A group of researchers led by Stephen Feeney tried to give an answer to that question. Their results showed that there was something else in the echo (echo) big bang. They started the analysis of different modeling universe called eternal inflation.
Eternal Inflation Theory
Eternal Inflation in the modeling, which can be observed universe would be in a bubble embedded in a vast parallel world (the multiverse / many of the universe). Part of the multiverse is undergoing development with super acceleration.
Tests of this scenario is not easy because eternal inflation is epoh pre-inflation (before inflation) and signals from outside the bubble of our universe will be drawn on the horizon / skyline super scale unobserved.
Nevertheless, there are other possibilities for this epoh can browse through collisions between vacuum bubbles. Maksutnya, the universe is observed in bubbles of the past clearly have a hard and collided with each other leaving a cosmic signs in the place they touch. The collision happened will generate inhomegenitas on the inside of bubbles, so that these markers will certainly be seen in the present in the cosmic microwave back lata.
The current results also show that the existence of collision between bubbles is feasible and compatible with cosmological observations. In some models, collisions tend to occur in our past light cone and collision may leave marks that can be observed.
The remaining traces of collision between bubbles
Well to be able to observe the collision bubble depends on several things, among others; scalar potential field that controlling inflation is eternal (and controlling the rate of formation of bubbles); duration of bubble inflation in our universe (the greater the inflation, the more thin the signal) and a particular realization of sky microwave background (CMB) and collision of bubble can be observed (even a clear signal could be obscured by the foreground). One thing to realize Feeney and his colleagues, though there is enough motivation to consider the model of eternal inflation, but concrete model that provides all the details of the model of eternal inflation is not yet available.
However, the collision will form a bubble is a sign that the target set analysis. Among them;
* Asimutal symmetry: the sign left by the bubble collisions in the CMB sky would have asimutal symmetry or size of the angle of symmetry as a consequence of the symmetry SO (special orthogonal group) of space-time that describes the collision two vacuum bubbles.
* Casual Boundary (Boundary Casual): The surface of last scattering (previously) only to diperngaruhi in the future light cone (cone that will happen) of a collision. The intersection of the past light cone (before), the future light cone (which will happen) when the collision and the surface of last scattering is a ring. The observed temperature of the CMB do not have to continuously within these limits.
* Length of the wavelength modulation: Collision bubble is a relic of pre-inflation. Effects of the collision has been withdrawn by the inflation and cause the overall CMB temperature modulation becomes anisotropic.
From observations on the data for 7-year Wilkinson Microwave Anisotropy Probe (WMAP), Feeney and his colleagues found signs that a collision is expected to fit as a bubble. This research group found 4 mark in the CMB sky corresponding to the bubble collision. That is, in the past of our universe was hit by another bubble at least 4 times.
If this evidence can be strengthened by the data to be retrieved by the Planck satellite, the researchers will be able to obtain information about the possibility of parallel universe or another universe or multiverse.