What is it with gravitons and black holes?

I occasionally wonder about what physicist really think regarding the hypothetical particles, gravitons, those carriers of the gravitational force mandated by the need* to quantize all the forces of nature.  Specifically, I wonder how they behave in and around black holes.

I know, from my understanding of General Relativity, that the influence of gravity travels at the speed of light, and the recent LIGO results, and all other experimental results of which I’ve heard, are consistent with that.  This must surely mean that the proposed gravitons travel at the speed of light, and are thus mass-less particles.  And if they are carrying a force, they must have some form of inherent energy, which means that, according to Einstein at least, their path would be affected by gravity.  This seems contradictory in some ways, but it’s my understanding that the electrical force produced by a moving electron also acts backward on itself, so I guess that’s not completely unreasonable…though here I’m veering further away from any deep knowledge, much to my sorrow.

My real question applies to the surface of an event horizon, that boundary in space-time within which all things are separated from the outside by the strength of the gravitational force – more particularly, according to Einstein, by the degree of curvature of space-time.  If gravitons are particles, carrying the gravitational force, are they constrained by the effects of the event horizon, or –  presumably because they wouldn’t be self-interacting – do they simply pass through it, it being irrelevant to their motion, unlike all other things with finite speeds…which means everything.  That sometimes seems contradictory to me, though by no means am I certain that I’m thinking correctly about this.  Could it be that the gravitons within and outside of an event horizon are two separate populations of gravitons, with the external ones somehow being generated at the horizon?  If not, then how can a particle ignore the degree of gravity, unless, of course, as a mentioned above, they are not self-interacting – which wouldn’t be unusual, since, if I understand correctly, photons also don’t interact with other photons.  But photons would, obviously, interact with gravitons, of course, otherwise they wouldn’t be effected by gravity, as we know they are…the most extreme example of this being at a black hole.

I know that a possible explanation for this might be found in M theory, in which we exist in a 3-brane that floats in a larger, higher-dimensional “bulk,” and that gravitons, unlike all the more “ordinary” particles are not constrained to remain within that brane, but can go above and below it, so to speak, thus bypassing any barrier that is exclusive to the brane.  But I don’t know if this really deals with the issue.

And, of course, how can the idea of gravity as a force, mediated by a quantum particle, be reconciled with the convincing and highly fruitful model of gravity as the consequence of the curvature of space-time?  Obviously, I don’t expect anyone to know the deep answer to this question, since it’s the biggest, most fundamental problem in modern physics:  our two best, most powerful theories of the world don’t work when brought together.  But if anyone out there has any idea of at least the form of such a possible reconciliation – i.e. do proponents of quantum gravity think that it will eliminate the notion of curved space-time, or do they think, somehow, that it will be an expression thereof – I would be delighted to hear from you.  My best reading to date on things like string theory hasn’t given me any real insight into the possible shape of such a unification.

Anyway, these are some of the thoughts that are troubling me this Monday morning.  I’d love to know any of your thoughts in response, or if you have any recommendations on further study materials, I would welcome those as well.


* due to the Uncertainty Principle, among other things.

In defense of scientism

[Originally posted on robertelessar.com on July 20th, 2017]

On this 48th anniversary of the Apollo 11 moon landing, I want to talk a little bit about science, and how it, in principle, can apply to nearly every subject in life.

The word science is derived from Latin scientia, and earlier scire, which means “to know.”  I am, as you might have guessed, a huge fan of science, and have in the past even been a practitioner of it.  But science is not just a collection of facts, as many have said before me.  Science is an approach to information, and more generally to reality itself, a blend of rationalism and empiricism that calls on us to apply reason to the phenomena which we find in our world and to understand, with increasing completeness, the rules by which our world operates.  Personally, I think there are few—and possibly no—areas into which the scientific method cannot be applied to give us a greater understanding of, insight into, and control of, our world and our experience. Continue reading “In defense of scientism”

Adulation and congratulations to Kip Thorne and his Nobel co-recipients for their confirmation of the existence of gravitational waves

Kip_Thorne_at_Caltech
Professor Kip Thorne of Caltech

I just wanted to write a brief posting about how delighted I was to learn that Kip Thorne was one of the scientists who shared the Nobel Prize for physics this year, for his part in the long-awaited confirmation of the existence of gravitational waves.

I’ve been a fan of Professor Thorne’s for more than two decades now (roughly), and have long regretted that he wasn’t more of a public figure, though that’s probably by his own choice.  I first heard of him in the post-script to one of the episodes of the original “Cosmos,” (added when the series was re-shown on TBS).  In that post-script, Carl Sagan mentioned that when he was writing his novel “Contact,” he wanted to ascertain if there was a legitimate, scientifically valid way for a sufficiently advanced race to travel great distances through space in reasonable lengths of time.  The person he asked, he said, was Kip Thorne, and it was Kip Thorne who gave him the information he used to create his worm-hole-using alien race in the book.*

If memory serves, Carl Sagan also mentioned that Kip Thorne had written a science book for popular consumption, called “Black Holes and Time Warps.”  (You can find it here on Amazon.)  The next time I was at a book store—probably Borders, my favorite book store, the loss of which has been a source of bitter heartache to me—I found a copy and bought it.

I have rarely been so pleased with a science book.  If you’re interested in a wonderful, thorough, but well-explained treatment of some of the more extreme aspects of General Relativity, I can’t recommend anything more highly.  Even Stephen Hawking and Brian Greene have not produced anything better (that I have read) on this subject, and if you know me, you know that’s high praise indeed.  This is one of those books that, when you read it, makes you feel brilliant.  This is because the author understands his subject so well that he can convey it in absolutely clear terms, illustrating it literally and figuratively so that these mind-warping (and space-warping) concepts make perfect sense.

Congratulations to Professor Thorne, and to his co-recipients for the recognition of their work on gravitational waves.  I remember that, when I first heard about the LIGO observatory, some years ago, and how it worked, I thought, “But wait, won’t the lasers and the space they pass through be compressed and stretched by gravitational waves exactly the same amount?  Won’t that negate the measurable effects of the waves and make the laser interferometry wash out?”  Obviously, this was not a question that wouldn’t have occurred to the people creating the observatory, and they knew why it wouldn’t be a problem, or at least not an insurmountable one.  I wish I’d thought to ask someone in the know when the question occurred to me.  I wish I’d known whom to ask (certainly at that time I could not have asked Professor Thorne himself, though nowadays he could probably be reached through Facebook or Twitter).

Anyway, I was more than happy to have my own dubiety (is that a real word?) smashed when the announcement was made that the waves had been detected, and then again, and now again, only within the past few months.  It’s not astonishing quite in the same way as when I first heard of the discovery that the expansion of the universe was accelerating (Wow, what an excellent, world-changing surprise that was!), but in other ways it’s just as awe-inspiring.  We (the human race) are on the leading edge of a whole new era of astronomy, one that could someday let us peer back past the last scattering surface that produced the CMB and catch glimpses of a time ever closer to the Big Bang.

I get chills.  Seriously.

So, despite all the other, horrible news, of disasters both natural and man-made, that we’ve all had to endure over recent days and weeks, we should take heart in the knowledge that knowledge is possible, and that, however easy it is to destroy things, the power to learn, the power to create knowledge, and thence to create new prosperity, is clearly much stronger.  If it were not, civilization would long since have been destroyed.

These are the sorts of thoughts that people like Professor Kip Thorne inspire in me…and I tend to be a gloomy person by nature.  Congratulations, Professor Thorne, and congratulations also to Rainer Weiss and Barry Barish, Kip Thorne’s co-recipients.  It’s people like you who help keep life worth living for people like me.


*Kip Thorne was also responsible for the bits of the movie “Interstellar” that were actually scientifically accurate, and he certainly cannot be blamed for any departures from legitimate scientific realism one finds therein.

Diabetes For Beginners – Part 2

First published on robertelessar.com on February 23, 2012

Welcome to Part 2 of my “freshman lecture” on Diabetes.

Now we get to Type 2 Diabetes Mellitus. Interestingly enough, although this is “Type 2”, it is in fact by far the Number 1 form of Diabetes numerically, with 90 to 95% of Diabetics falling into Type 2…and that number is likely, if anything, to become larger. Continue reading “Diabetes For Beginners – Part 2”

What Are Black Holes?

Originally posted February 23, 2012

A very old friend of mine—that is, one I’ve known a long time, he’s no older than I am, and I hope I don’t yet count as “very” old—suggested that I write an article about what exactly black holes are. So, I thought about it, for all of about two seconds, and realized that black holes would be a great topic for a general science article. Continue reading “What Are Black Holes?”

Diabetes For Beginners – Part 1

Diabetes is an illness of which I suspect almost all adults in America are aware. I also suspect that most people know that it has something to do with high blood sugar and that having high blood sugar is a bad thing. Still, I imagine there are a fair few people out there who haven’t really got a lot more understanding of it than that—including some people who have the disease—because they haven’t really had it explained to them in terms they can follow. After all, doctors—of which I am one—don’t often take the time necessary to make sure that their patients fully understand the ins and outs of a disease process. Partly this is because, when one understands something on a very complex level, it seems like it’s going to take serious effort to explain it to someone who doesn’t have the same educational background. However, I think this is a failure of imagination and a bit of mental laziness on our part as doctors. The Nobel-Prize-winning physicist Richard Feynman used to prepare “freshman lectures” about physics subjects when laypeople asked him about topics they didn’t understand. If he found that he couldn’t prepare one, he recognized that failure as an indication that the subject wasn’t well-enough understood! Continue reading “Diabetes For Beginners – Part 1”