Why do scientists think there was a big bang?

How does science work? And what's all this about quantum mechanics?

Moderators: AMod, iMod

gaffo
Posts: 4259
Joined: Mon Nov 27, 2017 3:15 am

Re: There are no ears in space.

Post by gaffo »

-1- wrote: Sat Oct 13, 2018 3:00 pm
If you can, uwot, please give me a picture of what "they" mean, when they seem to say time has not lasted forever since the infinite past; and how it relates to the seemingly contradictory reality, that time is a dimension, in addition to a three-dimensional space, where the dimensions are undeniably forever lasting?
I'm not uwot.

space dd not exist at the "time" of the BB (nor did Time -as you stated).

there is no reason to assume that "dimensions will last forever" - after the Big Rip. Space and Time just might end again.

who knows.
gaffo
Posts: 4259
Joined: Mon Nov 27, 2017 3:15 am

Re: a primitive conception of time I just pulled out of my keister

Post by gaffo »

henry quirk wrote: Sat Oct 13, 2018 3:17 pm In a perfect vacuum there'd be no time cuz time is change (and the possibility of measurement) and in a perfect vacuum there's nuthin' to measure.
nonesence. the space with no stuff in it is still expanding via time!

yes "time is change" space changes over time - it gets bigger - with or without atoms in that "Cubic yard" of space.
gaffo
Posts: 4259
Joined: Mon Nov 27, 2017 3:15 am

Re: Why do scientists think there was a big bang?

Post by gaffo »

A_Seagull wrote: Sat Oct 13, 2018 8:34 pm If one compares the radial velocity of distant galaxies with their distance one finds that there is a strong correlation. The greater the distance the greater the velocity.

If one then projects backwards in time, the inference is that all the galaxies were at one place some 14 billion years ago.

The inference of a big bang occurring at that time would not seem unreasonable.
yes. thanks for actually answering the question of the thread.

you are the first one!
User avatar
Greta
Posts: 4389
Joined: Sat Aug 08, 2015 8:10 am

Re: Why do scientists think there was a big bang?

Post by Greta »

gaffo wrote: Sun Oct 14, 2018 4:08 am
Greta wrote: Fri Oct 12, 2018 11:01 pm From an article I was reading this morning:
https://www.quantamagazine.org/big-boun ... -20180131/
With a single initial ingredient (the “inflaton field”), inflationary models reproduce many broad-brush features of the cosmos today. But as an origin story, inflation is lacking; it raises questions about what preceded it and where that initial, inflaton-laden speck came from. Undeterred, many theorists think the inflaton field must fit naturally into a more complete, though still unknown, theory of time’s origin.
In terms of narrative, I currently prefer the idea of a "big birth", where a new universe may form from the void left by the last.
assuming your thesis (for discussion's sake ( I'm lightyears too dumb to understand Astrophystics)) is correct, then when the "big Rip" happens, there will be "enough void" to birth a new future universe in 15 billion years time.
Not my thesis. I'm also not smart enough.

The big rip strikes me as an oddly mechanistic and unnatural notion. It's as if no thresholds or state changes will occur in the future. It's akin to imagining that a baby will grow to the point where it bursts out of its skin. Or thinking that a healthy baby will continue growing until it achieves hydrostatic equilibrium and becomes a spheroid object under the force of its own gravity.
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Shoulda called it something else.

Post by uwot »

gaffo wrote: Sun Oct 14, 2018 4:40 am
A_Seagull wrote: Sat Oct 13, 2018 8:34 pmIf one compares the radial velocity of distant galaxies with their distance one finds that there is a strong correlation. The greater the distance the greater the velocity.

If one then projects backwards in time, the inference is that all the galaxies were at one place some 14 billion years ago.

The inference of a big bang occurring at that time would not seem unreasonable.
yes. thanks for actually answering the question of the thread.

you are the first one!
Not really. Just in case you missed it, here's my original post:
uwot wrote: Fri Oct 12, 2018 11:03 amI'm revamping the book; making it clearer (hopefully) and getting rid of distractions. You can see the first part on the blog. If it still doesn't make sense, I would love to hear your comments. https://willijbouwman.blogspot.com
What A_Seagull says is pretty much the gist of what is written, but no one has actually commented on the revamp and quite a few clearly haven't read it. Ah well, people have read the title and waded in, which is fair enough; done it myself often enough.
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Re: a primitive conception of time I just pulled out of my keister

Post by uwot »

gaffo wrote: Sun Oct 14, 2018 4:36 am
henry quirk wrote: Sat Oct 13, 2018 3:17 pm In a perfect vacuum there'd be no time cuz time is change (and the possibility of measurement) and in a perfect vacuum there's nuthin' to measure.
nonesence. the space with no stuff in it is still expanding via time!
I think I'm with Henry on this one; unless you can explain what expanding via time means.
gaffo wrote: Sun Oct 14, 2018 4:36 amyes "time is change" space changes over time - it gets bigger - with or without atoms in that "Cubic yard" of space.
Well here's the thing; if it's still a cubic yard of space, what is getting bigger?
User avatar
Greta
Posts: 4389
Joined: Sat Aug 08, 2015 8:10 am

Re: Shoulda called it something else.

Post by Greta »

uwot wrote: Sun Oct 14, 2018 6:51 am
gaffo wrote: Sun Oct 14, 2018 4:40 am
A_Seagull wrote: Sat Oct 13, 2018 8:34 pmIf one compares the radial velocity of distant galaxies with their distance one finds that there is a strong correlation. The greater the distance the greater the velocity.

If one then projects backwards in time, the inference is that all the galaxies were at one place some 14 billion years ago.

The inference of a big bang occurring at that time would not seem unreasonable.
yes. thanks for actually answering the question of the thread.

you are the first one!
Not really. Just in case you missed it, here's my original post:
uwot wrote: Fri Oct 12, 2018 11:03 amI'm revamping the book; making it clearer (hopefully) and getting rid of distractions. You can see the first part on the blog. If it still doesn't make sense, I would love to hear your comments. https://willijbouwman.blogspot.com
What A_Seagull says is pretty much the gist of what is written, but no one has actually commented on the revamp and quite a few clearly haven't read it. Ah well, people have read the title and waded in, which is fair enough; done it myself often enough.
I can't speak for others but I have reviewed your material and provided positive feedback numerous times.

A couple of assumptions coming from you today, and each time you seem to have been wrong too.
surreptitious57
Posts: 4257
Joined: Fri Oct 25, 2013 6:09 am

Re: Why do scientists think there was a big bang?

Post by surreptitious57 »

uwot wrote:
https://willijbouwman.blogspot.com

from the moment you were born every arrangement of atoms that gave rise to every thought you have ever
had has been generating waves and patterns in Big Bang stuff that will spread out across the universe forever
The lifespan of a stable atom is limited by the lifespan of a proton which is estimated at I0 25 years
The lifespan of the Universe before heat death occurs [ assuming proton decay ] is estimated at I0 I000 years

The only thing in theory which could possibly exist forever is a photon in empty space but in reality they either disintegrate or are absorbed
The notion of forever therefore cannot apply to any thing including the Universe and so from a scientific perspective it is really meaningless
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Re: Shoulda called it something else.

Post by uwot »

Greta wrote: Sun Oct 14, 2018 7:56 amI can't speak for others but I have reviewed your material and provided positive feedback numerous times.
Indeed you have. It is very encouraging, and if I sound ungrateful, I apologise.
Greta wrote: Sun Oct 14, 2018 7:56 amA couple of assumptions coming from you today, and each time you seem to have been wrong too.
Well, I was just pointing out to gaffo that no one has mentioned the revamp.
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Re: Why do scientists think there was a big bang?

Post by uwot »

surreptitious57 wrote: Sun Oct 14, 2018 8:38 amThe only thing in theory which could possibly exist forever is a photon in empty space
Depends on the theory. I'm a sucker for quantum field theories, according to which, if there's no electromagnetic field, there is no photon. It's chicken and egg: do particles cause fields, in which case how? Or are particles disturbances in fields? I think the latter is more plausible,but as Greta's link points out, it doesn't answer the question of where such fields came from. Mind you, the same would be true of any particles that cause fields.
surreptitious57 wrote: Sun Oct 14, 2018 8:38 amThe notion of forever therefore cannot apply to any thing including the Universe and so from a scientific perspective it is really meaningless
Fair enough. I did think of qualifying that and saying 'For as long as there is a universe.' which in practical terms is forever, but I take your point, and thank you for reading the blog, and for the feedback.
surreptitious57
Posts: 4257
Joined: Fri Oct 25, 2013 6:09 am

Re: Why do scientists think there was a big bang?

Post by surreptitious57 »

The four fundamental forces were fused together at the Big Bang and only became separated after expansion
And as atoms did not exist then one can say that the field came before the particle not the other way around

So electromagnetism existed before electrons just as gravity existed before stars

Also quantum fluctuations cause virtual particles to pop in and out of existence
Because a state of nothing cannot persist for too long before becoming unstable
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Re: Why do scientists think there was a big bang?

Post by uwot »

surreptitious57 wrote: Sun Oct 14, 2018 9:53 amThe four fundamental forces were fused together at the Big Bang and only became separated after expansion
Well, that's one possibility that physicists are investigating.
surreptitious57 wrote: Sun Oct 14, 2018 9:53 amAnd as atoms did not exist then one can say that the field came before the particle not the other way around
I think that is probably true, and you get rid of spooky action at a distance as a bonus.
surreptitious57 wrote: Sun Oct 14, 2018 9:53 amSo electromagnetism existed before electrons just as gravity existed before stars
Are you sure that's what you mean? According to general relativity, the field is 'spacetime' or just space. This is a substance that is warped by things like stars. So if there are no stars, there's no warping, hence no gravity.
surreptitious57 wrote: Sun Oct 14, 2018 9:53 amAlso quantum fluctuations cause virtual particles to pop in and out of existence
Because a state of nothing cannot persist for too long before becoming unstable
It is true that particles pop in and out of existence, but we have no idea how long a state of nothing can persist, because there is no example that we can observe.
surreptitious57
Posts: 4257
Joined: Fri Oct 25, 2013 6:09 am

Re: Why do scientists think there was a big bang?

Post by surreptitious57 »

uwot wrote:
surreptitious57 wrote:
So electromagnetism existed before electrons just as gravity existed before stars
Are you sure that is what you mean ? According to general relativity the field is spacetime or just space. This
is a substance that is warped by things like stars. So if there are no stars there is no warping hence no gravity
It is only within and around galaxies that general relativity applies. Outside of them spacetime
is basically flat and can be treated as Euclidean even though Newtonian gravity is still universal
User avatar
henry quirk
Posts: 16379
Joined: Fri May 09, 2008 8:07 pm
Location: 🔥AMERICA🔥
Contact:

"the space with no stuff in it is still expanding via time!"

Post by henry quirk »

Yeah, I don't know what that means. I can wrap my head around the analogy of the bowling ball on the trampoline (to poorly explain gravity as the result of mass) but this whole 'space is expanding' thing eludes me.

Again: In a perfect vacuum (and I'm talkin' about a universe of perfect vacuum not a discrete volume of perfect vacuum in our universe) there'd be no time cuz time is change (and the possibility of measurement), and in a perfect vacuum there's nuthin' to measure.

So: the Doctor is shit outta luck...his Tardis is just a Police Box...he (or she :roll:) ain't a Lord of Time...Gallifrey is really just an asylum for the deluded.
uwot
Posts: 6092
Joined: Mon Jul 23, 2012 7:21 am

Re: Why do scientists think there was a big bang?

Post by uwot »

surreptitious57 wrote: Sun Oct 14, 2018 1:44 pmIt is only within and around galaxies that general relativity applies. Outside of them spacetime
is basically flat and can be treated as Euclidean even though Newtonian gravity is still universal
Well, it's rather that we only apply general relativity within and around galaxies, and it only works at the galactic scale if we bung in dark matter, which doesn't show up anywhere on a smaller scale. At the inter-galactic scale, we chuck in dark energy to account for the fact that Newtonian gravity apparently isn't universal.
Post Reply