“This hot, primordial soup expanded and cooled, creating a slight asymmetry between matter (slightly more) and antimatter (slightly less). The cooling continued, nuclei formed, and eventually, so did neutral atoms.
These atoms clumped together in gravitationally overdense regions, forming the first stars after tens of millions of years.”
In the beginning, before even the Big Bang, all that we had was space and time, expanding rapidly according to the rules of cosmological inflation. Today, we’ve got an observable Universe full of stars and galaxies, tens of billions of light years across, with at least one instance of intelligent life: on Earth.
The story of how we got to be here was a mystery to philosophers, theologists and poets for all of human history, but advances during the last century have brought that from the realm of the speculative to firm, scientific knowledge. We understand, at least in broad strokes, how the Universe began, evolved, and came to be the way it is today, from before the Big Bang to human intelligence here on Earth.
“Sometime in the distant past, likely when the Universe was less than 2% its current age, the very first galaxy of all formed when massive star clusters merged together, resulting in an unprecedented burst of star formation. The high-energy light from these stars struggles to escape, but the longer-wavelength light can penetrate farther through neutral atoms. The expansion of the Universe redshifts all the light, stretching it far beyond anything Hubble could potentially observe, but next-generation infrared telescopes should be able to catch it. And if we observe the right part of the sky, with the right instruments, for a sufficiently long time to reveal the right details about these objects, we’ll push back the cosmic frontier of the first galaxies even farther.
Somewhere, the most distant, first galaxy of all is out there, waiting to be discovered. As the 2020s approach, we can feel confident that we’ll not only shatter the current cosmic record-holder, but we know exactly how we’ll do it.”
13.8 billion years ago, our Universe as-we-know-it began with the hot Big Bang. There were no stars or galaxies back then; there weren’t even bound structures of any type. Everything was too energetic, and would immediately be destroyed by the unfathomably high temperatures and energies that every particle possessed. Yet, with time, the Universe expanded and cooled. Protons, nuclei, and neutral atoms formed; overdense regions gravitationally pulled-in mass and matter; stars were born, lived, died, and new stars were born in their aftermath. At some point, the first large star clusters merged together, passing a critical threshold and forming the first galaxy in the Universe.
“We still don’t know how life in the Universe got its start, or whether life as we know it is common, rare, or a once-in-a-Universe proposition. But we can be certain that life came about in our cosmos at least once, and that it was built out of the heavy elements made from previous generations of stars. If we look at how stars theoretically form in young star clusters and early galaxies, we could reach that abundance threshold after several hundred million years; all that remains is putting those atoms together in a favorable-to-life arrangement. If we form the molecules necessary for life and put them in an environment conducive to life arising from non-life, suddenly the emergence of biology could have come when the Universe was just a few percent of its current age. The earliest life in the Universe, we must conclude, could have been possible before it was even a billion years old.”
When the Universe was first born, life was absolutely impossible. There were no planets for life to reside on; there were no organic molecules to self-replicate; there were no energy gradients or sources of heat and light; there weren’t even heavy elements or neutral atoms. In order for life to exist, the Universe had quite a bit of work to do.
Our Earth formed after more than 9 billion years of cosmic evolution, and life began on our planet shortly after that. But there’s no reason to believe that Earth is the only world with life on it; in fact, if we put everything we know about the Universe together, many other locations should have gotten there billions of years earlier.
“Over time, galaxies merged together and grew, but small, faint galaxies still remain today. Even in our own Local Group, we’re still discovering galaxies that contain mere thousands of stars, and the number of galaxies we know of have increased to more than 70. The faintest, smallest, most distant galaxies of all are continuing to go undiscovered, but we know they must be there. For the first time, we can scientifically estimate how many galaxies are out there in the Universe.
The next step in the great cosmic puzzle is to find and characterize as many of them as possible, and understand how the Universe grew up. Led by the James Webb Space Telescope and the next generation of ground-based observatories, including LSST, GMT, and the ELT, we’re poised to reveal the hitherto unseen Universe as never before.”
How many galaxies are there in the Universe? If you had asked Carl Sagan a generation ago, the answer might have been something vague, like billions and billions. Just a decade or two ago, people would have guesstimated around 100 billion, as deep surveys from Hubble could give us a count of galaxies both near-and-far in a small region of the sky. But those estimates aren’t necessarily any good, except to serve as lower limits. In order to understand how many galaxies must truly be out there, it requires us to understand both what the Universe is made of and what constitutes a galaxy. Only in the last few years have we reached that level of sophistication, and come up with what we believe, for the first time, is an accurate number.
“For planets of any type, the quasar RX J1131-1231, lensed by rogue planets, holds the record: 3.9 billion light-years distant. The most distant normal star is known as Icarus, 9 billion light-years away, lensed and magnified by a massive galaxy cluster. 23 billion light-years away is the most distant supernova ever seen: SN 1000+0216.”
Our quest to learn about the Universe is a quest of ever-receding horizons. From planets, moons, and other objects in our Solar System to stars, galaxies, quasars, and gamma-ray bursts, we just keep shattering records as far distance goes. Improvements in technology, technique, and increased observing time allow us to reveal things that simply couldn’t be observed previously. Yet we’re by no means done, just because we’ve set a slew of new records in the opening two decades of the 21st century. With the launch of the James Webb Space Telescope, the hope of a Planet Nine, and the advent of 30-meter-class astronomy from the ground, the records we know and adore today may all be in the rear-view mirror just a few years from now.
Could the “big rip” lead to another “Big Bang”? When the universe expands fast enough to tear atoms apart then quarks… At this point would the universe create a quark-gluon soup?
The Universe is expanding, a fact we’ve known since the 1920s. That expansion isn’t just a race between gravity and some initially rapid state of expansion, but is affected by dark energy, which causes that expansion to accelerate. Well, there’s a possibility that dark energy isn’t just a cosmological constant (although it’s consistent with a cosmological constant), but that it increases in strength over time. Rather than expand forever, a Universe with increasing dark energy will end in a Big Rip.
There are the Sketches of the four moons of Jupiter (Io, Europa, Ganymede and Callisto), as seen by Galileo
through his telescope.
The drawing depicts observations from the time period January 7 to 24, 1610.
The above is the sequence of photographs taken by JunoCam aboard the Juno
spacecraft, in June 2016, of Jupiter and the motion of the four Galilean
moons, as the spacecraft approached the planet.
* There are 79 known moons of Jupiter.
“For more than 50 years, no alternative has been able to deliver on all four counts. No alternative can even deliver the Cosmic Microwave Background as we see it today. It isn’t for lack of trying or a lack of good ideas; it’s because this is what the data indicates. Scientists don’t believe in the Big Bang; they conclude it based on the full suite of observations. The last adherents to the ancient, discredited alternatives are at last dying away. The Big Bang is no longer a revolutionary endpoint of the scientific enterprise; it’s the solid foundation we build upon. It’s predictive successes have been overwhelming, and no alternative has yet stepped up to the challenge of matching its scientific accuracy in describing the Universe.”
The last adherents to alternative theories to the Big Bang are at last dying away. Advocates of tired light, steady-state, or plasma cosmologies have ceased arising among the scientific ranks for one reason: these ideas cannot even explain the Cosmic Microwave Background observations, much less the full suite of the four major cornerstones of the Big Bang. When all we had were Hubble’s data and the evidence for the expanding Universe, it was a great idea to explore all the conceivable alternatives. Now that the data has come in, the alternatives have been scientifically falsified, and the Big Bang is the foundation we use as the base for our future theorizing.
Pareidolia is a psychological phenomenon in which the mind responds to a stimulus, usually an image or a sound, by perceiving a familiar pattern where none exists.
These are merely some images of stars and galaxies taken by the Hubble Space Telescope. But what do you see ?