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Saturday, October 18, 2014


Almost everyone knows that light travels 186,282 (simplify to 186,000) miles per second, which means that if you were to go at that speed, you would circle Planet Earth 7.5 times in one second.  Or, sunlight takes 8 minutes and 20 seconds to travel from the Sun to us.  To be really picky, our orbit is not circular, so it can be 8 min 27 sec when we are furthest away.  If  you've ever been curious about how we get our sunlight (which is nuclear power, fusion, occurring at the center of our Sun), here is one explanation.

Yesterday, Richard Brill featured in his Star Advertiser column the long, hard trek of sunlight, or photons (this is a quantum of light), from the Sun to Earth:
  • A gamma ray photon is created at the core of the Sun at 27 F million degrees and 250 billion atmospheres.
  • As gamma rays are "dangerous," it is fortunate that this high energy photon has to pass through 432,000 (Brill says 400,000) miles to the surface of the Sun.
  • The first 300,000 miles is plasma denser than lead.
  • This gamma ray photon collides with mostly hydrogen molecules (really, the proton portion), bounces around, and loses energy.
  • It takes around 100,000 years for this photon to finally reach 100,000 miles from the surface of the Sun, and is now only one ten-millionth of its original energy as an X-ray photon.
  • The final 120,000 miles is "only" turbulent plasma (mostly ionized hydrogen), so this X-ray photon only takes a week more to get to the surface of the Sun, which is at around 10,000 F.
  • This photon is now only one-millionth as energetic, or one ten-trillionth of what it originally was.
  • Thus, this benign photon, called sunlight, takes a final 8 minutes and 20 seconds to reach the surface of Planet Earth.
  • The whole journey took about 100,00 years + one week + 8 minutes +20 seconds, or around 100,000 years to reach us.  However, Brill says in the first paragraph 120,000 years, so I suspect he meant that it takes 120,000 years, not 100,000 years, to reach a point 100,000 miles from the surface.  In any case, 100,000 years or 120,000 years is a long time and it doesn't matter much if scientifically accurate.
Unfortunately, the fundamental science is not as simple, for another analysis says this 100,000 years  estimate is, essentially, not really so!  Another source indicates 10,000 to 170,000 years, based on collisions.  A more accurate answer is:

 The calculation is a little tricky, but the conclusion is that a photon takes between many thousands and many millions of years to drunkenly wander to the surface of the Sun.

All three results from eminent individuals are sufficiently different, but such is the nature of advanced astrophysics.  They say dark energy is 73% of all mass and energy in the Universe, and 23% is dark matter, except that no one has yet seen or measured anything dark.  What we observe, thus, is ONLY 4% of everything.  Does this make any sense to you?

Here is something a little more understandable, and reveals the incredible vastness of our Universe.  This source says that a commercial jet would take from 118 billion to 143 billion years to travel from one  end of our Milky Way Galaxy to the other.  Of course, it would quickly run out of fuel first, and can't travel in a vacuum anyway.  Keep in mind, though, that the Big Bang was only 13.8 billion years ago.    The rule of thumb is that light would need 100,000 years to get across our galaxy.  The first biologically modern Homo sapiens evolved around 100,000 years ago, wall paintings perhaps 50,000 years ago, farming 12,000 years, and tale of Jesus Christ 2,000 years.  

The closest major galaxy, Andromeda (which is the farthest thing we can see with our unaided eyes), is 2.3 light-years away, or, in other words, light would take 2.3 million years to get here from there.  Again, other reports show the figure to be 2.5 million years.    Why can't they be consistent?

Incidentally, when you gaze at Andromeda, that light left that galaxy at a time when Homo habilis (right) lived,  and way before the Neanderthals (first appeared 400,000 years ago), where the earliest version of  Homo sapiens, us, only came, perhaps, 250,000 years ago.  In other words, if any signal is detected from that galaxy, if we respond, it will take another 2.5 million years to get there.

Incidentally, while it might be true that our Sun should be good for maybe another 5 billion years, it turns out that our Milky Way and Andromeda will begin to merge in 4 billion years.  With Andromeda to the left, here is what this collision will look like from Planet Earth:

Andromeda has a trillion stars, while at most, the Milky Way might have 400 million, so we will lose this battle.  But, we are only two of 225 billion galaxies that can be detected (there are more).  Inter-galactic travel?  There are suggested ways.  But dream on.

The eye of Hurricane Ana is 140 miles from Honolulu and moving west:

From my computer, here is Ana, beyond the horizon:

Perfectly calm, no rain, only cloudy, but regular screechy weather warnings about the potential of floods.


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