sunscreen makes you hotter?

On 3 Aug 2003 02:43:54 +0950, BaCardi
may have said:

What was the question?

Does sunscreen make you feel hotter, and why? Thread drift carried it
off into lala land as usual.

For the original question, my experience says "yes". As for why,
well, really, does it matter? There's not a lot of choice available;
use sunscreen, find shade, or stay inside.

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Joe Riel wrote:

Werehatrack writes:


Light and microwaves of the same frequency are not the same thing. A
microwave transmitter that is operating on the same wavelength as
visible light does not produce light.


Bull****. The phenomenon is identical. Microwaves have a significantly
higher wavelength then light, that is why we cannot seem them.
The shortwest wavelength of a microwave is about 1cm.
The longest wavelenght of visible light is less then a 1um,
orders of magnitude longer.
^
I presume you meant to say "shorter" here. Yes, radio waves, microwaves,
light, X-rays, gamma rays are all elecromagnetic waves that differ in
wavelength.

On Sat, 02 Aug 2003 21:59:29 GMT, Joe Riel may
have said:

Werehatrack writes:

Light and microwaves of the same frequency are not the same thing. A
microwave transmitter that is operating on the same wavelength as
visible light does not produce light.

Bull****. The phenomenon is identical. Microwaves have a significantly
higher wavelength then light, that is why we cannot seem them.
The shortwest wavelength of a microwave is about 1cm.
The longest wavelenght of visible light is less then a 1um,
orders of magnitude longer.

Infrared light ranges well above 1mm in wavelength. Microwaves range
down into that area. The ranges overlap. An IR filter which was
known to block the transmission of IR in that freq range had no effect
on the microwaves. Remember the existence of the wavicle known as a
photon, and the reason should become obvious. Yes, the two forms of
energy follow the same rules, but the conclusion is that they're not
the same.

As of last I heard, no tech was available to reliably modulate such a
signal or detect modulation beyond on/off, so it wasn't too useful.
That may have changed; this was a number of years ago. I'm told that
the limits of microwave freq generation have changed, but I don't know
what they are now.

None of this will make your bike work better.

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Werehatrack wrote:

On Sat, 02 Aug 2003 21:59:29 GMT, Joe Riel may
have said:


Werehatrack writes:


Light and microwaves of the same frequency are not the same thing. A
microwave transmitter that is operating on the same wavelength as
visible light does not produce light.

Bull****. The phenomenon is identical. Microwaves have a significantly
higher wavelength then light, that is why we cannot seem them.
The shortwest wavelength of a microwave is about 1cm.
The longest wavelenght of visible light is less then a 1um,
orders of magnitude longer.


Infrared light ranges well above 1mm in wavelength. Microwaves range
down into that area. The ranges overlap. An IR filter which was
known to block the transmission of IR in that freq range had no effect
on the microwaves. Remember the existence of the wavicle known as a
photon, and the reason should become obvious. Yes, the two forms of
energy follow the same rules, but the conclusion is that they're not
the same.

No, Joe is correct that they are both electromagnetic waves and the only
difference is the wavelength. If the filter stopped electromagnetic waves
of a certain frequency then it makes no difference if we call those waves
IR or microwave. Perhaps this page will help you 'see the light.'

http://imagine.gsfc.nasa.gov/docs/sc...mspectrum.html

In article ,
Werehatrack wrote:

On Thu, 31 Jul 2003 15:40:46 -0500, Tim McNamara
may have said:

In article eMdWa.33166$Ne.31813@fed1read03,
Bill Davidson wrote:

I'm pretty sure that's not true. Any time you absorb radiation,
you get heat. In other words, they all make you hot. It's
possible that UV results in less heat but even that I doubt.

If all radiation absorption results in heating equally, why don't
microwaves use UV frequency light and use radio waves instead?

Light and microwaves of the same frequency are not the same thing.

Umm, the question was rhetorical, in response to the post which I
quoted. I knew the answer. But thanks to the three or four people
who answered anyway.

I suspect- but don't know- that heat gain through a transparent
surface such as window glass, with subsequent heating of the air
volume enclosed by the windows, is a matter of different
wavelengths than is the case with skin.

Any incident photonic radiation which reaches the interior of a
car, regardless of its wavelength, may be absorbed and converted to
heat, just as with light hitting skin; a car's interior, however,
has much less ability to shed that heat unless the car's engine is
running and the A/C is operating, while skin can sweat. Most of
the light that gets to the surface of the planet isn't UV, so the
UV component is not the major player in car interior heating or
skin heating, but UV (as you noted) has other tricks to play with
skin.

Most window glass will block some UV, but usually far from all of
it. A photographic UV filter looks like just a piece of clear
glass, but it blocks 100% of UV. Visibly tinted glass doesn't
necessarily block UV, but it reduces the amount of visible light
that gets through, thus reducing the amount of heat produced by the
light-absorptive surfaces inside. The light that is blocked at the
glass translates largely into heat that is shed back to the
environment on the outside of the glass, and thus does not
significantly contribute to interior heating. The majority of the
light which gets through the glass is absorbed by, and therefore
heats, the surfaces inside. Some of the light is reflected by the
interior surfaces; if the reflection is back out of the window, the
heat load is not increased. If it's reflected to another interior
surface, the light may still contribute to interior heating. In
being reflected, of course, there is some heat produced since the
reflection is never 100%.

Thanks, that's pretty much as I suspected.

Being from southern california, and a swimmer/water polo
player/general pool and beach bum, i feel obligated to contribute to
the sunscreen debate.

Having gone out both with and without sunscreen for physical activity,
in high sunlight environments (water surfaces reflect a good deal of
light, forcing to fight the UV war on two fronts), I say a few things:

1. alcohol based sunscreen (bullfrog quick-dry). non-greasy, and
doesn't get your hands all yucky. if not that, then regular bullfrog
is less messy than all the others. (its also so slick that its as
greasy as you can get without being illegal for sports).
2. I've actually been hotter WITHOUT the sunscreen than with. then
again, i don't feel heat so much as I feel sweat, so maybe I sweat
more without the sunscreen.
3. the best thing you can do to protect from the sun is a shirt
(polypropylene,cycling jerseys, and the like are the best for sun/UV
protection) and a big floppy hat. zinc oxide is messy, so is titanium
dioxide, and they're hard to get right, cuz you really have to slop it
on there, then sweat screws it up big time.

BaCardi wrote:
Its pretty simple really. Sunscreen DOES make you feel hotter. You put
on a layer of sunscreen. Well duh. Common sense. Its going to be hotter
than not having a layer of sunscreen on.

Doesn't sound at all like common sense as it does an assumption.

There's really two parts to the original question:

1. Does it make you 'feel' hotter?
2. Does it impede cooling, thus making you hotter?

If I rub on something that's a mild skin irritant, or becomes one during
the ride due to the sunscreens exposure to perspiration, light and heat,
I may think I'm hot, where I'm actually the same skin surface temperature.

Any compound which holds water to the skin surface, by it's own surface
tension or bonding with water molecules could reduce the efficiency of
cooling through evaporization. (Turning water liquid to water vapor is
exothermic, taking away body heat, this is why your arm feels cool for a
moment after an alcohol swabbing.)

Perhaps some actual empirical tests should be peformed, rather than
simply hazarding guesses.

HUH? Better tell those guys sending information to your house. CATV
uses AM fiber optic cable (at 1310 or 1550nm) for the last mile. If
you're a dish subscriber, you get QPSK digital microwave (KA band)
data.

Don't even want to get started on all those modulation methods for
phone calls...

Seems to work well enough.

Eric

Werehatrack wrote in message . ..
On Sat, 02 Aug 2003 21:59:29 GMT, Joe Riel may
have said:

Werehatrack writes:

As of last I heard, no tech was available to reliably modulate such a
signal or detect modulation beyond on/off, so it wasn't too useful.
That may have changed; this was a number of years ago. I'm told that
the limits of microwave freq generation have changed, but I don't know
what they are now.

None of this will make your bike work better.

BaCardi wrote in message ...
Uhhh, it's like putting on clothes. The more you put on the
hotter you get.

No, it's not like clothes, which don't necessarily make you hotter, either, BTW.

"BaCardi" wrote in message
...

Uhhh, it's like putting on clothes. The more you put on the
hotter you get.

That's why sunscreen sales soar in the dead of winter!

Logical Bill