Physics 62 Special Relativity (18 of 43) A Relativistic Time Experiment

In this video I will explain and find t(relativistic)=? In a relativistic time experiment.

Next video in the Special Relativity series can be seen at:

[Stormsson]

I am astonished by the clarity of your explanation: I approached these concepts many times, but I did not find a lecturer with your ability of explaining the concepts via the examples. Thank you!

[valeriereid]

Thank you so very much for this excellent lecture. I am so inspired to learn even more physics! Thank you Professor for being an excellent educator.

[berghuisbs]

This is really excellent! Thank God for these videos by Prof. Michel. There is just no comparison between these videos and what ASU puts out.

[mescwb]

interesting stuff
4:05 path of light as saw by B is not the same path saw by A, hence there isn't actually "a same" event - unless considering "apparent" path: keep time as absolute (classical) then B's *apparent* space seen by A is what "warps", while it doesn't for B (and just for convention, since B's reference isn't privileged, one conversely can also say it's A's apparent space seen by B that warps) [whatever B or A, time stands still absolute)
8:53 if instead of =0.8c "u" were =c (like a photon being "divided" in half, the "original" throwing part of itself towards a mirror then this part being reflected and detected) this would lead to 1 - u2/c2, hence, 1 - 1, =0, under the square root in the denominator of that boxed formula, which leads to a singularity; like, tA would be infinitely larger than tB, then A would EVER "see" that light packet being emitted, reflected and detected (to A, all of that never "happened")

[zakirhussain-jsku]

Observer A is measuring 2 motions taking place simultaneously. Light completes vertical motion during the same time period as compartment completes horizontal motion. Light travels longer distance but is it not resultant of 2 motions taking place simultaneously.

[gorgig]

After one nano sec., light will be 30 sm. up, the train will be 24 sm. on the right. After 2 nano
sec. light will be 69 sm.up, the train will be 40 sm. on the right. If You follow the light will hit
left, top of the train, so the line will be on the left side, for the observer out of train.

[MrYahya]

If length also contracts with relativity, then wouldn't that compensate for the increased distance measured by observer A?

[gorgig]

Einstein said: then light is independent of observer and source.This mean that light will be
straight vertical line and will hit on the left side of ceiling. The bigger problem is Who, when
and where prof that the speed of light is constant and independent of source and observer.

[zakirhussain-jsku]

Reference my previous comments & your kind reply. I am curious how does photon move at an inclined angle as seen by Observer A standing outside the moving train compartment. Photon once born should move vertical. Both Observers should see it move vertically. It has no mass it can't have initial horizontal motion like ball which moves with the train.

[zakirhussain-jsku]

To Observer A light appears to be moving along an inclined path. Photons move in straight line i.e. vertically. During the time photon travels to mirror, the mirror would have moved out of photon's line of sight. How can light be reflected.

[chavab]

I'm trying to frame this using smaller numbers, specifically, postulating that the universal speed limit is 10 m/s; and therefore the train is moving 0.8 c or 8 m/s. Also assuming that H = 10 meters. In this case, I want to apply gamma to calculate the distance the train traverses during the time the round trip takes, according to the stationary observer "A". This should be simple to set up, but I'm having a brain block. My bigger issue is how to translate the length contraction using more conceptually accessible numbers.

[hotelmike]

In your example, why does the light move diagonally?

[이병철프란치스코]

Thank you for the video Sir, I have questions, There is a person (A) inside a train traveling with a speed of 0.8C and there is a person (B) outside the train (at stationary state). They are in the same space frame on earth. They are talking on the phone (assume the communication (or signal) transmission speed is the same as that of light - no signal delay between them.). B puts on a 1 minute long song through the phone and both of them are checking the time untill the end of the song. In the space where A is in, the music is finished in about 20 seconds ?

And one more thing, What if they boil the same 1 g of water using the same electric power (watt/sec) at the same time. The time to reach at a boiling temperature is different from each other even though the specific heat and the mass of water and the electric power being applied are the same for both A and B?

[chavab]

First, I love and appreciate your series. I'd like you (and others) to do more direct comparisons with SR and Galilean relativity. I took a parallel experiment in which an observer by a train watches a passenger on the train throw a ball to the ceiling (10 m tall) and then catch it. Using some 'quick and dirty' estimates based on G - 10m/s^2, I calculated that the passenger would calculate a path-length of 20 m and an average rate of 10m/s. On the other hand, the 'stationary' observer calculates the path as a partial isosoles triangle, with path-length of 28 m and average rate of 14 m/s. If I artificially set the velocity in the two systems to be the same, I would also find a difference in time. I'd love to have a more in-depth discussion of this. Thanks, Cate

[markmurphy]

Since first hearing this concept it has really made me think over the years. Say you had two of these light reflection devices setup exactly the same and the light beam was in sync when they were stationary next to you. They each have a counter with them to count the number of reflections. This is all just to eliminate the independent observers stop watchs. I'm told if you move one of the devices near the speed of light for some amount of time, and then return it back to a stationary position, the light beams will still be in sync, but the counters will be out of sync. Like the light slowed down for the experiment that moved. Even though each experiments reference frame was equal as nothing about them changed. Kind of seems like the experiment would be affected by a nonreference frame. Like some ultimate frame of reference exist.

[akildoktoru]

QUESTION -This video assumes that a moving inertial frame (i.e., the train car in this video) carries the light photons like particles of dust carried in moving air. Should not light follow a same stationary vertical path both for observer B and A? Please let me know what is wrong with the following argument:
For the sake of argument assume that the light in the diagram is a single photon. It is fired by observer B vertically and the horizontal velocity of the car should not add a horizontal velocity component to the photon. Hence both observers should see a vertical path : the observer B leaves this path behind him because he is moving with the car, and the observer A sees it at a stationary distance. (For example, if the ceiling of the car is high enough, the moving rear wall of the car might hit the photon before it reaches the ceiling.)

[altmashmalik]

Why light is moving in tilted direction

[chavab]

what is the pathlength of the isosceles triangle (2 sides) the stationary observer would detect?

[karimkhan]

explain  the  problem  of  pushing   roller  over   step

[ptyptypty]

I hereby Nominate Michel Van Biezen for the Nobel Prize in EDUCATION !!.. fantastic VIDEO!!.. And I nominate his Wife for a Nobel Prize in Graphic Artistry :) .... stay tuned for the Pulitzer and then the Presidential Medal of THANK YOU BOTH for these Wonderful Lecture Videos and Artwork on the Thumbnail Images.. :) ....