- Included in the Claudia de Rham Posts List.
- Claudia de Rham and her team started with two suppositions: What if the reach of gravity is not infinite? What if the graviton is not massless?
Martin Winfree
December 30, 2024 ·
Shared with Public
(Part III)
In developing their new theory of gravity, and as described in her book The Beauty of Falling, Claudia de Rham and her team started with two suppositions: What if the reach of gravity is not infinite? What if the graviton is not massless? The term used in her book is “massive”, meaning that the particle has some mass, not that it necessarily has a lot of mass.
The two suppositions might be tied together to some extent. She said that particles with no mass, like photons, always travel at the speed of light. If the graviton has some mass, then maybe its reach is automatically not infinite. Of course, an infinite reach for gravity only has meaning if the Universe is infinite. While, by definition, the known Universe that came out of the Big Bang is not infinite, that might be true of the Universe as a whole; Claudia de Rham is among those who believe that the Universe is infinite.
The problem that Claudia de Rham is tackling is difficult for me to understand or believe; and I don’t even have a clear conception of what could possibly be going on. Vacuum energy – not the same as the concept of “negative energy” that I have complained about in earlier posts – is present throughout the Universe, even in what appears to be empty space; but there are different ways to calculate how much is present, resulting in insanely different answers. Vacuum energy could explain the presence of dark energy, but the math at present is way off.
Apparently, the vacuum energy is wholly or largely driven by what she calls a “sea of quantum particles”; i.e., virtual particles that I have also posted about previously. She states: “We may not be able to directly catch such particles with our eyes or instruments, which is why we are unable to remove them from our vacuum chamber and why we refer to them as ‘virtual particles’, but the effects of the spontaneous creation and disappearance of pairs of these virtual particles have been measured and tested with incredible precision via various experiments.”
Claudia de Rham gives the example of the lowly electron. The vacuum energy generated from an electron has been calculated as, with tongue in cheek: “A ginormous amount! Following a similar comparison to that made by British physicist Sir Oliver Lodge in 1907, this would be as if ‘the total output of a million-kilowatt power station for thirty million years, exists permanently, and at present inaccessibly, in every cubic millimetre of space’.”
As if this were not enough, if this quantity of vacuum energy were actually present, the “observable radius of our Universe (the distance beyond which we wouldn’t be able to see beyond the horizon) ‘would not even reach to the Moon’.” And that is using electrons, among the smallest particles known.
In a nutshell, this quantity of vacuum energy as compared to the estimated amount of dark energy present in the Universe amounts to 34 orders of magnitude too much. In a subheading in her book, Claudia de Rham calls this the “greatest discrepancy in scientific history”. That’s not 34 times as much; it is more like 1034 times as much.
Obviously, there is something very wrong here, but I don’t know enough about the underlying physics to explain what it is. However, starting with her two suppositions, Claudia de Rham has gotten this discrepancy under control – but again, I couldn’t explain exactly how. Their full scientific paper is not available in her book, not that I could follow it if it were; The Beauty of Falling is a general-interest work. But let me at least try to sketch out the broad outlines.
While Claudia de Rham did not say this in her book, the thought experiments used by Albert Einstein to describe the special theory of relativity remind me of how she and her team are approaching these two suppositions – that gravity is not infinite, and that gravitons have some mass. Essentially, it is only at the farthest reaches of the Universe where these suppositions have some impact.
Einstein began with the idea that the speed of light is the only thing that is NOT relative: As others had already shown, the speed of light always looks the same – regardless of where an observer is, regardless of speed, regardless of acceleration, regardless of anything else you can think of. Therefore, as one approaches the speed of light, among other things, time itself slows down.
The idea of “approaching the speed of light” might seem fanciful, at least for us. According to Guinness World Records, the fastest speed human beings have ever flown is 24,816.1 miles per hour, which was achieved by the crew of Apollo 10 during their return from lunar flight on May 26, 1969. That equates to 0.004% of the speed of light, so clearly, we have a long way to go!
However, scientists have a way of measuring even the tiniest of tiny changes; and NASA came up with a “time dilation” experiment, since there happen to be two identical twin astronauts: Scott Kelly and Mark Kelly. Mark Kelly retired as an astronaut before his brother and is currently the junior Senator from Arizona. His wife, Gabrielle Giffords, who is a former Member of Congress from Arizona, is I believe the highest ranking elected official who has been the victim of a mass shooting. Gabby Giffords is a hero in every sense of the word, in my book.
For this experiment, Scott Kelly spent a full year aboard the International Space Station in 2015-2016, where he was flying through space at 17,500 miles per hour; while his brother remained on the surface. According to Einstein’s special theory of relativity, as Mark Kelly put it: “So, whereas I used to be just 6 minutes older [than Scott Kelly], now I am 6 minutes and 5 milliseconds older.” The reason is that time moved more slowly for Scott Kelly while he was in space during that year.
Those thought experiments have even entered popular culture. Charlie and I have a favorite comedian named Steven Wright who is known for his deadpan performances and cerebral jokes. In one of his routines, he said: “If you were on a train traveling at the speed of light and turned on the headlights . . . would they do anything?” Great line! And the answer is, yes, they would; despite that insanely high rate of speed, the lights would turn on the same as if the train were standing still.
Claudia de Rham introduces whimsical analogies and commentary on her new theory of gravity: that gravity need not be so “solemnly serious”, that gravity might “have a sense of humor”, “what if gravity, appreciating that the time has come, could simply let go?”, the idea that “there is a limit to everything, including gravity”.
In describing an early synthesis of her and her team’s theory – which includes at least one researcher who seemingly beat her to the punch by a few hours – she uses the old story of the Blind Men and the Elephant – or as she puts it, “who could well have been women” – who each gets an incomplete picture of what an elephant is like depending upon whether they grasped a leg, or the trunk, or the ear.
She also discusses “the ghost of massive gravity” – particles having negative energy that are incompatible with existence itself. (Again, this is not the negative energy that I previously posted about; it is something much more devastating). Also, the notion of additional dimensions – which are curled up and inaccessible, in my limited understanding of string theory – includes the possibility of at least one “large” extra dimension. I am still not entirely comfortable with the idea of space-time that includes time as a fourth dimension, never mind a fifth dimension on top of that. But Claudia de Rham’s theory dispenses with the need for that.
As the theory developed, the implications of a massive graviton, and the various “flavors” of gravity bound up in that concept, seem to offset the absurdly high vacuum energy, yielding the same curvature of space that we see today. The small amount of vacuum energy left over represents the dark energy that is fueling the accelerating expansion of the Universe.
In the final chapter of her book, Claudia de Rham talks about the scientific challenges to the new theory that she faced, and their final refinements. Since the effects of a massive graviton are evident only at extreme distances that are close to the edge of the known Universe, the maximum mass of a graviton can be inferred to be an incredibly small amount. Otherwise, it would have been noticed before now.
In a closing thought in her Conclusion section, Claudia de Rham says that the basic research and any practical applications are really not the point: “We chase gravity because we are creatures of gravity. Whether we walk, dive, fly, or explore space as an astronaut, as we soar and fall, succeed and fail, we all inhabit a Universe defined by gravity – and, as a scientist, I will forever pursue its secrets.”
In these posts, I do hope that I have done justice to the new theory of gravity developed by Claudia de Rham, and also her remarkable book with a great title, The Beauty of Falling. I cannot recommend this book highly enough for anyone who wants to know about gravity, a force that penetrates and permeates all of our lives.
