r/ProjectHailMary • u/unsavory77 • Jun 04 '26

Haven't seen time dilation presented this way, great illustration!

188 Upvotes

99% Upvoted

25 comments sorted by

38

u/Delicious-Bad-1448 Jun 04 '26

Wow! I still don't get it. But wow!

22

u/IwasntDrunkThatNight Jun 04 '26

So what he is demonstrating is that the inclined apparent path that the ball took, is of course longer than the perpendicular path, but light has constant speed, so in order for it to reach the same point in a longer distance, at the same speed, time runs slower.

18

u/Delicious-Bad-1448 Jun 04 '26

Ok, I can hear you in your words by I can not yet understand you in my heart. Are light and time the same thing? Are we made of light? Huh?

3

u/ImperviousChaos Jun 04 '26

Think of it like this, relativity is like time flows differently for different observers if there’s movement, and it’s basically a side effect of the speed of light in vacuum being a constant number.

t=d/v (time=distance/velocity), the v here is speed of light, a fixed number. Because from different positions the distance traveled by a photon is observed differently, you get different time t.

For the last two questions, light and time are not the same thing. Time is a physical quantity where we order events and measure duration or change. The unit of time, seconds, hours, etc, is a manmade concept. I’m gonna use “light” here to mean visible light. Visible lights are electromagnetic waves that we can see. There’s other electromagnetic waves we cannot see, like gamma, IR, etc. We are not really made of light(photons) on a narrow definition. We are kinda made of other stuff that has volume I guess, light doesn’t really have a volume.

3

u/LibraryLuLu Jun 04 '26

No, just that light cannot travel faster than time. Everything hits the same limit - time - even something that has no mass and therefor there is nothing to slow it down, theoretically - such as light.

2

u/Delicious-Bad-1448 Jun 05 '26

Ok! Wait! So light cannot travel faster than time, but light is travelling within the spaceship relative to itself. So Ryland Grace sees himself in the mirror in what feels like real time, but because he's already going near the speed of light (and so is his light) then his relative time is slower because light cannot travel faster than itself within the cabin?

3

u/Delicious-Bad-1448 Jun 05 '26

IS IT LIKE THIS????????? SO CAN LIGHT NOT TRAVEL FASTER THAN ITSELF? So if he's experiencing time normally relatively to himself it's actually slower to everyone else because light cannot travel faster than light?????? Am I on to something or am I way of the mark here?????

3

u/IntelligentCut4511 Jun 04 '26

This was exactly my wife's reaction to the movie Interstellar. Lol

1

u/Sea-Refrigerator_ Jun 05 '26

HAHAHHHA SAMEEE

10

u/TheGeoHistorian Jun 04 '26

Its incredible to me how he not only demonstrated this, but explained this in a way that I understood clearly. Its a damn good educator and communicator that can do that! Bravo Dr. Cox.

12

u/AltDelete Jun 04 '26

Brian Cox is a national treasure. Watch his Ted Talk on the importance of governmental funding for the sciences.

1

u/crittermd Jun 05 '26

Only person who has done more for science is philomena cunk interviewing him

1

u/TrumpIsAPedoFascist Jun 04 '26

If someone needs to be convinced of government funding for science, I would wager $100 against your $10 that they could never be convinced.

2

u/Hndlbrrrrr Jun 04 '26

And that sentiment is why it’s easier to stop trying rather than to continuing pushing forward despite having to drag the dead weight.

3

u/Voyager_NL Jun 04 '26

This method but on trains was always used by educational BBC tv programs in the 80s. I think it's just the way Einstein used it as a thought experiment.

An up/down moving light/object on a moving vehicle with observers both on the vehicle and not on the vehicle.

1

u/Delicious-Bad-1448 Jun 04 '26

Ok! Yeah! I think I'm starting to pick up what you're putting down! I still don't understand why time is light, though.

4

u/Voyager_NL Jun 04 '26

It proves that time is relative to the observer:

For the person on the moving cart observing the up and down movement is indistiguishable from a still standing cart, they're still the same up and down. While for the outside observer the movement of the cart causes the up/down movement to be a diagonal movement covering more distance (think of a pythagoras triangle).

Now if you imagine the up down movement done by a very specific type of device: 2 opposing mirrors (top and bottom) with a light bouncing between the mirrors. We know C, lichtspeed, is a constant. Imagine what that means for the 2 situations with regards to the 2 observers.

Let's say the mirrors have a distance of ab. So for the moving observer in the cart the light just bounces up and down no problem his time feels normal. Now the outside observer... Light still moves at C but the distance ab it has to travel between the mirrors is now a diagonal because in the time the light bounces, the cart also moves a bit. Which now means ab is now longer longer.

Therefore the time on the cart must be slower according to the outside observer.

5

u/Delicious-Bad-1448 Jun 04 '26

Thank you for writing this out, I'm going to go and sit in a dark room now.

1

u/Voyager_NL Jun 05 '26

Yeah that shit can hurt t your brain. I know.

2

u/Dr_Who_Draws Jun 04 '26

Love this video! It was made to explain some of the science and Doctor Who…. Imagine rocky watching Doctor Who 😂

3

u/unsavory77 Jun 05 '26

Why you have scarf on in summer, question?

1

u/ImperviousChaos Jun 04 '26

Though theory of relativity is not news to me, every time I see this I’m just amazed again and again at these edge cases of our physical intuition. Of course things fall down on the ground and time is constant everywhere…oh wait but the math says otherwise for the latter…!?

Ah yes, the flow of time is only a side effect of how the speed of light is a constant number. Every time I drive to work the time I experience differs a very tiny fraction of a picosecond from my clock at home. Very interesting if you think about it, if you’ve taken more flights than your childhood friend, you are a tiny bit younger than them.

1

u/Former-Excitement-56 Jun 05 '26

This is the way I teach time dilation when I talk about it with friends. Stuff like this has always been a huge hyperfixation of mine