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Name:    Matt
Status:   other
Grade: N/A
Location:   IL
Country: N/A
Date: 12/13/2005


Question:
I recently read an article in Discover Magazine that states: "A photon does not pass through time at all: Traveling at the full speed of light, it experiences being everywhere in the universe all at once." I understand that the photon does not experience time because it is traveling at the speed of light. However, could you explain what the author meant by "being everywhere in the universe at once?"


Replies:
I would like to add some sites relevant to this inquiry. I am not sure whether this will add understanding, or guarantee confusion, but when an inquiry, by its nature, involves a complicated response, it is important in my judgment that the response not be "dummied-down". This is such an inquiry.

There are three articles in the 01 Dec 2005 issue of "Nature", pg.534, 639, 643 that deal with the phenomenon of "entanglement" in quantum mechanics. A "Google" search on one of the authors, "Paul Kwiat" led to other citations that deal with the subject: http://www.metanexus.net/metanexus_online/printer_friendly.asp?5778 http://xxx.lanl.gov/PS_cache/quant-ph/pdf/0507/0507128.pdf

These are pretty advanced mathematically, but I think it offers our "clients" an opportunity to practice a useful scientific learning skill when faced with a mathematically-too-difficult article -- reading through the "math". By this I mean, read the abstract, introduction, and conclusions. If the article is in a peer-reviewed journal it is probably fair to assume that reviewers and/or editors have "checked the math", so skip it or skim it, and read the article for its physical content. After all that is why we have tables of trig identities, and integrals, etc. We seldom derive everything "from scratch" for ourselves.

The site below attempts to "explain" entanglement without math. It is less complete, but does present some of the basic concepts.

http://www.joot.com/dave/writings/articles/entanglement/index.shtml

Vince Calder


Well, at 1.0 x light speed, the time dilation is infinite, so the photon supposedly does not age any (experience any time passing) during the time we "see" (how?) it passing us. In the photon's frame of reference , you could imagine that it does one thing for one moment, said moment encompassing all the places and times of its trajectory. In its own frame of reference, it has zero time with us, so it cannot evolve in any sense in its own experience while it interacts with the universe we see. Who knows, maybe after it is done being in our universe, a lowly photon has an "afterlife" with running time. But all of our time is only a pinpoint in its time line.

More likely a photon is too simple a thing to care about its own experience, nor does it need to have more than 1 moment of subjective time. it is just a computational jot, a faint slash across the space-time continuum.

In our frame of reference, that "moment" is a thin diagonal line across a space-time plot, which can extend for billions of years of time and billions of light-years of distance.

Furthermore, that line is never infinitely thin or sharp. It spreads out sideways (space-wise), gradually diminishing in intensity but never really zero. You could imagine that, as a de-localized wave in space, it feels out the whole universe and then decides where to be strongest.

Thus it is everywhere in the universe, all at one moment of its own.

Hopefully that is something like what he meant. Admittedly only that last paragraph addresses your question.

Jim Swenson


Matt -

The reasoning for being everywhere at once likely comes from the math that describes the events occurring when approaching of the speed of light. As you noted, time slows and at the speed of light the math suggests that time would stop. Also, as speed approaches that of light dimensions decrease until at the speed of light - suggests the math - dimensions would cease to exist. In other words, height, width, and depth would no longer have significance. Could you then say you are everywhere at once? Hope that logic helps.

Larry Krengel



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