Where is the anti-matter?

Why is there more matter in the universe than anti-matter? If they were produced in equal amounts in the universe, they should have annihilated and just left radiation behind. Does this mean Dirac's theory of anti-matter is wrong? An if anti-particles are mirror particles of our normal matter could there be "anti-stars" in our galaxy, stars made of anti-matter? That's what we talk about today.

The anti-star paper is here:

0:00 Intro
0:30 Sponsor Message
1:38 Is anti-matter a problem?
3:25 What did Dirac say?
6:11 The matter anti-matter asymmetry
10:05 Anti-stars?!

[luca]

"Physicists make a living from solving problems so they have an incentive in creating problems where there aren't any"

I am a software developer and today I learned that physicists and programmers are very much alike.

Great stuff as always, thanks for sharing!

P.s. "it's a highly speculative idea, that is a polite way of saying that is nonsense" makes a great line for your merchandise imho

[frankschannel]

Wonderful truth-telling, as always! There's almost certainly more auntie matter than anti-matter. My mother had three sisters - and it did seem at times like they would annihilate each other.

[DrZedDrZedDrZed]

Sabine, you aren't merely a talented communicator and physicist, you're a super talented EPISTEMOLOGIST, which is something I feel a lot of modern science communicators forget in the face of catchy headlines and hype. We must take the world as it is, and meet it on its terms, and when we can't cut through the fog, we have to be comfortable enough with ourselves to understand where the limits of knowledge end. You do that consistently and with pluck, so THANK YOU for that!

[trickvro]

I've often wondered if the baryon asymmetry could just be a mundane statistical blip. Like, you can't flip a coin 10 times, or even 10⁹⁷ times, and expect to reliably get a perfectly exactly equal number of heads and tails, no matter how perfect the coin is or how perfectly you flip it.

[NoahFriedman]

I thought the entire point of this question is that when we produce antimatter ourselves, there is always a corresponding amount of matter particles created at the same time (edit: well, maybe not, according to some LHC results in 2010?). If no baryonic matter could exist at the moment of the big bang itself, what process created more matter than antimatter afterward and why are we unable to do the same, or perhaps even create more antimatter than matter?

[arctic_haze]

It is quite possible that our Galaxy has more ant-matter than anti-matter.

[jeffa]

As an engineer who is fairly well versed in how the "normal size" things around me work, I really appreciate your videos that talk about the really small and really big that often tend to behave differently. Thank you!

[Thomas-gk]

Thank you for a marvelous explanation again

[justchecking]

I watch a couple of your videos every day. Even as s a 79 year old retired physicist they all are mind-expanding and give me several hours of thoughtful pondering. Thank you.

[Joshua-byqv]

Sabine is a treasure for us who want to learn cosmology and physics but don't have formal training. She is brilliant and funny too.

[caseytailfly]

The low key humor in this video is on point. I love how you made this into a “teachable moment” about initial conditions and how our current theories work.

[bbartt]

I think the reason for '1' is quite simple: if matter and antimatter are same except for the charge, then these should be treated equally when it comes to creating matter/antimatter from 'nothing'. There should be no especial treatment for any of these. But that's more philosophy than physic I believe...

[niklas]

This reminds me a bit of the anisotropy stuff you touched on in a different video. The ratio could be 1 globally but fluctuate locally, so there's a hidden third question of, even if you assume that the ratio *should be* 1, you're sneaking in an assumption about the scale you'd expect to measure that at.

The ratio is 1.000..whatever..001 in the *observable* universe. What makes this scale privileged? Perhaps we just randomly live in a matter-antisymmetric pocket of a matter-symmetric universe?

[allenhonaker]

It's being kept in a secret vault by the aliens and we can't find them.😂😂😂

[ws]

The reason, as I understand it, why physicists believe there should have been an equal amount of matter to antimatter in the early universe is that they are assuming an initial condition where the universe consists entirely of photons. If that were the case, then one does indeed need to come up with some explanation why matter-antimatter particle pair production did not produce both in perfectly equal amounts. Of course, assumptions are not fact, but it seems justification enough to me why we would want to build experiments looking for matter-antimatter asymmetries.

[marcelob.]

The explanation is very simple: God didn't have a calculator with enough decimals.

[LandoCalrissiano]

From what I understand (which isn't much), in the initial moments after t=0, there were no particles but only energy which later formed particles and anti particles. Since a unit of energy creates equal masses of matter and antimatter, there should've been an equal amount of matter and antimatter in the early universe. What exactly is wrong here? Also I don't think number of particles should be part of the initial conditions since they didn't exist in first few moments after t=0.

[secret]

I think Baryon asymmetry is more interesting as to how it relates to conservation of baryon number, and what that may suggest about the laws of physics.

[hyperscience]

I'm more skeptical of this one from Sabine. She is usually spot on but here I think we have reasons beyond the Dirac equation to suspect that the pure energy of the very early Big Bang would have resulted in a 1:1 ratio of a. to m. Also, I do think that the CP violating interactions that have been seen in strange and bottom quarks may suggest the answer to question of why we have more matter. These quarks can only be produced in high energy particle collisions. I know Sabin is down on further investment into HEP but this problem seems to me to be one of the few reasons that might justify further exploration and particularly at current or future HEP facilities. Sabine, correct me if I'm overstated my position. I'm generally sympathetic towards less funding for HEP but here, I'm not.

[orangesite]

That introduction tho
"We are going to talk about them today"
😭😂😂😂