Let’s start by addressing the quantum-sized elephant in the room: Physics may not be everyone’s favorite school subject.
That might be a little more than an intuition or a relatable sentiment. Some interesting data does back up the hunch — especially in the US.
The chart above from the Cambridge International Global Education Census shows the self-reported favorite school subjects of approximately 9,400 students aged 12–19 across 10 countries [1]. As you can see, physics is clearly in contention for USA’s least favorite subject.
What gives? Another survey has probed into why students perceive physics as a difficult subject. Seemingly, the majority of students find the teachings of physics to be inapplicable in daily life [2].
To be fair, this seems more like a reflection of the shortcomings of our educational systems. After all, physics explains how your eyes are reading this very article on a smart device, how that device itself operates, and how we’re not all helplessly adrift in the vast expanse of the cosmos right now, thanks to the unyielding grip of gravity.
Nonetheless, that inapplicability premise simply doesn’t apply to our topic today, as we explore the role of physics in one of humanity’s most defining endeavors:
The Role of Physics in the Universal Pursuit of Longevity
While to many, longevity and aging research may seem strictly rooted in biology, physics helps us understand the fundamental processes that shape the passage of time and influence living systems. Many scientists have called for more research into the physics of lifespan and healthspan extension, including Professor Leonard Hayflick.
One of the most influential biologists in the last 100 years, Professor Hayflick disproved a previous belief that normal living cells are immortal. He demonstrated that non-cancerous cells possess a limited capacity for division — a phenomenon now known as the “Hayflick limit” [3].
Essentially, Professor Hayflick laid the groundwork for a new branch of research: cellular aging. In an interesting twist, however, he has been quoted to say that [4]:
“Aging is a problem in physics and not in biology.” Professor Leonard Hayflick
He’s also often referred to physics as “the science at the root of the questions” [5]. So if a scientist with such an illustrious legacy in aging biology like Professor Hayflick asserts so, then it’s probably wise to have this critical discussion about whether physics is indeed at the root of longevity.
And that’s exactly what we’re about to do. Below we’ll dive into the different concepts, principles, and technologies of physics that can hold sway over our longevity.
Entropy
Speaking of Professor Hayflick, he believes that age-related changes are characterized by increasing entropy, which results in the random loss of molecular function [6].
What exactly is entropy? As defined by the second law of thermodynamics, it’s the measure of disorder or randomness in a system. This law underlines the inherent tendency of energy to disperse and systems to move towards a state of maximum disorder. It stipulates that in any closed system, entropy tends to increase over time.
Several examples of entropy present themselves in our bodies as we age. For instance, the carefully folded shapes of proteins can’t stay perfect forever because their bonds are constantly hit by the chaotic movement of nearby water molecules, a process called thermal motion. Additionally, cells also deal with another problem: the creation of free radicals when metabolism goes wrong. These are highly reactive atoms that can harm DNA and mess up the structure and function of different cellular components. The energy stored in chemical bonds, crucial for maintaining structure and function, gradually dissipates, succumbing to the second law of thermodynamics [7].
But do humans have to succumb entirely to this law of increasing disorder? Scientists such as Dr. Andrew Steele, a physicist turned aging biologist, raise the critical point that the second law of thermodynamics applies only to closed systems. Living organisms, being open systems, can absorb energy from their surroundings and export entropy. This is evident in the various self-repair mechanisms employed by our bodies.
However, it appears entropy does eventually catch up to these mechanisms as well when we become old. Senescent cells accumulate, leading to inflammation, while stem cells may fail to activate or become depleted. Mitochondria, sustain damage, reducing energy supply and hampering DNA repair [8].
Dr. Peter Fedichev and his team have explored the concept of resilience — a measure of the intrinsic capacity of human systems to self-repair. Analyzing changes in DNA over time and electronic health records, they found that this resilience declines with age, indicative of increasing entropy [9].
While halting this entropy may be feasible, reversing it doesn’t seem plausible, according to the study. Dr. Fedichev suggests that understanding the molecular changes driving entropy’s rise could pave the way for interventions that stop, but not reverse, the aging process [9]. A little further on in the article, we’ll take a look at some of the potential mechanisms of physics underlying said molecular changes.
A key takeaway here is that tracking changes in entropy generation could also be a strategy to identify future longevity therapies. A study using a computational thermodynamic model in mice, for example, has found that caloric restriction led to decreased daily entropy generation which aligns with the observed lifespan impacts of caloric restriction in rodents [10].
Gravity and Time Dilation
Even if you’re not particularly drawn to physics, it’s hard not to be captivated by the powerful story of the movie Interstellar. In the climactic scene, Matthew McConaughey’s Cooper reunites with his daughter, who has aged to be significantly older than him during what he perceives as a brief absence.
That makes Interstellar one of numerous epic fictional works to utilize this “Year Inside, Hour Outside” narrative device. But, what might surprise you is that this trope is grounded in the real-life phenomenon of Time Dilation.
Time Dilation arises from the way gravity warps the fabric of spacetime, as described by Einstein’s general theory of relativity. Essentially, the closer an object is to a massive gravitational source, like the Earth, the slower time passes for it [11].
In Interstellar, Cooper’s proximity to a black hole results in an extreme manifestation of time dilation, where time passes at a drastically slower rate compared to distant observers. This phenomenon nearly halts aging in Cooper’s body relative to those outside the gravitational influence.
Now, you might be thinking, could we exploit this phenomenon to halt aging in real life? Well, scientists have indeed pondered this idea, examining locations with varying gravitational strengths, from Mount Everest to the moon’s surface.
Unfortunately, the practical implications are far from promising. Even spending years in areas with substantially stronger gravity would only yield negligible differences in aging. For example, spending three decades on Jupiter might shave off a mere 18 milliseconds from your age [12].
Thus, the feasibility of a “Year Inside, Hour Outside” as a longevity strategy remains firmly rooted in fiction rather than scientific reality for the time being.
But until we’re able to take advantage of gravitational time dilation to extend our lifespan, subjective time dilation might instead offer some hope — through, for instance, meditation. Indeed, expert meditators report feeling a generally slower passage of time [13]. Concurrently, randomized controlled trials have revealed that meditation can slow down biological aging [14].
Quantum Biology
Legend has it that Niels Bohr once said, “If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet.” That’s coming from one of the founding fathers of quantum theory himself. So, if you feel a bit rattled whenever the word “quantum” pops up, you’re not alone. Let’s try to simplify things.
Quantum mechanics studies the intricate behaviors of subatomic particles, such as electrons, exploring how they move, interact, and generate energy while exhibiting characteristics of both particles and waves. Quantum biology investigates how these particles, with their intriguing dual nature, behave within biological systems.
But why are we delving into quantum territory at all? It ties back to our discussion on entropy and the molecular mechanisms underlying it. And well, it appears some quantum antics might be at play.
Consider DNA mutations, a hallmark of aging. One way mutations occur is through the swapping of hydrogen atoms, which hold DNA strands together through bonds. If this swapping happens during DNA replication and the hydrogen atoms end up in the wrong positions, mutations arise.
Scientists haven’t been able to pinpoint precisely how these hydrogen atoms swap places. However, one intriguing theory proposed by nuclear physicist Jim Al-Khalili suggests a quantum mechanism called quantum tunneling. This phenomenon, confirmed to occur in various biological processes, including enzyme activation, entails particles traversing energy barriers seemingly impenetrable in classical physics [15].
What other quantum phenomena could be implicated in aging and longevity? Scientists remain on the hunt to answer this question.
Physical Agent Modalities
Physics has undeniably transformed healthcare through its applications in diagnostics, with innovations like X-Rays, MRIs, CT scans, and PET scans. Potentially as groundbreaking are the emerging advancements in therapeutics, collectively termed Physical Agent Modalities.
These modalities encompass a range of physical agents utilized to achieve therapeutic effects, including cold, heat, sound, electromagnetic waves, electricity, and light [16]. On our blog, we’ve previously tackled the applications of light and sound for longevity in depth. Let’s now explore some of the other modalities and their implications in aging and age-related diseases.
In a recent study, exposure to moderately cold temperatures was found to activate cellular mechanisms that combat protein aggregation and neurodegeneration. This phenomenon, observed in both tiny worms and human cells, hints at the potential anti-aging benefits associated with cold conditions [17]. Of course on the extreme end of the cold spectrum, Cryonics aims to halt entropy by suspending all biological functions, effectively preserving the body’s current state and stopping aging [18].
Electric current-based deep brain stimulation has risen as a promising therapeutic option for treatment-resistant depression. Studies have shown a significant response rate of approximately 60% in chronically depressed patients previously resistant to conventional treatments [19]. Given the crucial role of mental health in longevity, this application holds considerable promise.
Researchers have also investigated the effects of electromagnetic fields on living organisms, from the molecular to the organismal level. Their findings suggest that repeated exposure to these fields induces cellular processes that aid in waste cleanup and repair damaged components. This discovery opens avenues for using low-frequency electromagnetic fields as non-invasive treatments for age-related diseases like Alzheimer’s and Parkinson’s [20].
Lastly, High-intensity Focused Ultrasound (HIFU), popular for its aesthetic applications, is rapidly gaining recognition for its therapeutic potential in age-related diseases, particularly cancer. Promising outcomes have been reported in managing various malignancies, including pancreatic, prostate, liver, kidney, breast, and bone cancers. Additionally, HIFU shows promise in alleviating essential tremors and Parkinson’s disease-associated tremors, with a modified form facilitating drug delivery to the brain by temporarily opening the blood-brain barrier [21].
Conclusion
Physics may not be everyone’s cup of tea. But, its profound impact on our understanding of longevity cannot be overstated. While Professor Hayflick’s belief in aging strictly being an issue of physics rather than biology has garnered some controversy amidst the longevity scene, a more nuanced perspective is needed.
As Professor Peter Hoffman aptly puts it, “Life pits biology against physics in mortal combat.”
So as we continue to probe the intricate interplay between physics and biology, we move ever closer to unlocking the secrets of longevity and improving the health and wellness of all.
References:
[1] Cambridge Assessment Network and Research. (2019, July). Students’ favourite subjects around the world | https://www.cambridgeassessment.org.uk/our-research/data-bytes/students-favourite-subjects-around-the-world/
[2] Gafoor, A. (2018). Student Perception on Nature of Subjects: Impact on Difficulties in Learning High school Physics, Chemistry and Biology. https://files.eric.ed.gov/fulltext/ED617654.pdf
[3] Hayflick, L. (1965). The limited in vitro lifetime of human diploid cell strains. Experimental Cell Research, 37(3), 614–636. https://doi.org/10.1016/0014-4827(65)90211-9
[4] Hayflick, L. (2020). The greatest risk factor for the leading cause of death is ignored. Biogerontology, 22(1), 133–141. https://doi.org/10.1007/s10522-020-09901-y
[5] Hayflick, L. (2001). Anti-Aging Medicine: Hype, Hope, and Reality. Generations: Journal of the American Society on Aging, 25(4), 20–26. https://www.jstor.org/stable/26555098
[6] Hayflick, L. (2007). Entropy Explains Aging, Genetic Determinism Explains Longevity, and Undefined Terminology Explains Misunderstanding Both. PLoS Genetics, 3(12), e220. https://doi.org/10.1371/journal.pgen.0030220
[7] Hayflick, L. (2020). The greatest risk factor for the leading cause of death is ignored. Biogerontology, 22(1), 133–141. https://doi.org/10.1007/s10522-020-09901-y
[8] Ukraintseva, S., Arbeev, K., Duan, M., Akushevich, I., Kulminski, A., Stallard, E., & Yashin, A. (2020). Decline in biological resilience as key manifestation of aging: Potential mechanisms and role in health and longevity. Mechanisms of Ageing and Development, 111418. https://doi.org/10.1016/j.mad.2020.111418
[9] Tarkhov, A. E., Denisov, K. A., & Fedichev, P. O. (2022). Aging clocks, entropy, and the limits of age-reversal. https://doi.org/10.1101/2022.02.06.479300
[10] Ayşe Selcen Semerciöz-Oduncuoğlu, Mitchell, S. E., Mustafa Özilgen, Yilmaz, B., & Speakman, J. R. (2023). A step toward precision gerontology: Lifespan effects of calorie and protein restriction are consistent with predicted impacts on entropy generation. Proceedings of the National Academy of Sciences of the United States of America, 120(37). https://doi.org/10.1073/pnas.2300624120
[11] Lematre, A. G. (1931). A Homogeneous Universe of Constant Mass and Increasing Radius accounting for the Radial Velocity of Extra-galactic Nebulae. Monthly Notices of the Royal Astronomical Society, 91(5), 483–490. https://doi.org/10.1093/mnras/91.5.483
[12] Bothwell, T., Kennedy, C. J., Aeppli, A., Kedar, D., Robinson, J. M., Oelker, E., Staron, A., & Ye, J. (2022). Resolving the gravitational redshift across a millimetre-scale atomic sample. Nature, 602(7897), 420–424. https://doi.org/10.1038/s41586-021-04349-7
[13] Wittmann, M., Otten, S., Schötz, E., Sarikaya, A., Lehnen, H., Jo, H.-G., Kohls, N., Schmidt, S., & Meissner, K. (2015). Subjective expansion of extended time-spans in experienced meditators. Frontiers in Psychology, 5. https://doi.org/10.3389/fpsyg.2014.01586
[14] Le Nguyen, K. D., Lin, J., Algoe, S. B., Brantley, M. M., Kim, S. L., Brantley, J., Salzberg, S., & Fredrickson, B. L. (2019). Loving-kindness meditation slows biological aging in novices: Evidence from a 12-week randomized controlled trial. Psychoneuroendocrinology, 108, 20–27. https://doi.org/10.1016/j.psyneuen.2019.05.020
[15] Brookes, J. C. (2017). Quantum effects in biology: golden rule in enzymes, olfaction, photosynthesis and magnetodetection. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 473(2201), 20160822. https://doi.org/10.1098/rspa.2016.0822
[16] Chen, W.-S., Annaswamy, T. M., Yang, W., Wang, T.-G., Dong Rak Kwon, & Chou, L.-W. (2021). Physical Agent Modalities. Elsevier EBooks, 338–363.e6. https://doi.org/10.1016/b978-0-323-62539-5.00017-5
[17] Lee, H. J., Alirzayeva, H., Koyuncu, S., Rueber, A., Noormohammadi, A., & Vilchez, D. (2023). Cold temperature extends longevity and prevents disease-related protein aggregation through PA28γ-induced proteasomes. Nature Aging, 1–21. https://doi.org/10.1038/s43587-023-00383-4
[18] Moen, O. M. (2015). The case for cryonics. Journal of Medical Ethics, 41(8), 677–681. https://doi.org/10.1136/medethics-2015-102715
[19] Delaloye, S., & Holtzheimer, P. E. (2014). Deep brain stimulation in the treatment of depression. Dialogues in Clinical Neuroscience, 16(1), 83–91. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3984894/
[20] Perez, F. P., Bandeira, J. P., Perez, C. N., Lahiri, D. K., Morisaki, J., & Rizkalla, M. (2022). Multidimensional insights into the repeated electromagnetic field stimulation and biosystems interaction in aging and age-related diseases. Journal of Biomedical Science, 29(1). https://doi.org/10.1186/s12929-022-00825-y
[21] Hsiao, Y.-H., Kuo, S.-J., Tsai, H.-D., Chou, M.-C., & Yeh, G.-P. (2016). Clinical Application of High-intensity Focused Ultrasound in Cancer Therapy. Journal of Cancer, 7(3), 225–231. https://doi.org/10.7150/jca.13906