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Taming the multiverse: Stephen Hawking’s final theory about the big bang

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Professor Stephen Hawking’s final theory on the origin of the universe, which he worked on in collaboration with Professor Thomas Hertog from KU Leuven, has been published in the Journal of High Energy Physics . 

We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes. Stephen Hawking

The theory, which was submitted for publication before Hawking’s death earlier this year, is based on string theory and predicts the universe is finite and far simpler than many current theories about the big bang say.

Professor Hertog, whose work has been supported by the European Research Council, first announced the new theory at a conference at the University of Cambridge in July of last year, organised on the occasion of Professor Hawking’s 75 th birthday.

Modern theories of the big bang predict that our local universe came into existence with a brief burst of inflation – in other words, a tiny fraction of a second after the big bang itself, the universe expanded at an exponential rate. It is widely believed, however, that once inflation starts, there are regions where it never stops. It is thought that quantum effects can keep inflation going forever in some regions of the universe so that globally, inflation is eternal. The observable part of our universe would then be just a hospitable pocket universe, a region in which inflation has ended and stars and galaxies formed.

“The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean,” said Hawking in an interview last autumn. “The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse. But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite the theory can’t be tested. ”

In their new paper, Hawking and Hertog say this account of eternal inflation as a theory of the big bang is wrong. “The problem with the usual account of eternal inflation is that it assumes an existing background universe that evolves according to Einstein’s theory of general relativity and treats the quantum effects as small fluctuations around this,” said Hertog. “However, the dynamics of eternal inflation wipes out the separation between classical and quantum physics. As a consequence, Einstein’s theory breaks down in eternal inflation.”

“We predict that our universe, on the largest scales, is reasonably smooth and globally finite. So it is not a fractal structure,” said Hawking.

The theory of eternal inflation that Hawking and Hertog put forward is based on string theory: a branch of theoretical physics that attempts to reconcile gravity and general relativity with quantum physics, in part by describing the fundamental constituents of the universe as tiny vibrating strings. Their approach uses the string theory concept of holography, which postulates that the universe is a large and complex hologram: physical reality in certain 3D spaces can be mathematically reduced to 2D projections on a surface.

Hawking and Hertog developed a variation of this concept of holography to project out the time dimension in eternal inflation. This enabled them to describe eternal inflation without having to rely on Einstein’ theory. In the new theory, eternal inflation is reduced to a timeless state defined on a spatial surface at the beginning of time.

“When we trace the evolution of our universe backwards in time, at some point we arrive at the threshold of eternal inflation, where our familiar notion of time ceases to have any meaning,” said Hertog.

Hawking’s earlier ‘no boundary theory’ predicted that if you go back in time to the beginning of the universe, the universe shrinks and closes off like a sphere, but this new theory represents a step away from the earlier work. “Now we’re saying that there is a boundary in our past,” said Hertog.

Hertog and Hawking used their new theory to derive more reliable predictions about the global structure of the universe. They predicted the universe that emerges from eternal inflation on the past boundary is finite and far simpler than the infinite fractal structure predicted by the old theory of eternal inflation.

Their results, if confirmed by further work, would have far-reaching implications for the multiverse paradigm. “We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes,” said Hawking.

This makes the theory more predictive and testable.

Hertog now plans to study the implications of the new theory on smaller scales that are within reach of our space telescopes. He believes that primordial gravitational waves – ripples in spacetime – generated at the exit from eternal inflation constitute the most promising “smoking gun” to test the model. The expansion of our universe since the beginning means such gravitational waves would have very long wavelengths, outside the range of the current LIGO detectors. But they might be heard by the planned European space-based gravitational wave observatory, LISA, or seen in future experiments measuring the cosmic microwave background.

Reference: S.W. Hawking and Thomas Hertog. ‘ A Smooth Exit from Eternal Inflation? ’’ Journal of High-Energy Physics (2018). DOI: 10.1007/JHEP04(2018)147

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• Published: 21 December 2000

The Big Bang is bang on

• John Bahcall 1  

Nature volume  408 ,  pages 916–917 ( 2000 ) Cite this article

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Did the Universe really start in a hot Big Bang? New measurements of the temperature of the Universe when it was young provide exciting confirmation that it was indeed hotter in the past.

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New Paper Argues That the Universe Began with Two Big Bangs

Bang bang all over the Universe.

Two cosmological mysteries continue to fascinate scientists and science enthusiasts alike. The first is understanding in detail how the Universe came into existence. The second is the nature of dark matter , a substance which is thought to be far more prevalent than all the stars and galaxies in the Universe. A recent paper explores a possible intricate connection between these two phenomena and proposes that the beginning of the Universe included not one, but two, Big Bangs.

To understand the implications of this interesting new idea, we must first consider the prevailing understanding of both the Big Bang and dark matter.

In the Beginning

According to the accepted theory of the beginning of the Universe, a tiny fraction of a second after the Universe began, there was a period called “ inflation .” During inflation, the Universe expanded very quickly—faster than the speed of light. Inflation was driven by the existence of a form of energy called “ vacuum energy .” Inflation persisted only for a very short time, lasting far less than a second, during which our visible Universe expanded from a size smaller than an atom to about the size of a football stadium.

As the inflation period ended, the energy driving the expansion changed form and created the matter that evolved into the Universe we see today. The moment that the Universe transitioned from being governed by inflation to being filled with a hot and dense plasma is the beginning of what scientists call the Big Bang .

The other interesting phenomenon is dark matter, a proposed substance that, if it exists, explains some observed astronomical anomalies. Galaxies, like people, are made of ordinary matter, and we can use the laws of physics to predict how they should move. However, when astronomers study the heavens, they see some surprises. One example is that galaxies rotate faster than expected. A second example is that certain galaxy clusters shouldn’t exist, as individual galaxies are moving so fast that they should escape the gravitational attraction of their neighbors.

While there are several possible explanations for these and other astronomical mysteries, most scientists believe that in addition to the visible matter of stars and galaxies, there exists another form of matter, called dark matter . If dark matter exists, it is five times more prevalent than ordinary matter, and this additional mass exerts additional gravity, which means that galaxies can rotate faster and move more quickly than expected. The only way researchers have inferred the existence of dark matter is by how it affects nearby ordinary matter through gravitational attraction. There is no evidence that dark matter interacts in any other way.

Two Big Bangs

In the prevailing theory of the origins of the Universe, both familiar matter and dark matter were created at the same time, less than a second after the Universe began. Effectively, it is thought that a series of steps converted the energy that governed inflation into matter and dark matter.

However, the new paper raises a different possibility. Given that ordinary matter and dark matter only interact via gravity, perhaps they didn’t appear at the same time in the early Universe. This paper suggests that while the energy of inflation eventually transitioned into ordinary matter, dark matter might have had a different origin. In the new theory, there was a second form of energy, similar to the vacuum energy that caused inflation, but this new energy was dark vacuum energy, which became the origin of dark matter.

If it is true that ordinary vacuum energy and dark vacuum energy are different, it is not necessary that they convert into particles at the same time. Indeed, the new theory suggests that instead of being created a split second after the Universe began, vacuum dark energy could have created dark matter particles as long as a month later. This is still a short time compared to the lifetime of the Universe, but a long time compared to the timescales involved in particle physics .

Testing the Idea

Can this new idea be tested? If dark matter and ordinary matter interact only via gravity , the dozens of dark matter experiments currently underway will fail. All of them depend on dark matter and ordinary matter experiencing some sort of interaction beyond gravity. Thus, if this new theory is right, that would be disappointing.

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However, when the dark vacuum energy transitioned into dark matter particles, that change of energy would have shaken the structure of space and time, creating gravitational waves that would fill the Universe. Metaphorically at least, this would appear to be a “hum” in the structure of space.

Very precise experiments have already reported detecting a cosmic hum, but a bit of caution is warranted. There are several astronomical phenomena that can generate a similar hum. Thus, the recent detection is not a confirmation this new theory. That will take more data and far more sophisticated analysis. However, the fact that facilities exist that can detect the right kind of gravitational waves gives us hope that researchers will be able to confirm or disprove this idea within a few years.

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Dynamical screening effects on big bang nucleosynthesis

Eunseok Hwang 1 , Dukjae Jang 2 , Kiwan Park 1 , Motohiko Kusakabe 3,4 , Toshitaka Kajino 3,4,5 , A. Baha Balantekin 6,4 , Tomoyuki Maruyama 7,4 , Chang-Mo Ryu 2,8 and Myung-Ki Cheoun 1,3,4

Published 8 November 2021 • © 2021 IOP Publishing Ltd and Sissa Medialab Journal of Cosmology and Astroparticle Physics , Volume 2021 , November 2021 Citation Eunseok Hwang et al JCAP11(2021)017 DOI 10.1088/1475-7516/2021/11/017

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1 Department of Physics and OMEG Institute, Soongsil University, Seoul 156-743, Republic of Korea

2 Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 61005, Republic of Korea

3 School of Physics and International Research Center for Big-Bang Cosmology and Element Genesis, Beihang University, Beijing 100083, China

4 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

5 The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

6 Physics Department, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706, U.S.A.

7 College of Bioresource Sciences, Nihon University, Fujisawa 252-0880, Kanagawa-ken, Japan

8 Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea

• Received 17 May 2021
• Accepted 18 October 2021
• Published 8 November 2021

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A moving ion in plasma creates a deformed electric potential depending on the ion velocity, which leads to the distinct screening effect compared to the standard static Salpeter formula. In this paper, adopting the test charge method, we explore the dynamical screening effects on big bang nucleosynthesis (BBN). We find that the high temperature in the early universe causes the ion velocity to be faster than the solar condition so that the electric potential is effectively polarized. However, the low density of background plasma components significantly suppresses the dynamical screening effects on thermonuclear reaction rates during the BBN epoch. We compare our results with several thermonuclear reaction rates for solar fusion considering the dynamical screening effects. Also, we discuss the additional plasma properties in other astrophysical sites for the possible expansion from the present calculation in the future.

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Title: big bang nucleosynthesis as a probe of new physics.

Abstract: Big bang nucleosynthesis (BBN), an epoch of primordial nuclear transformations in the expanding Universe, has left an observable imprint in the abundances of light elements. Precision observations of such abundances, combined with high-accuracy predictions, provide a nontrivial test of the hot big bang and probe non-standard cosmological and particle physics scenarios. We give an overview of BBN sensitivity to different classes of new physics: new particle or field degrees of freedom, time-varying couplings, decaying or annihilating massive particles leading to non-thermal processes, and catalysis of BBN by charged relics.

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What is the Big Bang Theory?

The Big Bang Theory explains how the universe began.

The birth of the universe

• Big Bang theory FAQs

Modelling the Big Bang

• How old is the universe?

What are gravitational waves?

• Expansion vs explosion

The expansion of the universe

Jwst and the big bang.

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The Big Bang Theory is the leading explanation for how the universe began. Simply put, it says the universe as we know it started with an infinitely hot and dense single point that inflated and stretched — first at unimaginable speeds, and then at a more measurable rate — over the next 13.7 billion years to the still-expanding cosmos that we know today.

Existing technology doesn't yet allow astronomers to literally peer back at the universe's birth, much of what we understand about the Big Bang comes from mathematical formulas and models. Astronomers can, however, see the "echo" of the expansion through a phenomenon known as the cosmic microwave background .

While the majority of the astronomical community accepts the theory, there are some theorists who have alternative explanations besides the Big Bang — such as eternal inflation or an oscillating universe.

Related: What happened before the Big Bang?

Around 13.7 billion years ago, everything in the entire universe was condensed in an infinitesimally small singularity, a point of infinite denseness and heat. 

Suddenly, an explosive expansion began, ballooning our universe outwards faster than the speed of light . This was a period of cosmic inflation that lasted mere fractions of a second — about 10^-32 of a second, according to physicist Alan Guth’s 1980 theory that changed the way we think about the Big Bang forever. 

When cosmic inflation came to a sudden and still-mysterious end, the more classic descriptions of the Big Bang took hold. A flood of matter and radiation, known as "reheating," began populating our universe with the stuff we know today: particles, atoms, the stuff that would become stars and galaxies and so on.

This all happened within just the first second after the universe began, when the temperature of everything was still insanely hot, at about 10 billion degrees Fahrenheit (5.5 billion Celsius), according to NASA . The cosmos now contained a vast array of fundamental particles such as neutrons, electrons and protons — the raw materials that would become the building blocks for everything that exists today.

This early "soup" would have been impossible to actually see because it couldn't hold visible light. "The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds," NASA stated. Over time, however, these free electrons met up with nuclei and created neutral atoms or atoms with equal positive and negative electric charges. 

This allowed light to finally shine through, about 380,000 years after the Big Bang.

Sometimes called the "afterglow" of the Big Bang, this light is more properly known as the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948 but was found only by accident almost 20 years later .

Related: Peering back to the Big Bang & early universe

This accidental discovery happened when Arno Penzias and Robert Wilson, both of Bell Telephone Laboratories in New Jersey, were building a radio receiver in 1965 and picked up higher-than-expected temperatures, according to a NASA article . At first, they thought the anomaly was due to pigeons trying to roost inside the antenna and their waste, but they cleaned up the mess and killed the pigeons and the anomaly persisted.

Simultaneously, a Princeton University team led by Robert Dicke was trying to find evidence of the CMB and realized that Penzias and Wilson had stumbled upon it with their strange observations. The two groups each published papers in the Astrophysical Journal in 1965.

Big Bang theory FAQs answered by an expert

We asked Jason Steffens, assistant professor of physics and astronomy at the University of Nevada, Las Vegas, a few frequently asked questions about the Big Bang Theory. 

Jason Steffens is an assistant professor of physics and astronomy at the University of Nevada, Las Vegas.

Has the Big Bang Theory been proven?

This isn't really a statement that we can make in general. The best we can do is say that there is strong evidence for the Big Bang Theory and that every test we throw at it comes back in support of the theory. Mathematicians prove things, but scientists can only say that the evidence supports a theory with some degree of confidence that is always less than 100%.

So, a short answer to a slightly different question is that all of the observational evidence that we've gathered is consistent with the predictions of the Big Bang Theory. The three most important observations are:

1) The Hubble Law shows that distant objects are receding from us at a rate proportional to their distance — which occurs when there is uniform expansion in all directions. This implies a history where everything was closer together.

2) The properties of the cosmic microwave background radiation (CMB). This shows that the universe went through a transition from an ionized gas (a plasma) and a neutral gas. Such a transition implies a hot, dense early universe that cooled as it expanded. This transition happened after about 400,000 years following the Big Bang.

3) The relative abundances of light elements (He-4, He-3, Li-7, and Deuterium). These were formed during the era of Big Bang Nucleosynthesis (BBN) in the first few minutes after the Big Bang. Their abundances show that the universe was really hot and really dense in the past (as opposed to the conditions when the CMB was formed, which was just regular hot and dense — there's about a factor of a million difference in temperature between when BBN occurred and when the CMB occurred).

Is there any occurrence that contradicts the Big Bang Theory?

Not that I know of. There are some issues that arise with the simplest model of the Big Bang, but those can be resolved by invoking a physical process that is still consistent with the basic premise of the Big Bang Theory. Specifically, the fact that the CMB temperature is the same everywhere, that the universe does not appear to have any curvature, and that density fluctuations from quantum mechanical predictions do not produce galaxy clusters of the right size and shape today. These three issues are resolved with the theory of inflation — which is part of the broader Big Bang Theory.

When was the Big Bang Theory established?

Who came up with the idea?

Hubble was really the person who set up the observations. Evidence continued to mount, especially in the 1970s with the detection of the CMB. The term "Big Bang" was first used in the late 1940s by the astronomer Fred Hoyle — eventually, it caught on in the 1970s.

Because we can't see it directly, scientists have been trying to figure out how to "see" the Big Bang through other measures. In one case, cosmologists are pressing rewind to reach the first instant after the Big Bang by simulating 4,000 versions of the current universe on a massive supercomputer. 

"We are trying to do something like guessing a baby photo of our universe from the latest picture," study leader Masato Shirasaki, a cosmologist at the National Astronomical Observatory of Japan (NAOJ), told our sister website Live Science . 

With what is known about the universe today, the researchers in this 2021 study compared their understanding of how gravitational forces interacted in the primordial universe with their thousands of computer-modeled universes. If they could predict the starting conditions of their virtual universes, they hoped to be able to accurately predict what our own universe may have looked like back at the beginning. 

Other researchers have chosen different paths to interrogate our universe's beginnings. 

In a 2020 study, researchers did so by investigating the split between matter and antimatter. In the study, not yet peer-reviewed, they proposed that the imbalance in the amount of matter and antimatter in the universe is related to the universe's vast quantities of dark matter, an unknown substance that exerts influence over gravity and yet doesn't interact with light. They suggested that in the crucial moments immediately after the Big Bang, the universe may have been pushed to make more matter than its inverse, antimatter, which then could have led to the formation of dark matter .

The age of the universe

The CMB has been observed by many researchers now and with many spacecraft missions. One of the most famous space-faring missions to do so was NASA's Cosmic Background Explorer (COBE) satellite, which mapped the sky in the 1990s.

Several other missions have followed in COBE's footsteps, such as the BOOMERanG experiment (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck satellite .

Planck's observations, first released in 2013, mapped the CMB in unprecedented detail and revealed that the universe was older than previously thought: 13.82 billion years old, rather than 13.7 billion years old. The research observatory's mission is ongoing and new maps of the CMB are released periodically.

Related: How old is the universe?

The maps give rise to new mysteries, however, such as why the Southern Hemisphere appears slightly redder (warmer) than the Northern Hemisphere. The Big Bang Theory says that the CMB would be mostly the same, no matter where you look.

Examining the CMB also gives astronomers clues as to the composition of the universe. Researchers think most of the cosmos is made up of matter and energy that cannot be "sensed" with our conventional instruments, leading to the names " dark matter " and " dark energy ." It is thought that only 5% of the universe is made up of matter such as planets, stars and galaxies .

While astronomers study the universe's beginnings through creative measures and mathematical simulations, they've also sought proof of its rapid inflation. They have done this by observing gravitational waves , tiny perturbations in space-time that ripple outwards from great disturbances like, for instance, two colliding black holes or the universe's birth.

According to leading theories, in the first second after the universe was born, our cosmos ballooned faster than the speed of light . (That, by the way, does not violate Albert Einstein's speed limit. He once said that light speed is the fastest anything can travel within the universe — but that statement did not apply to the inflation of the universe itself.)

As the universe expanded, it created the CMB and a similar "background noise" made up of gravitational waves that, like the CMB, were a sort of static, detectable from all parts of the sky. Those gravitational waves, according to the LIGO Scientific Collaboration , produced a theorized barely-detectable polarization, one type of which is called "B-modes."

In 2014, astronomers said they had found evidence of B-modes using an Antarctic telescope called "Background Imaging of Cosmic Extragalactic Polarization," or BICEP2.

"We're very confident that the signal that we're seeing is real, and it's on the sky," lead researcher John Kovac, of the Harvard-Smithsonian Center for Astrophysics told Space.com in March 2014.

But by June, the same team said that their findings could have been altered by galactic dust getting in the way of their field of view. That hypothesis was supported by new results from the Planck satellite.

By January 2015, researchers from both teams working together "confirmed that the Bicep signal was mostly, if not all, stardust," the New York Times said .

However, since then gravitational waves have not only been confirmed to exist, they have been observed multiple times. 

These waves, which are not B-modes from the birth of the universe but rather from more recent collisions of black holes, have been detected multiple times by the Laser Interferometer Gravitational-Wave Observatory (LIGO), with the first-ever gravitational wave detection taking place in 2016. 

A major gravitational wave breakthrough was announced on June 28, 2023 when teams of scientists around the world reported the discovery of a "low-pitch hum" of these cosmic ripples flowing through the Milky Way. While astronomers don't definitively know what's causing the hum, the detected signal is "compelling evidence" and consistent with theoretical expectations of gravitational waves emerging from copious pairs of "the most massive black holes in the entire universe" weighing as much as billions of  suns , said Stephen Taylor, a gravitational wave astrophysicist at Vanderbilt University in Tennessee who co-led the research.

Read more: The gravitational wave background of the universe has been heard for the 1st time

Was the Big Bang an explosion?

Although the Big Bang is often described as an "explosion", that's a misleading image. In an explosion, fragments are flung out from a central point into a pre-existing space. If you were at the central point, you'd see all the fragments moving away from you at roughly the same speed. 

But the Big Bang wasn't like that. It was an expansion of space itself – a concept that comes out of Einstein's equations of general relativity but has no counterpart in the classical physics of everyday life. It means that all the distances in the universe are stretching out at the same rate. Any two galaxies separated by distance X are receding from each other at the same speed, while a galaxy at distance 2X recedes at twice that speed.

The universe is not only expanding, but expanding faster. This means that with time, nobody will be able to spot other galaxies from Earth or any other vantage point within our galaxy.

"We will see distant galaxies moving away from us, but their speed is increasing with time," Harvard University astronomer Avi Loeb said in a March 2014 Space.com article.

"So, if you wait long enough, eventually, a distant galaxy will reach the speed of light. What that means is that even light won't be able to bridge the gap that's being opened between that galaxy and us. There's no way for extraterrestrials on that galaxy to communicate with us, to send any signals that will reach us, once their galaxy is moving faster than light relative to us."

Related: 5 weird facts about seeing the universe's birth

— The 1st few seconds of the Big Bang: What we know and what we don't

— The universe: Big Bang to now in 10 easy steps

— Images: Black holes of the universe

Some physicists also suggest that the universe we experience is just one of many. In the " multiverse " model, different universes would coexist with each other like bubbles lying side by side. The theory suggests that in that first big push of inflation, different parts of space-time grew at different rates . This could have carved off different sections — different universes — with potentially different laws of physics.

Related: Best multiverse movies and TV shows: from Dr Strange to Dr Who

"It's hard to build models of inflation that don't lead to a multiverse," Alan Guth, a theoretical physicist at the Massachusetts Institute of Technology, said during a news conference in March 2014 concerning the gravitational waves discovery. (Guth is not affiliated with that study.)

"It's not impossible, so I think there's still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously."

While we can understand how the universe we see came to be, it's possible that the Big Bang was not the first inflationary period the universe experienced. Some scientists believe we live in a cosmos that goes through regular cycles of inflation and deflation, and that we just happen to be living in one of these phases.

A telescope is almost like a time machine, allowing us to peer back into the distant past. With the aid of the Hubble space telescope, NASA has shown us galaxies as they were many billions of years ago — and Hubble's successor, the James Webb Space Telescope , has the ability to look even deeper into the past. 

NASA hopes it will see all the way back to when the first galaxies formed, nearly 13.6 billion years ago. And unlike Hubble, which sees mainly in the visible waveband , JWST is an infrared telescope — a big advantage when looking at very distant galaxies. The expansion of the universe means that waves emitted from them are stretched out, so light that was emitted at visible wavelengths actually reaches us in the infrared.

The Big Bang Theory: becoming a household name

The name "Big Bang Theory" has been a popular way to talk about the concept among astrophysicists for decades, but it hit the mainstream in 2007 when a comedy T.V. show with the same name premiered on CBS. 

Running for 279 episodes over 12 seasons, the show "The Big Bang Theory" followed the lives of a group of scientists, which included physicists, astrophysicists and aerospace engineers. The show explores the group's nerdy friendships, romances and squabbles. Its first season premiered on Sept. 24, 2007, and the show officially ended on May 16, 2019.

Although the show itself didn't dive too much into actual science, the showrunners did hire UCLA astrophysicist David Saltzberg as a science consultant for the entire run of the show, according to Science magazine . Science consultants are often hired for sci-fi and science-related shows and movies to help keep certain aspects realistic.

Thanks to Saltzberg, the characters' vocabulary included a host of science jargon and the whiteboards in the background of labs, offices and apartments throughout the show were filled with a variety of equations and information. 

Over the course of the show, Saltzberg said, those whiteboards became coveted space as researchers sent him new work that they hoped might be featured there. In one episode, Saltzberg recalled, new evidence of gravitational waves was scrawled across a whiteboard that ostensibly belonged to famed physicist Steven Hawking, who also approved the text.

The show took some liberties , as it was fictional. This included fabricating some new scientific concepts and fictionalizing the politics of Nobel prizes and academia, according to Fermilab physicist Don Lincoln.

Related: How 'The Big Bang Theory' sent Howard Wolowitz to space

Notably, several characters in the series take trips. One episode sees main characters Leonard, Sheldon, Raj and Howard set out on a research expedition to the Arctic — many physics experiments are best performed at or near the extreme environments of the poles. Another put aerospace engineer Howard on a Russian Soyuz spacecraft and, later, a model of the International Space Station along with real-life astronaut Mike Massimino .  

Discover more about CMB on NASA's webpage on putting the Big Bang theory to the test. NASA has also put together what the Big Bang might have looked it in this animation . Here are 5 quick facts about the Big Bang from How It Works magazine. 

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Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for Space.com for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, " Why Am I Taller ?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace

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