Dear Mr. Scientist: In chemistry labs we're never allowed to wear contacts. My TA says that chemical fumes could cause contact lenses to fuse to your eyes. Are there actually chemicals that can do this?
–Carrie D.
Not really, but if your TA says no contacts allowed in lab, don't wear contacts in lab. Back in the day contacts were made of a different material and it was thought that the lenses would absorb chemicals and hold them against the eye.
Nowadays contacts are made of hydrophilic (water–loving) polymers with absorption characteristics similar to the cornea so anything a contact absorbs, the cornea will also absorb.
Also, any chemical capable of fusing your contacts to your eyes would also severely damage a naked eye. That aside, always wear goggles in the lab!
Dear Mr. Scientist: If it's true that hot air rises, how come mountain peaks are so cold but places like Death Valley so hot?
–Sarah K.
Places of low elevation have a lot of air above them which increases the air pressure, and as pressure increases, so does the temperature. On mountain tops there is less air overhead so the pressure is lower and, in turn, so is the temperature.
Another explanation is that at higher elevation, the air is less dense. Since the air is less dense there are fewer air molecules to collide, which is how heat is transferred. Therefore, the temperature will be lower.
With regards to the notion of hot air rising and colder air falling, this is only true when the air pressure is the same for both places of interest. This of course isn't true when comparing the summit of a mountain like Everest with Death Valley.
Dear Mr. Scientist: How do photons push a solar sail forward if photons don't any mass?
–James F.
For those unfamiliar with solar sails, they're like a stellar sailboat using energy from the sun instead of rockets to move. While photons (particles of light) are massless, to move an object all you need is a little bit of momentum.
Looking at the classical equation for momentum p=mv (momentum equals mass times volume) it seems like a particle without mass shouldn't have any momentum, but these photons are traveling at the speed of light so that equation goes out the window.
In the massless case of the photon, the momentum is defined as p=E/c where c is the speed of light and E is energy. This explains how a massless photon generates enough energy to move the solar sail.
To send your questions to Mr. Scientist feel free to email Michael at mleitch@wisc.edu.
