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

... the Trinity Bomb Test.

In conversation yesterday, about fabrics fading in strong sun through windows, my friend (who stands a good chance of knowing) said that Feynman viewed that event through the glass viewing port in the bunker, without eye protection.

I know the principle but thought the doing thereof a touch towards .
As a matter of interest, today I looked it up in Wikispitaedia:

http://en.wikipedia.org/wiki/Richard_Feynman

In section 1.3, The Manhattan Project, the 3rd para says
> ... Feynman claimed to be the only person to see the explosion without the very dark glasses or welder's lenses provided, reasoning that it was safe to look through a truck windshield, as it would screen out the harmful ultraviolet radiation.<
Which gives the impression that he did just that (unlikely, as he was senior on the project).

My questions are:

1. Can anyone confirm the bunker?

2. If so, is it worth my correcting it?
I feel that people who are even less well-informed than I might easily take it at face value.

[there seems to be no route to the author & I'm reluctant to edit someone else's work without their say-so].


Rod

I read a book on his life once, "Genius", but I don't remember the details.

He does write about it in 'Surely You're Joking...', but I have my (unverified) doubts.

The science is unverified, not my doubts. I think anyone can verify those.

I've looked in both 'Genius' and 'Surely you're joking...', neither of which mention a bunker. They seem to suggest that they were just out in the desert, twenty miles from the blast site. They were given welder's masks, but Feynman decided he didn't need it, he'd just sit in a weapons carrier truck and watch through the windscreen. So it would seem that wiki is right, or is a least repeating Feynman's own story. I sometimes feel that Feynman had a habit of telling stories in a way that cast him in a good light, and this one is a bit "How cool am I? The only guy to see the first bomb with the naked eye", but I don't think that he would have just made it up.

He certainly thought he was cool, but he wouldn't falsify a scientific result.

Thank you folks.

Next time I see my friend, I'll correct him. He'll enjoy that.

Rod

I think Feynman may have made that up in order to have a glib little boast like that, but apparently it's based on fact. He's well-known for buffoonery but that's probably why he was so loved and respected by the public (myself included). I certainly love listening to his lectures!

Here's some information from Richard Rhodes' excellent book "The Making of the Atomic Bomb," which I feel is pretty definitive. (not direct quotes, this is my own summary from Rhodes' text)

It was Ernest Lawrence who rationalized that he could sit in a car and look at the explosion at Trinity since the windshield would deflect the UV. Lawrence was at a place 25 miles northwest from ground zero on a hill (Compania Hill), which was not the concrete-earth sheltered control bunker (called S-10000 for being 10,000 feet from ground zero and to the south). Along with Lawrence on Compania Hill were a cast of Los Alamos scientists and engineers, among them a young Richard Feynman. Lawrence himself is quoted as saying that at the last moment he was so excited that he actually changed his mind and exited the vehicle at the very moment the flash hit him, bathing him in a bright yellow-orange light. In Rhodes' book, there are quotes from other observers that were on that hill that morning, among them an engineer who used no eye protection at all, saying he was flash-blinded for a second or two then was fine. They were 25 miles away, remember. Not in the 10,000 ft away bunker which was manned by Oppenheimer and the test director among a few others.

So I think Wiki was probably right in saying that Feynman made that claim ... I just don't quite think it was Feynman himself that actually got into a vehicle to use the windshield for UV protection.

Thank you, JD, for that background stuff.

That's padded it out a little for my friend's digestion...

Thank you, folks, for your help. My friend was suitably impressed by your collective erudition.

Somewhat less impressed however by my inability to answer the initial question that started it off:

1. If it's not UV, then what is it that rots carpets & fabrics through windows, where the sun falls?

A further observation raising an and:

2. My [photochromic] glasses darken when looking out of a window into sunlight - why?
(that was him speaking, I don't use those things 'cos of the long recovery time).


Any suggestions?

Rod

Question 1 - I&#39;d say it&#39;s just sunlight in general. Sunlight has energy and this gradually causes the chemicals in the surface to react. This is why it is great to hang washing out on a line to dry. The sunlight kills off all sorts of bacteria on the clothes and acts as a disinfectant.

Question 2 seems pretty obvious - they darken because it is bright outside and that&#39;s what photochromic glasses do. When you are indoors, it is about 50 times as bright outside, so the glasses need to darken. You don&#39;t notice it&#39;s so bright outside because your eyes do the same thing, narrowing the pupils almost instantly to compensate for the brightness.

I&#39;ve had to have a test on my eyes where they put drops in them to prevent the pupils narrowing (it was the old glaucoma test, now superseded by the puff of air test). When your eye can&#39;t react to the brightness, it is very painful looking out the window.

Glass will seriously attenuate wavelengths below about 350 nm. 350 nm and above (and into visible) is still pretty high energy light.

(visible wavelengths range from about 390 nm (extreme end of blue/violet) to about 750 nm (red) - the blue end going into violet and uv is high energy and the red end is low energy)

350-390 nm is still in the UV - although I wouldn't say UV gets fully ionising until about 220 nm remember that your coloured items are coloured because they absorbe visible light wavelenghts. The absorption process excites electrons and excited electronic states are highly reactive. So photobleaching does not require UV light - although I would say really red light is going to be too low in energy to do much I would think. Blue light is perfectly powerful enough though to do slow damage to things.

OK. Fabrics fade in light, brighter, faster. Fair enough.
(the disinfectant effect of sunlight - I'd always thought [assumed?] it was UV doing it).

That's sorted then. Thanks.


Now you've thrown me with the photochromic effect, which, again, I'd always assumed was UV (mainly). Even though yes, photo is light.

I hate it when that happens.

UV will do more damage. I expect your carpet will survive longer behind a window than in full unfiltered sunlight.

(taking no account of weather of course )

I think you've also got to be careful of not falling into the layman's trap of assuming that light and UV are two different things, when in fact they are the same thing with different wavelengths, and remember that something that 'emits UV' is almost invariably emitting a range of different radiations with a range of wavelengths, centred over UV frequency (wavelength and frequency being the same thing expressed in different units in this case).

The sun, of course, emits the whole gamut of electromagnetic radiation - there are electrons more excitable than a pre-pubescent girl at a Justin Bieber concert in there - of which most of the nasty stuff is thankfully absorbed by our atmosphere or deflected by our magnetic field. The only way to distinguish between 'light' and UV for us is whether we see it or not, which means bugger-all in the context of a chemical interaction.

B

Bees can see slightly into the ultraviolet, but can't see the deeper reds that we can see. Most digital cameras can't even see violet, never mind ultraviolet, so purple things often look different in digital cameras.

yea, all true - Mu, maybe you've got it. Perhaps I had fallen into that trap.

"Most digital cameras can&#39;t even see violet"

Aha, I shall don a violet outfit and go rob banks, I will appear as invisible to the security cameras!


What, is that not how it works?

I can see the headlines now...

Tall Thin Pimp Inexpertly Robs Bank

B

" Most digital cameras can't even see violet, never mind ultraviolet, so purple things often look different in digital cameras."

They make up for it though, by being able to see a good way into the infra-red.

I've seen this myself. For the experiment you will need one iPhone, and one TV remote control. Point the remote into your own face and press any button. You'll see nothing. Now activate the iPhone camera, and look at its screen. Point the remote at the camera and press a button on the remote. On the iPhone screen you will see the remote with a flashing light coming out of it. Your iPhone can see INVISIBLE THINGS!!! How cool is that?