Potential Evidence of Inflationary Big Bang

[JonathanL]

No, the answer is not gravity. Inflation is not caused by repulsive gravity.

Be that as it may, inflation is fair enough as an answer to the question of why the universe did not collapse into a black hole. But inflation itself is not caused by gravity.

Am I misunderstanding what Alan Guth is saying in the following article, or is he contradicting your claim that inflation is not caused by repulsive gravity?

http://www.counterbalance.org/cq-guth/howdo-frame.html

[sylas]

Am I misunderstanding what Alan Guth is saying in the following article, or is he contradicting your claim that inflation is not caused by repulsive gravity?

http://www.counterbalance.org/cq-guth/howdo-frame.html

He is contradicting me -- and you are thus teaching me something! Thank you. Go with Guth rather than with me.

[added in edit]Can't give you pearls, so I have given you 2 experience points![/added]

My understanding when I wrong my first reply above, which you quote, was that inflation is a consequence of energy released from the collapse of a scalar field, the "inflaton field".

My error was, I think, in considering this to be distinct from gravity.

Quoting a footnote by Guth from your link:

The possibility of repulsive gravity arises because, according to Einstein's theory of general relativity, gravitational fields are produced not just by energy or mass densities, but also by pressures. The direction of the field caused by pressure is what you would probably guess: a positive pressure - the kind that we normally see - produces an attractive gravitational field. But the peculiar state of matter that I'm talking about produces a negative pressure, which you might also call a suction. It is in fact a very large negative pressure, resulting in a repulsive gravitational field which is stronger than the attractive field produced by the mass density of the matter. The result is a net gravitational repulsion, which is the driving force behind inflation.

As I read this, Guth is not referring to conditions under which gravity between conventional matter is repulsive, but rather referring to a field (the scalar inflaton field) which has an equation of state different from conventional matter. It is the inflaton field that gives "negative pressure" and hence repulsive gravity. So it isn't that gravity used to be repulsive but is now attractive. It's rather that the universe used to be driven by a field which gives rise to negative pressure and repulsive gravity, in contrast to the fields from conventional matter which are our normal experience.

Thanks! -- sylas

[rwatts]

Sometimes I pretend to understand cosmology because it is so much fun, but there are people here who really do understand some of this and I love to listen in on the conversations and ask an occasional question to try and understand something a little better. We're all part of an amazing universe and it boggles my mind that some people are able to begin to contemplate the beginning of our universe scientifically.

This is only a popular account of what may be the beginnings of evidence for an Inflationary Big Bang. Possibly more evidence on the horizon. Enjoy!

http://www.space.com/25078-universe-...discovery.html

Other folk are chiming in with an "Hey. Not so fast", kind of comment. They think the results could be misleading:-

Star dust casts doubt on recent big bang wave result

The final paragraph of the above linked article is worth keeping in mind. This result could be firmed up next October. However, all of the signal detected might not be due to gravity waves.

[JimL]

He is contradicting me -- and you are thus teaching me something! Thank you. Go with Guth rather than with me.

Thanks! -- sylas

You're welcome.

[JonathanL]

You're welcome.

[sylas]

Jim was the first to describe inflation as caused by repulsive gravity. I corrected him, and then you corrected me. I then thanked you; but omitted to acknowledge Jim. So thanks also to you, Jim!

[shunyadragon]

Other folk are chiming in with an "Hey. Not so fast", kind of comment. They think the results could be misleading:-

Star dust casts doubt on recent big bang wave result

The final paragraph of the above linked article is worth keeping in mind. This result could be firmed up next October. However, all of the signal detected might not be due to gravity waves.

I listened to a PBS interview where cosmologist questioned the conclusion as not misleading but inconclusive based on several reasons. The above was one of them.

[tharkun]

For your consideration...see this analysis of the BICEP data and whether 'gravity waves' were actually detected:

http://milesmathis.com/guth.pdf

Incidentally, 'inflation' is a physical and logical non-starter because it requires time to be in an exponential relationship to distance (i.e. R^t). But this is an impossible situation because time is just a secondary measurement of distance; you cannot measure or calculate an elapsed time without measuring a distance. Since it is not possible for distance to be in an exponential relationship with distance (we don't see an x-direction growing at different rate than a y- or z-direction, do we?), it is also not possible for time to be in an exponential relationship with distance.

tharkun

[shunyadragon]

For your consideration...see this analysis of the BICEP data and whether 'gravity waves' were actually detected:

http://milesmathis.com/guth.pdf

Incidentally, 'inflation' is a physical and logical non-starter because it requires time to be in an exponential relationship to distance (i.e. R^t). But this is an impossible situation because time is just a secondary measurement of distance; you cannot measure or calculate an elapsed time without measuring a distance. Since it is not possible for distance to be in an exponential relationship with distance (we don't see an x-direction growing at different rate than a y- or z-direction, do we?), it is also not possible for time to be in an exponential relationship with distance.

tharkun

good post! Welcome to Tweb!!! Thank you for the reference.

[robrecht]

Princeton team publishes in Nature: Dust up casts further doubt on gravity wave discovery:

Toward an Understanding of Foreground Emission in the BICEP2 Region

Raphael Flauger, J. Colin Hill, David N. Spergel

(Submitted on 28 May 2014)

BICEP2 has reported the detection of a degree-scale B-mode polarization pattern in the Cosmic Microwave Background (CMB) and has interpreted the measurement as evidence for primordial gravitational waves. Motivated by the profound importance of the discovery of gravitational waves from the early Universe, we examine to what extent a combination of Galactic foregrounds and lensed E-modes could be responsible for the signal. We reanalyze the BICEP2 results and show that the 100x150 GHz and 150x150 GHz data are consistent with a cosmology with r=0.2 and negligible foregrounds, but also with a cosmology with r=0 and a significant dust polarization signal. We give independent estimates of the dust polarization signal in the BICEP2 region using four different approaches. While these approaches are consistent with each other, the expected amplitude of the dust polarization power spectrum remains uncertain by about a factor of three. The lower end of the prediction leaves room for a primordial contribution, but at the higher end the dust in combination with the standard CMB lensing signal could account for the BICEP2 observations, without requiring the existence of primordial gravitational waves. By measuring the cross-correlations between the pre-Planck templates used in the BICEP2 analysis and between different versions of a data-based template, we emphasize that cross-correlations between models are very sensitive to noise in the polarization angles and that measured cross-correlations are likely underestimates of the contribution of foregrounds to the map. These results suggest that BICEP1 and BICEP2 data alone cannot distinguish between foregrounds and a primordial gravitational wave signal, and that future Keck Array observations at 100 GHz and Planck observations at higher frequencies will be crucial to determine whether the signal is of primordial origin. (abridged)

http://arxiv.org/abs/1405.7351

Paul Steinhardt bursts multiverse bubble (not really but fun metaphor, lay version):
http://www.nature.com/news/big-bang-...bubble-1.15346

[robrecht]

Stephen Hawking hasn't given up on this idea:

This week, I have a visit from Thomas Hertog from Belgium. We are working on a new theory of the origin of the universe. It predicts there are gravitational waves from the Big Bang pervading all of space. These may already have been observed by the BICEP team with a radio telescope at the South Pole. However their signal might be caused by dust. If the observation is confirmed, it will open a new window on the universe and will be even more significant than the discovery of the Higgs boson. -SH

https://www.facebook.com/stephenhawk...type=1&fref=nf

[shunyadragon]

Stephen Hawking hasn't given up on this idea:

This week, I have a visit from Thomas Hertog from Belgium. We are working on a new theory of the origin of the universe. It predicts there are gravitational waves from the Big Bang pervading all of space. These may already have been observed by the BICEP team with a radio telescope at the South Pole. However their signal might be caused by dust. If the observation is confirmed, it will open a new window on the universe and will be even more significant than the discovery of the Higgs boson. -SH

https://www.facebook.com/stephenhawk...type=1&fref=nf

I agree with Hawking, IF the observations are confirmed then it is a very important discovery. I do not believe anyone has given up. They just stepped back, and put the present evidence in perspective.

[robrecht]

I agree with Hawking, IF the observations are confirmed then it is a very important discovery. I do not believe anyone has given up. They just stepped back, and put the present evidence in perspective.

I will let him know. Certainly, he will be very pleased to hear that you agree.

[shunyadragon]

I will let him know. Certainly, he will be very pleased to hear that you agree.

Sarcasm needle just pegged in the ridiculous.

[robrecht]

The quest goes on:

http://news.discovery.com/space/astr...tes-150130.htm