Michelle Thaller talks with three leading scientists about black holes - how do we know they exist, where do they come from, and how can we learn more about a black hole without getting too close?

Most of the time, science marches slowly forward in methodical, well-measured beats. But sometimes there is an exquisite agony to scientific discovery. Times where you see something unexpected, or something you did expect but never quite let yourself believe was real.

When it comes time to publish those results, when it’s time to claim that you have discovered something extraordinary, there is almost always a barrier of fear to get over. Did you really see what you thought you saw? Did you make some simple mistake that the readers of your paper or the listeners to your conference presentation will immediately see and use to dismantle your result? Of course you’ve passed this by some of your trusted friends and colleagues, but at the end, it’s just you up there, staking your professional reputation on a risky, if exciting assertion.

Do Black Holes Exist?

In astronomy, there are few topic more slippery than black holes. By their very nature, they are nearly impossible to detect, unless something is falling into them. And while the idea of black holes was postulated literally centuries ago, for ages no one could tell whether they were just an example of our mathematics run amok, or whether these beasts were real. Really, real.

It may surprise you to know that the existence of black holes, at least our current model of them, is still controversial. Prominent scientists such as Stephen Hawking still wonder if the laws of thermodynamics truly allow an event horizon, the point of no return around a black hole, to exist.

There is no doubt that there are super-compact bodies with huge gravitational fields that lie in the core of galaxies or can be watched sucking away the lifeblood of stars. But are they black holes, or something we have yet to understand? Do we understand how a black hole would really work? What is the best evidence we have the black holes exist? Could we, for the first time, have witnessed the birth of a black hole?

Black hole simulation frame
This simulation frame shows a black hole accretion disk. Created by Jeremy Schnittman and inspired by the movie Interstellar.

In this episode of Orbital Path, we speak to three astronomers who have worked to piece together the best evidence yet for the existence of black holes. Decades ago, Paul Murdin worked on early observations of an area of the sky that was mysteriously bright in X-rays, super high-energy light that shouldn’t have been present around a normal star. To make matters even more dramatic, that star was seen to be orbiting a massive object that was, except for its X-rays, invisible. These observations, among others, helped astronomers finally embrace the incredible idea that there really was a black hole in the constellation Cygnus.

Jeremy Schnittman uses mathematics and Einstein’s equations to model what the area close to a black hole would look like, and works on strategies to find the possible millions of black holes that lurk dark and unseen in the Milky Way.

And Christopher Kochanek may have had the tremendous luck (coupled with a brilliant program to monitor the skies) to catch the exact moment a black hole was born. What is it like to make that claim, that you are the first person to see the birth of a black hole? Do these people still suffer doubts about the reality of black holes? There may still be a good deal of wiggle room, but as you’ll hear in the podcast, Kochanek, at least, is willing to bet his life –and your dog’s!

Orbital Path is produced by PRX and supported by the Alfred P. Sloan Foundation. Don't miss PRX's other science podcasts: Transistor and Outside Magazine.


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GH Martin

October 29, 2016 at 10:30 pm

S&T -- Much prefer reading instead of listening, for a variety of reasons. Please stick to written articles. Thanks.

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October 31, 2016 at 10:25 pm

Could not agree more. Nothing is more disappointing than clicking on an apparently interesting link only to find a podcast, or a video of a talking head. What a pointless waste of bandwidth; I just close them.

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October 30, 2016 at 12:48 am

Thanks so much for the addition of the Orbital Path podcasts! Great fun and very well done. They are a wonderful science shot in the arm on my commute and when relaxing. I have subscribed on my podcast aggregator.

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November 3, 2016 at 3:10 am

It should be easy to post a transcript along with a podcast. While listening may be preferred in some situations, I can read the transcript in a fraction of the time and move on. Time is money!

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May 25, 2017 at 12:01 pm

No, Black holes as singularities of general relativity do not exist because Einstein's relativity theory has already been disproved both logically and experimentally (see "Challenge to the special theory of relativity", March 1, 2016 and a press release on Eurekalert website: https://www.eurekalert.org/pub_releases/2016-03/ngpi-tst030116.php).

The most obvious and indisputable experimental evidence, which everybody with basic knowledge of special relativity should immediately understand: is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which move at high velocities relative to each other while special relativity claims that time is relative (i.e. the time on each reference frame is different) and can never be synchronized on clocks moving with relative velocities.

Many physicists claim that clocks on the GPS satellites are corrected according to both special relativity and general relativity. This is not true. The corrections of the atomic clocks on the GPS satellites are nothing to do with relativistic effects because the corrections are absolute changes of the clocks, none of which is relative as claimed by special relativity. After all corrections, the clocks are synchronized not only relative to the ground clocks but also relative to each other.

Some people may argue that the clocks are only synchronized in the earth centered inertial reference frame, and are not synchronized in the reference frames of the GPS satellites. If it were true, then the time difference between a clock on a GPS satellite and a clock on the ground observed in the satellite reference frame would grow while the same clocks observed on the earth centered reference frame were keeping synchronized. If you corrected the clock on the satellite when the difference became significant, the correction would break the synchronization of the clocks observed in the earth centered frame. That is, there is no way to make a correction without breaking the synchronization of the clocks observed in the earth centered frame. Therefore, it is wrong to think that the clocks are not synchronized in the satellite frame. Actually, on the paper mentioned above, I have proved that if clocks are synchronized in one inertial reference frame, then they are synchronized in all inertial reference frames because clock time is absolute and universal.

Similarly, all the differences of the clocks in Hefele-Keating experiment were also absolute (i.e., they were the same no matter whether you observe them on the moon or on the space station). Therefore, they are nothing to do with relative velocity caused time dilation as claimed by special relativity. It is simply a wrong interpretation that the differences of the displayed times of the clocks are the results of relativity.
The increase of the life of a muon in a circular accelerator or going through the atmosphere is also an absolute change which is the same observed in all reference frames.

The simplest thought experiment to disprove special relativity is the symmetric twin paradox: two twins made separate space travels in the same velocity and acceleration relative to the earth all the time during their entire trips but in opposite directions. According to special relativity, each twin should find the other twin’s clock ticking more slowly than his own clock during the entire trip because of the relative velocity between them as we know that acceleration did not have any effect on kinematic time dilation in special relativity. But when they came back to the earth, they found their clocks had exact the same time because of symmetry. This is a contradiction that has disproved special relativity. This thought experiment demonstrates that relativistic time is not our physical time and can never be materialized on physical clocks.

That is, time is absolute and space is 3D Euclidean. There is nothing called spacetime continuum in nature. Therefore, there is no singularity of spacetime.

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