is 53 km too low. But these days, pointing that out will get one lynched - because science.

 

[Awesome Possum]

You know, your game doesn't work on me. Go annoy someone else.

 

[Amaris]

Anyway, am I the only one who's bewildered by the idea that the ancients ever seriously believed that we saw things because of beams emanated from our eyes? I mean, if that were the case, why can't we see things at night or in a darkened room? It's overwhelmingly obvious that we see when there is a light source such as the sun or a flame, and don't see things in the absence of a light source. It's also pretty obvious that the side of a thing that's facing the sun or a flame is easier to see than the side that's facing away from it.

So I have to wonder if the claim that the ancients used to believe that about vision is even true. Maybe it's a myth like the "People used to think the Earth was flat" meme. Educated and well-traveled people always knew the Earth was round; the myth that they thought it was flat was invented by Enlightenment-era writers like Washington Irving as a way of ridiculing the old social institutions by portraying them as too stupid to grasp the obvious. And yet generations of textbooks have reported it as fact because they didn't realize it was propaganda. So maybe the "people used to think we shot rays out of our eyes" thing is more of the same. I just can't believe people could've overlooked something so obvious for so long.

Apparently, it was called Emission Theory, and it was real.

 

[Greylock Crescent]

At the layers of Venus' atmosphere at Earth's sea-level pressure (about 53 km up), we could walk outside in T-shirts and be perfectly comfortable (except for a wee bit of sulfuric acid). Venus's problem is that the ground is 53 km too low.

Ah. The Garfield Defense™. Well-played.

Spoiler: The Garfield Defense

In other news ... I find that Tyson's on-screen presence seems to be getting better as the episodes progress. I suppose that could just be me getting more used to it, but I think this episode is an excellent example of him using his voice to elevate the subject matter into something ... almost as poetic as we saw from Sagan.

In other, other news ... I downloaded Volume 2 of the soundtrack and it's even better than Volume 1 (though, I had to get it through Amazon, rather that iTunes). Silvestri really pushes further into the "New Age" territory we saw from the original Cosmos.

 

[Christopher]

Apparently, it was called Emission Theory, and it was real.

Well, just because reference sources claim it was real, that doesn't mean it was. As I said, plenty of actual historians believe the myth that most people used to believe the Earth was flat, and teach that myth as fact in history books. It's important to question our sources. Although if the article is correct that a lot of college students today still believe it, I guess that's strong evidence that it's real (and that our educational system is deeply flawed, but I already knew that).

But now that I think about it, I can see how people could imagine this was true even though it doesn't fit the clear evidence. It's probably an artifact of the way our minds work -- related to the idea of consciousness as an attention schema, our own minds' model of what it is we're paying attention to. We instinctively think of our own attention to a thing, our own perception of it, as creating a connection to it, because of how our brains model our awareness of it. We think of ourselves as projecting our awareness out toward things and people around us. So the idea that our ability to see things is due to something emitted from within ourselves fits how we're instinctively predisposed to think about our interaction with the world. So people believe it even though it makes no objective sense. It's obviously wrong based on real-world evidence, but it feels right in the context of our mental models of the world.

 

[gturner]

^It might also be somewhat related to the way we "feel" someone's gaze, as if their eyes are actually emitting something towards us, which would go along with the common phrases about being transfixed by someone's stare, pinned by their burning eyes, how they can see right through us, etc.

 

[Amaris]

Apparently, it was called Emission Theory, and it was real.

Well, just because reference sources claim it was real, that doesn't mean it was. As I said, plenty of actual historians believe the myth that most people used to believe the Earth was flat, and teach that myth as fact in history books. It's important to question our sources. Although if the article is correct that a lot of college students today still believe it, I guess that's strong evidence that it's real (and that our educational system is deeply flawed, but I already knew that).

But now that I think about it, I can see how people could imagine this was true even though it doesn't fit the clear evidence. It's probably an artifact of the way our minds work -- related to the idea of consciousness as an attention schema, our own minds' model of what it is we're paying attention to. We instinctively think of our own attention to a thing, our own perception of it, as creating a connection to it, because of how our brains model our awareness of it. We think of ourselves as projecting our awareness out toward things and people around us. So the idea that our ability to see things is due to something emitted from within ourselves fits how we're instinctively predisposed to think about our interaction with the world. So people believe it even though it makes no objective sense. It's obviously wrong based on real-world evidence, but it feels right in the context of our mental models of the world.

Well, it may not have been something truly believed, I was just pointing out that it has an established history, whether real or not, so either way, Neil wasn't just pulling it out of his singularity.

 

[gturner]

^ I would bet, as an experiment, that you could convince elementary school kids that the eye emits rays because they can "feel" when people are looking at them. I'd also bet that many people would claim to definitely "feel it" when a large predator is looking at them. Sometimes we feel someone's gaze as intense and overpowering. The only way to explain this is to:

A) explain how evolution works, and that as animals we evolved to pay extreme attention to being stared at by predators.

B) explain that as we evolved further into advanced social animals, we gained the trait of staring at where the adults stared, which is thought by scientists to be the reason that our eyes so oddly show so much white, unlike a cow or other prey animal that doesn't want to give away what it's looking at. We use our eyes for signaling, and indicating what we're focused on to others around us.

C) Explain that the reason many animals react strongly to being stared at isn't something being emitted from our eyes, but that they too evolved to react to predators that are staring at them, so we can kind of freak them out.

D) Explain that all those tremendously powerful feelings we sometimes get when we look at each other is just an artifact of the way our brains are processing important social information, and that gazes can land you a mate or an axe through the head.

E) Combine all that with Christopher's comment.

or F), just note that our eyes apparently emit some kind of ray and be done with it.

You could also note that if you're reasoning form a very self-centric viewpoint, you'd have a notion that you can't see behind a tree because there's no path from your eye through the tree, which is actually how it looks. We wouldn't normally reason along the path from an object we can't even see to the back side of the tree.

I once met a warlock (a believing one) who said that the master of his coven had a gaze so intense that nobody could withstand it, and so all the other witches refused to look at him directly. He said he watched a video-tape of him (talking about something all witchy, no doubt) and that his presence was so intense that it physically burned him (via the magnetic fields on the video tape being converted to electrical signals that resulted in electrons slamming into a cathode ray tube's phosphor coating, cough cough), forcing him to flee the room lest his body catch on fire. The idiot was convinced that this really happened to him.