This Is How We Know There Are Two Trillion Galaxies In The Universe
“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.
That number? Two trillion. There are two trillion galaxies in the Universe. This is the story of how we know.
These Are The Most Distant Objects We’ve Ever Discovered In The Universe
“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.
What are the most distant objects of all different types in the Universe? Get the 2018 update right now!
Ask Ethan: Could The Big Rip Lead To Another Big Bang?
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.
But is it possible, rather than ripping everything, including space itself, apart, it rejuvenates the Universe, and leads to a new Big Bang? Find out what it takes!
This Is Why There Are No Alternatives To The Big Bang
“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.
This may disappoint some, but for the scientifically-minded among us, it’s a monument to the success of a fantastic theory. Here’s the scientific story of why no alternatives remain.
One Universe Is Not Enough
“If you accept that inflation is a stage that occurred in the Universe’s past prior to the hot Big Bang, and that the Universe itself is inherently quantum in nature, the existence of a multiverse is unavoidable. Even though we cannot observe these other Universes, we can observe a huge amount of evidence for inflation, indirectly pointing to its inevitability. We can also observe a huge amount of evidence that the Universe itself is quantum, even though we have no proof that inflation itself behaves as a quantum field. If you put these pieces together, it unambiguously leads to the prediction that our Universe should be only one of countlessly many Universes, all embedded in an eternally inflating, expanding background. One Universe is not enough. Even though we cannot detect it, the prediction of a multiverse is unavoidable.”
When Carl Sagan’s Cosmos began, the first words you heard were, “The cosmos is all there is, or was, or will be.” Only… what if it weren’t? What if what we know as our cosmos, i.e., the entire Universe, were only one of countlessly many, all embedded in a strange spacetime that was continuously creating more of them? This sounds like some sort of strange speculation, but it’s actually an unavoidable consequence of two of our best theories put together: cosmic inflation and quantum physics. Combine them, and you get a multiverse.
This doesn’t mean the multiverse is the answer to all our problems; far from it. But it does mean that one Universe is not enough. Come find out why!
The Universe Is Disappearing, And There’s Nothing We Can Do To Stop It
“Of the estimated two trillion galaxies in our Universe today, only about 3% of them are still reachable from the point of view of the Milky Way. This also means that 97% of the galaxies in our observable Universe are already out of humanity’s reach, owing to the accelerated expansion of the Universe caused by dark energy. Every galaxy beyond our local group, as time goes on, is destined for that same fate.
Unless we develop the capacity for intergalactic travel and head out to other galaxy groups and clusters, humanity will forever be stuck in our local group. As time goes on, our ability to even send or receive signals to what lies beyond in the great cosmic ocean will fade from view. The accelerated expansion of the Universe is relentless, and the gravity we have isn’t strong enough to overcome it. The Universe is disappearing, and there’s nothing we can do to stop it.”
One of the most profound discoveries about the Universe occurred just 20 years ago. Not only was the Universe expanding, with distant galaxies getting farther and farther away as time goes on, but that expansion was accelerating. Take a look at any galaxy that isn’t gravitationally bound to our own, and if you watch it as time goes on, it will appear to move away from us faster and faster. At some point, when it gets to about 15 billion light years away from us, it will appear to recede faster than the speed of light. When it reaches that point, it means that anything that occurs within it won’t be viewable by us, and that if we left immediately, even at the speed of light, we’d never reach it.
Moreover, with every second that goes by, approximately 20,000 new stars cross that threshold into unreachability. The Universe is disappearing, and there’s nothing we can do about it.
What Was It Like When We First Made Protons And Neutrons?
“But at this stage, the biggest new thing that occurs is that particles are no longer individual-and-free on all scales. Instead, for the first time, the Universe has created a stable, bound state of multiple particles. A proton is two up and one down quark, bound by gluons, while a neutron is one up and two down quarks, bound by gluons. Only because we created more matter than antimatter do we have a Universe that has protons and neutrons left over; only because the Higgs gave rest mass to the fundamental particles do we get these bound, atomic nuclei.
Owing to the nature of the strong force, and the tremendous binding energy that occurs in these stretched-spring-like interactions between the quarks, the masses of the proton and neutron are some 100 times heavier than the quarks that make them up. The Higgs gave mass to the Universe, but confinement is what gives us 99% of our mass. Without protons and neutrons, our Universe would never be the same.”
The very early Universe looks nothing like our Universe today. Not only are there no stars or galaxies, but there weren’t any atoms or atomic nuclei. If we go back early enough, there weren’t even protons or neutrons, but free quarks (and antiquarks) instead. This era lasted for just 10-to-20 microseconds in the early Universe, but the story of how we went from a quark-gluon plasma to a Universe filled with protons and neutrons is a fascinating true part of our shared cosmic history.
Here’s what the Universe was like when we first made protons and neutrons, along with a list of all the things we needed to line up to lead to the Universe we recognize today!
How The Planck Satellite Forever Changed Our View Of The Universe
“Most importantly, a spectacular agreement to a never-before-achieved precision now exists between the CMB we observe and the theoretical predictions of a Universe with 5% normal matter, 27% dark matter, and 68% dark energy. There might be wiggle room of 1-2% in some of those numbers, but a Universe without dark matter and dark energy, both, in great abundance, is a no-go in the face of these observations. They’re real, they’re necessary, and their predictions match the full suite of data perfectly.
Inflation, neutrino physics, and the Big Bang have additional pieces confirming them, while alternatives and specific variants are better constrained. Most definitively, the Planck collaboration states, “We find no compelling evidence for extensions to the base-ΛCDM model.” At last, we can state, with extraordinary confidence, what the Universe is made of.”
For centuries, the question of what the Universe was made of was one of the most unknowable wonders of existence. This week, the Planck collaboration, whose team made the most accurate, precision measurements of the Big Bang’s leftover glow, released their final results, providing unprecedented answers to that question. We now know what the Universe is made of, how old it is, how fast it’s expanding, and a whole suite of other information about it, better than we’ve ever known before. The Planck satellite has revolutionized our view of the Universe, and we’re unlikely to ever do better using this line of inquiry.
How has our view of the Universe changed as a result of Planck? Come find out today!
What Was It Like When The Universe First Created More Matter Than Antimatter?
“This is only one of three known, viable scenarios that could lead to the matter-rich Universe we inhabit today, with the other two involving new neutrino physics or new physics at the electroweak scale, respectively. Yet in all cases, it’s the out-of-equilibrium nature of the early Universe, which creates everything allowable at high energies and then cools to an unstable state, which enables the creation of more matter than antimatter. We can start with a completely symmetric Universe in an extremely hot state, and just by cooling and expanding, wind up with one that becomes matter-dominated. The Universe didn’t need to be born with an excess of matter over antimatter; the Big Bang can spontaneously make one from nothing. The only open question, exactly, is how.”
One of the biggest unsolved questions in physics today is how the Universe came to be filled with matter and not antimatter. After all, the laws of physics are completely matter-antimatter symmetric, and yet when we look at what we have today, every planet, star, and galaxy is made of matter and not antimatter. How did it come to be this way? The young, hot, but rapidly expanding-and-cooling Universe gives us all the ingredients we need for this to occur. We are certain of the exact mechanism, but theoretically, there are some enticing possibilities. Here’s a walk through one of those scenarios in great detail, but expressed so simply that even someone with no physics knowledge can follow it.
Here’s what the Universe was like when it was matter-antimatter symmetric, along with how it could have become matter-rich without breaking the laws of physics.
What Is (And Isn’t) Scientific About The Multiverse
“In this physical Universe, it’s important to observe all that we can, and to measure every bit of knowledge we can glean. Only from the full suite of data available can we hope to ever draw valid, scientific conclusions about the nature of our Universe. Some of those conclusions will have implications that we may not be able to measure: the existence of the multiverse arises from that. But when people then contend that they can draw conclusions about fundamental constants, the laws of physics, or the values of string vacua, they’re no longer doing science; they’re speculating. Wishful thinking is no substitute for data, experiments, or observables. Until we have those, be aware that the multiverse is a consequence of the best science we have available today, but it doesn’t make any scientific predictions we can put to the test.”
The multiverse is one of the most controversial topics in science today. On the one hand, it’s a remarkable story: perhaps our Universe, even beyond what we can observe, isn’t the only one out there. Perhaps there are many others, all generated in some early, pre-Big-Bang state, all disconnected from one another. This isn’t speculation; this part of it arises by combining the two well-established theories of cosmic inflation and quantum physics. Yet if we start trying to go further, such as making statements about the laws of physics, the values of fundamental constants, or the suitability of our Universe for life, we’ve lept out of the realm of science and into wild speculation or, worse, wishful thinking.
Come find out what is (and isn’t) scientific about the multiverse, and add a little bit of nuance to something you likely already have strong opinions on!