thank you

he could've said accelerating at a constant rate.

Thank you for all your kind comments.

@@howfarawayisit Anytime I love people who love physics btw!( because they can clear my doubt understand nothing out of Physics) Your one of them!❤️

@@howfarawayisit If the only force is from below then only by removing the strength of force in a structure can cause it to completely collapse in acceleration from the top down...9/11?

oh ser you should probably have 100 times the sum of both our bits of knowledge to make such claims. Regardless I am almost 100% sure you would not make such claims if you had the knowledge.

If the only force is from below then only by removing the strength of force in a structure can cause it to completely collapse in acceleration from the top down...9/11?

This is why we should be extremely careful with using light as an example. Light technically does bend (that is why gravitational lensing is observed: gravity also effects light). However, the reason we don't measure it on Earth or even in that elevator example is because light travels extremely, extremely, extremely fast compared to any object that will "accelerate" due to gravity that we could currently exist in. For most observers, light travels almost instantaneously. I mean, just compare the speed of a commercial plane and light. The average commercial plane travels at around 250m/s while light travels at around 299,792,458 m/s: light is faster than the average plane 1.199.170 times. This is especially difficult to measure if the distance between the light's origin on the elevator and the wall on the other side is small. Most elevators have at most around 2 m of width. So light will finish its journey from the origin to the end of the wall in about... well basically instantaneous for most observers. The "bend" could be observed and measured if we have an equally extremely, extremely, extremely precise and powerful equipment that can calculate extremely quickly and set to automatically register when the beam of light first sets off, but the acceleration would need to be significantly larger than anything we've ever observed or personally experienced that it's practically not noticeable.

The distance between the walls is perpendicular to the direction of the motion, so no change is happening.

David Butler so then time flow will be different, slower to the one accelerating. How was it decided that causality (or light) should be the constant, immutable among observers? Experiments do agree with that, but how was it theorised before practical data confirmed it?

The theory was that the speed of light was relative. But then the Michelson-Morley experiment showed that it was fixed. Take a look at the 'How fast is it' video on The Speed of Light.

thank you, I will =)

Yes. The outer observer would see that.

'up' and 'down' on the planet are defined as 'away from the center' and 'towards the center' respectively.

Still doesn't explain how the planet can move up to meet the ball? If the Earth was flat and moving up, it could meet the ball. I'm clearly missing something here.

if u r saying that we are feeling gravity because earth is moving upward then I m sorry,I dont beleive such principle.better with newton in this one..if we r going upward then those on the opposite side would b flown back to the sky since earth is a rough sphere..n regardless of air resistance a feather n a stone ll touch the ground simultaneously if the earth is moving upward n not the two objects that fall due to gravity

I know I'm late but for all those out there still asking, the laws of physics should be "equal for inertial reference frames" is specifically for special relativity, this video is about general relativity, a refined theory of relativity that also incorporates gravity and its effects.

@@renthearchangel9479 Ok, but the video is claiming Galileo's principle of relativity as being valid for all reference frames. Of course the laws of Physics can't be the same for accelerating ref frames.

@@renthearchangel9479 Thanks

Tidal forces do not affect humans as such. It would have mattered if our heads were very big, say the size of the earth. Then the moon's tidal forces might have stretched our heads. So yeah.. the principle of equivalence is exact.

@@sonutabitha4538 Not really!

@@sonutabitha4538 I already explained in the OP

@@sonutabitha4538 here it goes again. Acceleration due to gravity depends on the distance. If you were sitting at the event horizon of a black hole you'd be stretched so fast you'd be ripped apart, because the pull on your feet is much stronger than on your head, the difference is tremendous. A space ship accelerating in space has all of your body accelerating at the same rate, so the equivalence principle is only approximate.

@@ThomasJr First of all, let's revisit the statement on the Equivalence principle. It says "A uniform gravitational field is equivalent to a uniformly accelerating frame of reference." A uniform gravitational field has, by definition, no tidal forces and thus no space-time curvature. The mathematical quantity associated with space-time curvature is the Riemann tensor, also known as the curvature tensor or tidal force tensor. This tensor, as with any tensor, can be expressed as a matrix. It can be shown that if, for a given region of space-time, all of the components of the curvature tensor vanish then that region of space-time is said to be flat. Conversely, if a region of space-time is not flat then it’s said to be curved. Curvature is said to be a local quantity in that it is possible to detect its presence in an arbitrarily small region of space in an arbitrarily short amount of time. It is always possible to choose a coordinate system, which is inertial, at least locally. Such a coordinate system is said to be locally flat. Given experimental limitations one can establish criteria in which tidal effects maybe ignored. Thus EP can be applied to objects that are very small such that tidal forces can be neglected. It should be noted that the equivalence principle explains the result of a "local" experiment. The word local is very important and it emphasizes that the experiment must be small compared to variations in the gravitational field, tidal forces. It is true that an observer in free-fall into a black hole will experience strong tidal forces: he will notice a more powerful force on the parts closer to the black hole. But as far as the person on earth is concerned, the tidal forces experienced would be really very small that the person won't be able to distinguish between the gravitational acceleration on earth and the acceleration in the laboratory.

You would need a smaller box so the tidal accerlations between the 2 objects are obsolete.

this is the problem i have with this explanation. it is either oversimplifying, or leaving out some important facts. in the accelerated box, the dropped object is not accelerating, it is not traversing. it IS at rest. the box is accelerating and eventually collides with it. on a planet, as you say, the rate of acceleration towards the center of mass depends on your distance from the center of that mass...so yes...you are accelerating at an ever-increasing rate as you fall.

Peter, It is not a language issue. It is a mistake on my part. I meant to day constant acceleration. Thanks for noting it.

Sorry for editing my comment while you answered, and thanks for your videos. I started out with an assumption that it was an English language issue like in "ain't got nothing". I realized this was probably not the case so I edited my comment. Thanks for a very fast answer.

people n objects on the opposite side of the earth ll b flown back to the sky since the earth was accelerating upward.lol equivalent principle

Earth is experiencing gravity due to sun’s bending of space time ! It doesn’t need rockets or to go up !

@@shamsalveera Then can u explain why every thing on earth is falling at the same rate ? ?

Thanks for catching this error last year. I'm finally close to uploading the 2023 4K update. The fix is in it.

@@howfarawayisit Looking forward to it.

Please send me after you have written

@@suryasnatabhattacharyya1927 Sure np

if it actually theorized that the earth is going upward.then rip to this principle

Still waiting

The paper is a work in progress and is almost half finished. The first half is focused on non-equality and the second half will be focused on non-equivalence.

The force field in the elevator is uniform. The force field on Earth is from a point source and not uniform. So to that extent, you can measure the difference. But in a small enough region, it is the same. It's like in calculus where a small enough slice of a curved line is straight.

No offence sir , I enjoyed the video, but really this fundamental principle is surely flawed by the reason given by the previous post. Uniform and non uniform acceleration can never be considered as equal, no matter on what scale it is measured, it is still not equivalent.

The concept of uniform and non uniform acceleration diminishes when you reach at the limit of observation, such as when you put the limit (Del time ---> Zero ) to get the "instantaneous velocity" of an accelerated object. Here you aren't actually making that object static (in order to calculate its velocity) but limiting your observation to an instant where graph of velocity vs time gets linear, so that you can calculate it.

Khayyam Bahadur. I accept your argument of the " limit "if one considers the distances involved tending to zero, and thanks for your reply. However, how does the curvature of " spacetime " account for tidal forces? Isn't this a Newtonian description of gravity whereby forces are involved. I thought in spacetime there is no force involved just curvature.One is always presented with the example of a man near the edge of a so called " black hole " being stretched by tidal forces.......what mechanism of " spacetime " accounts for this "spahettification "Thanks again for your response.

I agree with @David Butler. First of all, let's revisit the statement on the Equivalence principle. It says "A uniform gravitational field is equivalent to a uniformly accelerating frame of reference." A uniform gravitational field has, by definition, no tidal forces and thus no space-time curvature. The mathematical quantity associated with space-time curvature is the Riemann tensor, also known as the curvature tensor or tidal force tensor. This tensor, as with any tensor, can be expressed as a matrix. It can be shown that if, for a given region of space-time, all of the components of the curvature tensor vanish then that region of space-time is said to be flat. Conversely, if a region of space-time is not flat then it’s said to be curved. Curvature is said to be a local quantity in that it is possible to detect its presence in an arbitrarily small region of space in an arbitrarily short amount of time. It is always possible to choose a coordinate system, which is inertial, at least locally. Such a coordinate system is said to be locally flat. Given experimental limitations one can establish criteria in which tidal effects maybe ignored. Thus EP can be applied to objects that are very small such that tidal forces can be neglected. It should be noted that the equivalence principle explains the result of a "local" experiment. The word local is very important and it emphasizes that the experiment must be small compared to variations in the gravitational field, tidal forces. It is true that an observer in free-fall into a black hole will experience strong tidal forces: he will notice a more powerful force on the parts closer to the black hole. But as far as the person on earth is concerned, the tidal forces experienced would be really very small that the person won't be able to distinguish between the gravitational acceleration on earth and the acceleration in the laboratory.

No.

Your Right

Noah Craig Vlogs you’re right.

If you have a moving object as a reference inside the lift, you can calculate the velocity at which it travels like the ball inside the elevator. Without the reference object, then you can't find out the speed

It only need to work at a point. Changing position and noting angle changes will tell you the difference, but the principle holds if you can't tell from a singe point.