Today our middle-aged Universe looks eerily smooth. Too smooth, in fact.
While a rapid growth spurt in space-time would explain what we see, science needs more than nice ideas. It needs evidence that whittles away contending arguments. We could finally know where to look for
A team of physicists from the Center for Astrophysics Harvard & Smithsonian (CfA) and Harvard University went back to the drawing board on early Universe's evolution to give us a way to help those inflation models stand out from the crowd
"The current situation for inflation is that it's such a "
" No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it. "
Avi Loeb from CfA, We have been convinced for some time that our Universe is expanding ̵
If we press rewind on the universe until it was barely 10 -43 seconds old, we arrive at the limit of what our knowledge of physics can handle. Before that moment?
Running the calculations backward, we also find the Universe would have had a radius of 10 -10 meters at this crucial moment. That sounds tiny, sure, but it's not tiny enough.
The light echoes of the Universe's first moments are still visible in the form of a cosmic microwave background. Oddly, this background radiation looks surprisingly uniform today.
Thermodynamics makes this observation hard to swallow. Such uniformity means zipping from one edge of the Universe to the other, balancing out temperature fluctuations.
For such a balancing act to be remotely feasible, the radius of the newborn Universe at that critical moment would have been magnitudes smaller
This itty-bitty cosmos would have shot through the early childhood at an exponential rate, blowing up to the size of a grain of sand in a few ten thousandths of a second
The story neatly fits what we observe, but so would other explanations where the Universe didn
"In some alternative theories, the size of the universe contracts, some do it very slowly, while others do it very fast," says Harvard physicist Zhong-Zhi Xianyu. "The attributes people have proposed so far to measure usually have a problem distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe."
Did time even exist before the Big Bang ? Was there a kind of reverse Universe? Everybody is welcome to their pet theory on how our universe came to look like it does, but only one can be a winner.
To help decide which ones stay and which ones go, the researchers proposed using observable attributes that we can link with discerning features of inflation-based models
The challenge is knowing how to interpret such observations as a sequence of events. What is needed is a sort of standardized cosmic time stamp that teases out relevant steps, some of which could potentially exclude inflation altogether
"If we imagine all the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played, "says CfA's Xingang Chen
The team suggests a mechanism by which quantum fluctuations can hint at sequences of events that are reflected in patterns of vast cosmic structures.
"These signals will be very subtle to detect," says Chen
"The cosmic microwave background radiation is one such place, and the distribution of galaxies is another one. We have already started to search for these signals and there are some interesting candidates already, but we need more data." cosmologists have also suggested searching for hints of our universe's hidden past in the swirls of light and matter in the sky
Some point to possible 'scars' left by a previous universe's black holes on our cosmic microwave background. Others say we might find signs that the physics-breaking boundary we call the Big Bang never happened.
There are lots of interesting ideas out there explaining how our Universe evolved. (19659002) This research has been accepted for publication by Physical Review Letters .