The History of Radio and
Radio Astronomy!
Radio waves haven't changed, but our usage of
them has...
The beginning...
When do you think the first usage of radio
waves was?
What was the first piece of technology to use
them?
The beginning...
- It all starts with math ● James Clerk Maxwell, in 1864, showed using
mathematics that electromagnetic force could be
propagated through free space at any wavelength
o He also went on to calculate the speed of light to
within 4% of what we know today!
- Wasn't until 1888 that Heinrich Rudolf Hertz
demonstrated in the lab that electromagnetic
waves existed by producing and detecting
radio waves
http://www.royalsoced.org.uk/cms/images/maxwell/maxwell.jpg
First uses:
- Wireless telegraph
o
o
o
It is not very clear as to whom to credit with the
overall invention of this device.
First device to be used to successfully transmit a
transatlantic message was invented by Guglielmo
Marconi.
Just like the regular telegraph machines, the
wireless version also sent information using Morse
Code.
http://www.successfuloffice.com/articles/marconi-invention.gif
Radio's Evolution:
- Soon after messages were successfully sent
via Morse code, it was hypothesized that
speech information could be encoded and
sent via radio waves.
● This was achieved by Reginald
Fessenden by Amplitude Modulation (AM
radio) in 1906
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imgaud/am.gif
Radio's Evolution:
- After World War I, AM Radio took off thanks
to the company RCA
- AM lingered around for awhile until the 1930s
when amatuer radio operators started
experimenting with frequency modulation
o
o
FM Radio gets its official start in 1933 thanks to
Edwin Armstrong
1938 marks the famous Orson Welles broadcast of
"The War of the Worlds"
http://0.tqn.com/d/webclipart/1/0/i/H/5/Alien-Night-Sky.jpg
Things take off...
- TV gets invented around the 50s and "Radio"
starts to take a backseat
● TV broadcasts also rely on radio waves!
- At this point a lot of things start to happen
including the transistor radio, radio satellites,
and its conversion into the digital age (all your
technologies rely on the transmission and
reception of radio waves!)
- The important thing is how radio waves
started to be used in astronomy in the 1930s...
Interlude:
A good breakdown of the history of Radio:
http://blog.sonos.com/culture/the-history-of-radio/
Radio Astronomy:
- The history of Radio astronomy again starts
with Maxwell and Hertz
- From these predecessors, many scientists
believed they could detect radio emissions from
celestial objects
o
2 notable scientists who experimented with this early
on were Thomas Alva Edison and Sir Oliver J.
Lodge in the 1890's.
http://lcweb2.loc.gov/service/pnp/cph/3c00000/3c01000/3c01700/3c01784v.jpg
http://1.bp.blogspot.com/-LYdTaArmYoM/UCXu_cDeTQI/AAAAAAAACrQ/b1Rbn8vHhtA/s1600/thomas-edison-lightbulb.jpg
Karl Jansky:
- In the early 1930s Karl Jansky was assigned
by the Bell Telephone Company to
investigate sources of static that might
interfere with radio transmissions.
- Jansky build an antenna that detected radio
waves of 20.5 MHz.
http://www.nrao.edu/whatisra/images/jansky1.gif
Karl Jansky cont.
- Using his antenna, Jansky discovered three
static sources:
1. Nearby thunderstorms
2. Distant thunderstorms
3. an unknown hiss that occurred
approximately once a day....
- What was that unknown hiss?
https://admissionblog.usc.edu/files/2013/05/Question-Mark.jpg
Karl Jansky cont.
- It turns out, the faint hiss that Jansky
discovered wasn't following the 24-hr day of the
sun, therefore wasn't coming from the sun.
Instead it followed a sidereal day (23 hrs. 56 mins)
which followed the path of a distant star
o Turned out he discovered the radio emissions of the
center of our galaxy
o His results of this were widely publicized in 1933, but
sadly he never worked in radio astronomy again
o
http://curiouspaul.com/you_are_here_galaxy.jpg
http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2010/11/milkyway.jpg
Grote Reber:
- Was very interested in
Jansky's discovery in 1933,
but was unable to get a job at
an observatory due to it being
the great depression
- He decided that wasn't
going to stop him:
o Built his own (very
impressive) radio
telescope in his
backyard
http://www.nrao.edu/whatisra/images/grote6.gif
Grote Reber cont.
- His telescope used a parabolic dish design
o Focuses all wavelengths to a single focus
- After many attempts, he confirmed Jansky's
discovery in 1938
- Overall, he used his telescope to chart the night sky and
keep track of the "brightness" of radio waves in our galaxy
o Used these to make the first "pictures" using radio
waves in the form of contour maps (based on the
brightness of the radiation
detected)
http://www.nrao.edu/whatisra/images/grote5.gif
Important times in Radio
Astronomy:
- 1942: James Stanley Hey
successfully detects radio
emissions from the sun
- 1944: Jan Oort and his student
Hendrik C. van de Hulst
predict the existence of the
21-cm hydrogen line (huge
in astrochemistry)
- 1951: Edward Mills Purcell and
Harold Irving Ewen discover
the 21-cm hydrogen line
http://www.nrao.edu/whatisra/images/inspectinghorn.jpg
Other important times:
- In the 1940s radio interferometry was used to perform the
first high resolution radio astronomy observations
- 1967: First VLBI (Very Long baseline
Interferometry) done by Canadian and U.S.
researchers
o From this point it was realized VLBI could be used to
perform many useful tasks in radio astronomy
- From this point on, VLBI has been on the dominant
techniques in the field of radio astronomy as it allowed
for greater and greater resolution as the baselines
became greater and greater
More Dates:
- 1963: the largest radio telescope to date is
built in Arecibo, Puerto Rico (1000-ft. aperture)
http://www.cv.nrao.edu/course/astr534/images/Arecibo.jpg
More Dates:
- 1966 and 1967:
Shapiro's 4th test
o
The '4th' test of Einstein's
general relativity done at
Haystack Observatory
http://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Cassini-science-br.jpg/250px-Cassini-science-br.jpg
The VLA:
http://upload.wikimedia.org/wikipedia/commons/6/63/USA.NM.VeryLargeArray.02.jpg
Local Efforts:
- A lot of improvements in radio astronomy
wouldn't have happened if it wasn't for the
efforts of MIT's Radiation lab during and after
WWII
o
Before, during and after the war, the military
invested a lot of research money into the
development of better radar systems.
Local Efforts continued:
- These two sources do a good job showing the
role MIT's Rad lab played in the war efforts:
1. http://www.ll.mit.edu/about/History/RadLab.html
1. http://www.ieeeghn.org/wiki/index.php/Milestones:MIT_Radiation_Lab
oratory%2C_1940-1945
Post-War efforts:
- During the Cold War, great emphasis was
placed on long range detection of ICBMs
At the time, radar only worked a maximum distance
of the horizon
o Made it necessary for much longer range of
detection
o Military again gave much of the refining work to MIT,
this time at Lincoln Labs:
 http://www.ll.mit.edu/about/History/SAGE_TOCpage.html
o
How research is done:
- The previous links are perfect
examples of how research is
done in the scientific
community:
o
o
The government / military see
shortcomings in technology
Research money is given out to
figure out how to improve the
technology (the more pressing,
the more money)
 rinse and repeat...
Example:
- Military needs a longer range radar for ICBM
detection:
o
Lincoln Labs given R&D money and develops SAGE
- Military notices a lot of false alarms due to
ionosphere and auroras:
o
MIT finds out what is causing these and figures out
how to fine-tune the system
- The improvements not only beneficial for the
military, but for the scientific community as a
whole
There is so much more...
But not enough time to cover it all!
If you are interested, look up research done in:
- Incoherent Scatter Radar (Space Weather)
- Sgr A* or NGC4258 (Black Holes!!!!) /
- Event Horizon Telescope
- Geodesy (plate tectonics)
- VLBI
- Astrochemistry (spectroscopy, chemicals in space, etc.)
- MASERs (basically radio lasers, everyone loves lasers!)