Mysteries So Bright

For His eternal power and divine nature have been clearly perceived, ever since the creation of the world, in the things that have been made. (From Romans 1:20)

My 3rd grade grandson is very alert and a deep thinker for his age.  We have some good talks and I enjoy swapping ideas with him.  We have been talking on our trips to the YMCA and back.

I asked him, “What should I write about this week?   How about vacuum chambers?”

He thought for a while.  “You were supposed to write about astronomy.  How about Black Holes?”

“O.K.  Do you know what a black hole is?”  I thought we had talked about it a long time ago.

His memory for details amazes me.   He said, “It’s a place where the gravity is so strong that not even light can escape.” (I’m not sure of his exact words, and he will correct me, I’m sure.)

I asked him, “Why can’t we see a black hole?” He wasn’t sure, so I told him, “If no light can get out, then there is no light to see it by.  Of course, if the whole sky is lit up by galaxies of stars, then we should be able to see a spot where there is an absence of light, and that might be a black hole.”

I continued, “But black holes are so small and so far away, that we have never been able to really see one, as far as I know.  But we have seen points in space that are radiating energy from what seems to be from material being sucked into a black hole, never to escape again – at least that is the theory.”

Why can light not escape?  It’s because light loses energy as it travels away from a star – it doesn’t lose speed – the speed of light is always the same; however we can see its loss of energy by its wavelength getting greater – its color shifts toward the red end of the spectrum.  If the gravity is strong enough, the light loses all of its energy and cannot get out.  In fact, it is thought the photons of light actually fall back toward the star.

If no light or any other radiation can escape from the massive star, then it has become a black hole. When stars have burned up all their fuel, the gravitational pull of the star upon itself causes it to collapse into a very dense object which is predicted to become a white dwarf (a star that is white hot, but cooling down to be a brown dwarf).  Or it could become a neutron star where protons change into neutrons because the gravity is so strong.  Or if the mass is great enough, it could become a black hole.

It is estimated that when a star about 10 times the mass of our sun collapses, it will become a black hole, smaller in diameter than the earth, but with a mass that is about 3 million times that of the earth.

And that concludes our brief description of black holes.

“For His eternal power and divine nature have been clearly perceived, ever since the creation of the world, in the things that have been made.” (From Romans 1:20)

Let all the earth fear the LORD: let all the inhabitants of the world stand in awe of him (Psalm 33:8)

I discussed last time that the speed of light is constant as measured by the observer no matter how fast he himself is moving.  For example, if a space ship were moving at a speed of 90,000 miles/sec, toward a star, a beam of light from that star would still measure as having a speed of 186,000 miles/sec, the same as it would measure when the space ship is at rest compared to the star.  Classical physics, and common sense, would say that it should measure 186,000 + 90,000 miles/sec, but common sense fails here.

This result, when predicted in 1900 or so by Einstein and Lorentz, did not seem credible, but it has been shown many times to be true with experiments.  Even more incredible are the consequences of this:   moving clocks slow down (as measured by an observer “at rest”), and moving objects get shorter along the axis of the motion, again as measured by a person at rest.  These are called “time dilation” and “space contraction“, respectively.

Why is it called relativity?  Let’s imagine 2 identical rocket ships coasting by each other in empty space at a high velocity.  Each could say that the other ship was moving and he himself was at rest.  There is no detectable way for them to say who is moving.  It is all relative.

And the time dilation, etc. is reciprocal.  Each space traveler would observe that the other ship’s clock was losing time compared to his own clock and that the other ship was shorter than his own.  How can this be?

Welcome to the weird world of relativity, the effects that normally can only be detected by very precise instruments,  like atomic clocks, or in the case of objects moving near the speed of light.  For example, one early observation was that certain cosmic ray particles (called mesons) created in the earth’s upper atmosphere, with well known, very short life spans, would not be seen as plentifully as they are at the  earth’s surface unless their life-spans were extended about 10 times by moving at about 99.5% of light speed.

There is an easy-to-read and entertaining fantasy book written by George Gamow in 1946, called Mr. Tompkins in Wonderland.  (An updated version, called Mr. Tompkins in Paperback, is available at bookstores – I just found some used ones on-line for $3).  Mr. Tompkins attends a lecture on relativity and then dreams he is in a wonder land where the speed of light is 10 miles/hour.  So these effects upon time and length are obvious just by watching ordinary motion.  For an example, a bicycle goes by and looks much shorter in length than it should.  And as the cyclist speeds up, the length of the bike shrinks even more.

Mr. Tompkins, then gets on a bicycle to catch the other rider.  When he gets to moving, he notices that the buildings on the street start getting skinnier and skinnier the faster he moves.  And then he realizes why it is called “relativity” – each observer sees things from his relative frame of reference,  He notices that the distance to the other biker shrinks, and that the other biker himself looks normal when they are traveling at the same speed.  The story is wonderful fiction, yet reflects a reality that we don’t ordinarily see because the speed of light is so great in our universe.

The discovery of the law of relativity has uncovered another mysterious wonder of creation that continues to amaze God’s sons and daughters and causes them to honor and glorify Him.

I asked my wife, “Do you want to hear more about Einstein’s theory of
relativity?”  She answered, “Not at the moment.  Why
don’t you tell Mei Mei about it.”  Said I, “Well, she doesn’t
really fit the clever title of this article.” “Sure she does.
She’s a member of the family, you know.” “But Shih Tzus are not known
for their complex thoughts,” I protested.   My wife
replied, “However, she will give you her full attention.”

“All right; listen up, Mei Mei,”  I announced to my loyal dog
as she chewed on one of her dozen chews currently in
circulation.  She lifted her head and looked at me, expecting
a kibble for her effort.

I began the story:  Once upon a time, actually in the late
1800’s, several scientists decided to detect for certain the ethereal
substance that supposedly filled the universe in which the waves of
light traveled.   Since all waves are vibrations of
something, then, they reasoned, light waves had to be traveling through
some medium.  This substance was called “aether”.

Since this must be true, the scientists speculated, then as the earth
whizzes through the aether on its trip around the sun, they should be
able to see an effect on the speed of light caused by that motion.

Two scientists, Michelson and Morley, set up a very sensitive apparatus
in 1887 that would detect even the slightest change in this speed by
using the interaction of two beams of light, one beam parallel to the
direction of the earth’s motion in space, and the other beam at right
angles to the first beam.

Mei Mei’s eyes were beginning to wander, so I added some zooming
motions with my arms and made swishing noises of the earth’s path in
the aether around the sun that would have made my grandson proud.

Michelson and his partner saw absolutely no change in speed.
Maybe the aether was moving at the same speed as the earth.
They waited 6 months later to repeat the experiment, when the earth’s
direction would be reversed in its solar orbit.  Again, no
change.  This was very puzzling,  for it seemed to
indicate that the speed of light was a constant which did not vary with
Earth’s movement.

In stepped the theoretical physicists, including Einstein.
They hypothesized that experimenters in a laboratory which was
traveling at constant speed in a straight line would always measure the
speed of light to be 186,000 miles/second no matter how fast the lab
was moving, and that aether did not exist.

Mei Mei kindly licked my face and went over to take a nap.  I
exclaimed, “Mei Mei, don’t you want to know what the consequences of
such a radical theory would be?”  No response.

Next week I will tell why this discovery requires rulers to get shorter
and clocks to slow down if they are traveling in a fast moving
laboratory.

The true light, which enlightens everyone, was coming into
the world (John 1:10)

Read more at BrightMysteries.net, or TinyURL.com/BrtMys, and you can write Boyd at BrightMysteries@verizon.net.

He has made everything beautiful in its time. Also, he has put eternity into man’s heart. (Ecclesiastes 3:11)

It is time for another lively discussion with my bride about physics and astronomy.

She declares, “I read today that the atomic clock in Denver gains time over its sister clock in Europe.  And that gravity is responsible.   See, I told you no one really knows what time it really is!”

“Oh, that’s right,” I reply.  “Before we got married every clock in your house was set to different times, all fast, so you could get somewhere early or at least not too late, right?”

“Yes, it worked very well, and then I married you, and I have been late ever since,”  she answered.  “You went around the house and set every clock and watch so that they read the exact time to the nearest second.  It was crazy!”

I patiently added, “But I left your wrist watch alone, so you could have your own standard time. Anyway,  do you know why gravity affects a clock?”

“No,”  she replied cautiously, not sure she wanted to endure one of my long-winded expositions.  “But, go ahead.”

“Well,  Einstein said to think of a rocket ship that is accelerating in gravity-free space with the same acceleration that earth’s gravity would cause a body to fall.  All experiments would give the same result on the moving rocket or on a rocket at rest on the earth.”

I took a sip of my tea and continued, “Now, suppose that you are on the rocket ship that is accelerating, lying on the floor looking ‘upward’ toward the ceiling.  If there were a clock on the ceiling, sending a flash of light every second toward the floor, the flashes of light would be seen by you as arriving at a faster rate than one each second.  This is because you are accelerating upward.  To you, the ceiling clock would be running faster than one on the floor.”

“Wait a minute (no pun intended),” she interrupted.  “The clock would also be accelerating, would it not?  And so the effect should cancel.”

“No, ” I argued, “the propagation of light is independent of the motion of the source (the clock).  So the blips of light would arrive somewhat bunched together in time.”

“Now, because of the equivalence between an accelerating rocket ship, and one resting with the equivalent gravity on the earth, a clock on the ceiling of the rocket ship, would be running faster than one on the floor by the same amount in both situations,” I continued.

I concluded, triumphantly, “Therefore, because Denver, the mile-high city, is further away from the center of the earth than the city in Europe where the other clock is, the signals from the higher altitude clock will be received at a rate slightly faster than the one at the lower altitude!”

Unruffled by my logic, she smiles, “Precisely.  So, in other words, no one really knows what time it is.”