# Space; Ripple; Time; Nipple

1. Mar 28, 2004

### deda

In the space - time ripple - nipple the space and the time are related i.e. for every position in one coordinate system there is corresponding time. I believe that even statically the space - time ripple - nipple is affected by contraction and dilation. But how are space and time actually related? The only possible way of estimating the time that corresponds to one known position is using the speed of the light. From the origin we must send a beam toward the object’s position, wait for it to return and divide twice the distance with c. We can also knowing the time necessary for the beam to reach the object and get beck to the origin estimate it’s corresponding position. But implementing this method always puts the photon in the origin of the system. Mainly the motive for this post is the possible confusion when one atom emits “several” photons in different directions. Actually, we cannot view the phenomenon from the atom’s rest frame because only the photons might be at the origin of the system. The fanny thing here is that we have many photons so how do we know which one to be at the origin. The answer might only be all the photons. This is what we have to do: make as many copies of the atom at its current position as many photons are present in the system. Group i - th copy of the atom with i - th photon (i different from 1) and shift the group until its photon’s position becomes same as the first photon’s position. This way we will put all the photons in one place - the origin of the system and will get many copies of the atom on different positions. Also the emission of these several photons in the atom’s rest frame can be understood as emission of several copies of the atom in the photon’s rest frame. The idea of several copies of one atom is somehow hard to digest, but being equivalent, is the idea about several photons in one system also hard to digest?

2. Mar 30, 2004

### Antonio Lao

What is the chance that the photon we see looking into deep space on a cloudless night is the same original photon that started the journey billions of years ago?

At the younger age of the universe, When the radius is equal to 186,000 mi and assuming the observer is at the center, the chance of seeing the same photon is 2 seconds of time.

At radius 372,000 mi, the chance is 4 sec; at 558,000 mi, the chance is 6 sec., so on..

When the universe expands, the chance of seeing the same photon get less and less within the same time period.

Last edited: Apr 1, 2004
3. Apr 1, 2004

### deda

The point is how do you measure the distance to those photon. The only thing you can be sure of is constant c. So you must send another photon from the origin and wait for it to back with the result.

4. Apr 1, 2004

### Antonio Lao

It's not necessary to send another photon. Photon don't really interact with each other although interference patterns (can be seen with light of the same wavelength or frequency but out of phase) do arise. Photon interact with matter as describe in quantum electrodynamics (QED).

The constant c is used to measure distance in the astronomical sense of light-year.

Last edited: Apr 1, 2004