* * * How much of the Universe is causally disconnected?

Forums: Science And Math
Email this Topic • Print this Page

Here's an interesting question - given the Universe has inflated past light speed (i.e. age 13.8 billion years, believed diameter 40 billion light years) - how much of the Universe is causally disconnected (so far away light nor any force can never bridge the gap) from large segments of itself?

Obivously the percentage disconnect raises as you move from the past epicenter of the big bang to the edge of the Universe today.

At a maximum the old epic centre of the big bang could observe a sphere of light bubble 13.8 billion light years in radius - so by simple maths and volume of a sphere 4/3 * pi * r^3 that means at the centre you could be affected by 13.8^3 / 20^3 = 33% of the known Universe.

Secondly as the Universe's expansion is accelerating I would guess over time this figure is continually decreasing, not static. So at 1 billion years old the causal connectivity of the epicentre of the big bang to the rest of creation I would view would be significantly higher than 33% (must check this)!

If you were at a point closer than 13.8 billion lightyears from the edge of the Universe this figure would be even lower. Close to the edge you'd have (less than) half a sphere so you would be affected by less than 12% of the Universe.

* * *

So is it true to say the Universe is large and significantly causally disconnected from itself? Maybe this is a prime factor leading to the increasing expansion of space itself.

Topic Stats
Top Replies
Link to this Topic

Type: Discussion • Score: 1 • Views: 1,653 • Replies: 6

No top replies

Causally disconnected? Assuming the Big Bang is real then everything in the universe is connected. Our galaxy is connected to every other galaxy. Of course, we can see the Milky Way and its interaction with Andromeda clearly. Somewhere along the way even the rate of expansion is influenced by every galaxy. Of course, on a cosmic scale we are dealing with something greater than the 6 degrees of separation.

0 Replies

You can only see or be connected by a force carrier because light or a force travels at a finite speed c.

During the first few moments of creation - less than a split second, the Universe expanded 50,000 times faster than c - that is called inflation. It lasted from time 10 ^ -35 to 10 ^ -34 of a second.

But in that trillionth of a trillionth of a trillionth of a second a discontinuity was created before the laws of Einstein's relativity set in. This discontinuity caused the Universe to become casually disconnected.

Gravity can only affect things after it has propogated. It propogates at speed c, from the epi-centre of the Big bang out. Now because of inflation the opposite edges of the univrse were inflating at over 2 * c because they were travelling in opposite directions; so the gravity wave of one edge / hemisphere of the Universe couldn't catch the receding edge / hemisphere (mostly).

Also if Gravity is quantised (I doubt this) it can't travel forever - because at some finite distance its energy would be less than the minimum energy packet - quanta.