Stephen Hawking now thinks "there are no black holes"

The physicist, whose pioneering work on black holes in the 1970s made him a household name, has proposed a radical fudge to try and resolve a baffling paradox.

For a scientist whose career was made by his work on black holes, it might seem a little confusing to read that Stephen Hawking now thinks that they don’t exist. But that’s what “Information Preservation and Weather Forecasting for Black Holes”, the study Hawking published last week on arXiv, says: “there are no black holes”.

While this might seem surprising - after all, there’s a huge amount of (indirect) evidence that black holes exist, including a massive one several million times the mass of our Sun at the centre of the Milky Way - it’s really not. It’s Hawking’s latest attempt to solve a paradox that he, and other astrophysicists, have been grappling with for a couple of years.

So what’s he talking about? Here’s the background: black holes are objects which are so massive, with such strong gravity, that even light can’t escape. The distance from the black hole, beyond which nothing gets out, is the event horizon. However, Hawking made his name in the 1970s when he published a paper showing that black holes don’t just suck stuff up, endlessly - they spew out a beam of so-called “Hawking radiation” as they absorb other matter. That means black holes actually lose mass over time, eventually whittling away to nothing.

Black holes are frustrating, though, because their extreme gravity exposes the major inadequacy in our current scientific understanding of the universe - we don’t know how to reconcile quantum mechanics and general relativity. With general relativity, we can make accurate predictions about objects with certainty, but on the tiny scale of quantum mechanics it’s only possible to talk about the behaviour of objects in terms of probability. When we do the maths on what happens to things that fall into black holes, using relativity gives results that break quantum mechanics; the same goes vice versa.

One of the key things about quantum mechanics is that it tells us information can’t be destroyed - that is, if you measure the radiation given off by a black hole, you should be able to build up a picture of what matter fell into the hole to create it. However, if general relativity holds, and nothing can escape from inside the event horizon, then that should apply to that quantum information - any radiation that’s coming out is, Hawking showed, random. It’s the black hole “information paradox”. Either give up quantum mechanics, or accept that information can die.

Hawking was in the “information can die” camp, until 2004, when it became clear - thanks to string theory - that quantum mechanics held up (and there’s an excellent in-depth explanation of this in Nature that explores this story more fully if interested). There was just one problem - nobody could work out *how* information was getting out of black holes, even if it was happening mathematically.

And, just in case this wasn’t all entirely confusing, it turns out that our best post-2004 theory about what’s been going on gives rise to an entirely new paradox - the “firewall”.

It’s to do with quantum entanglement, where two particles are created that are identical on the quantum level. The way it works isn’t exactly clear yet - it could be something to do with string theory and wormholes - but it means that measuring the properties of one particle will give readings that mirror those found on its entangled particle. It might lead to teleportation technology, but scientists aren’t sure yet.

Joseph Polchinski from the Kavli Institute for Theoretical Physics in Santa Barbara, California published a paper in 2012 that worked out the information paradox could be solved if Hawking radiation was quantum entangled with the stuff falling in. But, due to the limitations of entanglement, if this is true, that would mean that at the event horizon a massive amount of energy was given off by particles entering and leaving.

Hence “firewall” - anything crossing the event horizon would be burnt to a crisp. And even though most scientists, including Polchinski, thought this couldn’t possibly be right - it completely contradicts a lot of the stuff underlying general relativity, for example - nobody’s yet managed to disprove it.

The choice for physicists, once again, was to: a) accept the firewall, and throw out general relativity, or b) accept that information dies in black holes, and quantum mechanics is wrong.

Still with me? Here’s where Hawking’s latest paper comes in.

(That title - “Information Preservation and Weather Forecasting for Black Holes” - might make some more sense too, hopefully.)

Hawking’s proposed solution, building on an idea first floated in 2005, is that the event horizon isn’t as defined as we’ve come to imagine it. He instead proposes something called an “apparent horizon”, which light and other stuff can escape from:

"The absence of event horizons mean that there are no black holes - in the sense of regimes from which light can't escape to infinnity. There are however apparent horizons which persist for a period of time."

Black holes should be treated more like massive galactic washing machines. Stuff falls in and starts getting tossed around, mixed up with other stuff in there, and only eventually is allowed to escape out again when ready. This happens because the quantum effects around a black hole, like weather on Earth, churn so violently and unpredictably that it’s just impossible to either predict the position of an event horizon or expect uniform effects for stuff crossing it. While the theoretical basis, that information is preserved, remains, in practice it's so difficult as to be impractical.

It’s a fudge of an idea, which tries to have its general relativity and quantum mechanics cakes, and eat them, too. Possible weaknesses, as Nature points out, are that it could imply that escaping from black holes is easier than it is in reality. It could also be the apparent horizons are just as much of a firewall as the traditional conception of an event horizon. Hawking's peers have yet to have a go at assessing his idea, so we'll have to wait to see whether the idea has merit - or whether it merely gives rise to yet more paradoxes.

Hawking in Cambridge, September 2013. (Photo: Getty)

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

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Is Apple Music really deleting users’ songs without their consent?

It's hard to tell – but the iTunes Terms and Conditions seem to cover the company even if it does.

Musician James Pinkstone was a new Apple Music user when he realised that 122GB of music was missing from his computer.

According to a long blogpost he published on Wednesday, Apple Music attempted to “match” his music with songs in its online library via a function called “iMatch”. It then, Pinkstone claims, deleted all 122GB of his original files – collected from CDs, bought, and even created himself over a lifetime – from his hard drive.  

Luckily, Pinkstone was able to restore his library from a backup, but if what he says is true, it’s outrageous for a number of reasons. Apple Music streams music to users, meaning you need to be connected to Wi-Fi while you’re listening, so it isn’t the same as having an iTunes library of songs you actually own. You can download individual songs from the service to your device, but as Pinkstone writes, “it would take around 30 hours to get my music back” in this way. Your music and playlists also disappear if you stop paying your Apple Music subscription fee.

Meanwhile, iMatch has been notoriously rubbish at matching your files with music library entries, sparking lots of user complaints already. Pinkstone says a Fountains of Wayne song was replaced by a later version, for example, so he would have been unable to get the original song back.

So is it true? It’s not totally clear what happened to Pinkstone’s library, but here’s what we know so far.

Apple has said it doesn’t delete users’ music without their consent

Apple declined to give me a statement, but referred me to the piece “No, Apple Music is not deleting tracks off your hard drive – unless you tell it to” on the site iMore, which is not affiliated with the company but which the spokesperson described as “accurate background”.

Its author, Serenity Caldwell, explains that you have “primary” and “secondary” devices on Apple Music, and that on secondary devices (usually phones or tablets) in particular it’s advisable to delete your physical copies of songs to free up space – after all, you can stream everything via Apple Music anyway or download individual songs if you need them.

However, users should never delete files from their “primary” device (usually your desktop or laptop computer) because they’d lose the master copy of their songs forever.

…But customers might be giving that consent by accident

Jason Snell, a writer, speculated on Twitter that a misleading dialogue box may have caused Pinkstone his problems.

When you delete a song on any device, a dialogue box pops up offering to “delete” the song from “your iCloud Music Library and from your other devices” (emphasis mine). It’s more than possible that users would click this “delete” button rather than the less obvious “remove download” option which removes the song only from that device.

Apple Music’s terms and conditions cover it if it does delete your songs

Pinkstone seems to argue that he did no such thing, however, and it’s possible that there’s a bug as yet undiscovered by Apple which is deleting songs at will.

However, as Pinkstone points out, iTunes terms of use actually do cover it in the event the programme damages your files, or your property in general.

One section reads:

“IN NO CASE SHALL APPLE, ITS DIRECTORS, OFFICERS, EMPLOYEES, AFFILIATES, AGENTS, CONTRACTORS, OR LICENSORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, PUNITIVE, SPECIAL, OR CONSEQUENTIAL DAMAGES ARISING FROM YOUR USE OF THE APPLE MUSIC SERVICE OR FOR ANY OTHER CLAIM RELATED IN ANY WAY TO YOUR USE OF THE APPLE MUSIC SERVICE, INCLUDING, BUT NOT LIMITED TO, ANY ERRORS OR OMISSIONS IN ANY CONTENT OR APPLE MUSIC PRODUCTS, OR ANY LOSS OR DAMAGE OF ANY KIND INCURRED AS A RESULT OF THE USE OF ANY CONTENT OR APPLE MUSIC PRODUCTS POSTED, TRANSMITTED, OR OTHERWISE MADE AVAILABLE VIA THE APPLE MUSIC SERVICE, EVEN IF ADVISED OF THEIR POSSIBILITY.”

Elsewhere, it defends its right to withdraw access to Apple products at will  including songs and albums you're under the impression you bought from them outright:

Apple and its principals reserve the right to change, suspend, remove, or disable access to any iTunes Products, content, or other materials comprising a part of the iTunes Service at any time without notice. In no event will Apple be liable for making these changes.

Tl;dr: Until there’s some explanation for Pinkstone’s lost library, it might be a good idea to avoid using the iMatch function, or even Apple Music altogether. It seems very unlikely that the software would be able to delete files without your consent, but given you aren’t covered if they do, it’s better to be safe than sorry.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.