Spacetime Intervals: Not EVERYTHING is Relative | Special Relativity Ch. 7

This video is chapter 7 in my series on special relativity, and it covers the idea that some things AREN'T relative: there IS a sense of absolute length and absolute time, which can be agreed upon from all moving perspectives (as long as they're inertial reference frames). In particular, proper length and proper time, aka the spacetime interval. Essentially, this is the spacetime version of the pythagorean theorem, and we'll explore it using the Lorentz transformations of lengths and time intervals, enacted with a mechanical minkowski diagram, aka mechanical Lorentz transformation, aka spacetime globe.

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[canyadigit]

This video was relatively good, at least in my frame of reference.

[TheRomichou]

So you just went through 4 hours worth of complex lectures in an advance physics program in about 7 minutes, and I got it. brilliant.

[SchutzmarkeGMBH]

6:40 Age old debate? From what perspective?

[pranavbadrinathan]

As a supplement to actually reading a physics textbook and attending university lectures, this series is pretty cool for being able to make me view this in a completely different way I never had before. The textbook is great and I really love the math it goes through, but I also really enjoyed the different way of looking at these things with the spacetime globe of yours. Thanks a lot.

[Kraigon]

I finally caught up to this series, and it still just kind of blows me away. This is the kind of stuff that brought me to this channel way back when (I want to say close to 10 years ago). I realize that a lot of my disinterest in some of the videos that you were putting out about a year or two ago is because I already knew about a lot of what you made videos on, but this is just _so cool_ to watch and have that spacetime globe to have everything make immediate sense as you're describing it.

[sinom]

Things being constant is a lot more weird than things changing.

[tomerwolberg]

"not everything is relative" well, that's just like your opinion man.

[electrospecter]

I'm loving the time globe! it really helps with getting an intuitive feel of this subject

[jasonpeng]

i like how this channel explains everything in such a simple and direct manner that everybody can understand ^^

[Cosmalano]

This is my favorite video you’ve made in a long time! It’s elucidated the reason for wanting to define the interval in terms of the metric tensor for me, as I can see now that it lets us find the invariant interval regardless of the curvature we ourselves are surrounded by. Awesome!

[Xardis]

There is something else truly awesome about relativity. Lorentz transformation is a rotastion matrix, not a trygonometric rotation but hyperbolic one.

[micahphilson]

I'm starting to feel like you could lead half of an entire grad-level relativistic physics course on just this series.

Which I love, they're great videos, and that tool is super handy for visualizations, this series is so much fun!

[divyanshbhuwalka]

This was such an amazing theory to learn.
Wow.
Love the way it's taught here. So easy and quick.

[Diaming]

The way he says while “plugging and chugging” to get the interval sounds so poetic 😊😊

[BocookGaming]

Wow. Okay. Thank you for bringing this one around and making it make sense. I almost moved on to another video about a minute in, but stuck through because I love your content. By the end, I could actually conceptualize what you were doing because of how you explained it. It clicked. I don't know that I have the acumen to complete some of these equations myself, but I at least have an understanding of the underlying mechanics, and completely agree that "Spacetime Inversion" is a boring name and add that it sounds like something the crew of the USS Voyager would have to deal with.

[scottr]

It’s amazing how many videos he can make with this tool. I’m loving it

[raymondhu]

hyperbolic things incoming! x^2-t^2=spacetime interval.
Iff you are past high school, a hyperbola on a graph is defined by x^2-y^2=r, so the Spacetime graph is hyperbolic(if you plot the spacetime intervals on the spacetime graph regardless of what position you are in).

[TheScienceBiome]

Relatively cool! I’ll leave now...






At near the speed of light.

[ashesashes]

For your last note while it’s true that the signature of the metric matters, it is true in all metric sign conventions that the proper length and proper times have reversed signs under the square root. The idea is that for time like (more time change than space change) intervals, we can define proper time and not proper length, while for space like intervals (more space change than time change), we can define proper length and not proper time. These are two fundamentally different classes of interval so the constant quantity we are interested in changes it’s sign. The crossing point between these intervals is the light like interval.

I’m sure you will cover this all later but just be careful with that signature of the metric remark - it’s over complicating an issue which doesn’t actually exist

[KelseyPhillipPayne]

You have a gift for rendering the incredibly difficult into the relatively simple. Thank you!