The Straight Dope 03/23/2007

The Straight Dope -- By Cecil Adams
http://www.straightdope.com

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THE STRAIGHT DOPE 03/23/2007

Dear Cecil:

I've always heard that living under or near power lines was harmful to
your health. The other day after driving by a community located next to a
massive power station with so many cables running out of it that you could
actually hear the hum of electricity over the traffic, I got to wondering:
is there any truth to this common belief? --Carlos G., via e-mail

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Cecil replies:

Two ways you can look at this. To judge solely from the amount of
research, we're facing the gravest threat to humanity since nuclear war.
Over the past 30 years, scientists have published close to 25,000 articles
on the health effects of non-ionizing radiation (the kind emitted by power
lines). We've had population, occupational, and laboratory studies
scrutinizing everything from high-voltage transmission lines to electric
blankets. When you look at the results, though, you have to wonder why the
fuss. All the investigations to date have yet to produce any clear
indication that low-level electromagnetic fields from power lines are a
health hazard to the general public. I won't say there's no danger
whatsoever, but the perception bears no relation to the threat.

Some background. Magnets and moving electric currents radiate energy into
space, generating the invisible aura we call an electromagnetic field
(EMF). The stronger the magnet or current, the more pronounced the field.
These fields penetrate solid objects with relative ease and produce
readily detectable effects, one of the better known of which is the
broadcasting industry. Long ago some genius realized: Cheezit, if music
moguls can turn teenage minds to mush using nine-volt transistor radios,
what deviltry might we be unwittingly visiting on ourselves with a
128,000-volt high-tension line? Thus the busy investigative agenda
adverted to above.

For more, see:
http://www.straightdope.com/columns/070323.html

STAFF REPORT

Dear Straight Dope:

Sometimes you hear about a space vehicle getting extra speed by rounding a
massive object, like a planet. To reach Jupiter for instance, you aim at
Saturn, which will give you, with the right angle of approach, the extra
speed to get you there faster than a straight line. I can imagine that the
pull of gravity gives you extra speed, but escaping from this force will
slow you down. I suppose this process is not symmetric, but how? Does the
object lose energy to the passing vehicle?--Coen, Amsterdam, Holland

Guest contributor Stranger on a Train replies:   

You're about four fifths of the way to answering your own question, but
I'd better correct a couple misapprehensions. First, you probably wouldn't
swing by Saturn to get to Jupiter. Second, while the object or planet does
impart some kinetic energy to passing spacecraft, the main reason you
perform the maneuver is to change direction without additional thrust.

The phenomenon you're asking about is called a swingby trajectory or a
gravity-assist maneuver. (You sometimes hear it described in pop science
literature as a gravitational slingshot, but that's a misleading metaphor,
as we'll see.) Unlike a slingshot, the probe speeds up as it approaches
the planet or moon it plans to swing around, then changes direction using
the object's gravity field and escapes, slowing as it does so.

The maneuver has been used . . .

For more, see: 
http://www.straightdope.com/mailbag/mgravslingshot.htm

STRAIGHT DOPE CLASSIC - 05/11/1990

Dear Cecil: 

Can operatic sopranos really break glasses with their high notes? What
note does the trick? How come they don't break windows and eyeglasses and
whatnot at the same time? Can women do this better than men? Can I learn
how? Or have I been the victim of an elaborate hoax? --Vox Clamantis,
Chicago

Dear Vox:  

I dunno--you ever buy whole-life insurance? Now _there_ was a hoax.
Shattering glasses, on the other hand, is entirely legit. Enrico Caruso
and Italian opera singer Beniamino Gigli are said to have managed it, and
I seem to remember Ella Fitzgerald doing it once in a Memorex commercial.

The technique is simple. First you find somebody with perfect pitch and
leather lungs. Then get a crystal glass and tap it with a spoon to
determine its natural frequency of vibration (this varies with the glass).
Next have the singer let loose with precisely the same note. When he or
she is dead-on pitchwise, the glass will commence to resonate, i.e.,
vibrate. Then turn up the V. Bingo, instant ground glass.

What we have here is a graphic demonstration . . .

For more, see:
http://www.straightdope.com/classics/a3_333.html

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