OTish - how much bollocks

[Chris Hogg]

It was either an accidental mistake on his part (he misspoke, as Donald would say), or he doesn't know the difference between W and mW, which would speak volumes...

[Harry Bloomfield, Esq.]

Chris Hogg formulated the question :

Let's just hope he knows the difference between mg and g when prescribing :-)

[Tim Streater]

When you look at the Moon, you see it where it was 1.5 secs or so ago. You need to aim where it will be in 1.5 or so secs time.

Same with Mars, suitably scaled up.

[#Paul]

Beam divergence might well be significant here, not to mention the additional effects of early broadening or distortion in the atmosphere.

[Jeff Layman]

LOL!

The same short video was shown here on local BBC TV South news yesterday. There were no captions and no mention was made of the "3500W" laser!

I am surprised that the BBC did not see fit to issue a warning about shining a laser into the sky. Or maybe they were too interested in showing a local news item than having to cut it if raised possible safety issues.

[charles]

would you expect journalists to think about H&S?

There was reporter (Panorams, I think) who wanted his crew to follow him onto a building site where the signs said "Hard Hats & Safety boots to be worn." He said "That doesn't apply to us - we're journalists". He was sacked.

[Tim Streater]

It's worse than that. He's aiming at the centre of where Mars was 200 secs ago.

[Martin Brown]

It is a serious offence to point a laser at an aircraft. Although most commercial airliners do not have glass floors in the cockpit. Police helicopters are then most at risk of being targetted.

ISTR some pilots wear anti-laser line glasses in high risk regions.

Amateur astro*nomers* please.

And no they are not strictly legal but they are perfect for pointing at a star in the sky. The green beam quite literally appears to touch the star you are pointing at for anyone stood within a few hundred feet that can see the beam backscatter. 400nm laser is pretty useless for this.

The beam divergence and foreshortening gives a result that to someone stood nearby looks like a pencil beam reaching up into the sky.

[bert]

LOL

[Jeff Layman]

Are "about H&S" superfluous? (see your last paragraph...)

Actually, when there has been an article about someone doing something daft, the announcer will often add at the end "don't try this yourself" as a sort of throwaway safety comment.

[polygonum_on_google]

"microscopic carbon dioxide molecules"

Very impressive. The rest of us have to make to with ordinary carbon dioxide molecules. Which, when you think about it, are sub-microscopic.

[Chris Hogg]

Yea, but Greta can see them.

[Pancho]

Back to DIY, I was trying to level a floor the other day so tried using a toy keyring laser I had. I was very surprised how quickly the beam diverged. At about 5m a 1mm dot became 6mm. Pretty shit for levelling.

So I looked it up, 0.001 radian beam divergence is normal for a laser. So if this guy was trying to shoot Mars at 84,000,000 km. With a laser

0.001 rad beam divergence, the dot would be about 84,000 km, more than 10 times the diameter of Mars.

[Jethro_uk]

Back in the 70s, one suggestion for space propulsion was to fire a laser at a sail (presumably from the moon) to push the craft to it's interstellar destination. It didn't get far, as there was real science in those days.

The very first thing the scientists pointed out was that the divergence from the earth to the moon left a 400m diameter spot from a 1mm beam over

400,000 Km. Now imagine that over billions of kilometres.

I imagine dusting that down and prattling on about "hydrogen" and some such bollocks and you've a queue of investors round the block before you could say "asteroid mining".

[F Murtz]

Thought you would have similar laws to Australia special dispensation is given to stargazers here