The Universe is a mysterious place. We don't know why it exists, and there are a lot of unanswered questions as to the how. But what if it was created, on purpose, by an intelligent entity? Is there some way we could find out?

In 2005, a pair of physicists proposed that if there was a Creator, they could have encoded a message in the background radiation of the Universe, left over from when light was first unleashed to flow freely through space. This light is called the cosmic microwave background (CMB).

Now, astrophysicist Michael Hippke of Sonneberg Observatory in Germany and Breakthrough Listen has gone looking for this message, translating temperature variations in the CMB into a binary bitstream.

What he recovered appears to be utterly meaningless.

Hippke's paper describing his methods and findings has been uploaded to pre-print server arXiv, (and is thus yet to be peer-reviewed); the work includes the extracted bitstream so other interested parties can study it for themselves.

The cosmic microwave background is an incredibly useful relic of the early Universe. It dates back to around 380,000 years after the Big Bang. Prior to this, the Universe was completely dark and opaque, so hot and dense that atoms couldn't form; protons and electrons were flying around in the form of ionised plasma.

As the Universe cooled and expanded, those protons and electrons could combine to form neutral hydrogen atoms in what we call the epoch of recombination. Space became clear, and light could move freely through it for the first time.

This first light is still detectable today, albeit very faintly, suffusing all known space. That's the CMB. Since the early Universe was not uniform, density variations at the epoch of recombination manifest today in very slight fluctuations in the temperature of the CMB.

Because of this ubiquity, theoretical physicists Stephen Hsu of the University of Oregon and Anthony Zee of the University of California, Santa Barbara argued - entirely theoretically - that the CMB would make the perfect billboard on which to leave a message that would be visible to all technological civilisations in the Universe.

"Our work does not support the Intelligent Design movement in any way whatsoever," they wrote in their 2006 paper, "but asks, and attempts to answer, the entirely scientific question of what the medium and message might be IF there was actually a message."

They proposed that a binary message could be encoded in the temperature variations in the CMB. This is what Hippke has attempted to find - first by addressing the claims made by Hsu and Zee, and then by using the data to try and find a message.

"[Hsu and Zee's] assumptions were, first, that some superior Being created the Universe. Second, that the Creator actually wanted to notify us that the Universe was intentionally created," Hippke wrote.

"Then, the question is: How would they send a message? The CMB is the obvious choice, because it is the largest billboard in the sky, and is visible to all technological civilisations. Hsu and Zee continue to argue that a message in the CMB would be identical to all observers across space and time, and that the information content can be reasonably large (thousands of bits)."

There are, Hippke found, several problems with these claims. The first is that the CMB is still cooling. It started at about 3,000 Kelvin; now, 13.4 billion years later, it's 2.7 Kelvin. As the Universe continues to age, eventually the CMB will become undetectable. It may take another 10 duodecillion years (1040), but the CMB will fade.

Putting that aside, physicists found back in 2006, in response to Hsu and Zee's paper, that it's extremely unlikely the CMB would appear exactly the same in the sky to different observers in different locations. In addition, Hippke argues, we can't see the entire CMB because of foreground emission from the Milky Way. And we only have one sky to measure, which presents an inherent statistical uncertainty in every cosmological observation we make.

Based on these constraints, Hippke estimates that the information content would be much lower than that proposed by Hsu and Zee - just 1,000 bits. This gave him a good framework for the actual search for the message.

The Planck satellite and the Wilkinson Microwave Anisotropy Probe (WMAP) both observed and recorded the temperature fluctuations in the CMB. It was from these datasets that Hippke extracted his bitstream, comparing the results from each dataset to find matching bits.

The first 500 bits of the message are pictured below. The values in black were identical in both Planck and WMAP datasets, and are thought to be accurate with 90 percent probability. The values in red deviate; Hippke chose the Planck values, and they are only accurate with 60 percent probability.

binary(M. Hippke, arXiv, 2020)

Changing the values, he found, did not improve the situation. Searching the On-Line Encyclopedia of Integer Sequences returned no convincing results, nor did shifting the data to approximate the infinite future.

"I find no meaningful message in the actual bit-stream," Hippke wrote.

"We may conclude that there is no obvious message on the CMB sky. Yet it remains unclear whether there is (was) a Creator, whether we live in a simulation, or whether the message is printed correctly in the previous section, but we fail to understand it."

Whether or not any of these options is the case, the CMB has a lot more to tell us, as beautifully noted in a 2005 response to Hsu and Zee.

"The CMB sky does encode a wealth of information about the structure of the cosmos and possibly about the nature of physics at the highest energy levels," wrote physicists Douglas Scott and James Zibin of the University of British Columbia.

"The Universe has left us a message all on its own."

Hippke's paper can be read in full on arXiv.