--- title: "Meaning & Key Takeaway of: In general the fact that gravitational…" description: "\"“In general the fact that gravitational and inertial forces are both proportional to the mass of the body on which they act but depend on no other prop..." image: "https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png" --- # In general the fact that gravitational and inertial forces… ![“In general the fact that gravitational and inertial forces are both proportional to the mass of the body on which they act but depend on no other property of the body makes it possible at any point in any gravitational field to identify a "freely falling frame of reference" in which neither…” quote by Steven Weinberg](https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png) [Download](https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png) [Open image](https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png) > ““In general the fact that gravitational and inertial forces are both proportional to the mass of the body on which they act but depend on no other property of the body makes it possible at any point in any gravitational field to identify a "freely falling frame of reference" in which neither gravitational nor inertial forces are felt because they are in perfect balance for all bodies. When we do feel gravitational or inertial forces it is because we are not in a freely falling frame. For example, on the earth's surface freely falling bodies accelerate toward the center of the earth at 32 feet per second per second, and we feel a gravitational force unless we happen to be accelerating downward at the same rate. Einstein made a logical jump and guessed that gravitational and inertial forces were at bottom the same thing. He called this the principle of equivalence of gravitation and inertia, or the equivalence principle for short. According to this principle, any gravitational field is completely described by telling which frame of reference is freely falling at each point in space.”” [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) ## About This Quote This interpretation was drafted with AI assistance. It is one reading of the quote, not the author's own explanation. The equivalence principle states that locally, gravitational and inertial effects are indistinguishable, allowing a freely falling frame where neither is felt. **In simple terms:** In a falling frame, gravity and inertia cancel out. Key Takeaway Recognize that acceleration can mask gravity. Themes physics relativity principles Mood thoughtful inquisitive Type scientific educational When to use this quote - free fall experiments - spacecraft navigation - educational demonstrations Key Concepts equivalence inertial frames gravity Questions to Reflect On - How does this principle affect our understanding of gravity? - What limits does locality impose? A Different Perspective The principle holds only locally; tidal forces reveal differences over larger regions. ★ ★ ★ ★ ★ No ratings yet [Gravitation Inertia](https://sms4smile.com/quotes/about/gravitation-inertia-4245296/) [Gravitational Force](https://sms4smile.com/quotes/about/gravitational-force-486827/) [Gravitational Inertial](https://sms4smile.com/quotes/about/gravitational-inertial-4245295/) [Inertia Equivalence](https://sms4smile.com/quotes/about/inertia-equivalence-4245297/) [Inertial Forces](https://sms4smile.com/quotes/about/inertial-forces-4245294/) [Perfect balance](https://sms4smile.com/quotes/about/perfect-balance/) [Theory](https://sms4smile.com/quotes/about/theory/) ## Related quotes > [“Now let's assume that there is an external Mass acting gravitationally on some system that we observe. Then there are two possibilities: First the…](https://sms4smile.com/quotes/henning-genz/now-let-s-assume-that-there-is-an-external-mass-acting/) [Henning Genz](https://sms4smile.com/quotes/author/henning-genz/) > [With no gravitational force to work against, your body not only doesn't need the same amount of muscle and bone, it starts breaking them…](https://sms4smile.com/quotes/neil-degrasse-tyson/with-no-gravitational-force-to-work-against-your-body-not-only-doesn/) [Neil deGrasse Tyson](https://sms4smile.com/quotes/author/neil-degrasse-tyson/) > [The gravitational force cannot be held responsible for the people falling in love.](https://sms4smile.com/quotes/divya/the-gravitational-force-cannot-be-held-responsible-for-the-people/) [Divya](https://sms4smile.com/quotes/author/divya/) > [“Meaning … if enough people begin thinking the same thing, then the gravitational force of that thought becomes tangible … and it exerts actual…](https://sms4smile.com/quotes/dan-brown/meaning-if-enough-people-begin-thinking-the-same-thing-then-the/) [Dan Brown](https://sms4smile.com/quotes/author/dan-brown/) > [“It is the cosmological vacuum energy that contributes a repulsive lambda force to the gravitational force of Newton.”](https://sms4smile.com/quotes/john-d-barrow/it-is-the-cosmological-vacuum-energy-that-contributes-a-repulsive/) [John D. Barrow](https://sms4smile.com/quotes/author/john-d-barrow/) > [“The suggestion that the body really wanted to go straight but some mysterious agent made it go crooked is picturesque but unscientific. It makes…](https://sms4smile.com/quotes/arthur-stanley-eddington/the-suggestion-that-the-body-really-wanted-to-go-straight-but-some/) [Arthur Stanley Eddington](https://sms4smile.com/quotes/author/arthur-stanley-eddington/) > [People want to believe that every marriage is perfect balance but it isn't. One person always loves more deeply than the other](https://sms4smile.com/quotes/nicholas-sparks/people-want-to-believe-that-every-marriage-is-perfect-balance-but-it/) [Nicholas Sparks](https://sms4smile.com/quotes/author/nicholas-sparks/) > [“If you think of our planet as a living, breathing organism, the forests are the lungs. They create a perfect balance to our own…](https://sms4smile.com/quotes/hope-bohanec/if-you-think-of-our-planet-as-a-living-breathing-organism-the-forests/) [Hope Bohanec](https://sms4smile.com/quotes/author/hope-bohanec/) > [Always endeavour to create a state of Bliss where everything is in perfect balance.](https://sms4smile.com/quotes/steven-redhead/always-endeavour-to-create-a-state-of-bliss-where-everything-is-in/) [Steven Redhead](https://sms4smile.com/quotes/author/steven-redhead/) > [During one's 20s, one has the perfect balance of the energy and imagination of a kid and the wisdom of an adult. Your 20's…](https://sms4smile.com/quotes/tsepiso-makhubedu/during-one-s-20s-one-has-the-perfect-balance-of-the-energy-and/) [Tsepiso Makhubedu](https://sms4smile.com/quotes/author/tsepiso-makhubedu/) > [My aim is to be as open and as incomprehensible as possible. There has to be a perfect balance between open and shut.](https://sms4smile.com/quotes/maurizio-cattelan/my-aim-is-to-be-as-open-and-as-incomprehensible-as-possible-there-has/) [Maurizio Cattelan](https://sms4smile.com/quotes/author/maurizio-cattelan/) > [My favourite plant is the foxglove. I think they are a perfect balance between being a garden plant and a wild plant, as at…](https://sms4smile.com/quotes/clive-anderson/my-favourite-plant-is-the-foxglove-i-think-they-are-a-perfect-balance/) [Clive Anderson](https://sms4smile.com/quotes/author/clive-anderson/) > [“In our friendship I had spent a lot of time telling Lucy to pull herself up, to get over the past and move on.…](https://sms4smile.com/quotes/ann-patchett/in-our-friendship-i-had-spent-a-lot-of-time-telling-lucy-to-pull/) [Ann Patchett](https://sms4smile.com/quotes/author/ann-patchett/) > [“Just when you think world has found a perfect balance, someone starts a live video with terrible sound and shaky footage, often slow internet.”](https://sms4smile.com/quotes/crestless-wave/just-when-you-think-world-has-found-a-perfect-balance-someone-starts/) [Crestless Wave](https://sms4smile.com/quotes/author/crestless-wave/) > [I never understood how much running changes your life. I'm now obsessed. When not trying to beat my personal best, I'm talking to other…](https://sms4smile.com/quotes/sadiq-khan/i-never-understood-how-much-running-changes-your-life-i-m-now/) [Sadiq Khan](https://sms4smile.com/quotes/author/sadiq-khan/) ## More by Steven Weinberg > [On balance the moral influence of religion has been awful.](https://sms4smile.com/quotes/steven-weinberg/on-balance-the-moral-influence-of-religion-has-been-awful/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [“The apparent strengths of the forces in any field theory depend on two kinds of numerical parameter: the masses (if any) of the particles…](https://sms4smile.com/quotes/steven-weinberg/the-apparent-strengths-of-the-forces-in-any-field-theory-depend-on/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [“Many people do simply awful things out of sincere religious belief, not using religion as a cover the way that Saddam Hussein may have…](https://sms4smile.com/quotes/steven-weinberg/many-people-do-simply-awful-things-out-of-sincere-religious-belief/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [This is often the way it is in physics - our mistake is not that we take our theories too seriously, but that we…](https://sms4smile.com/quotes/steven-weinberg/this-is-often-the-way-it-is-in-physics-our-mistake-is-not-that-we/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do…](https://sms4smile.com/quotes/steven-weinberg/with-or-without-religion-you-would-have-good-people-doing-good-things/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [I would say it's a lot easier to develop a decoy system than to develop the intercontinental ballistic missile itself. I would think that…](https://sms4smile.com/quotes/steven-weinberg/i-would-say-it-s-a-lot-easier-to-develop-a-decoy-system-than-to/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [Rational argument can be defeated by refusing to argue rationally.](https://sms4smile.com/quotes/steven-weinberg/rational-argument-can-be-defeated-by-refusing-to-argue-rationally/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [The universe is an enormous direct product of representations of symmetry groups.](https://sms4smile.com/quotes/steven-weinberg/the-universe-is-an-enormous-direct-product-of-representations-of/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [Its a consequence of the experience of science. As you learn more and more about the universe, you find you can understand more and…](https://sms4smile.com/quotes/steven-weinberg/its-a-consequence-of-the-experience-of-science-as-you-learn-more-and/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [Our job in physics is to see things simply, to understand a great many complicated phenomena in a unified way, in terms of a…](https://sms4smile.com/quotes/steven-weinberg/our-job-in-physics-is-to-see-things-simply-to-understand-a-great-many/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [“Plato and the neo-Platonists taught that the beauty we see in nature is a reflection of the beauty of the ultimate, the nous. For…](https://sms4smile.com/quotes/steven-weinberg/plato-and-the-neo-platonists-taught-that-the-beauty-we-see-in-nature/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [An expert is a person who avoids the small errors while sweeping on to the grand fallacy.](https://sms4smile.com/quotes/steven-weinberg/an-expert-is-a-person-who-avoids-the-small-errors-while-sweeping-on/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [If (the antiproton) had not been discovered, the foundations of physics really would have crumbled.](https://sms4smile.com/quotes/steven-weinberg/if-the-antiproton-had-not-been-discovered-the-foundations-of-physics/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [Even though I knew pretty early that I was going to be a scientist, it wasn't the science that interested me in science fiction;…](https://sms4smile.com/quotes/steven-weinberg/even-though-i-knew-pretty-early-that-i-was-going-to-be-a-scientist-it/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) > [If history is any guide at all, it seems to me to suggest that there is a final theory. In this century we have…](https://sms4smile.com/quotes/steven-weinberg/if-history-is-any-guide-at-all-it-seems-to-me-to-suggest-that-there/) [Steven Weinberg](https://sms4smile.com/quotes/author/steven-weinberg/) [Explore all 137 Steven Weinberg quotes ](https://sms4smile.com/quotes/author/steven-weinberg/) ## More Perfect balance quotes > [I never understood how much running changes your life. I'm now obsessed. When not trying to beat my personal best, I'm talking to other…](https://sms4smile.com/quotes/sadiq-khan/i-never-understood-how-much-running-changes-your-life-i-m-now/) [Sadiq Khan](https://sms4smile.com/quotes/author/sadiq-khan/) > [“Just when you think world has found a perfect balance, someone starts a live video with terrible sound and shaky footage, often slow internet.”](https://sms4smile.com/quotes/crestless-wave/just-when-you-think-world-has-found-a-perfect-balance-someone-starts/) [Crestless Wave](https://sms4smile.com/quotes/author/crestless-wave/) > [“In our friendship I had spent a lot of time telling Lucy to pull herself up, to get over the past and move on.…](https://sms4smile.com/quotes/ann-patchett/in-our-friendship-i-had-spent-a-lot-of-time-telling-lucy-to-pull/) [Ann Patchett](https://sms4smile.com/quotes/author/ann-patchett/) > [My favourite plant is the foxglove. I think they are a perfect balance between being a garden plant and a wild plant, as at…](https://sms4smile.com/quotes/clive-anderson/my-favourite-plant-is-the-foxglove-i-think-they-are-a-perfect-balance/) [Clive Anderson](https://sms4smile.com/quotes/author/clive-anderson/) > [My aim is to be as open and as incomprehensible as possible. There has to be a perfect balance between open and shut.](https://sms4smile.com/quotes/maurizio-cattelan/my-aim-is-to-be-as-open-and-as-incomprehensible-as-possible-there-has/) [Maurizio Cattelan](https://sms4smile.com/quotes/author/maurizio-cattelan/) > [During one's 20s, one has the perfect balance of the energy and imagination of a kid and the wisdom of an adult. Your 20's…](https://sms4smile.com/quotes/tsepiso-makhubedu/during-one-s-20s-one-has-the-perfect-balance-of-the-energy-and/) [Tsepiso Makhubedu](https://sms4smile.com/quotes/author/tsepiso-makhubedu/) > [Always endeavour to create a state of Bliss where everything is in perfect balance.](https://sms4smile.com/quotes/steven-redhead/always-endeavour-to-create-a-state-of-bliss-where-everything-is-in/) [Steven Redhead](https://sms4smile.com/quotes/author/steven-redhead/) > [“If you think of our planet as a living, breathing organism, the forests are the lungs. They create a perfect balance to our own…](https://sms4smile.com/quotes/hope-bohanec/if-you-think-of-our-planet-as-a-living-breathing-organism-the-forests/) [Hope Bohanec](https://sms4smile.com/quotes/author/hope-bohanec/) > [People want to believe that every marriage is perfect balance but it isn't. One person always loves more deeply than the other](https://sms4smile.com/quotes/nicholas-sparks/people-want-to-believe-that-every-marriage-is-perfect-balance-but-it/) [Nicholas Sparks](https://sms4smile.com/quotes/author/nicholas-sparks/) > [There can never be any real opposition between religion and science; for the one is the complement of the other. Every serious and reflective…](https://sms4smile.com/quotes/max-planck/there-can-never-be-any-real-opposition-between-religion-and-science/) [Max Planck](https://sms4smile.com/quotes/author/max-planck/) > [Every time I get a chance to be out in the ocean, it's like hitting a reset button for me where I just feel…](https://sms4smile.com/quotes/jack-johnson/every-time-i-get-a-chance-to-be-out-in-the-ocean-it-s-like-hitting-a/) [Jack Johnson](https://sms4smile.com/quotes/author/jack-johnson/) > [“- 'Poise is perfect balance, an equanimity of body and mind, complete composure whatever the social scene. Elegant dress, immaculate grooming, and perfect deportment…](https://sms4smile.com/quotes/muriel-spark/poise-is-perfect-balance-an-equanimity-of-body-and-mind-complete/) [Muriel Spark](https://sms4smile.com/quotes/author/muriel-spark/) > [Often the lack of clear direction and goals can waste away our time and energy and contribute to imbalance in our lives. A life…](https://sms4smile.com/quotes/m-russell-ballard/often-the-lack-of-clear-direction-and-goals-can-waste-away-our-time/) [M. Russell Ballard](https://sms4smile.com/quotes/author/m-russell-ballard/) > [Bands speak for us in this inevitable way that you can't get anywhere else because it is this perfect balance of artistic expression and…](https://sms4smile.com/quotes/taylor-goldsmith/bands-speak-for-us-in-this-inevitable-way-that-you-can-t-get-anywhere/) [Taylor Goldsmith](https://sms4smile.com/quotes/author/taylor-goldsmith/) > [“A Great Rabbi stands, teaching in the marketplace. It happens that a husband finds proof that morning of his wife's adultery, and a mob…](https://sms4smile.com/quotes/orson-scott-card/a-great-rabbi-stands-teaching-in-the-marketplace-it-happens-that-a/) [Orson Scott Card](https://sms4smile.com/quotes/author/orson-scott-card/) [Browse all 86 Perfect balance quotes ](https://sms4smile.com/quotes/about/perfect-balance/) ```json { "@context": "https://schema.org", "@graph": [ { "@type": "Quotation", "text": "“In general the fact that gravitational and inertial forces are both proportional to the mass of the body on which they act but depend on no other property of the body makes it possible at any point in any gravitational field to identify a \"freely falling frame of reference\" in which neither gravitational nor inertial forces are felt because they are in perfect balance for all bodies. When we do feel gravitational or inertial forces it is because we are not in a freely falling frame. For example, on the earth's surface freely falling bodies accelerate toward the center of the earth at 32 feet per second per second, and we feel a gravitational force unless we happen to be accelerating downward at the same rate. Einstein made a logical jump and guessed that gravitational and inertial forces were at bottom the same thing. He called this the principle of equivalence of gravitation and inertia, or the equivalence principle for short. According to this principle, any gravitational field is completely described by telling which frame of reference is freely falling at each point in space.”", "creator": { "@type": "Person", "name": "Steven Weinberg" }, "isPartOf": { "@id": "https://sms4smile.com/quotes/#website" }, "url": "https://sms4smile.com/quotes/steven-weinberg/in-general-the-fact-that-gravitational-and-inertial-forces-are-both/", "about": { "@type": "Thing", "name": "Perfect balance" }, "@id": "https://sms4smile.com/quotes/steven-weinberg/in-general-the-fact-that-gravitational-and-inertial-forces-are-both/#quotation", "image": { "@type": "ImageObject", "@id": "https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png", "contentUrl": "https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png", "url": "https://sms4smile.com/quotes/i/27c/steven-weinberg-3159_perfect-balance_in-general-the-fact-that-gravitational-a_1296953.png", "width": 1080, "height": 1080, "caption": "“In general the fact that gravitational and inertial forces are both proportional to the mass of the body on…” — Steven Weinberg", "creditText": "SMS4Smile Quotes", "creator": { "@id": "https://sms4smile.com/quotes/#organization" } } }, { "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://sms4smile.com/" }, { "@type": "ListItem", "position": 2, "name": "Quotes", "item": "https://sms4smile.com/quotes/" }, { "@type": "ListItem", "position": 3, "name": "Steven Weinberg", "item": "https://sms4smile.com/quotes/author/steven-weinberg/" }, { "@type": "ListItem", "position": 4, "name": "“In general the fact that gravitational...", "item": "https://sms4smile.com/quotes/steven-weinberg/in-general-the-fact-that-gravitational-and-inertial-forces-are-both/" } ], "@id": "https://sms4smile.com/quotes/steven-weinberg/in-general-the-fact-that-gravitational-and-inertial-forces-are-both/#breadcrumb" }, { "@type": "WebSite", "@id": "https://sms4smile.com/quotes/#website", "name": "SMS4Smile Quotes", "url": "https://sms4smile.com/quotes/", "publisher": { "@id": "https://sms4smile.com/quotes/#organization" } }, { "@type": "Organization", "@id": "https://sms4smile.com/quotes/#organization", "name": "SMS4Smile Quotes", "url": "https://sms4smile.com/quotes/", "logo": { "@type": "ImageObject", "url": "https://sms4smile.com/quotes/wp-content/themes/sq/assets/icons/icon-512.png", "width": 512, "height": 512 } } ] } ```