Expert: Tom Whiting - 7/10/2004

Question
-------------------------
Followup To
Question -
  Thank you very much Tom, for the detailed answers, altho it is mind boggling for me.  Nevertheless, I can roughly understand the explanation.  However, this leads me to more questions and further confusion!  Can you please clarify the following?

1) In everyday life, light enables us to see objects as they are actually situated over there.  That is how we view the world in 3 dimensions.  In real sight we project our visual ability towards an object and to see it over there at a distant.  From your explanation, light source from outer space travelled great distances and for long duration of time to "bring" towards us the images of distant objects.  As this light source carries with it a continuous series of events it should have a continuous body of mass stretching from the original location up to front of the light, just like a laser beam.  How do you explain this?

2) As I understand from your explanation, photons from a far off star that strike our eyes will have reached the end of their journey, and cease to exist.  When we look through a telescope, we are actually projecting our visual ability to look towards the light source, and see the objects over there and not infront of our eyes.  The light source i.e. the photons do not actually touch the eye or the lens of the telescope.  At least that is what I think.

3) If light travels towards us then what we need to do is just stand and wait for the light to reach us and lo! all the images from outer space will project towards us like watching a film show.  We know this is not the case.

4) Again, if light "brings" in objects, then each day we will only see images and objects from the sun right infront of our eyes!  Again this is not the case.

5) From my ignorant perspective it seems to me that the physics of light and sight in our daily lives are different from that of astrophysics, unless there are clear answers to my questions, which I believe are in expert hands.

6) Now I am getting more confused! HELP!

Cloudy Sky From Justinchoo

Answer
Justinchoo...
Sorry I missed this question on my E-mail, as I was out of
town observing at Cherry Springs State Park this past weekend.

Well, light (and any other electromagnetic radiation) does
not need a medium to travel in, and as I stated earlier,
from the photon's viewpoint, time elapsed remains at zero
because at lightspeed, elapsed time = 0.  It only appears
to travel a great distance over a great time because we
are in a different reference frame relative to those photons.
(Remember, with Einstein's special relativity, you have to
first state and explain your reference frame, otherwise all other observations are meaningless, and if you aren't in the same reference frame of the object you are discussing, your results are going to be different than someone elses
reference frame, even though you are both correct for
your reference frame.)

I don't agree with your statement...."brings us towards the
images of distant objects"....light simply allows us to
view them, not bring us toward them.
And there is "no series of events" onboard a photon, as
stated earlier, an imaginary clock onboard a photon would
show NO passage of time, therefore there are no "events"...
the photon would think it just left the source less than
an instant ago in its reference frame, even though in our
reference frame, it has taken millions of years to get here.
(Please review Einstein's special relativity).  And there
is no "series of events" to any particular photon...the given photon does not know that there is another photon ahead of it, or another one behind it...each photon has to be looked at individually.  And each could care less about
the other photons.

And BTW, I don't explain it...I merely report on what is actually happening to that photon based upon Einstein's
special Theory of relativity.

2.  Well those particular photons pass thru the lens of
a scope, their direction of travel is bent slightly from
a straight line (as that is what a lens does, refract light)
then they strike the retina and are absorbed by it, causing
a chemical reaction in the retina which generates a small
current, which the brain interprets as visible light.
We aren't "projecting" anything...we are simply the
receptor receivers of those photons that think they just
left the light source...there is no projection, the photons
do indeed reflect off a mirror, or are passing thru a
transparent lens, and do indeed strike the retina...that's
how we perceive them.  There is no "magic" here.  There is
no "visual projection toward the object"...we (our visual
receptors-eyes) are simply intercepting a very small amount of the total photon production of a distant star or body.

3. YES, it IS the case!  A very perceptive observation on
your part, except you didn't think so!...Yes, we are actually watching a time movie out in front of us unfolding, as you stand there and stare at the night sky!
That is exactly what is happening! Just as if we were watching a slow moving meteor streak across our sky!
(Which BTW, you are seeing a nano-second after the fact).

With the exception that each object, being situated at different distances, we are viewing ancient photons of various ages (in our reference frame), but again, each photon thinks it just left the source.

If a star 10 light-years distant explodes tonight, then 10 years from now we will witness that explosion as the light arrives...the time movie has to run its course.

4. Light does not "bring in" objects, any more than
sound "brings in" a thunderstorm cloud any closer to you.
You are simply a witness to photons (or sound waves from
a distant thunderstorm) that departed the source, no matter
how far away the source.

5. Well, you need to review the physics of electromagnetic
energy, and Einstein's Relativity, and what happens as you approach the speed of light,
which matter cannot do, because mass becomes infinite
and time becomes zero, as you approach light-speed.
It's only those massless photons that can travel light-speed and have a time = zero in their reference frame.  We can
never do that because we have mass.  Astrophysicists are
well aware of the physics of light and other electromagnetic
radiation, which all works the same way. Photons are simply
the massless messengers of energy...they don't physically "bring in" or "transport us magically" to any particular
star or body.  We have to keep "science" and "science-fiction" on their separate levels.

Hope I've been of some minor help..
Clear Skies,
Tom Whiting