Episode 58: Inflation

[Fraser]

We interrupt this tour through the solar system to bring you a special show to deal with one of our most complicated subjects: the big bang. Specifically, how it's possible that the universe could have expanded faster than the speed of light. The theory is called the inflationary theory, and the evidence is mounting to support it. Einstein said that nothing can move faster than the speed of light, and yet astronomers think the universe expanded from a microscopic spec to become larger than the solar system, in a fraction of a second.

<strong><a href="http://media.libsyn.com/media/astronomycast/AstroCast-071015.mp3">Episode 58: Inflation (17.0MB)</a></strong><br />&nbsp;<br />

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[EvilEye]

I understand 99% of what Pamela explained, but have a problem with ONE single analogy.

The Little kid walking 4 sidwalk-blocks per second, and then the builders adding sidewalk-blocks between him and the school....

She is adding him to the blocks.

BUT... that wouldn't make him go faster toward school. It would slow him from the perspective of the school. He would have 4 times as far to go if the sidewalk blocks were added in front of him even though he was still moving at the same speed.

A better analogy would be walking on a static mover, like at a theme-park and the people are walking 1 MPH on the mover, but the mover is moving at 1mph. So the person covers twice the distance in the same amount of time.

[EvilEye]

Nevermind... I just listened again. He was walking away from the school, and the block were added BEHIND him.

I get it now.

[4tune8chance]

Tough episode!

I was interested in the comment about the expansion of the universe that it may have pockets of non uniformity, given that these are too far away to be observed, I think it was inferred that the expansion may not be linier.

This got me to thinking, we picture the universe as expanding from a single point out to a sphere. Is it at all possible that the universe is more like a running crack in a pane of glass? i.e. the crack (expanding) but continuing?

[Jerry]

Einstein said that nothing can move faster than the speed of light, and yet astronomers think the universe expanded from a microscopic spec to become larger than the solar system, in a fraction of a second.

The paradox is real, the expansion of space as an answer to this paradox is not. There are energy issues: If the space has increased, then the net gravimetric energy between two objects on either side of the expanded space has also increased, and where did this come from?

Builders adding blocks adds energy, just as an expanding loaf of bread requires energy from the oven. Inflation does not address this energy issue. This explanation for the size of the universe is thermodynamically bankrupt. It is as phony as perpetual motion, and should be summarily dismissed.

[EvilEye]

Perhaps you are looking at it wrong.

Put a tiny marshmallow into a vacuum jar, and suck all the air out. The Marshmallow attempts to fill the entire volume.

There is no lost energy, no gained energy. All the same Marshmallow, just expanding.


That is to say... our universe has no container, so it is trying to fill an infinite volume with finite matter.

[Calculon3000]

Wouldn't it require energy to suck out the air to create the vacuum?

It's the same physical marshmallow, but the properties of it's physical location have changed.

[EvilEye]

Wouldn't it require energy to suck out the air to create the vacuum?

It's the same physical marshmallow, but the properties of it's physical location have changed.

To force the air out of the jar...yes.

But space itself is already a vacuum.

[Steve Limpus]

To force the air out of the jar...yes.

But space itself is already a vacuum.

If inflation is the expansion of space itself, and if you accept that a vacuum requires space (and time), then the jar isn't even really a vacuum, but something...else?

The 'expanding universe' explanation I've most often heard is that spacetime has its own intrinsic 'vacuum energy' or pressure that drives expansion; so as spacetime expands so does the amount of pressure--hence the accelerating universe. It all sounds pretty tidy, but I must confess inflation has always seemed just a little arbitrary. There is something about 'phase transitions' (like when water turns to ice) which sounds appealing as a way to explain the difference between inflation and expansion, that may also be related to the fundamental forces 'condensing' out of the grand unified force. (Think of the universe as frozen energy, cooling from its original hot-dense state. The universe as a giant popsicle!)

I've also heard the 'vacuum energy' of spacetime linked to the idea of 'virtual particles'. I'm sure others more knowledgeable than me can elucidate.

I haven't had a chance to download the cast yet so apologies if I'm off topic.

[Steve Limpus]

There are energy issues... where did this [energy for inflation] come from? Inflation does not address this energy issue.

Hey Jerry

I thought about this a bit.

It seems science doesn't have a good handle on the properties of the universe prior to the planck epoch, save it was very hot and very dense. Could it be that the energy for everything that has happened to the universe since, was already there at the start?

To me, the idea of the universe condensing out of this unimaginably hot, dense, and energetic state has always appealed. If you compare the young universe to steam: steam doesn't require any energy added to condense into water...the 'steam' actually gives up energy to it's environment in the process, right? I think the technical term is 'exothermic phase transition'. To a lay man like myself, does this address your thermodynamic objection in any way? I still haven't listened to the podcast so I don't know if Fraser or Pamela have mentioned the idea already, apologies if they have.

Of course, the really big mystery would be how did the 'steam' get there in the first place?

For me, the 'expansion' of the universe and this idea of 'phase transition' are inextricably linked. Did one somehow cause the other... or each other? And then you have the 'arrow of time.' Its all wonderfully evocative to imagine when I look out at the night sky with my two little boys. (They already love to tell people they're made of Stardust, I think I'll get them to try Condensed Big Bang!)

Anyways... back to work for me...

[damian1727]

In the inflationary theory, matter, antimatter, and photons were produced by the energy of the false vacuum, which was released following the phase transition. All of these particles consist of positive energy. This energy, however, is exactly balanced by the negative gravitational energy of everything pulling on everything else. In other words, the total energy of the universe is zero!


there is no energy lol

your just imagining it

great episode really got the flatness problem over well

http://abyss.uoregon.edu/~js/ast123/lectures/lec17.html

[BigStan]

Have enjoyed Astronomy cast for several months but not tempted til now to register and comment--for the purpose of asking: What caused inflation and what halted it? Dr. Gay's reference to "inflaton" particle as causing inflation floored me. I had thought inflation was the "intrinsic" rate of big bang expansion until slowed by emergence of "mass" and gravity, i.e. graviton. If "inflaton" caused inflation, what caused its decay? graviton? Are "inflaton" and graviton related? I'm afraid your Inflation explanation raises more questions than it answered. Why did inflation last 1-33 seconds? What happened to cause expansion to slow to "historic" rates.

Thanks for all the hard work.

[Steve Limpus]

Finally got some spare time to listen to the show--wow! Great work Fraser and Pamela. I was really excited to hear Pamela say that the observable universe is thought to be three or four percent of the entire universe; it's something I've wondered ever since I 'got' the size and shape of the observable universe and our place in it.

If Pamela says its three or four percent that's good enough for me. Does anyone know *how* we figured out that percentage?

[Steve Limpus]

Dr. Gay's reference to "inflaton" particle as causing inflation floored me.

I'm with you Stan--although I read the term 'inflaton' recently rather than hearing it first on the podcast. I'm still trying to 'get' the Higgs Boson, then along comes the Inflaton! So far I've decided the science of inflatons is a bit beyond me yet.

Even Wikipedia doesn't have a lot to say about it:

The inflaton is the generic name of the unidentified scalar field (and its associated particle) that may be responsible for an episode of inflation in the very early universe. According to inflation theory, the inflaton field provided the mechanism to drive a period of rapid expansion from 10−35 to 10−34 seconds after the initial expansion that formed the universe.

The inflaton field's lowest energy state may or may not be a zero energy state. This depends on the chosen potential energy density of the field. Prior to the expansion period, the inflaton field was at a higher energy state. Random quantum fluctuations triggered a phase transition whereby the inflaton field released its potential energy as matter and radiation as it settled to its lowest energy state. This action generated a repulsive force that drove the portion of the universe that is observable to us today to expand from approximately 10−50 metres in radius at 10−35 seconds to almost 1 metre in radius at 10−34 seconds.

I would love it if anyone had a nice simple explanation or link that describes what a 'scalar field' is?

[Steve Limpus]

your just imagining it

Hey Damian

That's the thing isn't it. I can go outside and kick the road and its like 'whoa! the earth is big', then I can look at the night sky and 'wow! look at all that...stuff'.

And then, 'where does it all come from?'... and it turns out it is all virtually from 'nothing'.

Or go the other way: the earth is made of atoms, atoms are made of quarks, quarks are made of what? Strings? Nothing?

Way better than any Star Trek episode!

Good link too.

[Burt]

I was really excited to hear Pamela say that the observable universe is thought to be three or four percent of the entire universe; ... If Pamela says its three or four percent that's good enough for me. Does anyone know *how* we figured out that percentage?

Hi Steve. The closest answer that I found is that cosmologists think that the minimum size of the total universe is some 133 billion light years radius. This gives a volume of around 10 billion billion cubic light years. The observable universe has a present radius of about 46 billion light years, giving a volume of about 400 thousand billion cubic light years. The observable volume is then about 4% of the whole.

One must remember though, that the observations are also compatible with an infinitely large universe, which makes the observable portion, well, zero %?

[Steve Limpus]

One must remember though, that the observations are also compatible with an infinitely large universe, which makes the observable portion, well, zero %?

Hi Burt

Are the observations such that the entire universe is either

a: very large (and ours is 4%)
or
b: infinite

or is it just that the very large universe is the miniumum size?

The reason I ask is that the idea of 'infinity' makes my brain explode! I'd be happy to know the 4% deal is a 50/50 proposition.

There's a good show on the BBC World Service website where various experts debate infinity and I get the impression that infinity is a mathematical construct that can't actually exist anywhere in reality. Your example above is a good one: if the entire universe is infinite then the observable universe is 0% - and yet here we all are, and it is rather a lot of stuff! (Actually I'm not sure about the maths--is it 0% or just an 'infinitely' small % but not quite 0?)

I'm gonna buy 4% - at least I'll be able to sleep nights!

A Brief History of Infinity: Space and the Universe
http://news.bbc.co.uk/2/hi/programme...ve/5349064.stm

A Brief History of Infinity: Mathematics
http://news.bbc.co.uk/2/hi/programme...ve/5349364.stm

[Burt]

Hi Burt

... or is it just that the very large universe is the miniumum size?

The reason I ask is that the idea of 'infinity' makes my brain explode! I'd be happy to know the 4% deal is a 50/50 proposition.

Hi Steve.

Yea, infinite size doesn't really make sense, does it. I think present observation indicates that the universe is at least 25 times the size of the observable universe (which is then at most 4% of the total). The universe may possibly be millions of times larger than our observable patch, but no one knows just how BIG and we may never know.

Burt

[damian1727]

as i understand it no one has any idea how big our ''bubble is beyond the observable universe.....tho i have heard much much larger estimates then 25 0/0...... one i liked i cant remember where from was that the observable universe was the size of a photon then the entire bubble was the size of the earth.....

but no one knows... (apart from douglas adams)

but to cut a long story short if the edge of the universe is receding from us faster than the speed of light then it is to us on any practical level unending

?

i love this stuff

lol

[Steve Limpus]

but to cut a long story short if the edge of the universe is receding from us faster than the speed of light then it is to us on any practical level unending

Yep.. I get that. Interesting way to think about it.

I read somewhere that there will be future civilisations who will be unable to observe the universe beyond their own gravitationally bound galaxy (or perhaps cluster?) because everything else (even the CMBR) will have receded beyond the Hubble limit. I don't know all the details, or if the timing is such that the universe is likely to support intelligent life at that time, but it's a sad thought: entire civilisations who can never know the rest of the universe exists... I wonder what they will make of things?

Douglas Adams... yes, got that too. Had to google first though.

[Burt]

I read somewhere that there will be future civilisations who will be unable to observe the universe beyond their own gravitationally bound galaxy (or perhaps cluster?) because everything else (even the CMBR) will have receded beyond the Hubble limit.

Hi Steve.

Yes, according to present theory, this may happen in the unforeseeable distant future! I do not think that the CMB will ever drift 'out of view', so to speak, but it may just become so redshifted that it is undetectable. Sad...

[Steve Limpus]

Came across these quotes:

"...the entire universe is expected to be at least 10²³ times larger than the observed universe! ...if the inflationary theory is correct, then the observed universe is only a minute speck in a universe that is many orders of magnitude larger." Alan Guth (found this in a post from Cougar on this thread: Episode 28: What is the universe expanding into?)

"It is also possible that the universe is smaller than the observable universe. In this case, what we take to be very distant galaxies may actually be duplicate images of nearby galaxies, formed by light that has circumnavigated the universe. It is difficult to test this hypothesis experimentally because different images of a galaxy would show different eras in its history, and consequently might appear quite different.
A 2004 paper claims to establish a lower bound of 24 gigaparsecs (78 billion light-years) on the diameter of the universe, based on matching-circle analysis of the WMAP data. This is a lower bound (not an estimate) for the size of the whole universe (not the observable universe). If the universe is smaller than the observable universe, then light has had time to circumnavigate it since the big bang, producing multiple images of distant objects in the sky. Cornish et al looked for such an effect at scales of up to 24 gigaparsecs (78 billion light years) and failed to find it. 24 gigaparsecs is simply the upper limit of the search space of this study; it has no physical significance." http://en.wikipedia.org/wiki/Observable_universe#Size

...so I guess this really is one of those no-one really knows things.

Here's another question: if the idea from the Wikipedia quote above were correct (that apparently distant galaxies are actually earlier images that have circumnavigated a compact universe) would we then observe the same apparent recession of those apparently distant galaxies? I wouldn't have thought so - but it does illustrate that there isn't one really satisying answer yet (ever?).

[CPMosh]

Someone, please help me understand the expansion of the universe. As space expands, are there more units of distance between objects or are the units of distance getting bigger? If the units get bigger, will the amount of units (meter sticks) between objects will remain constant?

How many meter sticks will fit between the sun and another star now as compared to a billion years from now?

If the units of measure are getting bigger (the same number of growing meter sticks), does light cover less of them in a certain period of time (light’s time based on a fixed size meter stick)? What do we have remaining as our frame of reference?

If the units of measure are getting bigger, how is the expansion of the universe to be distinguished from light simply getting slower over time?

If the units of measure are not getting bigger, how is this distinguished from a simple explosion of matter into existing space?

Thank you

[NHR+]

I think the expansion occurs only in larger scales, galaxy clusters or something like that. Individual stars in a galaxy are not moving away from each other, or they sure can be, but that's not due to the expansion of the universe. Andromeda galaxy is also "comin' right for us", only all of the "far-far-away-galaxies" seem to be receding. Galaxies and galaxy clusters (local group, Virgo cluster?) are called "gravitationally bound", if they're not moving away from each other. I'm not sure just where exactly this boundary lies...

I guess it's rather that there would become more room for "metre-sticks" than the sticks themselves expanding. Light in the process gets redder, that means its wavelength is increasing.

Also, in an explosion of matter into pre-existing space, there would be some kind of center point visible, I suppose...

Not very helpful now, is it...

[damian1727]

?

errr the space between stars is expanding

units of measurment are a human conveniance and have no physical reality.....tho i guess a light year is a unit of measurement,,,,

as space expands there will be more light years between objects

light is not getting slower

things would have to be shrinking as well lol...well u never now...

the simple answer is yes you are correct as the universe expands there is more distance between things....

errrrrr

:/

[CPMosh]

Okay, so units of measure are staying constant while space expands. Based on this, what would happen in this example?

Suppose NHR+ purchases one Megaparsec of rope at the hardware store. The rope is carefully measured out at 2×10(to the)19 miles. Frasier takes one end and Pamela takes the other. They move off in opposite directions.

Now, as I understand, the length of the rope stays consistent (relative to the speed of light?), so once Pamela and Frasier get the rope taught, they have to hold on pretty tight as the expansion of space tries to pull them apart at 73.5km/sec (correct?).

What do we observers in the middle see happen if damian1727 sneaks up with scissors and cuts the rope. How fast do the ends move apart? What do Frasier and Pamela experience out on the ends?

What if the test is repeated with a 2 Megaparsec piece of rope?

Thanks to you both for jumping in and helping clear this up.

[Steve Limpus]

...so once Pamela and Frasier get the rope taught, they have to hold on pretty tight as the expansion of space tries to pull them apart at 73.5km/sec (correct?).

I don't think they would have to hold on 'tight'.

The strong and electro-magnetic forces of the atoms and particles of the rope (and of Fraser and Pamela) would easily overcome the expansion of space and they would hardly notice--just like we don't notice here, nice and comfy in the Milky Way, where (even the incredibly weak) force of gravity also easily overcomes the expansion of space.

I imagine Fraser and Pamela easily hanging on with one hand, and chugging back beers with the other. (What happens when you crack a beer in a vacuum?)

73.5km/sec sounds violent, but I'm pretty sure if you state the expansion of the universe as a percentage it would seem pretty small and 'gentle'? The expansion of the 'local' space around Fraser for example would be very small--it's only when you sum the expansion over a large volume of space that the velocities become large? Kinda like compound interest?

And it's not like Fraser or Pamela are moving through space at 73.5km/sec--rather space itself is gently expanding at 73.5km/sec per megaparsec... or something.

"...the cosmic microwave background radiation that we see right now was emitted about 13.7 billion years ago by matter that has, in the intervening time, condensed into galaxies. Those galaxies are now about 46 billion light-years from us, but at the time the light was emitted, that matter was only about 40 million light-years away from the matter that would eventually become the Earth." http://en.wikipedia.org/wiki/Observable_universe

So our observable universe has expanded by over ten thousand percent, but has taken over ten billion years to do so--thats about one ten thousandth of one percent per year... I think?

[damian1727]

snip snip lol i always get the good jobs

i dont know any figures but they could as steve said hold the rope easy but if the rope was very very long and i waited say 100 years even tho pam and steve had not moved(after chugging beers 4 100 years who could blame them!!) i would not be able to join the ends up......

lol

i know its a small effect on the local level but it must be happening in my house !!!

a little?

[Steve Limpus]

What do we observers in the middle see happen if damian1727 sneaks up with scissors and cuts the rope. How fast do the ends move apart? What do Frasier and Pamela experience out on the ends?

This is my (barely) educated guess...

If Fraser and Pamela bought the rope on Earth, and flew off 0.5 Mpc in opposite directions: I suspect they wouldn't experience anything unusual (except a marvelous view) because they would still be within the gravity well of the local galaxy cluster.

If we had all teleported to a large void, and were not bound by any local gravitational system: we observers in the middle of the rope would observe Pamela and Fraser receding at 36.75km/sec (and they, us); Fraser and Pamela would observe each other receding at 73.5km/sec, but they would not experience any acceleration, just the expansion of the space between them. Whether the gravity of Pamela, Fraser, the rope, and we observers, would make a difference I don't know... but I expect such a little mass (how much does a Mpc of rope weigh?) over such a large distance would make little difference (due to the inverse square law).

...relativity might have something to say about it too? And red-shift etc.

I suppose you just 'times two' if you double the length of the rope.

[Steve Limpus]

I know its a small effect on the local level but it must be happening in my house !!!

...Beer, or the Hubble Constant?