a reply to: crunchypeople
Thanks for the delightful OP, which involves at least three individually interesting questions: 1) Can a far-away telescope see what happens on earth?
2) Could we travel in a faster-than-light way and hence view history? 3) Are physicists "dicks"?
As a rough estimate to answer question 1, let's estimate that a 16 Watt light bulb is enough to illuminate and clearly see the details on a one meter
radius sphere surrounding it and ask how many photons per meter squared there are at certain distances. Our 16 Watt bulb produces 16 J/s, or
[16/(1.6e-19)] eV/s, = 1e20 eV/s. With each photon having an estimated 2 eV we see the bulb produces 5e19 photons per second. The density of photons
gets diluted as the distance grows. At one meter from the bulb, we have [5e19 photons/s]/[4pi(1m)(1m)] ~ 4e18 photons per second per meter squared.
Enough to see things quite well indeed! But consider how many photons there are by the time we get "just" one light-second away. That number falls by
3e8 squared - and we now have only 45 photons per second per meter squared. Not very many, even when collected over an area of a powerful telescope.
By the time you get to "just" one light year away you have far too few photons to see anything at all, as the number of photons per square meter now
drops by an additional factor of about 1e15. It would take roughly a million years to get one photon per square meter. So this tells us that we really
won't be able to see much of the past in any detail, at least on the level of individual humans. The reason we can see stars is because of the
enormous energy output they have. I will leave it as a homework exercise for others to estimate larger scale things like asteroid strikes or the
formation of the moon. (Hint: those events will have much more than 16 W of output, but then again, they occurred a long time ago so the light sphere
radius will also be much larger than one light-year.)
As for whether we can travel in a faster-than-light way, Einstein's special theory says no. The problem is that as you get closer to the speed of
light (as observed by someone staying at rest) it is harder and harder to accelerate due to the intrinsic nature of space and time. Some general
relativity concepts such as worm-holes and other odd things have been proposed, but I don't know if there is any real hard evidence for any of that
nor am I expert on such matters. I do know that there is abundant evidence for the Lorentz force equation, and that the evidence agrees with
Einstein's treatment. However, there are other treatments that also agree with the Lorentz force equation. If we return to the aether theories of
Lorentz and others, then yes, you could travel in a faster-than-light way. I hope to post more about this if I ever get my aetherial Lorentz Force
derivation done. The essential observation is this - Einstein's theories explain known effects as being caused by alterations of time and space as
observed by observers in relative motion, while the classical theories explain the same effects as being caused by an absolute motion with respect to
a physical aether. Hence, ala Einstein, nothing can be done about the situation since the effects are just a by-product of the intrinsic nature of
space and time. But via the classical aether, the possibility is there to control the aether itself, since the aether is a material body, and this
could lead to some rather wondrous things, one of which would be faster-than-light travel.
As for whether physicists are "dicks", well, that is rather subjective. One aspect involves those who know things versus those who seek knowledge.
When we know things, we are sure, since knowledge is the acquisition of facts. And when we know, then we become superior in knowledge to those who
don't know, and that can lead to arrogance and condescension (an apparent "dick"-like behavior) aimed at those who don't know what we do. On the other
hand, when we seek knowledge it leaves us more humble (and less prone to "dick"-like behavior) since our quest inevitably involves stumbles and
bumbles and failures along the way, and that leads to more empathy with and understanding of our fellow, frail, human brothers and sisters.
Unfortunately, when you ask a question you'd usually like an answer, and you'd generally not want some philosophical ramblings about stumbling and
bumbling from some "seeker of truth". And so, you seek advice from an "expert". Those experts must of course have some body of knowledge from which to
give an answer, and hence if you ask questions about things that presume something contrary to their "known facts" then it can be an entirely proper
response for such experts who "know" to dismiss the question as impossible and hence outside the realm of proper discussion. So imho its really not a
matter of being a "dick" but rather one of being in the right forum. ATS is a pretty good place for such questions. The Physical Review, not so
Well, it was great to check back in here. I peruse the topics here regularly, and this OP was a pretty good one to chime in on. It's tax prep and
proposal time for me now, but I hope soon to get back to my stumbling and bumbling and with any luck I might have some aetherial advances to pass on
in the coming months.