Spacetime pixels probably smaller than predicted

Paul Raven @ 06-07-2011

Just because I get a deep kick of joy from being able to type out a post title like that and have it actually mean something. From Wired UK, reassurance that we’re (probably) not living in a holographic universe:

Hogan’s interpretation of results from the GEO600 gravitational wave experiment had shown a quantum fuzziness — a sort of pixellation — at incredibly small scales, suggesting that what was perceive as the universe might be projected from a two-dimensional shell at its edge.

However, a European satellite that should be able to measure these small scales hasn’t found any quantum fuzziness at all, contradicting the interpretation of the GEO600 results and indicating that the pixellation of spacetime, if it exists, is considerably smaller than predicted.

Well, I’ll be sleeping more soundly tonight.

 


Is the universe a hologram?

Paul Raven @ 25-10-2010

Wrap your head around this on a Monday morning, if you can: what we think of as the three dimensional universe we inhabit may in fact just be a holographic projection, and Craig Hogan is trying to prove it [via BigThink and Ian Sales].

The idea that spacetime may not be entirely smooth – like a digital image that becomes increasingly pixelated as you zoom in – had been previously proposed by Stephen Hawking and others. Possible evidence for this model appeared last year in the unaccountable “noise” plaguing the GEO600 experiment in Germany, which searches for gravitational waves from black holes. To Hogan, the jitteriness suggested that the experiment had stumbled upon the lower limit of the spacetime pixels’ resolution.

Black hole physics, in which space and time become compressed, provides a basis for math showing that the third dimension may not exist at all. In this two-dimensional cartoon of a universe, what we perceive as a third dimension would actually be a projection of time intertwined with depth. If this is true, the illusion can only be maintained until equipment becomes sensitive enough to find its limits.

“You can’t perceive it because nothing ever travels faster than light,” says Hogan. “This holographic view is how the universe would look if you sat on a photon.”

Coming soon to a Greg Egan short story collection near you…

I just never get tired of these existential cosmology ideas. As I’ve said before, this is the sort of stuff that makes me wish I’d actually paid attention at university and gone on to study hardcore physics… though given how much I sucked at calculus, it’s probably best that I didn’t.


Time is running out

Paul Raven @ 30-09-2010

There’s never enough time in the day, is there? Well, turns out that there may be a finite limit on the number of days, too… though not a limit so hard that it’s going to impact our expected personal life-spans very much.

The prevalent theory among cosmologists and physics heads is that the universe can and should expand indefinitely, meaning that time is essentially infinite and unending, but an apostate little gang of researchers are now suggesting that there’s a 50% chance that the universe – and hence time – will run out in around 3.7 billion years. Given that our own Sun is supposed to last another 5 billion years, that’s something of a curtailment of scope…

Their argument against an infinite universe is simple. In an infinite universe, anything can happen and will happen, no matter how unlikely it is. When there’s an infinite amount of every possible observation occurring, then it becomes impossible to determine probabilities of events, making the laws of physics similarly impossible to determine.

Of course, this makes an important philosophical assumption. Do we need to be able to understand the laws of physics, rather than just observing that they work? If so, then the Universe has to have an end.

I love a bit of epic-scale philosophical wrangling (if only as a layman watching from the sidelines), but it’s a little early in the day for it. My head hurts; I think I’ll go and have a little lay down. If Greg Egan calls, please take a message and tell him I’ll get back to him as soon as I’m able.


Goodbye, Big Bang?

Paul Raven @ 29-07-2010

Everyone knows about the Big Bang, right? The explosion-into-being of the entire universe, however many billions of years ago? Of course they do. Trouble is, the Big Bang has always been something of a fudged theory… and now Wun-Yi Shu of the National Tsing Hua University in Taiwan has come up with a new theory that fits a lot of observed evidence far more thoroughly… while dumping on some accepted truths.

Shu’s idea is that time and space are not independent entities but can be converted back and forth between each other. In his formulation of the geometry of spacetime, the speed of light is simply the conversion factor between the two. Similarly, mass and length are interchangeable in a relationship in which the conversion factor depends on both the gravitational constant G and the speed of light, neither of which need be constant.

So as the Universe expands, mass and time are converted to length and space and vice versa as it contracts.

This universe has no beginning or end, just alternating periods of expansion and contraction. In fact, Shu shows that singularities cannot exist in this cosmos.

As with all such theories, not everything fits perfectly:

One of the biggest problems he faces is explaining the existence and structure of the cosmic microwave background, something that many astrophysicists believe to be the the strongest evidence that the Big Bang really did happen. The CMB, they say, is the echo of the Big bang.

How it might arise in Shu’s cosmology isn’t yet clear but I imagine he’s working on it.

Even if he finds a way, there will need to be some uncomfortable rethinking before his ideas can gain traction. His approach may well explain the Type-I supernova observations without abandoning conservation of energy but it asks us to give up the notion of the Big Bang, the constancy of the speed of light and to accept a vast new set of potential phenomenon related to the interchangeable relationships between mass, space and time.

So, yeah, bit of a revolutionary idea. Reading stuff like this always makes me wish I’d knuckled down more at college and gotten to grips with the heavy-lifting end of physics; that way I might have ended up making a living from speculating about how the universe works. What could be more fun?

And while we’re talking cosmology, here’s a Fermi Paradox rethink [via SlashDot]:

… a new approach by Igor Bezsudnov and Andrey Snarskii at the National Technical University of Ukraine.

Their approach is to imagine that civilisations form at a certain rate, grow to fill a certain volume of space and then collapse and die. They even go as far as to suggest that civilisations have a characteristic life time, which limits how big they can become.

In certain circumstances, however, when civilisations are close enough together in time and space, they can come into contact and when this happens the cross-fertilisation of ideas and cultures allows them both to flourish in a way that increases their combined lifespan.

[…]

The parameters that govern the evolution of this universe are simple: the probability of a civilisation forming, the usual lifespan of such a civilisation and the extra bonus time civilisations get when they meet.

The result gives a new insight into the Fermi Paradox. Bezsudnov and Snarskii say that for certain values of these parameters, the universe undergoes a phase change from one in which civilisations tend not to meet and spread into one in which the entire universe tends to become civilised as different groups meet and spread.

Bezsudnov and Snarskii even derive an inequality that a universe must satisfy to become civilised. This, they say, is analogous to the famous Drake equation which attempts to quantify the number of other contactable civilisations in the universe right now.

Of course, the only way to prove the theory is to wait until we can get more data… so you might want to read a book or something in the meantime.


“We have a moral obligation to seed the universe with life”

Paul Raven @ 10-02-2010

Centaurus A galaxies eruptingThat’s the opinion of Michael Mautner, Research Professor of Chemistry at Virginia Commonwealth University:

As members of this planet’s menagerie, and a consequence of nearly 4 billion years of evolution, humans have a purpose to propagate life. After all, whatever else life is, it necessarily possesses an incessant drive for self-perpetuation. And the idea isn’t just fantasy: Mautner says that “directed panspermia” missions can be accomplished with present technology.

“We have a moral obligation to plan for the propagation of life, and even the transfer of human life to other solar systems which can be transformed via microbial activity, thereby preparing these worlds to develop and sustain complex life,” Mautner explained to PhysOrg.com. “Securing that future for life can give our human existence a cosmic purpose.”

Hasn’t the relentless drive of self-propagation been shown to be somewhat problematic over the long term? Do we need a cosmic purpose? More importantly, does the cosmos need us to have a cosmic purpose? When evangelical ideology and colonialism run out of planetary surface, I guess they have to start looking further afield for things to interfere with… [image via badastronomy]


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