Recent content by jrv

Oops - photon, phone, whatever! ;D fixed! The "m" in that equation is the rest mass. The increased energy from the acceleration shows up as momentum, which is a different term. If I'm remembering correctly that is - my last college class was almost 30 years ago ...

As was said you can't accelerate and reach the speed of light. To figure out what seems to happen you have to ask where the observers are, because they don't always see things the same. For example your starship may have a magical engine that always produces 1G of acceleration on the ship. At...

On mine you can just see the beam in the dark if you long down the beam from *behind* the laser (no I will not try from in front). Unfortunately I'm not sure how to interpret this as violet 405nm is poorly handled by the eyes.

It's not the output level but the wavelength that worries me - on the edge of UV, not to mention the fluorescence which seems like a warning sign of something. I don't have a spare pair of eyeballs. PS. I forgot to mention that skram0 included a piece of glow-in-the-dark material. The laser was...

I bought the previous one so I'll comment, though I haven't used it much for lack of goggles. The unit is as it appears in the picture: very clean, very well done. The cap over the optics in front is glow-in-the-dark. skram0's packaging was excellent and delivery was remarkable (shipping was...

Re: Why do blu-ray players use expensive blue diod Most of thee 100's of GB proposals I've seen so far would just stack many layers atop each other. 100 GB is quite doable today with 405nm lasers using four layers. If any of the ~ 300nm laser diodes work out then 100 GB in a single layer will...

Re: Why do blu-ray players use expensive blue diod Indeed CDs, LDs, DVDs and BluRay/HD-DVD have always used the shortest wavelength diode available at the time to get the highest data-density possible. It's more than just focusing per se: a smaller Airy disc is important too for greater track...

Optotronics makes quality handheld lasers at high output powers. For small and cheap AtlasNova is good. He sells both red 635nm and green at <= 1mW for those who actually want to use it as a pointer and not a death ray. ;D

For pointing consider the AtlasNova 635nm red. This is a bright red, and a diode not DPSS so it's inherently more rugged and presumably more efficient. Depending on the situation consider a smaller laser than 5 mW. AtlasNova sells both a green DPSS and 635nm red pointer at <= 1 mW which might...

Both DX and KD are the ultimate at cost-removal. Don't assume it has anything unless they say it does; an IR filter costs money so I'd assume it's not there. I don't think DX says what "True" means in the name so it probably doesn't mean anything. And, even if they did start selling lasers and...

Signs of manipulation in that picture: Both the laser source - entirely green - and the lighted instruments are in the picture. Yet the laser source is not much brighter than the other light sources, some of which are also green. Even so, the pilot's face shows only illumination by green...

The picture is certainly a fake, or artist's rendition. You could not hold a laser on a moving target at that distance if you tried, and certainly could not get the timing right to push the camera shutter just when the laser was shining in the cockpit. Hitting an airplane is likely to be very...

I saw a link in a post on candlepowerforums.

I think a donation is a fine topic for a first post. 8-) Paypal sent!