Posted
on August 18, 2015
On
this date in 1868, French astronomer Pierre Janssen discovered
helium.
It
was the first time that a chemical element had been discovered
somewhere else in the universe before it was discovered here on
Earth. Helium was discovered in the Sun's spectrum, and so it is
named after the Greek sun god, Helios.
During
an eclipse on this date in 1868, Janssen used a spectroscope and
observed bright lines in the spectrum of the Sun's chromosphere
(which is the middle layer of the three main layers in the Sun's
atmosphere). Those bright lines showed that the chromosphere was gas,
Janssen said. There was a bright yellow line that didn't correspond
to any known element (and of course, this was the helium line), but
Janssen didn't actually write about that. Instead, he realized that
the Sun's chromospheric spectrum could be observed even without an
eclipse, and THAT innovation is what he spent his time and effort on.
Later
that same year, Joseph Lockyer of England set up a spectroscope to do
what Janssen had pointed out could be done – to observe the Sun's
chromosphere without waiting for an eclipse. And it was he who
commented on that bright yellow line, and it was he and a chemist
named Edward Frankland who named the element.
Meet
Helium
Helium
is the second lightest element in the universe, with an atomic number
of 2.
Only hydrogen (atomic number 1) is lighter.
Helium
is also the second most common element in the universe. (Again,
hydrogen is the most common.)
Hydrogen
is colorless, odorless, tasteless, non-toxic, inert. It is a noble
gas. Inert and noble gas basically mean the same thing
– helium doesn't react with other elements. That's because it's
outer shell of electrons is full up – it doesn't have an extra
electron or two it wants to get rid of, and it's not lacking an
electron or two to make a full shell. It's “just right,” just as
it is!
Have
you ever tried talking on helium? The gas is so light that our
voices get much higher. Take a listen to one,
two,
or three videos!
IMPORTANT NOTE: Because helium is inert, it doesn't react with our bodies, so it is pretty safe to "talk on helium" once in a very long while BUT there are three big "buts."
1. Be sure to take some regular breaths in between so you are getting plenty of oxygen!
2. It can be quite dangerous to breathe straight from the tank. Be sure to put helium in a balloon, and then breathe it in from the balloon. Again, do NOT breathe straight from the tank.
3. Hold onto the balloon! Don't suck in the thin rubber along with the helium!
Because of these three safety reasons, it's important that little kids not try this trick, and that older kids do it with adult supervision.
 |
| Don't try this at home! |
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on this date:
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