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Physicists Debate Hawking’s Idea That the Universe Had No Beginning

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Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#171

Post by will_brown »

dugluak wrote: post #127
djsumdog wrote: post #10

This seems different than the concept of infinite time, where prior to the big band there was something the collapsed into a ball of energy and maybe someday our universe will collapse back again (which has lost merit since we've seen matter in the universe isn't slowing down in spreading apart, but accelerating .. meaning in a few trillion years, atoms may be so far apart that light can't reach anything .. the event…

>> Are we sitting in a ball on some gigantic alien's coffee table? sometimes I have the same question but quite opposite. What if there are miniscule worlds right on our coffee table.

Or both...we can simultaneously exist on some aliens coffee table while they simultaneously exist on your coffee table.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#172

Post by pbhjpbhj »

klank wrote: post #145
canada_dry wrote: post #143

> Just as a shuttlecock has a diameter of zero at its bottom most point As a lay person this - right from the starting block - is what messes me up. I.e. something that exists cannot logically have a zero diameter part. Anything zero does not exist. Most related theories have similar kinds of initial premise that you must just accept.

> something that exists cannot logically have a zero diameter part Do elementary particles exist?

No, only observations of them do ;o)

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#173

Post by [deleted] »

EMM_386 wrote: post #118

Pure nothingness has no potential for creation. The laws of physics don't invent themselves, so it would seem that true "nothing" never existed. I'm not talking about the quantum soup of the vacuum of space, because that is something. If we take Hawking's idea that the universe smoothed out to a zero point where there was no time and nothing else, how does that point because laws of physics, gravity, etc? What proper…

[deleted]

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#174

Post by will_brown »

pbhjpbhj wrote: post #166
dugluak wrote: post #127

Earlier quoted context omitted.

>> Are we sitting in a ball on some gigantic alien's coffee table? sometimes I have the same question but quite opposite. What if there are miniscule worlds right on our coffee table.

On being given the planetary model of an atom I think it's relatively common to consider that maybe atoms are mini star systems. That was one of my early "aw shucks, someone else had that idea already!?" deflationary moments.

That was exactly the early thought and why the commonly accepted image of an atom with a nucleous and orbiting electrons looks just like a solar system.

Of course that’s not at all what atoms look like or how they behave.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#175

Post by throwawaymath »

SomeOldThrow wrote: post #117
ASalazarMX wrote: post #40

Earlier quoted context omitted.

It's nonsensical to wonder what happened in our universe before it existed, but if our universe has an external superuniverse, it's not illogical to wonder what happened there that caused our universe to exist.

> if our universe has an external superuniverse This is also meaningless, scientifically: there is nothing you can measure which is outside the universe. Things like a holographic universe are inherently untestable. I hope we continue looking for testable things, but this speculative path rapidly leads away from science and physics and into "linguistic tricks to confuse humans". It's not even philosophy at that point…

> This is also meaningless, scientifically: there is nothing you can measure which is outside the universe. Things like a holographic universe are inherently untestable.

This is incorrect. Are you familiar with the inverse-square law? In 3-dimensional Euclidean space, the rate at which any force decays over a distance is inversely proportional to the square of the distance. This generalizes to n dimensions; but instead of the drop off rate being inversely proportional to the square of the distance, it becomes inversely proportional to the n - 1th power of the distance.

Suppose our universe is a 3-dimensional embedding of a n-dimensional manifold. Every local force we could empirically test would adhere to the inverse-square law, i.e. have drop off over distance k of ~ 1/(k^2). But theoretically speaking we could empirically test the dimensions of the manifold we reside in by identifying which power of distance is proportional to the drop off rate of extremely small forces where the compactified dimension can be detected.

For practical purposes this would require us to increase the precision with which we can empirically test (and reason about) forces at the subatomic level.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#176

Post by selestify »

heimdall wrote: post #131
newsoul2019 wrote: post #126

Earlier quoted context omitted.

Is there a theory that the beginning and the ending of the universe are directly connected to each other? And that time doesn't so much start over and return to the starting point on a circle, so to speak?

The Big Bounce! https://en.wikipedia.org/wiki/Big_Bounce To me it's more satisfying than the idea of https://en.wikipedia.org/wiki/Heat_death_of_the_universe

I once heard of the hypothesis that once the last proton decays, the universe will once more be completely uniform in every way. With nothing to distinguish any part of the universe from any other part, space becomes meaningless and the universe has once more entered a state of nothingness much like how it was "before" the Big Bang.

So, in a sense, the heat death is not so different from the big bounce.

Unfortunately I did not bother to bookmark what I had read, and can no longer find a name or anything referring to it on the internet.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#177

Post by tutfbhuf »

baxtr wrote: post #136
irrational wrote: post #62

Earlier quoted context omitted.

This kind of discussion always reminds me of the Asimov story "The Last Question" https://www.multivax.com/last_question.html

Reading this, I am again reminded that technological progress is sometimes way slower than people think. Think about how the folks in the 50s/60s envisioned the time around 2000s, flying cars etc. I think the same might happen to autonomous delivery, general AI and the like.

I wouldn't necessarily say slower, but rather different. The folks in the 50s/60s couldn't imagine how something called the Internet would change the world.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#178

Post by om3n »

irrational wrote: post #62
Balgair wrote: post #54

Earlier quoted context omitted.

Wikipedia's 'Timeline of the Far Future' is a great article on the posibilities of our universe's fate [0]. Of note are the entries near the end of the list. Year 10^(10^(50)) : Estimated time for a Boltzmann brain to appear in the vacuum via a spontaneous entropy decrease [1] Year 10^(10^(120)) : High estimate for the time for the universe to reach its final energy state, even in the presence of a false vacuum. Year…

This kind of discussion always reminds me of the Asimov story "The Last Question" https://www.multivax.com/last_question.html

An excellently illustrated version of "The Last Question":

https://imgur.com/gallery/9KWrH

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#179

Post by Koshkin »

EMM_386 wrote: post #118

Pure nothingness has no potential for creation. The laws of physics don't invent themselves, so it would seem that true "nothing" never existed. I'm not talking about the quantum soup of the vacuum of space, because that is something. If we take Hawking's idea that the universe smoothed out to a zero point where there was no time and nothing else, how does that point because laws of physics, gravity, etc? What proper…

> Pure nothingness has no potential for creation

In mathematics, at least, this is not true. For example, a set consisting of the empty set is not empty.

Re: Physicists Debate Hawking’s Idea That the Universe Had No Beginning

#180

Post by AgentME »

SomeOldThrow wrote: post #164
AgentME wrote: post #148

Earlier quoted context omitted.

There are still ways we can reason about it. If we come up with a model of a super-universe and then find that model says that universes like ours are more likely to exist, then it can be evidence for the super-universe. We could possibly use the model of the super-universe to make predictions about our own universe.

> If we come up with a model of a super-universe and then find that model says that universes like ours are more likely to exist, then it can be evidence for the super-universe. That's not evidence FOR the superverse, just like we can inherently not rule out the idea of the https://en.wikipedia.org/wiki/Evil_demon deceiving our every perception. At best, this is untestable philosophy that's fun to debate over drinks.…

If the evil demon theory made specific predictions that turned out to be right and weren't predicted by other theories, then it would be a useful theory. It's possible for a theory of a super-universe to do that.

Imagine if we came up with a super-universe theory that said that the super-universe could only spawn sub-universes which followed conservation of energy plus several other laws no one had ever thought to test before (and weren't implied by any other theories), and as we started testing for those other laws, every single one we tested turned out to hold in our universe.

(If that happened, it would be reasonable to look for simpler theories that also predicted those other laws too, but it's possible that the super-universe theory would turn out to be the simplest possible theory that fits. Theories should be judged by the complexity of their rules, not by the number or complexity of things they predict; a simple theory that implies a large ensemble of universes can be better than a more complex theory that implies only our world or what we can see is real.)

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