Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: black holes and entanglement

Learn more physics!

Most recent answer: 06/03/2013
Q:
Questions that still perplex me and make me wake up in a sweat in the early hours of the dawn Have you considered why light does not lose energy with distance? A red photon with stay red evidently for billions of years of travel. Why does the earth not spiral into the sun? It seems clear that it has been in orbit for over 4 billion years. Why do entangled particles transfer information at least 10,000 times faster than the speed of light & possibly instantaneously over any distance? Why do objects placed in motion, stay in constant motion (presumably forever) unless acted upon by a force? We know that black holes translate through space. Sagittarius A* is moving toward Virgo at 600 km per second. We also know that black holes are frozen stars for which time has stopped. How can this be?
- Dick Vader (age 34)
South Africa
A:

Hi Dick,

Several of your questions boil down to conservation of energy and conservation of momentum. (Why these laws are true, no one knows for sure. But they've proven true experimentally countless times, so we have great faith in them.)

1. We've answered this before. () Light doesn't lose much energy in vacuum, since there is nothing for it to interact with. However, it loses a tiny bit of energy due to the expansion of the universe. ()

2. Again, energy and angular momentum are conserved in the absence of external forces. The only significant forces on the earth are gravitational pulls from the sun and moon. These forces maintain the earth's orbit, but don't perturb it much.

There are small external forces, like asteroids, radiation pressure, and tidal forces, but the earth is much too massive for these effects to matter much.

3. First, I want to correct two false things which you assumed. First of all, entangled particles do affect each other somehow, but they do not transfer information. Secondly, the interaction is precisely instantaneous, not just "a lot faster". That said, your question of how this interaction occurs instantenously is a fantastic one, and no one knows the answer yet. [Let me add a couple of comments. "Precisely simultaneous" in one reference frame is very fast one way or very fast the opposite way in other reference frames. The issue of whether "interaction" is the right word is one of those subtle questions of interpretation/ /mw]

4. Objects in motion stay in motion because momentum is conserved. 

5. Within a black hole, we have no idea what happens. Outside the black hole's event horizon, there is nothing fishy: the black hole is just another celestial object with a known gravitational pull, charge, spin, etc. Just as you could fly by a black hole in a spaceship at a safe distance, the black hole can fly through space. [In fact, no matter what your state of motion, not everybody could say you were at rest, since the other things move with respect to each oher. So everything has to "translate through space."/mw]

Even if we can't see what's going on inside a black hole, there is no reason why this particular phenomena can't travel through space like everything else.

Hope that makes sense,

David Schmid


(published on 06/03/2013)

Follow-up on this answer.