My parallel universe has the speed of light set at half that of Earth's (1.5*10^8 m/s).

How would a Badminton player (P.V Bindu) from Dearth (my universe) fare against a player (P.V Sindhu) from Earth ?

Match Venue: India, Earth (your universe)

  • 3
    $\begingroup$ So if one enters the other universe to play a match, what happens to him? Do the particles in his body still have the same speed of light? I think you should define pretty well what happens and how this match is played $\endgroup$
    – Raditz_35
    Jun 22, 2017 at 7:57
  • $\begingroup$ This probably depends on which universe they play in and whether their speed of light adjusts to whichever universe they are in. Which would affect their playing exactly how? $\endgroup$
    – a4android
    Jun 22, 2017 at 9:45
  • $\begingroup$ Maybe you should send this question to XKCD's What If - it has already covered relativistic baseball $\endgroup$
    – G0BLiN
    Jun 22, 2017 at 10:41
  • $\begingroup$ Welcome to the site, Nishanth. Please note that the Worldbuilding SE is dedicated to providing detailed answers to specific problems you are having in the process of building a fictional world. We would be happy to help with issues you have concerning communication or movement between your universes, but this doesn't appear to be related to building a world as is. If you haven't already, I would suggest taking the tour to get a better understanding of the site. $\endgroup$
    – Frostfyre
    Jun 22, 2017 at 12:11
  • $\begingroup$ My question deals with the problems my world will face because of the decreased speed of light and how it will affect my people's reflexes. $\endgroup$ Jun 23, 2017 at 6:44

4 Answers 4


The biggest problem with this is that everything involving electrons changes drastically which means that molecules would be different and certainly not compatible. Not only electrons of course, but mainly them.

My guess is that the player that tries to enter the other universe disintegrates very quickly. If the speed of light is the only thing that changes, there might not even be people in that universe because molecules would look so different.

Edit: I should note of course that the other universe would be completely different and nothing would exist as we know it, but let's ignore that part and focus on the players turning into a pile of "something".


This answer started as a comment. This that comment: This probably depends on which universe they play in and whether their speed of light adjusts to whichever universe they are in. Which would affect their playing exactly how?

Exactly how seems to be, most probably, absolutely not at all (where most probably means with a probability of one hundred percent, or complete certainty).

It also seems unlikely that relativistic effects play any part in their badminton playing -- assuming that their atoms and molecules are governed by the same value of lightspeed. if this is so, it might affect the behaviour of their electrons and thus the biochemistry of the player who is the other universe might be affected. if those affects are adverse to his playing, then he is in trouble and could possibly lose the match.

However, in the interests of fair play the Multiverse Badmintion Premiership League should arrange all matches are played with each player located in his or her own universe. By using a wormhole (or to be strictly correct, an Einstein-Rosen bridge) and the players play at either end where their material bodies are governed by their own set of physical laws. Now it is simply a matter of which player is the more skillful. This is not a matter for science to decide, but is firmly in the realm of sports and therefore undecidable by rational means.

So place your bets, ladies and gentlebeings, and may the better player win.

  • $\begingroup$ @G0BLiN Tricky! I agree with your compensatory physics models. You can assume there is some way(s) mass-energy evens up between the two universes so they are equivalent. I assumed there is an equivalence, because explaining how factors like this are compensated gets too long winded and interminably detailed to little point. $\endgroup$
    – a4android
    Jun 22, 2017 at 12:07
  • $\begingroup$ (Resending with correct styling) Shouldn't E=mc^2 have some additional effects even for non-relativistic speeds? If for the other universe (let's mark all their units with ') E'=m'c'^2 still holds, and if c'=0.5c, than for that universe E'=m'0.25c^2. Meaning either that masses there are radically greater (m'=4m), energy is much lower (E' = 0.25E), or some combination of the two. $\endgroup$
    – G0BLiN
    Jun 22, 2017 at 12:42

Speed of light would affect the match in two ways:

  • creating relativistic effects for fast enough objects

I have no specific knowledge of badminton, but let's say a skilled player can hit the "ball" at 100 km/h. That is 28 m/s. In both cases that speed is peanuts when compared to the speed of light for both Sindu and Bindu. There would be no difference in the gameplay of the two.

  • influencing the reaction time of the receiver since he will see "too late" what the opponent did

Signal processing in our brain takes about milliseconds, which is way more than the time photons need to go from the "viewed object" to the "viewer" on a badminton court, which is in the range of tens of nanoseconds. Again, no appreciable difference.


PV.sindhu vs PV.bindhu in both the universe , result ll be the same.

I think....

Depends not only speed of light and depends on various factors.

  • Considering only the speed of light alone : Comparing both the players from outside of both the universe , we can see the speed difference relative to each other. But measuring them in their own universe , we cant find diff in speed and skill, because every atom is relative (brain thinking freq, his speed, cork /racket speed..etc).
  • Now let's analyze the speed of light: it is constant only in vacuum, it changes on different media (say water, air), gravity, ...etc. The factors may be the reason for speed of light (From out of both universe). So even if the persons have the same skill , these factors changes their plays definitely... so we cant compare them only with speed of light .

Replies are welcome.

  • 4
    $\begingroup$ "Replies are welcome" - no no no, please don't do it. This site is Q&A, not a discussion forum. $\endgroup$
    – Mołot
    Jun 22, 2017 at 10:08
  • $\begingroup$ Speed of light doesn't change with gravity. It is c here on Earth, there on Jupiter, out there on the Sun and ever far out there on that black hole. $\endgroup$
    – L.Dutch
    Jun 22, 2017 at 11:42
  • $\begingroup$ Welcome to WorldBuilding.SE subash! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$
    – Secespitus
    Jun 23, 2017 at 6:54

Not the answer you're looking for? Browse other questions tagged .