How did the universe begin?

In this video I go through the different theories which physicists have for how the universe began.

To learn more about inflation and the inflaton field, this is an excellent starting point:

Here is more about the Ekpyrotic Universe:

I wrote about Penrose's Cyclic Cosmology here:

You find more about the idea that universes are born inside black holes in Zeeya Merali's book:

The idea that the universe started from a 4+1 dimensional black hole is explained here:

I have explained the idea of "Asymptotic Silence" here

Finally, the theory of String Gas Cosmology is from Robert Brandenberger:

[johnkeck]

Excellent. Your honest confession of our ultimate scientific ignorance on this matter is so refreshing!

[theosib]

The unicorn shit hypothesis is by far my favorite.

[Beevreeter]

I love your deadpan delivery at 3:02: ' we have equally good evidence, namely none, that the inflaton field exists' ! You have a great sense of humour.

[fleetingmoment]

Just as with the universe, I too was also hotter and denser when I was younger. Luckily though, I haven't expanded physically.

[kenj]

"The year is almost over and a new one about to begin."

NO! Go back, before it's too late!

[trajtemberg]

Mah, Sabine is bullying scientists again.

[TheFrankHuda]

I just found your channel a couple weeks ago. Thank you for your honesty, creativity, and hard work. It’s very interesting hearing perspectives differing from “scientific consensus”.

[michaelblacktree]

"And then there is the so-called Unicorn Cosmology..."
*Butt Stallion has entered the chat*

[ant]

It's alright to say, "we don't know".

[booJay]

I'm always amazed by how much Sabine is able to cram into such a short video that's not only informative, but digestible. That's some good (unicorn) shit.

[Darkanight]

Since it's probably the last one this year... I think it's ok for me to share my little amateur physics adventure. 


Discovering this channel was one of the best things that happened to me lately, and when I read on the blog that Sabine Hossenfelder was going to be in Genoa, I bought the tickets for the science festival right away. But I had been so busy that I didn't buy plane tickets in advance, so I had to take the coach... 


After the 15 hour long journey from Southern Italy... I finally got there on the 24th, just in time to find out that I was 5 days early for Sabine. I ended up rescheduling my whole trip, cancelled several business appointments and even went to Nice for a couple of days... 


Upon returning to Genoa,  with no hotel booked for the night BEFORE Sabine...  I realised that I had left some things in France, including my wallet... Then I tried booking some room, but the hotels kept refusing the other cards I had at hand. At that point it was already late and I wasn't gonna solve anything, so I just sat at the door of a church, waited till morning, and checked into the only room I had actually booked correctly. by then I was pale and felt sick... 


There was a queen bed in front of me. I was desperate to sleep,  but, i didn't give up. I persisted and went to the lecture, after being awake for almost 40 hours. 


Boy... was it worth it? I was lucky enough to see this brilliant scientist from the first row and I even had time to ask a question about black holes and got a picture with her, before the crowd came.



but... I must also confess the reason of my fascination and what drove me to go through all that with a smile on my face 


maybe I'm just a science groupie? well, to be honest... no. 


The one thing that motivated me the most, I swear to God, was the anthropic principle... for some reason I have always wondered if things did exist while we were not seeing them. perhaps the concept was subconsciously seeded onto my mind when I was a baby, or perhaps it's an archetype and some of us do tend to feel it.... or could it be real? 


Also, despite the fact that the videos are about rather complex subjects, they're still way easy to understand. I felt like I was mentally connected with them... 


Things are explained so well that I could swear that "Sabine Hossenfelder" was created by an algorythm fed from my mind somehow... 


After trying to ignore several coincidences, like I do most of the time... one day, as I watched her anthropic principle video, in that exact moment, causality has me focus on her, saying: 

-how can you not say that I am but an image created by a computer? 


and it all triggered an enourmous reaction with these memories of my early solipsism inclination. I wanted proof that she was real... 


and you guys have no idea how elegant and polite she is in person as well


I could do it all over again!



now, after the intellectual uplift that this channel has given me and this "practical research" that I indulged in...


whenever I look at the picture from that day, my brain plays "I can't forget" ;)


In conclusion: I got happy because I visually "acknowledged" her... so I can now feel like she is as real as me, at least from my point of view.  but it's possible that none of us are, at least in the way we think.


I may be still far from an actual answer, but... the more I study quantum phenomena, the more magical it seems. 

(pardon me for writting the new star wars intro lol)

[LiLi-orgm]

I love listening to you talk about cosmology, Ms Hossenfelder! You're very matter-of-fact approach and unbridled honesty is so refreshing. I am eager to hear more from you in the new year, and also hope to hear you being interviewed by someone like Sean Carroll, or Lex Fridman. All the best for the upcoming year!

[younanm]

some of the best "just the facts ma'm" no nonsense science being presented.. keeping science intellectually honest

[jamesdriscoll]

Lol - Unicorn theory - I need that on a coffee mug.
Thank you for this video, Good to hear some reasoning.

[AndraDare]

Finally. I was beginning to think I’m crazy or incurably stupid. Both of these things may still be true, but it’s good to hear someone as smart as you calling all of this into question.

[RCSVirginia]

I am personally going for the Uriel the Unicorn Theory of Creation. However, I don't think that it came from any defecatory processes due to squeamishness on my part. I think that it came about when he shook his rainbow mane and tail, and with one whinny and snort, and toss of his horn, the multi-coloured hairs that were shaken out sailed forth to create the universe as we know it. In fact, methinks that a whole new religion could be built out of that ancient, primordial event.

[cybervigilante]

"Enter your pin number and press START to begin Universe program."

[MostlyIC]

I wish science magazines etc would stop drawing "inflation" in their diagrams of space-time expansion. I've never believed in "inflation", the evidence is that there's no observed magnetic monopoles and there's a theory that this is because of "inflation", but that isn't the only possible reason there aren't any magnetic monopoles, so it isn't conclusive. In the mean time I think I'll get a Tee-Shirt made showing a unicorn at the beginning of space-time 🙂 !!!

[JohnStephenWeck]

Sabine, thanks for your efforts. Your videos are always interesting. :)

[Stadtpark]

It seems like Sabine is the only one with a name who is willing to stop where the evidence ends. Everybody else’s heads just keep going and going and then start to rely on beauty and elegance to explain why their theory is preferable... - which made Sabine angry enough to write a whole book about it... - I liked it.


Which in turn means, that she probably will never pick a favorite final theory for herself.
Which means, that I will come here again and again in vain, when looking for definitive answers.
All Sabine will ever give us, is better questions. - I hope this counts as a compliment.

Still I have problems actually following her approach: how can you not be tempted and compare those models, use Ockham’s razor or whatever other measure of simplicity, beauty, elegance and pick a favorite? It seems almost super-human to stay in limbo / non-committed. All too often there is tempting shortcuts from valid questions to not so valid answers... - how do you keep the brain from just settling for one thing, when it so desperately wants?