Category: big bang

Ask Ethan: How Well Has Cosmic Inflation Been …

Ask Ethan: How Well Has Cosmic Inflation Been Verified?

“To what margin of error or what level of statistical significance would you say you say inflation has been verified?”

So, you’ve got an alternative theory to our best mainstream scientific ideas? Well, guess what: those are the same shoes that every scientific idea we accept today were wearing at one point in the distant past. The thing that separates them from the ideas that fell by the wayside were three remarkable feats:

1. They reproduced all the earlier successes of the previous prevailing model.
2. They resolved or explained puzzles or problems that the previous model had no sufficient answer for.
3. And, perhaps most importantly, they made new predictions that we could go out and test about the Universe, and those predictions were proven correct by the appropriate experimental or observational test.

Although most people don’t appreciate it, inflation has hurdled all three bars, and has no fewer than four spectacular predictions that have since been confirmed. Come learn how well cosmic inflation has been verified today!

Could All Our Scientific Knowledge Come Tumbli…

Could All Our Scientific Knowledge Come Tumbling Down Like A House Of Cards?

“Now, think about what would be required to do today to tear down one of our leading scientific theories. It’s not as complicated as you might imagine: all it would take is a single observation of any phenomenon that contradicted the Big Bang’s predictions. Within the context of General Relativity, if you could find a theoretical consequence of the Big Bang that didn’t match up with our observations, we’d truly be in store for a revolution.

But here’s the important part: that won’t mean that everything about the Big Bang is wrong. General Relativity didn’t mean everything about Newtonian gravity was wrong; it simply exposed the limit of where and how Newtonian gravity was successful. It will still be accurate to describe the Universe as having originated from a hot, dense, expanding state; it will still be accurate to describe our observable Universe as being many billions of years old (but not infinite in age); it will still be accurate to talk about the first stars and galaxies, the first neutral atoms, and the first stable atomic nuclei.”

There are a great many people out there who absolutely cannot wait for the day where one of our greatest scientific theories is demonstrated to be wrong. Where an experiment or observation comes in that cannot be reconciled with our leading ideas of how the Universe works. At last, perhaps an unintuitive part of our existence, like relativity or quantum mechanics, might be replaced with something that’s a closer approximation of our actual reality. But that won’t invalidate what we already know; it will merely extend it. 

Scientific revolutions aren’t what most people think, but they are going to come, eventually. Here’s what the revolution will actually look like.

Could All Our Scientific Knowledge Come Tumbli…

Could All Our Scientific Knowledge Come Tumbling Down Like A House Of Cards?

“Now, think about what would be required to do today to tear down one of our leading scientific theories. It’s not as complicated as you might imagine: all it would take is a single observation of any phenomenon that contradicted the Big Bang’s predictions. Within the context of General Relativity, if you could find a theoretical consequence of the Big Bang that didn’t match up with our observations, we’d truly be in store for a revolution.

But here’s the important part: that won’t mean that everything about the Big Bang is wrong. General Relativity didn’t mean everything about Newtonian gravity was wrong; it simply exposed the limit of where and how Newtonian gravity was successful. It will still be accurate to describe the Universe as having originated from a hot, dense, expanding state; it will still be accurate to describe our observable Universe as being many billions of years old (but not infinite in age); it will still be accurate to talk about the first stars and galaxies, the first neutral atoms, and the first stable atomic nuclei.”

There are a great many people out there who absolutely cannot wait for the day where one of our greatest scientific theories is demonstrated to be wrong. Where an experiment or observation comes in that cannot be reconciled with our leading ideas of how the Universe works. At last, perhaps an unintuitive part of our existence, like relativity or quantum mechanics, might be replaced with something that’s a closer approximation of our actual reality. But that won’t invalidate what we already know; it will merely extend it. 

Scientific revolutions aren’t what most people think, but they are going to come, eventually. Here’s what the revolution will actually look like.

Earliest Signal Ever: Scientists Find Relic Ne…

Earliest Signal Ever: Scientists Find Relic Neutrinos From 1 Second After The Big Bang

“This cosmic neutrino background (CNB) has been theorized to exist for practically as long as the Big Bang has been around, but has never been directly detected. Because neutrinos have such a tiny cross-section with other particles, we generally need them to be at very high energies in order to see them. The energy imparted to each neutrino leftover from the Big Bang corresponds to only 168 micro-electron-volts (μeV) today, while the neutrinos we can measure have many billions of times as much energy. No proposed experiments are theoretically capable of seeing them.

But there are two ways to see them indirectly: from their effects on the CMB and on the large-scale structure of the Universe.”

When we look at the Universe, one of our great cosmic quests is to go earlier than ever before. To the first galaxies, the first stars, the first atoms, and even earlier, if possible. That’s how we put the best theories of our cosmic origins, like the Big Bang, to the ultimate test. The earliest observable signal from the classical Big Bang is a bath of neutrinos and antineutrinos, which froze-out when the Universe was just 1 second old. For generations, this was regarded as an undetectable prediction, but there are two ways that they might affect observable features of the Universe.

It’s 2019, and we’ve now seen them both. The results? The cosmic neutrino background looks exactly like the Big Bang predicts. Come get the incredible scoop!

The Five Ways The Universe Might End

The Five Ways The Universe Might End

4.) Dark energy could transition into another form of energy, rejuvenating the Universe. If dark energy doesn’t decay, but instead remains constant or even strengthens, there’s another possibility that arises. This energy, inherent to the fabric of space today, may not remain in that form forever. Instead, it could get converted into matter-and-radiation, similar to what occurred when cosmic inflation ended and the hot Big Bang began.

If dark energy remains constant until that point, it will create a very, very cold and diffuse version of the hot Big Bang, where only neutrinos and photons can self-create. But if dark energy increases in strength, it could lead to an inflation-like state followed by a new, truly hot Big Bang once again. This is the most straightforward way to rejuvenate the Universe, and create a cyclic-like set of parameters, where the Universe gets another chance to behave like ours did.”

Based on the best knowledge and data that we have today, it’s clear that the Universe isn’t just expansion, but the expansion is accelerating. Does this determine the fate of our Universe unambiguously? If we extrapolate what the data indicates about dark energy into the future, we fully expect that structures (like our local group) that are gravitationally bound today will remain so into the future, but that larger-scale structures which are unbound (like our supercluster, Laniakea) will eventually dissociate. But extrapolation is tricky, and assumes that dark energy doesn’t change over time.

If we allow the possibility of change, though, many more possibilities arise. Here are the five most likely, and how we’ll distinguish between them!

Ask Ethan: Are We Deceiving Ourselves By Searc…

Ask Ethan: Are We Deceiving Ourselves By Searching For B-Modes From Inflation?

“I have a question about B-Modes. I’ve read Dr. Keating’s book, Losing the Nobel Prize. In the book, he details his team’s search for B-modes, and claims this would be smoking gun for inflation. Dr. Hossenfelder, in a blog post, says this isn’t true and there are other ways to produce B-modes. What is the correct view?”

Perhaps the greatest danger in science is to go out, look for a predicted effect, find it, and declare victory. Why is that such a danger? Because your idea for how the effect was generated might not be the only possibility, or even the most accurate one. If I have a wild new theory that predicts some far-distant star will have a habitable planet around it, the detection of that planet does not necessarily mean the wild new theory is correct. When it comes to the origin of the Universe, our leading theory is cosmic inflation, which predicts a B-mode polarization signature in the cosmic microwave background. Are there other ways to generate those B-mode signatures, though? And if we find them, does that mean that inflation is correct, or might that be a premature conclusion?

This is a key problem, and a hard problem, in theoretical physics. But we can say a whole lot that’s intelligent on this topic, and still be correct. Let’s find out.

What Was It Like When The Universe Made The Ve…

What Was It Like When The Universe Made The Very First Galaxies?

“The first galaxies required a large number of steps to happen first: they needed stars and star clusters to form, and they needed for gravity to bring these star clusters together into larger clumps. But once you make them, they are now the largest structures, and can continue to grow, attracting not only star clusters and gas, but additional small galaxies. The cosmic web has taken its first major step up, and will continue to grow further, and more complex, over the hundreds of millions and billions of years to follow.”

For millions upon millions of years, there were no stars in the Universe. As the first one finally formed, the star clusters that birthed them became the largest structures in the Universe. Yet these were too small and limited to be considered galaxies. For that, we need more than one massive star cluster in the same place. We need for them to merge, triggering a starburst and creating a larger, more luminous object. It takes much longer for that to happen than to merely form stars, and the Universe was a very different place by then. The Big Bang may have started everything off uniformly and without anything more than the seeds of structure, but gravity, and time, are awfully powerful tools.

Come learn what the Universe was like when we made the very first galaxies. It’s a story you won’t soon forget!

Ask Ethan: Could The Big Rip Lead To Another B…

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 How We Know The Cosmic Microwave Backg…

This Is How We Know The Cosmic Microwave Background Comes From The Big Bang

“The outer layers are extremely tenuous and rarified, and the radiation we receive here on Earth doesn’t all originate from the very edge of that plasma. Instead, much of what we see originates from about the first 500 kilometers, where the interior layers are significantly hotter than the outermost ones. The light coming from our Sun — or any star, for that matter — is not a blackbody, but the sum of many blackbodies that vary in temperature by many hundreds of degrees.

It’s only when you add all these blackbodies together that you can reproduce the light we see coming from our parent star. The cosmic microwave background, when we look at its spectrum in detail, is a far more perfect blackbody than any star could ever hope to be.”

If you get your science from the internet, you might hear about all sorts of alternatives to the Big Bang. Grandiose claims are often made, decrying the Big Bang as a religion that can never be falsified, while simultaneously touting ideas that most scientists discarded decades or even centuries ago.

But there is no ideology at play; science is a game that we play with predictive power and evidence. The Big Bang makes explicit predictions, and so do alternative ideas that rely on atomic emissions, reflected starlight, photonic energy loss, or heated-up dust.

We can look at every idea we can conceive of, but in the end, only one matches what we observe. Here’s how the Cosmic Microwave Background points to the Big Bang, and away from every other alternative.

What Was It Like When The First Stars Began Il…

What Was It Like When The First Stars Began Illuminating The Universe?

“After the Big Bang, the Universe was dark for millions upon millions of years; after the glow of the Big Bang fades away, there’s nothing that human eyes could see. But when the first wave of star formation happens, growing in a cosmic crescendo across the visible Universe, starlight struggles to get out. The fog of neutral atoms permeating all of space absorbs most of it, but gets ionized in the process. Some of this reionized matter will become neutral again, emitting light when it does, including the 21-cm line over timescales of ~10 million years.

But it takes far more than the very first stars to truly turn on the lights in the Universe. For that, we need more than just the first stars; we need them to live, burn through their fuel, die, and give rise to so much more. The first stars aren’t the end; they’re the beginning of the cosmic story that gives rise to us.”

We like to think of the Universe evolving as a story that follows a particular order: first we had the Big Bang, then things expanded and cooled, then gravitation pulled things into clumps, we formed stars, they lived and died, and now here we are. But in reality, things are messier than that! The very first stars didn’t immediately spread light throughout the Universe, but instead had a cosmic ocean of neutral atoms to contend with: one that they weren’t energetic enough or numerous enough to break through. The first stars in the Universe fought a battle against the clumping, neutral, atomic-based matter that surrounded them… and lost.

Come get the valiant but ultimately unsuccessful story of the first stars in the Universe, and learn why “letting there be light” didn’t illuminate the Universe!