# Speed of light suddenly doubles -- what changes? **URL:** \ **Category:** Factual Questions\ **Created:** [March 22, 2013, 3:56am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609 "2013-03-22T03:56:15Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Octans](https://avatars.discourse-cdn.com/v4/letter/o/5f8ce5/32.png) [@Octans](https://boards.straightdope.com/u/Octans)\ **Post date:** [March 22, 2013, 2:47pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/21 "2013-03-22T14:47:44Z")
Coulomb’s constant increases by a factor of four, so electrical interactions between charged particles are now four times stronger. Magnetic force reduces by a factor of four. So in addition to life and matter as we know it probably not being able to exist, you’d also have a hell of a time getting those pizza coupons to stick to your fridge. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 22, 2013, 2:50pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/22 "2013-03-22T14:50:53Z")
Fortunately, other people have already done the math, at least for something similar. John E. Stith wrote the amazing sf novel [Redshift Rendezvous](http://www.amazon.com/Redshift-Rendezvous-John-E-Stith/dp/1880448580/ref=sr_1_1?ie=UTF8&qid=1363963593&sr=8-1&keywords=Redshift+Rendezvous) set on a spaceship whose every level has a different speed of light, down to 10 m/s. Each area is meticulously worked out to show the relativistic effects that occur. It’s the hardest of hard science fiction but a lot of fun, too. ---
**Author:** ![Martin\_Hogbin](https://avatars.discourse-cdn.com/v4/letter/m/58f4c7/32.png) [@Martin\_Hogbin](https://boards.straightdope.com/u/Martin_Hogbin)\ **Post date:** [March 22, 2013, 3:06pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/23 "2013-03-22T15:06:49Z")
Changing the speed of light ‘today’ has no real meaning but if the seed of light doubled in our locality today and the equations of physics remained the same the result would still be dramatic. Life would certainly end and even matter might not take the forms we know. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [March 22, 2013, 3:25pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/24 "2013-03-22T15:25:06Z")
> [@njtt](#): > > I don’t think red-shifts will be affected. They depend on the frequency of the light, not its speed. I didn’t do the math, but I suspect there’s a flaw here based on a simple thought experiment. What would the red shift be if light were instantaneous? Seems to me it would be zero, because you’d always see the exact same phase of the (whatever) as would anyone at the same location. If I’m right, doppler shift is a function of the speed of transmission in the medium – so, the doppler shift for a given frequency at a given speed would be smaller underwater than in the air. > [@squeegee](#): > > I’m not sure quite how to state this, but e=mc^2, right? Well, under the new rules e=m(old-c\*2)^2. Stars (and nukes) would now have a much bigger bang-badda-boom, right? I remember seeing Einstein write somewhere that the “c^2” was a bit of a trick; it’s a constant with the given units, and to the extent that units are arbitrary, you could make any number work by choosing units to fit. So, in our imaginary exercise, might it not be possible for the units to require changing to make the “e=mc^2” equation fit, rather than e changing? ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [March 22, 2013, 3:32pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/25 "2013-03-22T15:32:05Z")
According to Wikipedia, I’m right about the doppler effect: In classical physics, where the speeds of source and the receiver relative to the medium are lower than the velocity of waves in the medium, the relationship between observed frequency and emitted frequency is given by: f = (c + Vr)/(c + Vs) f0 where [ul] [li]c is the velocity of waves in the medium[/li][li]Vr is the velocity of the receiver relative to the medium; positive if the receiver is moving towards the source (and negative in the other direction);[/li][li]Vs is the velocity of the source relative to the medium; positive if the source is moving away from the receiver (and negative in the other direction)[/li][/ul] ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [March 22, 2013, 3:37pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/26 "2013-03-22T15:37:19Z")
Faster flashlights. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [March 22, 2013, 4:02pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/27 "2013-03-22T16:02:05Z")
> [@John\_Mace](#): > > “G” is not a function of the speed of light. It’s an independent, fundamental constant of the universe. > > BTW, if your analysis were correct, “m” and “M” would be reduced by a factor of 4, not increased. Mass is inversely proportional to “c^2” in Einstein’s famous equation. No my math was correct, my assumption was different. I was assuming the force of gravity is proportional to the energy content which is essentially what is true for GR. Then **if** rest masses remain the same, the energy content of any particle does up by a factor of 4. If energy content remains the same, then rest mass would go down by a factor of four, but gravity will remain the same if ti’s based on energy content. But this highlights the basic problem of the OP. What are you assuming remains fixed when the speed of light doubles. “Everything else” is usually the default answer to questions like this, but that certainly not be valid when something as fundamental as we believe c is is changed. ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [March 22, 2013, 6:15pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/28 "2013-03-22T18:15:05Z")
> [@OldGuy](#): > > But this highlights the basic problem of the OP. What are you assuming remains fixed when the speed of light doubles. “Everything else” is usually the default answer to questions like this, but that certainly not be valid when something as fundamental as we believe c is is changed. Well, yeah pretty much everything else. Sorry, if I could balance out all the other constants satisfactorily, I wouldn’t need to ask this sort of thing on a message board, I’d be counting my Nobel winnings. 🙂 ---
**Author:** ![smiling\_bandit](https://avatars.discourse-cdn.com/v4/letter/s/e9a140/32.png) [@smiling\_bandit](https://boards.straightdope.com/u/smiling_bandit)\ **Post date:** [March 22, 2013, 8:08pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/29 "2013-03-22T20:08:35Z")
> [@Chronos](#): > > Quadruple, actually. :smack: I’m an idiot. > [@](#): > > But at the same time, you’d also be quadrupling the energy thresholds, and quartering the energy sensitivity, of anything that could detect those particles, so the net effect would be the same. Detect, yes. But there would be actual physical effects stemming from it, would there not? ---
**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:** [March 23, 2013, 3:43pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/30 "2013-03-23T15:43:58Z")
> [@](#): > > Detect, yes. But there would be actual physical effects stemming from it, would there not? Ultimately, actual physical effects can’t stem from anything other than detections. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [March 23, 2013, 5:07pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/31 "2013-03-23T17:07:40Z")
> [@StJoan](#): > > The atomic fine structure constant would halve, thus halving the strength of the electromagnetic self-interaction on an electron. > [@Octans](#): > > Coulomb’s constant increases by a factor of four, so electrical interactions between charged particles are now four times stronger… Isn’t there something contrary here? ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [March 24, 2013, 7:19am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/32 "2013-03-24T07:19:56Z")
> [@squeegee](#): > > We’re not doing it from the big bang, we’re changing it today. Retroactive physics need not apply. I think this is the biggest problem. You have “old” light that has already begun its travel to us, and “new” light that is being generated, starting now. Sunlight is the most immediate example. You have light that has already left the sun arriving here in 8 minutes, 20 seconds. Added to that, you have “new” light overtaking it, and getting here in half the time, in addition to the “old” light. So for 8 minutes and 20 seconds, we’ll be getting twice the amount of sunlight than normal. And as far as the universe is concerned, the light from Alpha Centauri will remain normal for 2 years, then twice as bright for another 2 years, then normal again. The light from anywhere else in the universe will follow the same principal. One by one, the light from the stars in our galaxy will increase the same way, depending on their distance from us. So will everything else in the universe, though most of it is so far away that we won’t have to worry about it for a long time. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [March 24, 2013, 4:58pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/33 "2013-03-24T16:58:54Z")
> [@panache45](#): > > I think this is the biggest problem. You have “old” light that has already begun its travel to us, and “new” light that is being generated, starting now. Sunlight is the most immediate example. You have light that has already left the sun arriving here in 8 minutes, 20 seconds. Added to that, you have “new” light overtaking it, and getting here in half the time, in addition to the “old” light. So for 8 minutes and 20 seconds, we’ll be getting twice the amount of sunlight than normal. > > And as far as the universe is concerned, the light from Alpha Centauri will remain normal for 2 years, then twice as bright for another 2 years, then normal again. The light from anywhere else in the universe will follow the same principal. One by one, the light from the stars in our galaxy will increase the same way, depending on their distance from us. So will everything else in the universe, though most of it is so far away that we won’t have to worry about it for a long time. Oh come on, you’re not applying the magic correctly! All light in transit changes speed, even if it’s old. So, light that’s 4 minutes and 10 seconds away takes 2 minutes and 5 seconds to get here, light at the sun’s surface takes 4 minutes and 10 seconds to get here. The ordering domain is preserved. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [March 24, 2013, 5:34pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/34 "2013-03-24T17:34:51Z")
> [@panache45](#): > > I think this is the biggest problem. You have “old” light that has already begun its travel to us, and “new” light that is being generated, starting now. Sunlight is the most immediate example. You have light that has already left the sun arriving here in 8 minutes, 20 seconds. Added to that, you have “new” light overtaking it, and getting here in half the time, in addition to the “old” light. So for 8 minutes and 20 seconds, we’ll be getting twice the amount of sunlight than normal. > > And as far as the universe is concerned, the light from Alpha Centauri will remain normal for 2 years, then twice as bright for another 2 years, then normal again. The light from anywhere else in the universe will follow the same principal. One by one, the light from the stars in our galaxy will increase the same way, depending on their distance from us. So will everything else in the universe, though most of it is so far away that we won’t have to worry about it for a long time. In addition to what \*\*Learjet \*\*said, even if the old light did keep its original speed, the time that you would have double brightness from the Sun is 4 minutes and 10 seconds, not 8 minutes and 20 seconds, since it takes 4:10 for the new light to reach us while the old light continues to pass, after which the last of the old light has 4:10 to reach us (this may have just been a typo, since you put the correct numbers for Alpha Centauri, which is about 4 light years away). ---
**Author:** ![ekedolphin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ekedolphin/32/10003_2.png) [@ekedolphin](https://boards.straightdope.com/u/ekedolphin)\ **Post date:** [March 24, 2013, 8:17pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/35 "2013-03-24T20:17:04Z")
Do you suppose it would have a noticeable impact on everyday, face-to-face interaction? Would people have faster reflexes, or would their brains have a hard time adapting to the lightspeed change? ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [March 24, 2013, 8:53pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/36 "2013-03-24T20:53:16Z")
> [@Learjeff](#): > > Oh come on, you’re not applying the magic correctly! > > All light in transit changes speed, even if it’s old. So, light that’s 4 minutes and 10 seconds away takes 2 minutes and 5 seconds to get here, light at the sun’s surface takes 4 minutes and 10 seconds to get here. The ordering domain is preserved. Does that mean the Earth receives twice as much sunlight per second, or would the sun end up producing half as much light? If it’s twice as much, we’ll all get a real good tan. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [March 25, 2013, 2:56am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/37 "2013-03-25T02:56:20Z")
> [@Michael63129](#): > > In addition to what \*\*Learjet \*\*said, even if the old light did keep its original speed, the time that you would have double brightness from the Sun is 4 minutes and 10 seconds, not 8 minutes and 20 seconds, since it takes 4:10 for the new light to reach us while the old light continues to pass, after which the last of the old light has 4:10 to reach us (this may have just been a typo, since you put the correct numbers for Alpha Centauri, which is about 4 light years away). Crap, I meant 4:10. ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [March 25, 2013, 3:36pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/38 "2013-03-25T15:36:54Z")
Huh. I kind of assumed all light (old or new) would travel at whatever was the current speed of light. If that’s not the case, then everything would get weird for an appreciable time, right? I mean, gravity propagates at the SOL, so gravitational forces would double for a short time, wouldn’t they? ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [March 26, 2013, 5:17pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/39 "2013-03-26T17:17:40Z")
> [@ekedolphin](#): > > Do you suppose it would have a noticeable impact on everyday, face-to-face interaction? Would people have faster reflexes, or would their brains have a hard time adapting to the lightspeed change? On the human scale, “speed of light” is already so close to “instantaneous” that it seems like it wouldn’t make a difference. ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [March 27, 2013, 12:49am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/40 "2013-03-27T00:49:53Z")
> [@chorpler](#): > > On the human scale, “speed of light” is already so close to “instantaneous” that it seems like it wouldn’t make a difference. Wouldn’t our synapses fire faster, giving us superhuman intelligence, portending an end to war, aggression and reality television? [Previous page](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609.md?page=1) [Next page](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609.md?page=3)