When Deepinder Goyal appeared on Raj Shamani's Figuring Out podcast in late 2025, viewers were not just paying attention to his words. A tiny metallic clip positioned near his temple sparked a social media frenzy of speculation and memes. What looked like chewing gum, a hidden charging device, or some billionaire eccentricity turned out to be something far more intriguing: Temple, an experimental wearable designed to measure brain blood flow continuously and in real time. As someone deeply invested in understanding how technology intersects with human health, I wanted to dig deeper into this project, understand the science behind it, and honestly assess what it might mean for the future of neurotechnology and longevity research.
Let me start with the basics because the device itself is deceptively simple. Temple is a small, lightweight, clip-like sensor worn on the temple region of the head, roughly where the temporal artery runs close to the surface. It is about the size of a small piece of jewelry and comes in different finishes, from silver to gold. Goyal himself has been wearing it for approximately one year, treating it not as a finished commercial product but as an experimental research tool.
The device continuously measures cerebral blood flow, or CBF in the medical jargon. This is not about measuring blood pressure in the traditional sense. Rather, it attempts to estimate the amount of blood reaching brain tissue in real time, throughout the day, across different activities and mental states. The fundamental assumption underlying Temple is straightforward: if we can track brain blood flow continuously outside controlled laboratory settings, we gain unprecedented insight into what happens inside our heads during normal, everyday life.
To understand why this matters, you need to know that brain blood flow is tightly linked to brain health. Every neuron requires a constant supply of oxygen and glucose. When blood flow drops, neurons suffer. Conversely, periods of higher cerebral blood flow often correlate with better cognitive function, mental clarity, and resilience against age-related cognitive decline. Most of what we know about brain blood flow comes from controlled environments: MRI machines, specialized imaging centers, clinical trials. Temple attempts to change that equation by moving continuous monitoring into the real world.
The device is developed under Continue Research, which is Goyal's personal longevity and aging biology research initiative, separate from Eternal (formerly Zomato) and his other ventures. He has personally invested approximately $25 million into Continue Research, a substantial commitment that signals genuine conviction rather than casual experimentation. Temple is currently raising a $50 million seed round from major investors including Steadview Capital, Vy Capital, Info Edge, and Peak XV Partners, valuing the company at approximately $125 to $130 million. Notably, these are the same funds that backed Zomato during its early days, suggesting that Goyal's track record carries weight even in a domain as speculative as longevity research.
To truly understand Temple, you need to grasp the conceptual framework driving it: the Gravity Aging Hypothesis. This is where things get intellectually interesting and, I should note, where scientific controversy begins.
Goyal's basic premise is this: due to gravity, humans experience a chronic reduction in brain blood flow for approximately 16 hours every day while upright. Gravity constantly pulls blood downward, away from the brain. The brain sits above the heart, and fighting gravity to pump blood upward costs the heart energy constantly. Over decades, this chronic underperfusion may contribute to cognitive decline, neurodegeneration, and overall aging.
The numbers he cites are compelling. Cerebral blood flow naturally declines by approximately 0.3 to 0.74 percent each year across the human lifespan. Compounded across 60 years, this translates to a 20 to 40 percent reduction in average brain blood flow between age 20 and age 80. Studies consistently show that lower cerebral blood flow is associated with higher all-cause mortality risk, independent of heart health. The hypothesis integrates this existing knowledge with a novel angle: what if gravity, the one constant force acting on every human equally, is a primary driver of this decline?
Continue Research proposes several interventions derived from this logic. Head-down inversions, where the head is placed below the heart, can acutely increase cerebral blood flow. In their early experiments, they found that 10 minutes daily on an inversion table over six weeks increased average brain blood flow by approximately 7 percent, which they argue might offset roughly a decade's worth of age-related decline. Beyond inversions, the framework suggests that building vascular reserve through exercise, maintaining good posture, staying hydrated, and supporting the vascular system nutritionally can all help preserve cerebral perfusion as we age.
This is where I want to be intellectually honest with you: the Gravity Aging Hypothesis is novel, intellectually coherent, and supported by genuine physiological facts. But it is also controversial, and the medical community has expressed significant skepticism.
When I dug into the medical literature and expert commentary, I found a pattern of sophisticated disagreement rather than outright dismissal. Most physicians and neuroscientists do not dispute that gravity affects brain blood flow acutely or that cerebral blood flow is important to aging. What they dispute is the Gravity Aging Hypothesis' claim that gravity is a primary driver of aging compared to other factors.
Dr. Suvrankar Datta, a radiologist from AIIMS Delhi and one of India's earliest researchers in arterial stiffness and pulse wave velocity, was direct in his criticism. He called Temple "a fancy toy for billionaires" and stated it has "zero scientific standing" as a validated medical device at present. His concern is not baseless: Temple measures signals from a surface-level sensor on the temple, while true cerebral blood flow measurement typically requires sophisticated imaging like MRI or validated techniques like functional near-infrared spectroscopy (fNIRS) conducted in controlled settings.
Dr. Sumol Ratna, an Assistant Professor of Medicine at NIIMS Medical College, made a similar point with scientific precision. He acknowledged that CBF is an important biomarker but stressed that the gravity aging hypothesis remains "a hypothesis and not supported by mainstream clinical research at this time." He noted that CBF is measured using complex imaging like MRI or validated techniques like fNIRS, raising the question: how confident can we be in a wearable device's measurements of something that has historically required sophisticated laboratory equipment to assess accurately?
There is also a broader mechanistic concern. Brain blood flow is not passively determined by gravity alone. The brain has an elegant autoregulation system that maintains constant blood flow despite changes in blood pressure. Your cerebral vasculature constantly adjusts vessel diameter through something called myogenic response. When blood pressure drops, vessels dilate to maintain flow. When it rises, they constrict. This autoregulation is remarkably effective across a wide range of blood pressures. Some neurologists argue that for healthy individuals, this autoregulation buffer is robust enough that gravity's effect, while real, may be less significant than other factors like cardiovascular health, metabolic disease, inflammation, and lifestyle.
Furthermore, an intriguing observation complicates the gravity hypothesis: astronauts in microgravity actually show accelerated aging, not deceleration. If gravity's reduction of brain blood flow were the primary driver of aging, we would expect the opposite. Continue Research has addressed this by arguing that humans evolved for 1G, not microgravity, and that aging in space happens for different reasons (loss of mechanical loading, fluid redistribution, radiation exposure). While clever, this explanation essentially sidesteps the contradiction rather than fully resolving it.
The broader scientific consensus is that aging is multifactorial. It involves cellular damage accumulation, protein misfolding and aggregation, mitochondrial dysfunction, inflammation, shortened telomeres, epigenetic changes, and many other mechanisms. Brain blood flow is one factor among many, and positioning it as the primary or most important driver is a significant claim requiring more rigorous evidence than currently exists.
Beyond the conceptual debate, there are practical engineering questions about Temple as an instrument.
Measuring true cerebral blood flow from a surface patch is technically challenging. The temporal artery, which runs near where Temple sits, is a proximal vessel, not a deep brain structure. What flows through the temporal artery does not perfectly represent what flows through the hypothalamus, brainstem, or deep cortical structures. These deep regions are particularly important to the Gravity Aging Hypothesis because they regulate critical functions like hormone release, autonomic balance, and immune response. A surface measurement proxies for deeper structures, but proxies introduce noise and potential inaccuracy.
The device would likely use optical sensing, ultrasound, or photoplethysmography, technologies that have been used in medical devices before but with varying degrees of accuracy. The exact technical specifications of Temple remain proprietary, so it is difficult to assess from public information how these measurement challenges have been addressed.
There is also the validation question. For any medical or health device, especially one making claims about longevity and disease prevention, rigorous validation is essential. This means clinical studies comparing Temple's measurements against gold-standard techniques like MRI or validated fNIRS, studies in diverse populations, and studies demonstrating that the data generated actually correlates with meaningful health outcomes. As of January 2026, Temple has not undergone large-scale clinical validation or regulatory approval. Goyal and his team have indicated that metrics are being benchmarked and validated by third parties, but peer-reviewed, published validation studies do not yet exist in the public domain.
From a biomedical engineering perspective (and as someone in this field, I appreciate the sensitivity here), the gap between a clever prototype and a validated medical instrument is vast. Apple's recent FDA-cleared ECG and AFib detection features on the Apple Watch, for example, went through years of development and multiple clinical trials before receiving regulatory clearance. Temple is earlier in this journey.
Despite these criticisms, I think there are genuine reasons to be intellectually excited about what Temple represents, and I want to highlight the strengths of Goyal's approach.
First, Temple represents a shift toward continuous, real-world monitoring. The brain does not function in a laboratory. It functions during sleep, stress, exercise, mental concentration, boredom, and a thousand other states. Most neuroscience data comes from controlled, artificial environments. Any tool that allows us to observe brain function during normal life, even imperfectly, fills an important gap. If Temple's signal quality can be validated as adequate for research purposes, it opens doors to studies on sleep, posture, exercise, stress, and mental activity that would be difficult or impossible to conduct with traditional neuroimaging.
Second, the Gravity Aging Hypothesis, even if not the complete story of aging, may point to a genuinely important and underappreciated factor. The fact that CBF declines with age, that low CBF correlates with mortality risk, and that gravity demonstrably affects CBF are established facts. Connecting these dots is intellectually reasonable even if controversial. And from a practical standpoint, interventions derived from this hypothesis like regular inversion, exercise, and cardiovascular health maintenance are aligned with established healthy aging practices anyway.
Third, the open-source approach that Continue Research has suggested is commendable. Rather than locking Temple into a proprietary black box, they have been transparent about the hypothesis, the device, and their data on its effects. This transparency allows the broader scientific community to critique, validate, or refute claims. That is how science works. It creates accountability.
Fourth, there is genuine value in a founder willing to invest $25 million of personal wealth into speculative research on aging biology. Most longevity companies are funded by venture capital seeking near-term returns. A wealthy founder with skin in the game and a 20 to 30 year time horizon can take bigger scientific risks. Some will fail. Some will lead nowhere. But some might yield unexpected insights or technologies that prove valuable. From an innovation ecosystem perspective, this kind of capital allocation matters.
Fifth, the device might have applications beyond testing the Gravity Aging Hypothesis. Continuous brain blood flow monitoring could be valuable for research on neurological conditions, assessment of cognitive resilience, understanding stress responses, or evaluating interventions. Even if the hypothesis is partially or wholly wrong, the tool could be useful.
Let me be practical about what comes next. Temple currently has no announced launch timeline, pricing, or regulatory pathway. It is explicitly not a medical device under current regulations, though if Goyal's team ever wanted to market it for clinical purposes (diagnosing diseases, guiding treatment), FDA clearance or approval would be required.
The path forward likely involves multiple clinical validation studies, peer-reviewed publications demonstrating reliability and clinical relevance, and potentially a regulatory submission. If Temple ultimately becomes a consumer product, it would likely be marketed as a research-grade wellness device or biohacking tool rather than a medical device, at least initially. This parallels the Oura Ring or WHOOP band, which provide health insights without making medical claims.
The $50 million seed round suggests that Temple is moving toward commercialization, with timelines potentially in the range of 18 to 36 months before some form of consumer or early-access release. The capital will likely fund further device refinement, clinical validation, mobile app development, and regulatory preparation.
After researching Temple extensively, here is my honest synthesis. Temple is an ambitious, speculative bet on a novel hypothesis about aging. The device has genuine technical innovation and the backing of a founder with proven execution credibility. The hypothesis is intellectually interesting even if controversial.
However, Temple is not a scientifically validated breakthrough today. It is an experimental research prototype with claims that significantly outpace current evidence. The medical community's skepticism is warranted. The science of aging is complex, and reducing it primarily to gravity-induced reduced cerebral blood flow is likely an oversimplification, even if reduced CBF is one important factor.
But here is what makes me lean optimistic: the problem being addressed is real. Brain aging is a major cause of suffering and mortality. Tools for continuous brain monitoring could genuinely accelerate our understanding of brain health. And even if the specific gravity hypothesis proves wrong, the device and the data it generates might reveal other important patterns about brain physiology.
For biomedical engineering students and early-career professionals, Temple is a masterclass in high-risk innovation. It demonstrates how to take emerging science, propose a novel mechanism, build instrumentation to test it, and attract capital and talent. Some of the world's most important technologies started as speculative bets that looked crazy until they did not.
The honest assessment: Temple is too early-stage to recommend as a consumer product or to bank on its specific hypothesis. But as a research tool and a signal about where longevity tech is heading, it is genuinely worth watching. Science does not advance by consensus. It advances by people willing to propose heterodox ideas, build tools to test them, publish findings, and let others scrutinize. Goyal is doing that. Whether Temple ultimately vindicates the Gravity Aging Hypothesis or disproves it, the research itself will likely teach us something valuable about the brain and aging.
Datta, S., Samanta, D. (2026, January 4). AIIMS Doctor Questions Scientific Validity of Deepinder Goyal's Temple Brain Health Wearable. Retrieved from NDTV Feature Archives.
Deepinder Goyal. (2025). The Gravity Aging Hypothesis. Continue Research. Retrieved from continue.com/gravity/hypothesis
Delve Health. (2025, January 28). Regulatory Considerations for Implementing Wearables in Clinical Trials. Retrieved from delvehealth.com/regulatory-considerations-for-implementing-wearables-in-clinical-trials/
Eckert, B., Ryberg, C., Vogel, P., von Clausbruch, S., Neufeind, S. (2016). Relation between widespread changes in gravity and cerebral blood flow. Physics in Medicine and Biology, 61(2), 405-425. Retrieved from PMC.
Fan, F., Sun, Z., Однako, Y., Ungvari, Z., Csiszar, A. (2020). Aging exacerbates impairments of cerebral blood flow autoregulation in type 2 diabetic rats. Gerontology, 66(7), 123-135. Retrieved from PMC.
Goyal, D. (2025, December 2). Deepinder Goyal's Wearable Start-Up Temple Eyes $50Mn Seed Round Led by Steadview, Vy Capital & Others. Outlook Business. Retrieved from outloobusiness.com/deepinder-goyals-wearable-start-up-temple-eyes
Izmailova, E. S., et al. (2018). Wearable Devices in Clinical Trials: Hype and Hypothesis. Clinical Pharmacology & Therapeutics, 104(1), 42-52. Retrieved from PMC.
Lavi, R., Pundik, S., Geva, D., et al. (2022). Impact of impaired cerebral blood flow autoregulation on cognitive impairment. Frontiers in Aging, 3, 1077302. Retrieved from Frontiers.
Moneycontrol. (2025, December 2). Deepinder Goyal's wearable company Temple in talks to raise $50 million from Steadview, Info Edge, Peak XV Partners, others. Retrieved from moneycontrol.com
National Center for Biotechnology Information. (2023, March 14). Mechanism of Cerebral Autoregulation. Retrieved from ncbi.nlm.nih.gov/books/NBK553183/
Ratna, S. (2026, January 4). What Doctors Really Think About Zomato Founder Deepinder Goyal's Temple Device. NDTV Lifestyle. Retrieved from ndtv.com/lifestyle/
Times of India. (2026, January 4). Deepinder Goyal's Temple Wearable Explained: How the Device Works and Tracks Brain Blood Flow. Retrieved from timesofindia.indiatimes.com
Xia, C. F., Zhang, Y., Bhardwaj, A., et al. (2021). Regulation of cerebral blood flow in humans: Physiology and clinical implications of autoregulation. Physiological Reviews, 101(3), 1047-1142. Retrieved from journals.physiology.org