Mystery of the CO2 Balloons!

Filled some balloons w  co2  from dry ice in a soda bottle.   As expected, they act like a lens, a magnifier of sound. No mystery there. Just as a dense glass refracts light, the denser gas refracts sound. The mystery is why balloons filled with co2  leak down faster than identical balloons filled by mouth. Yes, there is some co2 in my exhaled breath, but it is mostly  n2,  and  o2.  I would hav expected the n2 and o2 to leak out more quickly, being smaller molecules. So whatzup wit dat?

Topic by Toga_Dan   |  last reply


The Future of Invisibility

It is reported that a team of researches at the University of California, Berkeley claim to be on the doorstep of invisibility. Using a special type of metamaterial they are bending electromagnetic waves and negatively refracting visible light. Their ultimate goal is to render entire objects invisible to the naked eye. After reading this, I conducted some invisibility experiments of my own. Based on my initial experiments with invisibility cloaking, I must concede that we are not quite there yet, but are getting close (see image).For more information, read the full news report

Topic by randofo   |  last reply


Any suggestions for a 5mm - 10mm telescope eyepiece?

I am currently using a home built 3'' refracting telescope, and want to build a shorter focal length eyepiece to get some detail for observing planets (lunar surface, rings on Saturn, more of the moons of Jupiter. The current setup uses a plossl eyepiece with about a 25mm focal length, giving 30 to 40x magnification, and allowing very clear viewing of the moon, and will pick out three of Jupiters moons on a clear night. Ideally I'd like a 5mm to 10mm focal length, for a 100 to 200x magnification. I've considered using the lens out of a DVD drive, which looks as though it could work, although I've only seen one example of it done before. I also have a selection of reasonable quality prisms and lenses about 1'' diameter, with focal lengths from about 2'' to 4''. So, how well would a DVD drive lens work, and are there any interesting designs that make an eyepiece with a focal length significantly shorter than any of its component lenses (in the same way the focal length of a plossl is about 1/2 the focal length of the lenses used). Thanks in advance for any help. (Would this get better response in the photography section)

Topic by The Skinnerz   |  last reply