Black holes are a never ending source of scientific intrigue. They form when a star of appropriate mass, approximately 5 to 10 times the mass of our own star, reaches the end of its life and begins to fuse heavier and heavier elements. At this stage the outward pressure exerted by those fusion reactions cannot overcome the gravity from its mass and it slowly begins to collapse inwards. Eventually, in a calamitous event known as a supernova, it shrinks down to a point mass of infinite density and nothing, not even light, can escape its gravitational bounds. Properties like that mean black holes do very strange things, most of which aren’t explained adequately by current models of our universe. One such thing is called the Information Paradox which has perplexed scientists for as long as the idea as black holes has been around.
The paradox stems from the interaction between general relativity (Einstein’s description of gravity as a property of spacetime) and quantum mechanics (the processes that affect atoms, photons and other particles). Their interaction suggests that physical information about anything that crosses the black hole’s event horizon could be destroyed. The problem with this is that it violates the generally held idea that if we have information about a system in one point in time we should be able to determine its state at any point in time. Put simply it means that, when you’re looking at a black hole, if something falls into it you have no way of determining when that happened because the information is destroyed.
However renown physicist Stephen Hawking, whose work on black holes is so notable that one feature of them (Hawking Radiation) is named after him, has theorized that the information might not be lost at all. Instead of the information being lost or stored within the black hole itself Hawking states that the information is stored as a super-translation (or a hologram, a 2D representation of 3D data) in the event horizon. Whilst for all practical purposes this means that the information is lost, I.E. you likely wouldn’t be able to reconstruct the system state prior to the particles crossing the event horizon, it would solve the paradox.
The idea might not be as radical as you first think as other researchers in the area, like Gerard t’Hooft (who was present at the conference where Hawking presented this idea), have been exploring similar ideas in the same vein. There’s definitely a lot of research to be done in this area, mostly to see whether or not the idea can be supported by current models or whether it warrants fundamental changes. If the idea holds up to further scrutiny then it’ll solve one of the most perplexing properties of black holes but there are still many more that await.
Since its inception back in 1960 the Search for Extraterrestrial Intelligence (SETI) has scanned our skies looking for clues of intelligent life elsewhere in our universe. As you might have already guessed the search has yet to bear any fruit since, as far as we’re concerned, no one has been sending signals to us, at least not in the way we’re listening for them. The various programs that make up the greater SETI aren’t particularly well funded however, often only getting a couple hours at a time on any one radio telescope on which to make their observations. That’s all set to change however as Russian business magnate Yuri Milner is going to inject an incredible $100 million into the program over 10 years.
SETI, for the unaware, is a number of different projects and experiments all designed to seek out extraterrestrial life through various means. Traditionally this has been done by scanning the sky for radiowaves, looking for signals that are artificial in nature. Whilst the search has yet to find anything that would point towards a signal of intelligent origin there have been numerous other signals found which, upon further investigation, have turned out to have natural sources. Other SETI programs have utilized optical telescopes to search for communications using laser based communications, something which we have actually begun investigating here on earth recently. There are also numerous other, more niche programs under the SETI umbrella (like those looking for things like Dyson Spheres are other mega engineering projects) but they all share the common goal of answering the same questions: are we alone here?
Since these programs don’t strictly advance science in any particular field they’re not well funded at all, often only getting a handful of hours on telescopes per year. This means that, even though such a search is likely to prove difficult and fruitless for quite a long time, we’re really only looking for a small fraction of the year. The new funds from Yuri Milner will bolster the observation time substantially, allowing for continuous observations for extended periods of time. This will both increase the chances of finding something whilst also providing troves of data that will also be useful for other scientific research.
As Yuri says whilst we’re not expecting this increased funding to instantly result in a detection event the processes we’ll develop along the way, as well as the data we gather, will teach us a lot about the search itself. The more we try the more we’ll understand what methods haven’t proved fruitful, narrowing down the possible search areas for us to investigate. The science fiction fan in me still hopes that we’ll find something, just a skerrick, that shows there’s some other life out there. I know we won’t likely find anything for decades, maybe centuries, but that hope of finding something out there is what’s driving this program forward.
Undoubtedly black holes are one of the most intriguing phenomena in our universe. The current interpretation of them, being a point mass that’s infinitely dense, is quite modern being only formalized some time back in the 1950s although the scientific roots can be traced back a bit further than that. Still they’re far from being a solved problem space as, like all things that use the word “infinite” in some capacity, their behaviour is a little strange especially when you try to explain them using different theories for how the universe works. To us laypeople we tend to be rooted in the general relativity explanation, however once you step into the world of quantum mechanics suddenly they start behaving differently creating quite the paradox.
In the world of general relativity passing across the event horizon, the point at which nothing (not even light) can escape, would be a somewhat peaceful affair. Since you would be in complete free fall at the time you wouldn’t experience a sudden jolt or anything that would indicate to you that this had happened (which makes black holes nightmare material for someone like me who has aspirations for space travel). After a while though you’d start to feel rather uncomfortable as the difference between the gravity at your head and feet became vastly different, eventually leading to a rather untimely demise at the hands of what has been dubbed spaghettification. However if you approach the same problem from the view of quantum mechanics you might not even get a chance to experience that as the world past the black hole’s event horizon is something vastly different.
The current hypothesis say that instead of the event horizon being a peaceful transition (although usually even getting to the event horizon would be quite nasty thanks to the accretion disks they usually sport) there instead exists a violent firewall of energy, ready to tear anything apart that crosses that horizon. Whilst the mechanics of this are well above my understanding it appears to be a quirk of Hawking Radiation, the process by which black holes “evaporate” over time. This evaporation occurs via entangled particles, one which leaves the black hole and another that falls back in. However this must mean that the entanglement is broken at some point which would release a lot of energy. This has led to a paradox which means that we have to either modify or abandon certain principles in physics, something which scientists don’t really like to do unless there’s a good reason to.
Hawking has recently weighed in on the topic through a paper on ArXiv which was then famously misinterpreted as him saying that there were no black holes at all. What he was actually saying was that there were no black holes in the traditional sense that there were distinct event horizons which, when passed, would not allow anything to escape. Instead Hawking has propose apparent horizons which are temporary artefacts, shifting around the black hole. This would then allow information to escape without necessitating the quantum firewall, preserving the more peaceful theory.
The new theory hasn’t been hit with resounding approval however as it raises almost as many questions as it answers. I’ll admit its quite intriguing, definitely worthy of further research, but with so many fundamental changes to the model of how black holes operate it’s hard to take it at face value. Still the mere fact that this has caused such ripples, even outside the scientific community, shows just how important this is to the wider world of physics.