GPS Uses Einstein's Relativity 24/7 — Why Parents Should Use It to Spark Kids' Interest in Physics

Every time your kid opens Google Maps and gets accurate turn-by-turn directions, they are relying on a correction factor calculated from Albert Einstein’s general theory of relativity. This is not metaphorical. Without that correction, GPS position estimates would drift by roughly 10 kilometers per day — compounding daily, accumulating to errors so large the system would be useless within weeks. Einstein published the general theory of relativity in 1915. The first GPS satellites launched in 1978. The engineers who designed the system had to decide, right at the start, whether to include the relativistic correction. Some argued that the effect was too small to matter. Others did the math.

The others were right.

This is one of the most useful physics facts a parent can know. Not because it’s trivia — though it is spectacular trivia — but because it’s a door. Once a kid understands that physics is not just equations in a textbook, that it’s the reason the map on their phone works, the reason their hearing aid can process sound, the reason the LED in their desk lamp emits light at all — the subject transforms from abstract to urgent. This article gives you the tools to open that door.

Why Parents Should Know This

Physics consistently ranks among the subjects students find most difficult and least connected to real life. A 2019 survey by the American Institute of Physics found that fewer than 40% of high school students who take physics say they understand how it connects to careers or everyday technology. That’s a problem — not because every kid should become a physicist, but because physics is the foundation under engineering, medicine, materials science, electronics, and nearly every physical technology.

The gap is largely a framing problem. When physics is taught as F=ma and memorized constants, it feels arbitrary. When it’s taught as the explanation for why specific, real things work the way they do, it becomes interesting. Parents can close part of that gap outside the classroom, with minimal effort, by keeping a short list of “physics is already in this thing you use” examples and deploying them in casual conversation.

The GPS example is the best of these, because the relevant physics — special and general relativity — sounds impossibly advanced, and yet the correction is embedded in every civilian GPS receiver ever made. Your kid’s phone does Einstein every time it finds itself on a map.

How the GPS Relativistic Correction Actually Works

The GPS constellation consists of 31 operational satellites orbiting at an altitude of approximately 20,200 kilometers. Each satellite carries extremely precise atomic clocks. A GPS receiver on the ground (your phone) calculates its position by measuring the time it takes signals from at least four satellites to arrive — tiny differences in arrival time translate into distances, and four distance measurements triangulate position in three dimensions.

The accuracy of this calculation depends entirely on the satellite clocks agreeing with each other and with ground-based reference clocks to within nanoseconds. A timing error of one microsecond (one millionth of a second) translates to a position error of about 300 meters, because that’s how far a radio signal travels in one microsecond at the speed of light.

Two effects from Einstein’s theories push the satellite clocks in opposite directions:

Special relativity (time dilation from velocity): The satellites move at approximately 14,000 km/h relative to a ground observer. Einstein’s special theory of relativity — published in 1905 — predicts that moving clocks run slow relative to stationary ones. At GPS satellite speeds, this causes the satellite clocks to lose approximately 7 microseconds per day compared to ground clocks.

General relativity (time dilation from gravity): Einstein’s general theory of relativity — published in 1915 — predicts that clocks in stronger gravitational fields run slower than clocks in weaker fields. GPS satellites are far from Earth’s center, where gravity is weaker. This causes them to run faster than ground clocks by approximately 45 microseconds per day.

The net effect: satellite clocks run fast by 45 − 7 = 38 microseconds per day relative to clocks on the ground. At 300 meters per microsecond of timing error, 38 microseconds translates to roughly 11.4 kilometers of accumulated position error per day. In less than two weeks, the system would be useless.

The correction is built directly into the satellite hardware. Before launch, satellite clock frequencies are deliberately set slightly slow — offset by exactly the amount needed to cancel the relativistic drift once the satellite reaches operational orbit. The satellite’s clock ticks at a slightly different rate on the ground than it does in orbit, intentionally, so that in orbit it matches ground clocks. Einstein’s field equations are, quite literally, burned into firmware.

This was described in detail by Neil Ashby of the University of Colorado Boulder in a paper for Living Reviews in Relativity (2003), which remains one of the clearest technical accounts of GPS relativity available to non-physicists.

Physics in Objects Your Kid Already Owns

GPS is the most dramatic example, but it’s not the only one. Every major category of modern technology contains physics that is genuinely fascinating once you pull the cover off.

Everyday Object	Physics Inside	Core Concept	When It Was Understood
GPS receiver	Special + general relativity correction	Time dilation (velocity + gravity)	1905, 1915
MRI machine	Nuclear magnetic resonance	Quantum spin of protons	1940s–1950s
LED lights	Semiconductor band gap emission	Quantum mechanics of electron energy levels	1920s theory; practical 1960s
Microwave oven	Resonant microwave absorption in water	Molecular rotation, electromagnetic frequency	1940s
Touch screen	Mutual capacitance sensing	Electric field distortion by conductive touch	1970s
Noise-canceling headphones	Destructive wave interference	Wave superposition	Classical physics, 1800s
Lithium-ion battery	Intercalation electrochemistry	Ion movement through crystalline lattice	1970s–1980s
Smoke detector	Alpha particle ionization chamber	Nuclear decay, radioactivity	Early 1900s

Each row in this table is a conversation starter. The question “wait, how does an MRI actually work?” leads naturally into a discussion of proton spin, magnetic fields, and why hydrogen atoms (abundant in water and fat) are particularly useful. The question “why does my LED bulb make light but not heat like an incandescent?” leads into quantum band gaps — the idea that electrons in a semiconductor can only exist at specific energy levels, and when they drop from a higher level to a lower one, they emit a photon of a specific wavelength (color).

None of these conversations require a physics degree to have. They require curiosity and a willingness to look things up together.

Special Relativity: The Two-Sentence Version

Einstein’s special theory of relativity rests on two postulates. First: the laws of physics are identical in all inertial reference frames (any frame that isn’t accelerating). Second: the speed of light in a vacuum is the same for all observers, regardless of their motion relative to the light source.

From those two premises, time dilation follows mathematically. If the speed of light must remain constant for all observers, and a clock on a moving satellite is measuring time by the round-trip behavior of light, then time itself must be running at a different rate for that satellite compared to an observer on the ground. This sounds paradoxical. It isn’t — it’s just counterintuitive to beings who evolved at walking speeds.

The famous example: if you sent a twin on a spaceship at close to light speed and they returned after what felt to them like two years, they would find their sibling had aged 20 years or more. The “twin paradox” is not a paradox — it’s a prediction of special relativity that has been confirmed experimentally using atomic clocks on aircraft. The experiment was done by Hafele and Keating in 1971, published in Science, and the results matched relativistic predictions to within measurement uncertainty.

General Relativity: Gravity Curves Time

The general theory extends special relativity to include gravity and acceleration. The key insight — the equivalence principle — is that being accelerated upward at 9.8 m/s² feels indistinguishable from standing still in Earth’s gravitational field. Gravity and acceleration are equivalent, locally.

This leads to the prediction that gravity slows time. A clock at sea level (where Earth’s gravity is stronger) ticks more slowly than an identical clock at altitude (where gravity is weaker). This is not an engineering approximation — it’s been measured directly using precise atomic clocks placed at different elevations. The effect is real and measurable at differences of just a few meters of altitude.

For GPS satellites at 20,200 km, the gravitational effect is large enough to dominate. Without the correction, the satellites would function as inaccurate timekeeping devices, and the inaccuracy would compound at a fixed rate every day.

Quantum Mechanics Is Also in Your House

Relativity is not the only counter-intuitive physics embedded in consumer technology. Quantum mechanics — the physics of very small objects — is equally present.

LED lights emit light through a quantum mechanical process. In a semiconductor like gallium nitride (used in blue LEDs), electrons exist in discrete energy bands. When a voltage is applied, electrons drop from the conduction band to the valence band, releasing a photon whose energy — and therefore color — corresponds exactly to the energy difference between the two bands. The wavelength of light an LED emits is determined by the quantum band structure of its semiconductor material. This is why different semiconductor compounds make different colors. Shuji Nakamura’s invention of the blue LED, for which he received the 2014 Nobel Prize in Physics, completed the trio of primary colors needed to make white LEDs practical.

MRI machines use nuclear magnetic resonance. Protons (hydrogen nuclei) have a quantum property called spin, which means they behave like tiny bar magnets. In a strong external magnetic field, protons align with the field and precess (wobble) at a specific frequency — the Larmor frequency — determined by field strength. An MRI machine pulses radio waves at that exact frequency, knocking the protons out of alignment. When the radio pulse stops, the protons realign and emit radio signals that vary depending on the tissue environment. A computer reconstructs those signals into images. The machine is essentially a large quantum mechanical instrument that listens to hydrogen atoms responding to radio waves.

What This Means for Your Kid’s Future

The habit of asking “what physics is actually doing this work?” is one of the most valuable intellectual tools an engineer or scientist can have. It prevents cargo-cult engineering — applying techniques without understanding why they work — and it enables first-principles reasoning when a problem is genuinely novel.

Physics education in the U.S. is uneven. According to the American Institute of Physics, only about 39% of high school graduates take any physics before graduation, and calculus-based physics — the version that actually connects to engineering and physics careers — reaches a much smaller fraction. Students who arrive at university having already built intuitions about real physical phenomena — not just formulas, but why the phenomena exist — have a measurable advantage in engineering and science programs.

Careers in physics and engineering physics remain among the highest-compensated in STEM. The AIP’s 2023 workforce data shows a median starting salary of $85,000 for bachelor’s-level physics graduates entering industry, rising significantly with graduate degrees. More importantly, physics training develops quantitative reasoning and comfort with abstraction that transfers across essentially every technical field.

For parents wondering how to connect this to space and systems thinking, the GPS story links directly to the kinds of real careers space systems engineers pursue — positions where understanding relativistic corrections and signal propagation is a genuine day-one requirement.

What Parents Should Do

Use the “10 km drift” fact as a conversation starter

The next time your kid uses navigation — in a car, on a hike, on a bike — say: “Did you know this only works because of Einstein? Without a correction for general relativity, the position would drift by about 10 kilometers every day.” Then let them ask “wait, how?” That question is worth following. Don’t answer immediately — see if they want to figure it out.

Keep a short “physics in this object” list on your phone

Pick five objects your kid uses regularly and briefly research the physics inside. You don’t need deep expertise — one good paragraph about why LEDs make light, or why touch screens detect touch, is enough to generate a real conversation. Wikipedia’s articles on these topics are accurate and accessible. The habit of connecting physical objects to underlying principles is worth more than any single factual explanation.

Watch a Hafele-Keating video together

The 1971 Hafele-Keating experiment — flying atomic clocks on commercial aircraft to test relativistic time dilation — is described in multiple accessible videos and articles. The experiment is simple enough that a middle schooler can understand the setup, and the result is concrete enough to be genuinely surprising: the clocks on the aircraft disagreed with the ground clocks by amounts that matched Einstein’s predictions. Real physics, tested with real airplanes.

Try the MIT OpenCourseWare introductory physics sequence

MIT’s 8.01 and 8.02 courses (classical mechanics and electricity/magnetism) are available free at ocw.mit.edu. For high schoolers who want more than AP Physics offers, these are the actual courses MIT undergraduates take. They’re demanding, but a motivated 16-year-old can engage with substantial portions of them. The problem sets are available, the lecture videos are excellent, and they are free.

Make the Larmor frequency tangible with a simple demonstration

You can demonstrate wave resonance — the principle underlying MRI — with a simple pendulum. A pendulum has a natural frequency determined by its length. Push it at that frequency and the swings build; push it at a different frequency and the energy doesn’t transfer efficiently. This is the same principle as nuclear magnetic resonance: systems absorb energy most effectively at their natural (resonant) frequency. The demonstration is imperfect as an MRI analogy, but it makes the resonance concept concrete before the quantum version.

Connect physics to the careers they’re already interested in

Almost every career a kid might currently find interesting has physics in it. Interested in cars? Thermodynamics, fluid dynamics, electric motors. Interested in music production? Wave physics, digital signal processing. Interested in medicine? MRI (quantum mechanics), X-rays (photoelectric effect, discovered by Einstein in 1905 — same year as special relativity). The goal is not to make every interest “secretly physics” in a way that feels manipulative — it’s to accurately note that physical principles run through more fields than most people realize.

Frequently Asked Questions

Do I need to understand Einstein’s equations to appreciate why GPS needs the correction?

No. The key insight is conceptual: moving clocks run slow (special relativity), and clocks in stronger gravity run slow (general relativity). For GPS satellites moving fast and high above Earth, these two effects push in opposite directions but don’t cancel — the gravity effect wins, so the satellite clocks run fast relative to ground clocks. That net difference, uncorrected, causes position drift. You can hold all of this without a single equation.

Is this really why GPS works, or is it a popular oversimplification?

The relativistic correction is genuinely required and has been confirmed by removing it experimentally. Neil Ashby’s 2003 paper in Living Reviews in Relativity is the definitive technical account. When the GPS system was being designed, there was debate about whether to include the correction from the start or add it later if needed. The corrections were included before launch, and tests confirmed their necessity. This is not a simplification — it is accurate.

Why don’t we notice relativistic effects in everyday life?

Because relativity’s effects are only significant at speeds close to the speed of light (for special relativity) or in very strong or very different gravitational fields (for general relativity). At human speeds and at the same altitude on Earth’s surface, the effects are too small to notice without atomic clocks. GPS satellites move fast enough and are at a different altitude than ground stations that the accumulated effect over a day is large enough to matter practically.

Can a kid really learn the math behind this before college?

Special relativity’s core mathematics — the Lorentz transformation — requires algebra and some familiarity with the concept of invariance. A strong algebra-2 student can work through the math. General relativity is much harder, requiring tensor calculus; the conceptual framework is accessible, but the full equations are genuinely graduate-level. Many university special relativity courses are accessible to students who have completed high school algebra and trigonometry.

What’s the best first book about physics for a curious teenager?

The Feynman Lectures on Physics (available free online at feynmanlectures.caltech.edu) are the gold standard — written by Nobel laureate Richard Feynman for incoming Caltech students, they are famous for building physical intuition. For younger students, Physics for Future Presidents by Richard Muller (a Berkeley physicist) covers real-world physics applications at a very accessible level. For relativity specifically, Spacetime Physics by Taylor and Wheeler is challenging but rewarding for motivated high schoolers.

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About the author

Ricky Flores is the founder of HiWave Makers and an electrical engineer with 15+ years developing consumer technology at Apple, Samsung, and Texas Instruments. He writes about how kids learn to build, think, and create in a tech-saturated world. Read more at hiwavemakers.com.

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Sources

1. Ashby, N. (2003). “Relativity in the Global Positioning System.” Living Reviews in Relativity, 6(1). https://doi.org/10.12942/lrr-2003-1

2. Hafele, J. C., & Keating, R. E. (1972). “Around-the-World Atomic Clocks: Predicted Relativistic Time Gains.” Science, 177(4044), 166–168. https://doi.org/10.1126/science.177.4044.166

3. Einstein, A. (1905). “Zur Elektrodynamik bewegter Körper.” Annalen der Physik, 17(10), 891–921. (English translation widely available.) https://doi.org/10.1002/andp.19053221004

4. Nakamura, S., Senoh, M., & Mukai, T. (1993). “High-Power InGaN/GaN Double-Heterostructure Violet Light Emitting Diodes.” Applied Physics Letters, 62(19), 2390–2392. https://doi.org/10.1063/1.109374

5. American Institute of Physics Statistical Research Center. (2023). Physics Workforce Report 2023. https://www.aip.org/statistics

6. Kaplan, E. D., & Hegarty, C. J. (Eds.). (2006). Understanding GPS/GNSS: Principles and Applications (2nd ed.). Artech House.

7. U.S. Naval Observatory. (2024). GPS: The Global Positioning System. https://www.gps.gov/systems/gps/

8. MIT OpenCourseWare. (2024). Physics I: Classical Mechanics (8.01). https://ocw.mit.edu/courses/8-01sc-classical-mechanics-fall-2016/