This Will Be A Rather Naive/Junior Question Coming From A Senior!

[MattA777]

If I shine a laser pointer against a reflective surface and observe two points if light simultaneously; is that the same as a single photon being in two places at the same time?
My lack of knowledge in Quantum Phenomena requests any replies to be in layman’s terms.Please!

[bhg481]

Light takes a finite time to get from one place to another. The light leaves the laser travelling at 30000000000 metre/sec (about 1foot in a nano-second) so, if you observe the laser and its reflection, you are not looking at the same photons as the reflected ones will have been "born" a short time ago.

[TheChair]

A typical laser pointer emits 3.2x10^15 photons every second.

[jim360]

As far as I am aware, nothing has ever been *observed* to be in two places at once, although I'd be happy to be corrected on this point. But all the experiments I've seen explained in terms of a photon or other particle being "in two places at the same time" refer to something called quantum superposition, which isn't quite the same thing as being seen in two places at once. What's going on is about how you describe things before they are observed, or in between observations and measurements.

The following isn't perfect, but hopefully it helps.

1. Imagine tossing a coin. We know that we can get only two results from this: heads and tails. But before the coin lands it isn't either really.

2. But we *could* say that the coin is both while it's spinning, and write the coin's spinning state as "(1/2)[Heads] + (1/2)[Tails]". This is a "superposition", which is really just a posh word for "adding". The (1/2)'s appearing are the probabilities, chances, that we get a Head or a Tail.

3. When the coin lands, we "select" one or the other with probability 1/2 -- and to be honest that's about it, this is a mathematical trick*, but the point I'm making is that quantum superposition is similar to this.

4. Write all of the possible results a quantum system can have when it's measured, add them together so that the answer has something to do with how likely that result is.

5. The "two places at once" is an (arguably too literal) interpretation of this, when the states being superposed (added) are positions.

My hope is that even if this doesn't make things clear, it's clear *enough* to provide something that you can ask questions about.

*Although it's fun to note that every result of coin tossing probability follows from writing it like this and treating it in a similar way to quantum mechanics.

[vulcan42]

jim 360, does this alter your answer?

[jim360]

You can just add a correction +0.00000000001[side] and that fixes it :P

[Theland]

Or try this example from my pub days.
On the way home, Mrs T was in a superposition of being both happy and angry at the same time, and only when I arrived home and observed her, did this wave function collapse into one or the other.

(Sometimes I collapsed!)

[mibn2cweus]

Following on from TheChairs response -
Splitting a beam so that it reflects or refracts in two directions creating two spots is not the same as splitting a single photon, which to my knowledge cannot be done.

[Theland]

Correct.
The photon is fundamental, massless, and therefore has no constituents.
'' Let there be light.''

[MattA777]

Thank you to all who used their valuable time to reply....
The old spirit of Answerbank lives on! I was here before the Millenium ! -How time has flown on the Internet It is good to be back and see interesting stuff you don’t always find with Google! “Let There Be Light”

[Theland]

Your thread is a spark of light indeed.