Video

De nada

Bob and I are happy that the video is helpful

You are welcome

One kg of blocks or just one kg?

The answer is that your calculator is withholding information... czcams.com/video/qxp35e7bY70/video.htmlsi=4oAbVuuwoZ74DJHO

In parts yes... But the main reason is that the speed of the light is the same in all reference frames, even if those frames move relative to the source of the light.

Displacement indeed ... oopsie. thanks for pointing it out ;-)

Sorry I failed to help you with this video... The definitions of proper time and proper length are only mentioned (and displayed on screen) shortly as the goal of the video is to figure out who measures which one. If you happen to find a video with focus on clear definitions, please come back here and post the link, as it might be helpful to others learning about special relativity.

@@StefanBracher thanks for your kind reply.

Usually that is how we do it. As here, it is the difference in volume we are after, we can also take the middle or the top - as long as we use the same for the initial and final volume.

For a second I was considering using a 😺... That would have been difficult too (a toy cat that is)

Thanks

Glad it helped.

Proper length is measured by all inertial reference frames in which the two points between which the distance is measured do not move relatively to the frame of reference.

teaching physics is always dangerous, but so much fun ;-)

What was the shelf - Half-Life of Half-Life 2? Maybe after 2 Half-Lifes of Half-Lifes, we get Half-Life 4? ;-)

@@StefanBracher It would be a miracle😂

@@johannesburstrom7314 well, in each Half-Life, there is a 50% chance for the "event" to happen ;-) (okok...next time I do a video about ☢️...I will have to build-in a reference to the game)

Haha... should have built a reference in the video ;-)

Glad it helped

Hi, virtual means the light rays only appear to come from there, in the real image, the light rays pass through the image.

There are indeed two "forces": The gravity the moon exerts on Earth, and the gravity the Earth exerts on the moon. However, when evaluating Newton's 337-year-old Second Law of Motion on the system "moon", only the force the Earth exerts on the moon must be considered. The result gets fairly close to "a month"... or a "monath" as we used to call it.

Thanks

This first one (this video) was plexiglass... much cheaper, but it does scratch easily while cleaning, so after a while the plexiglass needs replacement to avoid lines in the video. The second one (czcams.com/video/JgvB0AQikYQ/video.htmlsi=-UvvPotJE3vdJS9N) is ultra-clear glass. Much more expensive.

Proper time is measured in the reference frame in which the event occurs at the same location. So if you are travelling at 0.5c and the event (the two events between which you measure the time) happen at the same location relative to you (for example a timer on your wristwatch), then you have proper time. (Starting the timer and the timer beeping happens at the same location for you... But for someone traveling in another direction, the watch would have moved location between event one: timer started, and event two: timer beeps)

​@@StefanBracher, two events cannot be determined as simultaneous, so one cannot say they are in the same frame if moving relatively.

@@geronimomiles312 Relativity of simultaneity is another aspect of special Relativity not covered in this video. It means that two observers will not agree if events are simultaneous or not - just like they do not agree on length and time. To determine proper time between two events, you need the events to happen at the same location, not at the same time.

Glad Bob helped

Thanks

Hi, total cost was in the low hundreds... So far no breaking. The main difference to the "commercial" ones might be the size.

In both cases you forgot the minus... for the object at infinity, the image will form at -0.5 m, which means in front of the lens. A normal sighted person can see objects 50 cm in front, so possible but resulting in a headache (from the eye muscles never able to relax again). When reading a book at 0.25m distance, the image of the -2D lens will form at -1/6 m... thus still in front of the lens but it might be closer than the nearpoint (closest distance to see sharp) and cause a trouble. An interesting question could be to figure out how close the new closest distance to read would be when wearing the glasses. Put the "no glasses nearpoint" in q and find the new limit to p. (Should be further away, so the person has to hold the book much further)

This video does not require calculus, but sure high-school math helps. It shows that in theory, when cutting a few corners, a month takes 27.4 days (the time it takes the moon to go around earth). Not sure what "proof" you were looking and how that would have convinced your family. Good luck. (Maybe in a few years, we can go visit the landing sites and then you can settle the debate for good)

@@StefanBracher I appreciate it 👍 I've showed them the LRO images and stuff then explained why it couldn't be faked without being able to imitate(which wouldn't be possible) the lunar gravitational acceleration 1.62 m/s² like in the Rover videos with the dust and all that lol 😆 My cousin is a very stubborn person though and doesn't seem to get it 🤷‍♀️ Some people just can't be convinced. But either way it was a great video and I learned stuff at least 😊

@@LisaAnn777 actually, you could fake that... (dropping the studio at the required rate rate, play slow motion etc...). ;-)

I am using the zame akkzent as Einstein ;-)

i never tried only one side... wrapping them all around seems easier.

That is the beauty of physics: there are always multiple ways to solve a problem. In case you ever want to impress someone but don't have the test lenses with you (or someone asks for it in a test), the video might come in handy.

Yes it does... but you have to set it up to do so.

Bob is going to be famous ;-)

@@StefanBracher Relativity is just an optical illusion, and because all of modern physics is based on Relativity, modern physics is fundamentally wrong and needs to be rethought. Relativity has a simple built in logical fallacy, and no theory based on a logical fallacy can be true, no matter how many experiments seem to prove it, or how many people say it is true. Below is a very simple logical argument highlighting the logical fallacy, using the same terminology Einstein used to derive Relativity. According to Relativity, observers on a moving train and on a stationary train platform will disagree on the size of the ""Train"" and the passage of time on the ""Train"". This is a complete logical contradiction if the size and the passage of time of the train are real. If the size of the train is real, then the ""Train"" can not be both contracted and not contracted. The same goes for the observed passage of time on the ""Train"". If these effects are observed, then the only possible conclusion is that it is an optical illusion. Things that are real must appear to be same from all frames of reference. If not, then by definition it is an illusion. Again the argument is very simple and it is the argument Einstein used to derive Relativity, and no acceleration is used in the argument. A train with length (L) traveling at constant velocity (v) relative a stationary observer on a station platform. According to Relativity, the stationary observer will see the train contracted (L/r, where r is the Relativistic gamma), whereas an observer on the train will see it not contracted (L). So the train is both contracted (L/r) and not contracted (L) depending on the observer. This is a complete contradiction (L not equal L/r) and can not be true if length is real. The same argument applies to passage of time on the Train, where both observers will disagree on the passage of time. If time is real, it can not be both dilated and not dilated (T not equal rT). If space and time are observed to be both large and small simultaneously for one inertial reference frame, such as the ""Train"", then it must be an optical illusion. This argument is only the tip of the iceberg. There is much more evidence including both theoretical and experimental, so please keep reading. Hi my name is Dr William Walker and I am a PhD physicist and have been investigating this topic for 30 years. It has been known since the late 1700s by Simone LaPlace that nearfield Gravity is instantaneous by analyzing the stability of the orbits of the planets about the sun. This is actually predicted by General Relativity by analyzing the propagating fields generated by an oscillating mass. In addition, General Relativity predicts that in the farfield Gravity propagates at the speed of light. The farfield speed of gravity was recently confirmed by LIGO. Recently it has been shown that light behaves in the same way by using Maxwell's equations to analyze the propagating fields generated my an oscillating charge. For more information search: William Walker Superluminal. This was experimentally confirmed by measuring radio waves propagating between 2 antennas and separating the antennas from the nearfield to the farfield, which occurs about 1 wavelength from the source. This behavior of gravity and light occurs not only for the phase and group speed, but also the information speed. This instantaneous nature of light and gravity near the source has been kept from the public and is not commonly known. The reason is that it shows that both Special Relativity and General Relativity are wrong! It can be easily shown that Instantaneous nearfield light yields Galilean Relativity and farfield light yields Einstein Relativity. This is because in the nearfield, gamma=1since c= infinity, and in the farfield, gamma= the Relativistic gamma since c= farfield speed of light. Since time and space are real, they can not depend on the frequency of light used. This is because c=wavelength x frequency, and 1 wavelength = c/frequency defines the nearfield from the farfield. Consequently Relativity is an optical illusion. Objects moving near the speed of light appear to contract in length and time appears to slow down, but it is just what you see using farfield light. Using nearfield light you will see that the object has not contracted and time has not changed. For more information: Search William Walker Relativity. Since General Relativity is based on Special Relativity, General Relativity must also be an optical illusion. Spacetime is flat and gravity must be a propagating field. Researchers have shown that in the weak field limit, which is what we only observe, General Relativity reduces to Gravitoelectromagnetism, which shows gravity can be modeled as 4 Maxwell equations similar in form to those for electromagnetic fields, yielding Electric and Magnetic components of gravity. This theory explains all gravitational effects as well as the instantaneous nearfield and speed of light farfield propagating fields. So gravity is a propagating field that can finally be quantized enabling the unification of gravity and quantum mechanics. The current interpretation of quantum mechanics makes no sense, involving particles that are not real until measured, and in a fuzzy superposition of states. On the other hand, the Pilot Wave interpretation of Quantum Mechanics makes makes much more sense, which says particles are always real with real positions and velocities. The particles also interact with an energetic quantum field that permeates all of space, forming a pilot wave that guides the particle. This simpler deterministic explanation explains all known quantum phenomena. The only problem is that the Pilot Wave is known to interact instantaneously with all other particles, and this is completely incompatible with Relativity, but is compatible with Galilean Relativity. But because of the evidence presented here, this is no longer a problem, and elevates the Pilot Interpretation to our best explanation of Quantum Mechanics. *CZcams presentation of above argument: czcams.com/video/sePdJ7vSQvQ/video.html *Paper it is based on: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145

glad you liked it

The shown method is to determine the diopters for reading glasses. And the maximum diopters you could get with the method is +4 D (projecting a text at reading distance to infinity). So it won't be possible to apply it to your case.

@@StefanBracher Yea I see this as the default method whenever I see a physics person talk about diopters. But I know people who uses prescriptions that is more positive than +4 Diopters. So it makes me wonder what type of reasoning or perspective is being used by optometrists to prescribe people with more than +4 diopters.

@@AznDudeIsOn That most be for an other "eye" problem then... there is more than just glasses for reading or "simple" myopia (the two cases usually covered in highschool physics.

@@StefanBracher Thanks for the perspective!

You can play it slower ;-) Basically I out the LED strip inward facing on the edge of the glass, attaching it with electrical insulation tape.

Hi, only ONE significant figure (the last one) should be uncertain. Had I left 0.58 +- 0.18, the 5 and the 8 in the average would be not certain (changed by the uncertainty)... therefore I had to round the average to 1 SF (0.6).... Then rounding the uncertainty to the same digit (that one is not really a rule, but stating 0.6 +- 0.18 is just weird.). With 0.6 +- 0.2 the message of significant figures matches the one of uncertainty...meaning my cat could be anything from 0.4 to 0.8m. Two SF, 0.58 would mean 0.50 to 0.60, what with the given measurements and calculated uncertainty is not true.

Glad it helped! Old and low quality, but apparently still helpful.

you are welcome

Thanks. Good to know it was useful.

It is not a question of believing Einstein or not. His model of special relativity is better than Galilean relativity in predicting the weird observations when there is a high relative motion between the observer and what is being observed (the observed effects are not Einstein's "inventions" they are repeatable observations that predated Einstein). Of course there are even better models that also work if the relative velocity is not constant. What model do you prefer?

@@StefanBracher Sorry, it is quite clear Relativity is an optical illusion. See my post at the top.