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What Caused the Big Bang?

Every astronomy textbook tells us that soon after the Big Bang there was this period of exponentially accelerating expansion called Cosmic Inflation. In a tiny fraction of a second, inflationary expansion multiplied the size of the universe by a larger factor than in the following 13 and a half billion years of regular expansion. This story seems like a bit of a… …stretch. Is there really any mechanism that could cause something like this to happen? Well, that’s what we’re covering today: the real physics of cosmic inflation. Most cosmologists buy some variation of the inflation hypothesis. It seems to have very neatly solve some of the biggest questions in cosmology, those being: why is matter and energy so smoothly spread out across the entire observable universe? – and why is the geometry of the universe so flat? Neither should be expected unless the universe expanded much more rapidly early on. Another problem fixed by inflation is the absence of magnetic monopoles. And these are strange particles predicted to have been produced in the early universe. We’ll come back to those another time. The inflation hypothesis solves these problems with a single simple idea. In addition, inflation gives us an explanation for why the universe is expanding in the first place. It puts the ‘bang’ in Big Bang. After the exponential expansion ended the universe would have continued to coast outwards just like a thrown ball continues to rise after it leaves your hand. This is the Hubble expansion that we observe today. Inflation trades four mysteries for one: the problems of smoothness, flatness, missing monopoles, and expansion are all solved if we assume a single phenomenon. But physicists are a skeptical bunch and most of the time they don’t just make up stories and start believing them without good reason. Especially something as extravagant as inflation. For a hypothesis like this to be taken seriously, the physics also has to make sense. In the case of inflation part of the appeal is that it fits extremely nicely into our modern understanding of gravity and quantum mechanics. Let’s dig into each of these one at a time. First up, the equations of Einstein’s general theory of relativity. Our modern theory of gravity can be used to predict the behavior of the universe as a whole. They describe how its expansion or contraction depend on the matter and energy it contains. Mostly, the stuff in the universe pulls the universe back together; resists the expansion with a positive gravitational effect. But there’s one type of energy that can have an anti gravitational effect. Anything that causes the fabric of space itself to have energy – anything that has a constant energy density pushes rather than pulls. Now, we know that something like this exists because we’ve observed it in the accelerating expansion produced by dark energy. We’ve covered how this works for dark energy in a lot of detail. Check out the playlist if you want to get an insight into the actual math. But the upshot is that if the vacuum of space has a constant energy density, then Einstein’s equations end up having a term that we call the cosmological constant – A positive value for the cosmological constant means a constant doubling rate for the size of the universe. That means exponential expansion. The speed of that exponential expansion depends on the strength of the vacuum energy density. For dark energy, that number is incredibly small and so dark energy only works because it adds up over an enormous amount of space. On the other hand, in order to solve the smoothness, flatness, and monopole problems inflation needs to expand the universe by a factor of 10 to the power of 25 in less than 10 to the power of negative 30 seconds. To do this, the energy density of the vacuum during inflation would need to be vastly stronger than dark energy. Also, for inflation to make sense presumably the universe also needed to stop inflating at some point giving way to the regular Hubble expansion that we see today. So, the vacuum energy would need to drop from a very high value to basically zero. To see how this could happen we need to move beyond Einstein’s general relativity. We need some quantum physics. In fact, we need some quantum field theory. QFT can explain how a vacuum can have energy, which – surprise surprise – we also covered in a playlist. There’s some more homework for you. For now, a review: the universe is filled with quantum fields. Now, a field is just some property that takes on a numerical value at every point in space. We call that the “field strength”. The field strength determines how much force a quantum field exerts on other fields and particles. A familiar example is the magnetic field. The stronger the field, the more it pulls or pushes. By the way, an elementary particle is just an oscillation in this field strength – a little packet of energy held by the field. If a quantum field has energy in the form of particles and if space is expanding – as is the case for our universe – then that energy gets more and more spread out over time. Particles get dispersed and so the energy density goes down. A quantum field can contain an intrinsic energy even without particles. In that case, it will always try to drop to the lowest energy state and typically that means losing all energy besides whatever is bound up in particles. For example, a magnetic field will quickly fade away if we take away the electric currents that created it. Now, a field doesn’t just jump to the lowest energy state, it makes its way there by changing the field strength one step at a time. If we graph a quantum field potential energy versus field strength, it might look something like this: If the field finds itself at a high energy – high field strength state, it’ll sort of roll down to the minimum and stay there. And by the way, the lowest energy state of a field is called its vacuum state. But sometimes, the energy contained by a field has a more complex relationship with the field strength. I’m gonna have to save the how and why of these potential energy curves for another video. For now, let’s just go with it. One possibility is that the field could have what we call a local energy minimum. If such a quantum field found itself near that local minimum then it would roll to the bottom and get stuck there. It would have a lot of energy but no particles. We would call this a false vacuum and it gives us exactly the constant vacuum energy density needed for inflation. There are other ways for a field to end up with a positive vacuum energy density and I’ll come back to these. But for now, let’s just assume that such a field exists and give it a name: “the inflaton field”. The original idea for inflation proposed by Alan Guth in 1979 goes something like this: In the early universe this mysterious in flattened field has a high field strength due to the extreme temperatures of that time. As the universe cools the field loses strength and energy. But then, it gets stuck in this local energy minima. The universe keeps cooling, but the inflaton field can’t lose more strength. It would have to get over this potential energy barrier to do that. Stuck at a constant very high energy density, inflation takes hold; the exponential nature of inflation quickly blows up the volume of the universe, rendering it, basically, empty and cools it to a low temperature. In fact, it super cools the inflaton field. The field remains in a vacuum state that doesn’t matches temperature – in the same way that water can become a supercooled liquid, much colder than ice. If you cool it prevent ice crystals from forming. Inflation and the corresponding super cooling would go on forever if the inflaton field stays stuck. But quantum fields have a tendency to randomly fluctuate to different values, thanks to the Heisenberg uncertainty principle. Somewhere in the inflating universe, the inflaton field is going to fluctuate to the other side of this local minimum barrier. It’s going to quantum tunnel and on that other side, it sees a deeper truer minimum – perhaps the true vacuum state – and suddenly starts to lose energy again racing towards that minimum. Inflation would stop at that point. Regions of space adjacent to that point would also be dragged out of the local minimum towards the true vacuum and so the entire inflaton field would cascade down in energy. The analogy with supercooled water still works. Introduce an ice crystal or even a speck of dust to the water and it will quickly turn to ice. Now, that’s a phase transition. The inflaton field also undergoes a phase transition towards the new vacuum state. And just like a growing ice crystal, this effect will propagate outwards from the starting point, which we call a nucleation point, by analogy. This bubble would grow into the surrounding inflating regions at the speed of light. And inside the bubble, inflation would end. Inside the bubble, space would still be expanding out whatever speed it had at the end of inflation, but that expansion would no longer be exponentially accelerating. The energy that existed in the inflaton field doesn’t just go away, it remains in that field very briefly, but now in the form of inflaton particles. It’s like the entire floor of the field is shifted down at every point in space; what was once pure inflaton field is converted to a stack of inflaton particles. Those particles are unstable and they very quickly disperse their energy into the other quantum fields. The inflatons decay into the familiar particles of the standard model – quarks, electrons, etc. So, the vacuum of inflation is converted into an extremely hot ocean of particles. We say the universe was ‘rethermalized’ or reheated by this process. In fact, this process would reheat the universe to the extreme energies that we expect existed right after the Big Bang. At this point, the universe should evolve as the rest of the Big Bang story predicts: An extremely hot dense ocean of matter and radiation that slowly cools and disperses and forms structure as the universe expands. This is the rough sequence laid out in Alan Guth’s original paper. But, right from the start Guth admits a number of problems with his story. The big one is about how inflation stops. See, when these non inflating bubbles form, all of the energy gets released at their boundaries; their expanding spherical fire walls – that are otherwise empty – which isn’t exactly what our universe looks like. The only way to get the sort of evenly distributed temperature we see in the Cosmic Microwave Background, is if lots of these bubbles collide and then have time to mix. But in order for inflation to last long enough to do its job, the probability for the appearance of a bubble can’t be too high and that rules out sufficient collisions. The upshot is that the lumpiness of the CMB is not consistent with lots of colliding bubbles. Guth’s idea is now called old inflation. It solved several problems in cosmology and it also inspired other physicists to find even better solutions, mostly by changing the nature of the in flattened field so that allows a smooth exit from inflation across the universe rather than in a series of bubbles. bThese new inflation models are much more successful and we’ll get into them in an upcoming episode. But, by delving deeper into the physics of inflation, physicists discovered some pretty crazy predictions. If inflation happened at all, that it’s hard to avoid two conclusions: Once started, inflation should continue… eternally – Only stopping in patches where a bubble universe forms. And once started, inflation should produce infinite such universes. But these will have to wait for a follow-up episode when we step into the multiverse of an infinitely inflating… Space Time.

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100 thoughts on “What Caused the Big Bang?

  1. Wow, I watched the quantum tunnel 'birthing' of uncountable universes in the inflaton field after taking 900mg of mescaline, had not realized this theory was behind it until now.

  2. Hi, is it not quite possible that, light from our sun even from our planet earth traveled through space and bend due to gravitational force of Black holes and other heavy stars and hit earth again later in time. We may be able to see our solar system far back in time.

  3. The question doesn’t make sense, before Big Bang there is no space time. The real Nothing, so there cannot be “what”

  4. You are my favourite thing to fall asleep to… I put on old videos and crash out to them. You should have a bedtime channel because you have a warm, comfortable voice mate. X

  5. Can't you explain the so called "dark energy" by having multiple universes or bubbles of the universe beyond our visible universe? If it would be like the gravity we all know, created by whole other universes or other massive thigns near the part of the universe we can observe, it'd provide the tension, thus making the universe "flat".

  6. how do i tell whether this even makes sense or is just a word salad created from quantum jargon? if he said a complete nonsense from physical point of view, i wouldnt be able to tell it.

  7. inflaton infused space=serious scientific theory
    inflaton infused water=quack bullshit

    now, inflaton infused atomic nuclei would be legit or bullshit?

  8. lets posit infinite amount of infinitely infinite multiverse bubbles, all infused with inflaton fields. now a spontaneous breaking of the symmetry of false vacuum leads to an emission of gravitational wave noise. Legit theory or bullshit?

  9. the outer limits of the universe calculates to 13.7 billion light years away. That means that the furthest light source has been traveling for 13.7 billion years.. just a little c4 explosion travels at 25000 feet per second or 17045.454 miles per hour. Or 149,314,200 miles per year.. multiply that times 13.7 billion. The earth is only 4.5 billion years old.. and the light that we see is 13.7 billion light years away. This means that the light is traveling at 670 616 629 miles per hour for 13.7 billion years .. this means that it is not possible that the light that we see in the furthest galaxy did originally start at the same place as earth I say there was no big bang and the galaxies are moving toward something . Much like atoms that follow DNA instruction to build a life form….

  10. A great video maker, very clear and accurate. But you're still trying to view your own eyes with your own eyes, and only getting as close as observing the rim of the iris, which is as close as 'external observation' and 'mathematics' can get. When we take on human consciousness, 'what we are' gets super compressed into a tiny mote of the original form, causing the perception of outwards expansion. Everything we measure will support this seeming expansion, but we'll never observe states before the birth of human consciousness while in the physical body. An out of body experience will make this fact plainly clear.

  11. Question: how can a singularity with zero size expand ‘exponentially’? The statement has no meaning. It could go from zero size to some non-zero size in the first Planck time, and then expand exponentially from there, but whether a theory of inflation is even needed depends entirely on the magnitude of that first size, no?

  12. I'll have to ask Jesus to explain this information to me as if I'm 5year old kid.
    ( I'm sure he himself will have to watch it 23 times, to understand)

  13. Dark energy sounds an awful lot like the rationalization hoops flat earthers go through. I call bullsht. Why cant you just admit you have no clue instead of making up crap like expanding universes and big bangs

  14. I've seen some cosmologists put inflation first and then the big bang. Is this important? Or is it just a difference in semantics?

  15. The Big Bang is sheer stupidity. A farce. A fairy tale.

    Fossils cannot take millions years to form. I live on a farm. Dead things disappear quickly.

    A domestic rabbit died this past summer. He was gone, all but some hair, in three days.

    Even secular scientists now admit fossils form quickly.

    How to explain "cross strata fossils" like upright, fossilized trees?

    There is abundant evidence for God's creation. As a former biology major and someone who was a skeptic for four decades, I can no longer deny the evidence:

    Earth is only about six thousand years old.

    As secular scientists admit, we are all one race, descended from a single Male and female.

    Fossils form quickly.

    The big bang is laughably silly. Nothing exploded from nothing making everything? Ha!

    Evolution is impossible. The odds of a single protein forming by chance is 1×10^250. Even then ya only have a single protein.

    If SETI were to find an intelligent radio signal, it would be defined intelligent by its containing information. What is DNA?! As Bill Gates said, "DNA is like a computer program, but far more advanced than any software ever created."

    Mutations remove information from the genome  mutations NEVER add information. Do dogs change? Sure. Into what? Dogs.

    Its not about the evidence. Its about worldview.

    If God exists, then we are obligated to Him. Folks can't have that. So they worship the god of self, the word of man, and the religion of humanism.

    Check out Dr. Jason Lisle "Science Proves Biblical Creation".

  16. Do most physicists agree that all matter collapsed down into itself into a relatively small singularity point of mass before exploding in all directions in the Big Bang and that all of that material is still expanding in all directions spherically into otherwise empty space and doing so at a rate faster than the speed of light?

  17. What if the expasion is infinite in the form of free electrons. Electrons are the only irreducible partice wirh a negative repelling field that do not interact with other electrons.
    A field of electrons free of gravity and protons would expand exponentally until it collided with another expanding field of electrons, creating gravity, matter and time along the high velocity membranes of their expasion field. This explains the voids and even distribution of matter and temperature throughout the CMB.

  18. I assume we all agree that dark energy is present throughout the universe as well as throughout all space beyond our universe. Let’s examine the definition of dark energy for a moment. According to Oxford, it is a theoretical repulsive force that counteracts gravity and causes the universe to expand at an accelerating rate. Now, we know that space itself is dark and always has been. We also know that dark energy itself is dark. Now, let’s also take a moment to define energy. In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. So, after examining these facts, we can conclude, based on the laws of physics, that dark energy has (one) always been present throughout all of space and (two) was ultimately accountable for the big bang or big bounce (whichever you prefer.) What does this mean? This means dark energy is timeless and limitless. And, what does that mean? It means that according to the laws of physics, dark energy wasn’t created by anything physical. So, what does this mean essentially? If nothing physical created dark energy then there’s only one conclusion as to what created it.

  19. Wait, if universe is expanding at exponential rate, does this mean its expanding faster then a speed of light? Can this be measured? If its slowing down will it ultimately colapse and start contracting into a new big bang? Is the universe just pulsating? If there is energy in the vacuum does this mean E = mc2 does not apply everywhere? So energy is everywhere around us we just dont know how to extract it…Or do we ( governments hidding ufo objects ) I mean comon u cant talk space without mentioning aliens 🙂

  20. I love how most of these are not "dumbed down," a bit challenging, and highly informative … and then there are the ones like this one…… where just a little "dumber" would help me out 😉 But that's a good thing IMHO.

  21. Was it really expansion? Or was space time dilating so that from our perspective looking back it seemed like hyper inflation, because from our perspective its the lensing of time? Perhaps from an outside observer, it was energy writing information into our universe in a “non hyper” time frame creating our universe as an emergent result. The point at which space and time became entangled.

  22. Quran chapter An Nazi'at verse 27 – 33 already tell us that Allah create 7 layer of earth and 7 layer of universe from a tiny dot of singularity and from that come what scientist called a big bang

    A super-duper-smart-scientist found it in the modern age, Muhammad talk about it 1.400 years ago

  23. Explanation of the Universe. The measurements of space at the micro level are repelled, which makes the universe expand. Matter is the conserved deformations of space that are attracted. This is the stored energy of repulsion of micro-measurements of space. More.

  24. Now my curiosity is expanding exponentially while the field of my expectations gets bounded by old inflation limitations… When/where is the follow-up?

  25. "We know for certain for instance, that for some reason for some time in the beginning, there were hot lumps."—Firesign Theater

  26. The more we seem to discover things, the more that we realize that we know exponentially, less than we thought when we started studying. I love cosmology, but too many physicists speak like they're talking about facts; when 99.9% of what we talk about is hypothesis or theoretical.

    Maybe the day will come when we finally get some facts on what's really out there, but that will take major advancements towards traveling near the speed of light. That objective, at best, is 500-1000 years away, if ever.

  27. I like to imagine a process by which antimatter in the early universe was converted into dark energy for inflation and counter-inflation dark gravity.

  28. Space is not expanding. Only the galaxies are. The expansion of the galaxies is due to a gargantuan collision. The reason scientists are confused is because they are finally seeing the galaxies that left the collision faster than the ones around us because of better technology. If you think space itself is expanding, you will mistakenly think that the whole universe is expanding because of this observation. Trying to include space in the expansion was the biggest mistake science has ever made. Occams razor proves that is was simply a collision. All the energy needed to create the big bang is accounted for. All matter was already here when the big bang happened. The galaxies are shrapnel from the collision. They were all born the very second the big bang happened, not later. They were born made of plasma.
    The confusion about our universe must end. Science cannot expect to solve anything if it keeps using the wrong theory. Besides, how can space reverse to nothing? Physics laws say it is impossible.

  29. Big Bang: may not be.
    Explosion: could be.
    For the basic state of universe
    watch IJSR vol.7, issue3, pages273-275

  30. Ok but wait! if a Atto sec is 31billion years to a Sec? Then the universe took at least 31billion years to come to our measurements of existence? Yeah sure fast but,, that was a long time in some 90 degree angles frame of reference?….

  31. Just a simple question, the total amount of matter in the universe was the same at the time of big bang, before and after?

  32. What if the "bubble" hypothesis is instead a model for the multiverse itself, and our entire "universe" is mere one of those bubbles that coalesced from it? With such an insane rate of expansion of the larger multiverse field, the bubbles would be sufficiently spread out that they'd rarely collide. And if any other bubble was close enough to eventually collide with ours, the collision boundary would likely be too far away for us to ever witness (assuming the spread of the boundary is bound by the speed of light, otherwise…it would happen too fast for us to worry about such a trans-universe apocalypse).

  33. You guys don't know shit about what created the universe and the real crazy people say it came out of nowhere from nothing

  34. 9:30 Or a minor perturbation (flick the bottle with your finger). This perturbation causes a wave of higher density to traverse the supercooled water with a region behind the wave being even colder. This can cause a small ice crystal to form, which then slowly moves across the container freezing the rest of the water.

  35. Big Bang?

    There is nothing in physics like the Big Bang because there is nothing in physics that violates Thermodynamics as the Big Bang does.

    Inflation is another invention to make the Big Bang plausible.

    Establishment physics is hooked to the big bang and still has a problem with entanglement.

    Obviously, there exists a principle which has not been imagined nor discovered yet which can be verified by competent experiments.

    As long as establishment physics insists on their Big Bang and inflation theories and forces other ideas under the rug, physics will never advance.

  36. Much too complicated. Family Guy explained things much simpler and in only 22 seconds:

  37. The more cosmos and physics videos I watch, the more I get the feeling that our matter has been forced into space, into this universe full of dark energy (general relativity) that doesnt share the same laws with our matter (quantum mechanics).

    And if it’s been forced there, who or what did that??

  38. I though inflation happened after the big bang? I mean, they put a time on how long it was between the two events lol although I may be remembering incorrectly. Also, I think if I remember correctly I heard there was two seperate periods of inflation?

  39. You're not a very good liar, scientists make up things all the time.
    Today's hard core indisputable facts are nothing but tomorrow exposed fabricated lies.
    I wouldn't trust you with oxygen.
    You're on youtube spewing your science rubbish while your people are being held in a chinese concentration camp, well done.

  40. the big bang refers to the art of making babies.. you parents bang and then the egg gets fertilized… evoloution is the stages that the child goes through in the womb.. fish..reptile…human.. so in theory there has to be a creator to start the big bang…

  41. At least my theory explains how this universe came into existence. No physicist is yet to explain how the
    Big-Bang actually happened, nor will they ever, for their math is jargon, their theory fallen like a disgraced
    angel. God decides who He shares true knowledge with (Matthew 13:11, Luke 8:10). Johnrfocus, Tumblr

  42. In my opinion, information and energies contain inherent, inert disparities and potentials that could manifest in a confined scenario. These potentials may have compounded in the singularity inception, forming the initial potent reaction. This is not a 1+1=2 circumstance, the subtle properties of the potential energies and information are catalysts that cannot be easily gauged. Differences between energies and information created an emergent property, and this impulse was converted into explosive power. The potential that resided within the informational and energetic gaps of the singularity was violently and mathematically extrapolated, probably due to forced quantum entanglement and high density in such close quarters. In other words, there was more to the original singularity than "a simple ball of energy", it contained enormous hidden potential.

  43. Yes it's a whole lot of stomach. Stretch.
    Actually this world was once a piece of the sun.. that's why this world was once molten lava. And the center of the earth is still molten lava. If you can understand anything about the universe, you would understand that. The universe was already their. The other solar systems are much older than that, of our world. Batleguise, for example.

  44. A now classical Illogical question about existence itself. In essence, the illogical question is asking did something originate from nothing?

  45. If gravity means energy how is the universe not a massive black hole how is the universe so smooth distributited while the universe inflated faster on 1side science the language of the stupid

  46. Universal expansion is due to "free" electron fields. Dark "potential" energy are "scalar" fields of laminar flow, gravity free, negatively charged, exponentially repelling electrons that collide and compress along their outer perimeters and create fusion of electrons into quarks, muons and gluons within vortexes of matter around the core of a black hole in a thermodynamic "vector" field of gravity. These thermodynamic fields are known as galaxies. Gravity is simply the flow of electrons attracted to the protons in an atomic neuclious. Only an equal number of electrons and protons can produce the orbital of electrons within an atom, the rest of the electrons being attracted to the protons in a neuclious will drag or, attract other neucli together, effectively creating more mass within a thermodynamic, energy conserving vector field of gravity..
    Galaxies maintain their spiral vortex due to the density of electrons (dark matter) being attracted around a spiral galaxy with a supermassive black hole.

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