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Scientists Claim 'Cold Spot' In Space Could Offer Evidence of a Parallel Universe (inhabitat.com)
New submitter LCooke writes: A international research team led by the University of Durham thinks a mysterious cold spot in the universe could offer evidence of a parallel universe. The cold spot could have resulted after our universe collided with another. Physicist Tom Shanks said, [...] "the cold spot might be taken as the first evidence for the multiverse -- and billions of other universes may exist like our own." From the report via Inhabitat: "NASA first discovered the baffling cold spot in 2004. The cold spot is 1.8 billion light years across and, as you may have guessed, colder than what surrounds it in the universe. Scientists thought perhaps it was colder because it had 10,000 less galaxies than other regions of similar size. They even thought perhaps the cold spot was just a trick of the light. But now an international team of researchers think perhaps the cold spot could actually offer evidence for the concept of a multiverse. The Guardian explains an infinite number of universes make up a multiverse; each having its own reality different from ours. These scientists say they've ruled out the last-ditch optical illusion idea. Instead, they think our universe may have collided with another in what News.com.au described as something like a car crash; the impact could have pushed energy away from an area of space to result in the cold spot." The study has been published in the journal Monthly Notices of the Royal Astronomical Society.
While that is a perfectly reasonable explanation, and there are even certain ways it may be correct, but the issue is that the cold spot isn't actually at the edge of the visible universe.
The cold spot begins roughly 6 billion light years away from us, and extends to roughly 10 billion light years away.
That leaves roughly 3.5 billion light years of space "behind" it before reaching the edge of our visible universe.
It also doesn't appear to be a sphere of temp difference either, as from our vantage point it only extends about 1 billion light years across at its widest points.
Also of note, while our view from Earth outwards is fairly spherical for the most part, using the term "depth" or "distance away" can become confusing if simplified to the point of ignoring the measurements and math behind what we are actually observing.
The distance is measured as an amount of red shift, not what would be considered travel time.
The temperature of the cold spot is only being compared with the mean temperature of the other areas of space at the same measured red shift.
If you exclude the cold spot for a moment, the mean temperature of any other point of space we can observe at the same red shift amount is just under 20 micro-kelvin.
Including the cold spot again, it differs from the mean temperature by 70 to 140 micro-kelvin.
No where else in space at this red shift has a difference in temperature even close to 4-8 times colder.
Thus it is perfectly reasonable to consider this spot an anomaly.
Back to the postulation you made, like I mentioned you could still actually be correct.
From our point of view the edge of the visible universe is 13.5 billion light years away, which contains the cold spot and roughly 3.5 billion light years more space "behind" it.
But from the point of view of the cold spot itself, being roughly 4 billion light years in size along one particular axis, the cold spots visible universe extends 9.5 billion light years away from it, which is very roughly 20 billion light years away from us, far past our visible universe.
So it is quite possible for something Else to be going on in space basically on the other side of the cold spot, past where it is possible for us to observe, but close enough to the cold spot to cause an effect on it.
Sadly once we leave "theoretical science" and come back to "science", both of the explanations (actually most any explanation) is not within the realm of testable/verifiable observation.
Given a multiverse explanation, we likely can never know if that is the case.
Given your explanation, we certainly can't know now if that's the case, and we would need to still be around in 20+ billion years to do so.
(Which technically means it's safe to say "humanity" will never know. Whatever our decedents call themselves at that time, assuming they exist, may know, but it won't be humanity)
The odds of such a spot forming randomly by chance are embarrassingly tiny.
(On the other hand, it seems the odds of intelligent life emerging at random chance are similarly tiny too, and we know that happened at least once!)
So it would be very nice to at least rule that possibility out first, before worrying about an explanation on what caused it.
But both the resolution of our observations, and the detail level of our simulations, are so poor still that we can't rule out chance yet. Some even argue it wouldn't be possibly, so there is no "yet".
Your "if" evaluates to false. The (very) early universe expanded far faster than the speed of light. This is possible because it was spacetime itself expanding FTL, not something trying to travel through it.
-- Alastair