Tag Archives: New Scientist

Living in a black hole?

A scientist on a research project hijacks a spaceship which he prepares to enter a black hole, with the expectation that exiting out the other side will take him into a whole new universe. Sounds like science fiction? Well, it was the basic plot of a rather poor movie from the 1970s with the stunningly original title ‘The Black Hole‘, but if a recent paper in the Physical Review, one of the most prestigious journals,  is right, it might not be so mad after all…  

The gist of the paper is described in an article in this week’s New Scientist. According to Nikodem J. Popławski of Indiana University, it is possible that our universe exists inside a black hole, or that by passing through a black hole in our universe, we could enter a whole new world. This apparently bizarre concept requires some explanation:  

It’s hard to underestimate the impact Einstein had on the way we view the world. Working in mid-seventeenth century Cambridge (ironically at Trinity College when he was a Unitarian), Sir Isaac Newton formulated his theory of gravity that stood as the best explanation for nearly three-hundred years till a lowly clerk in the Swiss Patent Office changed everything. The results of this change of dominant theory ranged from the gradual shift in physics (as new ideas often take time to gain credibility, and this really was a revolution) to the impact on theology and philosophy, in which it arguably contributed to the collapse of the Enlightenment world-view that relied heavily on Newton’s mechanistic, clock-work view of the universe for its origins in the thought of the English Deists such as John Locke.  

Newton’s view of the world was essentially a common-sense one. The universe could be modelled by taking time as an absolute, independent quantity and having the usual three spatial dimensions we experience every day. When Einstein formulated his theories of relativity, he took it to be axiomatic that the speed of light was constant in a vacuum and that the laws of physics are the same in every inertial frame (for which read frame of reference, or point of view if you will). One consequence of this is that time is no longer an absolute, but rather is bound up with space and affected by the motion of particles and the presence of massive objects such as stars. That’s why physicists talk about ‘space-time’.  

Now, one perhaps surprising thing to note is that Newton could never pin down was what gravity actually is. He could model its results (and his theory is still a very useful approximation to Einstein’s) yet couldn’t define it. Einstein, faced with the same problem, conceptualised it as being a result of the shape of space-time. In other words, in general relativity (GR),  gravity is geometry. The classic example of this is nicely illustrated in this video.  

A black hole is the result of the gravitational collapse of a massive star – we’re talking something like thirty times the mass of the Sun. When this occurs, the fabric of space-time is severely distorted. In the heart of  a black hole, there is understood, in classical GR, to be a singularity, which is a point where all the laws of physics break down and of infinite density and space-time curvature (which is very bad, as infinities in equations cause no end of bother!). This singularity is surrounded by an event horizon. This marks the point at which even light, the fastest thing there is, cannot escape the gravitational pull upon it. If you go pass that point, you’re stuck in the inevitable path towards destruction at the singularity. In a black hole, no-one outside can hear (or see) you scream…  

Another key object we need to know about here is properly called an Einstein-Rosen bridge (but is commonly known as a wormhole) which is sort of like a tunnel that connects two different regions of space-time, allowing fast travel between them. The problem is the stability of these ‘tubes’; they are liable to collapse upon being entered by matter. This gets us into the wonderful world of quantum theory and negative energy (which is not supposed to be allowed, but might be after all…), and means that such structures are at most theoretical as yet. However, for the sake of the argument, let’s suppose that somehow or other, they exist.  

Now, there are different regions of space-time with differing properties either side of an Einstein-Rosen bridge or a singularity in a black hole. This means that passing through into the interior of a black hole or going through an Einstein-Rosen bridge (if it were possible) would result in us emerging into a different universe or part of the universe. Popławski’s paper suggests that, with a slight modification of classical GR, it could be that “observed astrophysical black holes may be Einstein–Rosen bridges, each with a new universe inside that formed simultaneously with the black hole. Accordingly, our own Universe may be the interior of a black hole existing inside another universe”.  

Crazy, but the maths seems to make sense (I knew there had to be advantages to doing this PhD stuff!). The problem of how to get through a wormhole still remains, alas, but it could be the substance (pardon the pun) for some new sci-fi…  

In terms of the implications for science, I reckon that if true, this research renders problematic the idea of a ‘theory of everything’ as the limits on our ability to travel between universes are such that we would only have very partial knowledge of the way the network of universes operates. We can only talk about our visible universe.  

Cosmic inflation

 

In that sense, it’s a bit like inflationary theory, which predicts a period of rapid expansion shortly after the Big Bang in which quantum fluctuations result in different parts of the universe having different values for the fundamental constants, such as the speed of light, the charge on the electron and so on. 

In the immediate aftermath of the Big Bang, before the fundamental particles, quarks, electrons and so on, have formed we are dependent on the murky and random world of quantum mechanics. One key rule here is the Uncertainty Principle of Heisenberg, which states that we cannot know the position of a particle and its velocity simultaneously with complete accuracy. The more we know about one, the less we can know about the other. This has implications for the vacuum of energy that would be present at that early stage of the universe, in that it would cause fluctuations in that field (as zero is too precise a value for it to take) that result in areas with different values of fundamental constants. As the universe expands, we end up with discrete regions, our visible universe being just one of many. This limits our ability to speak about the universe as a whole, as we can only know anything about our little portion. 

Now, I’ve explored some of the theological implications in my talk on physics and Christianity of current physics thinking, and think the questions raised by the inflationary model apply here. Moreover, in what sense can we speak of the cosmic implications of the life, death and resurrection of Jesus? Does it only apply to our visible universe, or what? I don’t know the answer to this and will, when I get the time, do some reading around what others think, but it’s a fascinating question.

Cosmic Inflation

Image: Detlev Van Ravenswaay/SPL

There’s an interesting article in the current issue of New Scientist about cosmic inflation. Allow me to explain.

We’ve known since the 1920s that the predictions of Einstein’s general relativity about the expansion of the universe are correct, and that the further away one looks, the faster distant galaxiesare moving away from us. Extrapolating back in time, the universe is thought to have exploded out from an infinitesimally small point of infinite energy and spacetime curvature, known as a singularity. This explosion has come to be known as the big bang theory.

Current physical theories can take us back in time to within a tiny fraction  of a second after this explosion. Very close to the explosion, we have to rely on quantum theory, which is essentially the science of fundamental, subatomic particles. One quirk of the theory is Heissenberg’s Uncertainty Principle, which tells us we cannot know the position and momentum of  a particle with perfect accuracy simultaneously; the more accurately we know one, the less accurately we know the other.

Now, in the early universe (in that tiny fraction of a second after the big bang) there would have been fluctuations in the energy field caused by this uncertainty, as having zero energy at a given point is too precise to be allowed by the Uncertainty Principle. It is thought that these fluctuations gave rise to a period of rapid expansion of the universe, which is known as cosmic inflation.

From this stage of expansion, we have a mixture of fundamental particles, quarks and gluons, floating around. How we get from those to the protons and neutrons that make up the nuclei of atoms, the building blocks of life, is a mystery. Recent research by Tillmann Boeckel and Jürgen Schaffner-Bielich at the University of Heidelberg in Germany suggests that this may have been caused by a second, less dramatic period of inflation.

Why do we care? Well, in the Large Hadron Collider (LHC) at CERN in Geneva, they are hoping (when they can get the thing working!) to find evidence of dark matter. Dark matter is the extra matter that theory predicts is necessary to produce the universe we currently experience but is not the usual matter we can see around us and that makes up stars, planets and life. The properties that this matter has under this theory of an extra period of inflation will be quite different from what is currently being looked for at CERN. It raises big questions about what the early universe looked like and what’s out there now. Exciting stuff… 😀