Did Repulsive Gravity Jumpstart the Cosmos?

For decades, inflation has been the dominant cosmological scenario, but recently the theory has been subject to competition and critique. Two renowned pioneers of inflation -- Alan Guth and Andrei Linde -- join Brian Greene to make their strongest case for the inflationary theory.

This program is part of the Big Ideas series, supported by the John Templeton Foundation.

Participants:
Alan Guth
Andrei Linde

Moderator:
Brian Greene

00:00 - Introduction
05:58 - Participant introductions
08:23 - Problems with the Big Bang
28:07 - Realizing the Inflationary Paradigm
42:13 - Observational Support for the Inflationary Theory
56:37 - Eternal Inflation and the Measure Problem
01:17:09 -The Future of Cosmology

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[Smood]

Sometimes I listen to people telling about random political issues or about random garbage drama. When I come here I think to myself why waste a second on something that isn't enlightening like listen to Dr. Greene speak?

[linkgunther]

The world is extremely lucky to have Brian and the World Science Festival. I imagine if we lived in an intellectually healthy society, these videos would top the trending charts. It is unfortunate this video has only 25K views in 48 hours when one considers the kind of trash on YouTube that gets millions of views in only a few hours.

[brothermine]

What Linde described beginning at about 12:58 -- the problem of how to explain how the Big Bang started at exactly the same moment throughout the small hot dense clump of primordial mass -- finally helps me understand why Feynman assigned a strange homework problem in a class at Caltech that I audited in the 1980s. He called it the "firing squad" problem. Suppose there are N members of the firing squad arranged in a row. Each member can communicate only locally.. only with its nearest neighbor on its right and its nearest neighbor on its left. They can communicate only at regular periodic intervals (like cellular automata). None of them know how many members are in the squad. All of them are programmed with the same communication & firing algorithm. Their goal is to all fire at exactly the same moment. Assume that at a random moment, one of them initiates the (local) communication that is to eventually lead to all of them firing at the same moment. Design the simplest algorithm that achieves the simultaneous firing goal.
Feynman didn't tell us why he wanted that algorithm. But it would solve the problem Linde described, in a 1-dimensional toy primordial universe. So I'm guessing the Big Bang problem is what motivated Feynman to assign the "firing squad" homework.
I submitted my solution, which seemed reasonably simple. But I don't know if it was the simplest algorithm, because Feynman didn't review any of the answers with the class.

[PurpleChevron]

Wow I've been huge fans of Guth and Linde for years for their work on inflation. What a treat to see such a competent interview with both of them by Brian Greene.

[mandeepsingh-fdmh]

Thank you so much wish to meet Mr green one day.

[rainajackson]

Im 60 this year and I can remember thinking about where is the end of space, when I was about 7 years old. Is there a birick wall? But what's behind that? I know you guys know heaps, but at 60 I still can't get past what was before and where does space it end? And if it never ends, what does that mean? Sorry Im so basic, however I love watching this stuff and I kind of understand upqurks down quark nutrinos etc.

[LucAnderssen]

Guth and Linde, heavy weights of Cosmology 🚀🪐🛰️🔭🍺

[treborg]

I love this lecture. It helps me understand the underpinnings of inflation that many others have either glossed over or ignored.

[michaelogden]

1:00:10 or so: "Anything that CAN happen WILL happen an infinite number of times". I would add: given an infinite amount of time.

Another fascinating presentation of the World Science Festival featuring Dr. Brian Greene.

[mehridin]

eternal inflation sounds like the zimbabwean economic model

[cosalidra]

( That's my excitement because a new WSF has dropped ) 💃💃💃💃

[cirusMEDIA]

Did i miss something? When was the Big Bang Theory proved as factual?

Tunnel vision is a hell of a drug.

[danielpaulson]

What if our universe is occurring within a much older and larger universe? Thinking. Thinking. Thinking.

[joegordon-px]

Brian needs to explain how he does the animations at the precise time they are needed as the guests talk about them, seems Magical, what is goin on? this defies Physics!!

[OpenWorldRichard]

I don’t buy the idea of repulsive gravity. The hypothetical matter doesn’t exist. This concept seems completely contrary to all observations of the behaviour of matter. There is no such thing as negative mass. Richard

[NoRiceNoRice-wxsb]

As if to commentarily represent your colleague & 1 other pioneer proponent of Inflation, Alex Vilenkin, the problem of the physically unknown "beginning"' or the beginning 'singularity' in the original BigBang turned out to be unavoidable even in the Inflation Theory.

[Smood]

By the way the way hes sitting in a chair the 3d animations and dr guth and the other physicist are around him is truely amazing.

[markoszouganelis]

All particles in the universe are entangled, since the big bang?
Thank you for your comments! The purpose of my question was: "It is GOOD to think about a beginning of our existence as the Big Bang Theory"🌈

[blengi]

has it been empirically validated that a piece of stretch rubber (29:13) has repulsive gravity _"that efffect is real"(guth)_ due to negative pressure by some indirect test?

[rolz]

"A fantastically dense nugget...." best quote ever!!!!