December 14 – Happy Birthday, Tycho Brahe

nPostednon December 14, 2014

n
n

nTodaynwe celebrate one of the biggest of Europe’s early astronomers: TychonBrahe.

n
n

This drawing shows Ptolemy’s
theory of a geocentric
(Earth-centered) universe.

nAnlong time ago some very intelligent, learned, and wise men in AncientnGreece thought long and hard about a lot of things, and they decidednthat the heavens – the stuff we see in the sky – was perfect andnunchanging. Everything in the skies seemed to move in regularnrhythms, and they shone with perfect, unblemished light, and thingsnstayed the same year after year, century after century. The perfect,nunchanging heavens became a part of the Greeks’ philosophy about thenuniverse.

n
n

nAnothernthing that was self-evident as these learned men looked upwards:neverything circled us! We Earthlings were the center of itnall! The Moon and Sun clearly circled the Earth, as did the stars.nThe planets had more complicated motions – with a little bit ofnbackwards action interrupting their progression across our skies –nbut they also basically traveled around our world.

This is a modern diagram of Ptolemy’s
system. Note that the Sun and Moon
and the sphere of stars simply orbit
around the Earth…but those pesky planets
with their back-and-forward motion must
be doing cycles in their cycle, Ptolemy thought.

n
n

nButnthe Scientific Revolution upset all of these notions:

n
n

Innthe 1540s, Nicolaus Copernicus published his theory that the Earthnwas NOT the center of the universe. His theory was that the Earth andnother planets traveled around the Sun – although he kept thosenperfect circular orbits thought up by the Greeks.

n
n

nThisnwas SO not cool with people – after all, we liked being the centernof things!

Inn1609, Johann Kepler published his theory that the Earth and othernplanets actually traveled around the Sun in non-perfect oval orbits.

n
n

nNon-perfectnorbits?!? What’s the universe coming to?

Thennext year, Galileo Galilei published his findings from studying thenuniverse with his newly built telescope. He had discovered four tinynlights that clearly revolved around the planet Jupiter. This wasnproof that Copernicus was right, at least in the idea that notnEVERYTHING in the universe revolved around us! And Galileo arguednthat Copernicus was right about the big idea of the Earth circlingnthe Sun, rather than vice versa, as well.

nStillnnot cool with most people! Galileo was put under house arrest.

nSandwichednbetween Copernicus, on the one hand, and Kepler and Galileo, on thenother, was today’s birthday, Tycho Brahe. His big contribution tontearing down the Greeks’ perfect heavens was proving that the heavensnwere not unchanging.

n
n

One of the supernovas
that Tycho observed was
one that appeared in 1572.

nBrahen(who was born on this date in 1546) carefully observed a number ofn“new stars,” called stellae novae – now called novas andnsupernovas. Because of that “the heavens can’t change” rule,npeople thought that new stars in the sky were local phenomena, foundnin Earth’s atmosphere, or at least closer to Earth than the Moon. ButnBrahe knew that, if the new stars were that close, they should appearnto be in slightly different spots in the sky, compared to the distantn“fixed stars,” when seen from different observers positioned manynmiles away from one another. This parallax didn’t occur, however,nthus proving that the stars were, in fact, much farther away from thenEarth than the Moon – that they were, in fact, part of the heavens.

n
n

nAnd,nvoila, Tycho had proved that the heavens could change!

n
n

Bynthe way, Tycho did not think that Copernicus was right about thenEarth traveling around the Sun. He didn’t go along with the AncientnGreek idea of everything circling the Earth, either – instead, hencame up with his own system:

n
n

nThen other planets circled the Sun.

n

nThen Sun and the Moon circled the Earth.

n

nThen “fixed stars” circled everything.

n

n
n

nYounmay be wondering why Tycho didn’t agree with Copernicus. He had two important arguments:

n1) the Earth was too sluggish and heavy to be continuously innmotion, and

n2) the Earth’s orbit around the Sun, if itnexisted, would cause stellar parallax.

n(Actually, there IS stellar parallax – the Sun, planets, and nearby stars can be seen to be in slightly different positions, compared to farther away stars, when the Earth is on opposite sides of its orbit. But thenangles are very small and difficult to measure. Tycho knew that the apparent lack of parallax wouldn’t be a problem if there was an enormous gap betweennthe outermost planet – which at the time was Saturn – and the stars. But such annenormous gap seemed ridiculous to Tycho and other scientists.)

nAbout that enormous gap…

nTycho Brahe thought an enormous gap between Saturn and the rest of the farther-off universe (stars and such) was ridiculous. But that enormous gap is true!

n
n

nSaturnnis only hundreds of millions of miles away from Earth, but even thennearest stars are TRILLIONS of miles away!

n
n

nAndnjust one trillion is a million millions! So think about how far manyntrillions of miles are!

n
n

nTongive you just a bit more perspective on how much a trillion is, thinknof it this way:

n
n

nCountnone second. It’s about as long as it takes you to say “A thousandnone.”

n
n

nNownconsider this: The United States has not yet existed for a trillionnseconds! As a matter of fact, almost nothing in your history booksnhad happened yet, a trillion seconds ago! Not Tycho Brahe’s birth,nnot the Ancient Greeks, not even the Ancient Egyptians!

nAsna matter of fact, a trillion seconds ago is about 31 THOUSAND yearsnago, and humans were just figuring out how to fire pottery andninventing the bow and arrow!

nTonlearn more about Tycho Brahe, check out this earlier post.

nAlsonon this date:

n
n

nArrival of the Yule Lads in Icelandn

n

nDaynof the Horse

nAnniversarynof the first “modern-day” imitation pearls

nMonkeynDay

nAnniversarynof President LBJ saying, “Some geniuses at Stanford Universitynhave created life in the test tube!” –when that wasn’tnwhat actually happened!