The Truth About The Creation
God's Glory, God's Handiwork, God's
Word, The Genesis Account
A Dissertation by Pastor Ed Rice January 2017
13: Measuring
The Speed Of Light And Distance to Stars
A couple of essays that have been used to document how we know the
speed of light and the distance to stars will be useful in this
effort.
Essays
in Science – Speed of Light
Five hundred years ago man supposed that light had a measurable
speed. The speed of light cannot be seen nor measured by clicking a
light switch on, because the speed of light is imperceptibly fast.
Today, the speed of light is very accurately measurable. Ole Romer
(1644-1710), a Danish astronomer was studying the periodic cycle of
one of Jupiter's moons when he calculated the speed of light. Sixty
five years earlier, in 1610 Galileo, armed with a 20 power telescope,
noticed that Jupiter had 4 moons. Ole Romer was calculating the time
it took for one large moon to emerged from Jupiter's shadow. His
measurements showed a 40.5 hour period for this moon. As winter set
in Ole noticed that the expected rising of Jupiter's moon was getting
later and later, gradually changed by 20 minutes. As spring came the
rising moon started getting earlier and earlier until it was restored
to its original schedule.
Obviously the orbit of Jupiter's moon did not change because the
Earth moved further away from Jupiter. It was the speed of light that
was taking the extra time to reach the Earth as it traveled from the
moon rise on Jupiter. Ole correctly concluded that this time
difference was due to the extra distance that the light had to travel
to reach Earth. With this information Ole Romer, in 1676, remarkably,
calculated the speed of light at 225,000 kilometers per second. Even
though he had only rough numbers for the Earth's orbit and Jupiter's
orbit, he was only 25% low in his calculations. Today we measure it
at 299, 792 kilometers per second. Ole Romer was the first person to
demonstrate that the speed of light is measurable. With more accurate
instruments and many more observations we can now accurately
calculate the speed of light in free space; that is accurate for our
little galaxy, without the effect of black holes, relative
velocities, rotational dynamics or other limiting errors caused by
theories of relativity. The speed of light is thus finite and
measurable.
Notice in this treatise the emphasis that the speed of light is
measurable in this galaxy and with our current units of time and
distance understood without relativity. The genius of Albert Einstein
has allowed us to recognize that the speed of light and the time
clock that measures it, are not necessarily constants but very
flexible and even relative, warped by gravitational forces in space
and time. Most of us have heard some of this theory of relativity in
the sci-fy stories about intergalactic travel where a person does not
age when approaching the speed of light. Einstein's theories of
relativity can alter time and distance, the speed of light and even
the speed of gravity, which is not yet measured.
Theories about intergalactic travel of light, time dilation or
relativity can readily support an idea that out there on the edge of
our universe a single day could be as a thousand years, and here in
our 'time zone' a thousand years could be as a single day out there.
Marvelous possibilities exist for a mere 6000 year old Earth, even
with the speed of light 'fixed' at 300,000 kilometers per second and
Supernova 87a measured at 168,000 light years away. How did they
measure that distance? That's the subject of another essay.
Essays
in Science – Measure of Space Distance
“It is the glory of God to conceal a thing: but the
honour of
kings is to search out a matter “ (Prov 25:2).
Let's do just
that concerning how far away Andromeda or Supernova 87a might
actually be. Since it seems immutable that light travels at a finite,
albeit very very fast speed, and we view the Andromeda galaxy from a
young Earth,
perhaps the scientists have exaggerated the distances in
inter-galactic space. How can you tell how far away a star is anyway?
A distance measure for space can be likened to a ride on a twenty
five foot diameter merry-go-round. Board the merry-go-round at night
while three birthday candles are placed 50, 500 and 5,000 feet away.
Of course the brightness of the candles can first be used to estimate
their distance. This brightness measure has been a mainstay of
distance determination. A star's absolute luminosity was found to tie
directly to a very measurable Cepheid cycle
and its distance could then be measured via r^2
attenuation of its absolute luminosity. But consider also that as
one rotates through revolutions on the merry-go-round and watches the
nearest light, they will have to pivot their line of sight back and
forth 27 degrees (tan-1 (25/50) degrees); for
the second
light one will pivot their head only 3 degrees (tan-1
(25/500) degrees); and for the farthest light one will pivot their
head only 0.3 degrees (tan-1 (25/5000) degrees).
With some
precise instruments one could measure these angles and then determine
the distance to each flickering candle. Indeed your brain does this
sort of calculation every day; your two eyes are spaced roughly 3
inches apart, and their vision crosses at a measured angle which
determines the distance you are focused at.
Now consider that from June to December or March to September the
merry-go-round that the Earth is riding moves quite a distance in
space. By definition we are 1 a.u. (astronomical unit) from the sun,
that is 8.317 light minutes or 0.00001581 light-years (1.581e-05
light-years). Just like the distance to the birthday candles can be
approximated or carefully measured from the merry-go-round, so too
the distance to stars can be approximated or carefully measured from
the Earth's orbit.
In 1987 we watched a supernova that was supposedly 10.12 billion
a.u. away. So between Dec and June the line of sight to the supernova
changed by 0.0004 mili-arc-seconds (mas) or .006 billionths of a
degree (tan-1 1/10,120,000,000 degrees). The
W.M. Keck II
400 inch telescope in Hawaii can achieve an amazing five
mili-arc-seconds spacial resolution.
Here, however, we needed to measure .0004 mili-arc-seconds,
significantly smaller than 5 mas. Obviously we cannot measure these
great space distances with these means. The 1989 European Hipparcos
space observatory measured this 'parallax' distance for 120,000
stars, but it is only effective for stars within two to three
thousand light years.
Going back to our merry-go-round example for birthday candles greater
than a mile away one could still perceive various distances by the
size and brightness of the flames. We do this based on what we know
and observe about the nearer birthday candles at known distances.
Some birthday candles may be larger than others and cause slight
error in this means of gauging this distance, but this error would be
relatively small. In like manner astronomers measure a star's size,
emissions, Cepheid variable, and pulsations and can come up with a
reasonably accurate distance estimate for deep space stars.
Again in our illustration, if the birthday candles were all set in
motion we could judge the distance to any candle by its perceived
motion. This is especially true when it is discerned in relation to
some known closer birthday candles. Lights clustered together with
this perceived motion may be more accurately discerned. A rotation,
will likewise more accurately differentiate these distances. This is
basically how the calculations of astronomical distances to stars,
clusters, and galaxies are accomplished. It is indeed an art in the
world of science. Each measurement leans on observations from all
three methods. The art does have its sources of error, but over all,
the errors will not be orders of magnitude. The 1987 supernova
observed within the large Magellanic Cloud is measured (estimated) at
168,000 light years away. Throwing in a plus or minus 10,000 light
year error still leaves it a very long distance away. Thus it still
begs the question, “Just when did that star
explode?” Suffice it
to say that time and space warp in the outer regions of God's
universe. It does not take light 168,000 years to travel from the
large Magellanic Cloud.
It is shown elsewhere in this effort that God can bow the heavens and
dilate time as he pleases, just trust him. “He bowed (bowed,
streached out, extended, spread … ) the heavens also, and
came
down: and darkness was under his feet” (Ps 18:9).
To Continue in this series click the link below:
13:
James Ussher's Calendar and Dating
Methods. . . 254
www.truthaboutthechrist.com/thetruthaboutthecreation/14ussher_dates.html
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