# Physics/Astrophysics Questions **URL:** \ **Category:** Factual Questions\ **Created:** [May 23, 2019, 3:23pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411 "2019-05-23T15:23:33Z")\ **Posts on this page:** 8\ **Page:** 3
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [May 28, 2019, 7:38am UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/41 "2019-05-28T07:38:33Z")
On the OP’s question, you may find [this episode](https://www.youtube.com/watch?v=msVuCEs8Ydo) of PBS space time interesting. That is, if you have an IQ of 200+ To summarize the bit at least I think I understand: 1. The speed of light is better referred to as the speed of causality. It’s the fundamental way space and time are coupled. As accurately as we can measure right now, gravitons also propagate at this speed. There’s nothing special about light; it’s just the first thing we found that moves at this fundamental speed. 2. It’s possible to show that the speed of causality must be finite based on simple axioms like Galilean relativity. I didn’t quite follow this part of the video though. As for why it is 3x10^8 ms-1, well it’s a fundamental constant. We don’t know why it has the value it has. But of course as the only fundamental speed, we could just as well say it is 1.0, and other speeds should be in “fraction of c in Earth’s reference frame”. But it would make speedometers harder to read. ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [May 28, 2019, 9:19am UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/42 "2019-05-28T09:19:20Z")
> [@Jackknifed\_Juggernaut](#): > > From my understanding, from the perspective of the photon, it IS moving at infinite speed. The photon experiences no time. Nah: from the perspective of the photon, everything else moves at 300000km/s. The photon is completely still in relationship to itself. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [May 28, 2019, 10:33am UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/43 "2019-05-28T10:33:43Z")
> [@Nava](#): > > Nah: from the perspective of the photon, everything else moves at 300000km/s. The photon is completely still in relationship to itself. Well it has zero seconds to look around. ---
**Author:** ![Shodan](https://avatars.discourse-cdn.com/v4/letter/s/9f8e36/32.png) [@Shodan](https://boards.straightdope.com/u/Shodan)\ **Post date:** [May 28, 2019, 12:36pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/44 "2019-05-28T12:36:50Z")
> [@Steven Estes](#): > > I realize that our measurement system is arbitrary and we could call the speed of light, say, one flurble. > But the question remains: In this measurement system why isn’t the speed of light two flurbles or thre flurbles or 1/2 flurble? Because there are some questions that science cannot answer. That is not to denigrate science, but meta-questions like this are unanswerable by the scientific method. If the speed of light were not 3 x 10[sup]5[/sup] km/sec, things would be different. But that’s not an answer to the question, because things aren’t different. Regards, Shodan ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 28, 2019, 12:50pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/45 "2019-05-28T12:50:51Z")
There is no “perspective of a photon”. Trying to describe a reference frame moving at c is meaningless. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [May 28, 2019, 6:19pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/46 "2019-05-28T18:19:03Z")
> [@Chronos](#): > > There is no “perspective of a photon”. Trying to describe a reference frame moving at c is meaningless. But we can look at the limit as v approaches c. At a velocity arbitrarily close to c, an anthropomorphized particle has a journey time arbitrarily close to zero and therefore doesn’t see any movement, or indeed anything. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 28, 2019, 9:35pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/47 "2019-05-28T21:35:36Z")
Even in the limit as v -\> c, you get weird things. Like, the limit of c - v as v -\> c = c. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [May 28, 2019, 9:57pm UTC](https://boards.straightdope.com/t/physics-astrophysics-questions/834411/48 "2019-05-28T21:57:01Z")
> [@DPRK](#): > > Unlike those other numbers, “pi” is not a physical constant, nor is it measured by units- it is dimensionless. > > ETA we should regard pi as a true mathematical constant; in fact its value cannot change. It is true that different manifolds can have positive or negative curvature but that does not have to do with the value of pi. [The value of pi very nearly changed in 1897](https://en.wikipedia.org/wiki/Indiana_Pi_Bill), but only in Indiana. 😉 [Previous page](https://boards.straightdope.com/t/physics-astrophysics-questions/834411.md?page=2)