But seriously folks,
Earlier I made the assertion that by Hubble’s law objects whose distance is greater than c/H would have recession velocity greater than that of light. I also figure there would be an event horizon at a distance of c/H making such objects undetectable (except for their mass, charge, and angular momentum). I think the only two assumptions I am making are the universe is infinite (or has diameter at least 2c/H) and that Hubble’s law applies at all distances.
I don’t think Hubble’s Law applies at all distances, at least not in the form you stated it. I would expect that something analogous to the Lorentz transformation would need to be applied in some way in order for it to be strictly true. However, I’m not an astrophysicist, so I could very well be wrong.
It’s interesting you use the term “event horizon”, though. I recall reading many years ago, when black holes first began being mentioned in popular culture, that as black holes became more massive they also became less dense. The article I was reading said that the observable universe had an average density which was a sizable percentage (roughly 10% IIRC) of the expected density for a black hole of the same size.
torq I was wondering wheither there is some Lorentz-type correction.
Thank you.
I used the term event horizon because an event horizon is something such that nothing can cross from the other side to “us” without exceeding the speed of light. I admit this is a unique event horizon but I think it fits the definition.
Of course if I am wrong about Hubble implying FTL then there might not be such an event horizon.
From the National (USA) Institute of Standards and Technology
[quote}
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.
[/quote]
Note, however, that this definition assumes the idea that the speed of light is invariant. If this were to be overturned, a new definition would be found.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams
If we position two rulers at a small enough angle and move them so that they approach each other, their point of intersection can be made to move as rapidly as we desire by decreasing the angle. The speed can reach infinity by making the angle zero. I would be interested in knowing how this involves a fallacy.
Well, yes…
One of the assumptions of GR is that the speed of light (in a vacuum) is constant for all observers. The current definitions of our units of time and distance are based on this assumption. If this were to be overturned, more than just the definition of the meter would have to be reexamined. All of relativity would be affected.
You’re making the unstated assumption that your two rulers are infinitely rigid. If infinitely rigid objects existed, you could transmit information faster than light much more easily just by pushing and pulling a long rod.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams
Imagine a stationary ruler and a second parallel and approaching the first. When they meet the point of contact moves with infinite speed.
If a second observer moves along the ruler fast enough for special relativity to be taken into account the points of contact will still have space-like separation and therefore be moving faster than light. The aparent direction of this movement will be in the opposite direction to the direction of the second observer’s motion. I would note that even though the point of contact moves faster than light, this cannot be used to transmit information faster than light.
If you assume one stationary ruler and one ruler that “was always spinning”, then, yes, you might get the point of “contact” moving faster than light, at which point, of course, there is no transfer of information.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams