# 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:** 1
**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, 3:56am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/1 "2013-03-22T03:56:15Z")
So today I’m gonna wave my magic wand and change the speed of light from 300,000 km/sec to 600,000 km/sec. But I’m hesitating, because I don’t know what all the effects will be. - Communications will get quite a bit faster, and satellite internet will suck a bit less as the latency is halved (though it will still be appreciable). - The observable universe will double, right? But would the light still be as red-shifted, or would that stay the same? - Will a bunch of (probably modest sized) black holes stop being black, because their escape velocity no longer exceeds light speed? What happens then, do they evaporate, explode, or continue to exist as naked non-black singularities? What else would change if ‘c’ changes? For better or worse? ---
**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, 4:15am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/2 "2013-03-22T04:15:21Z")
> [@squeegee](#): > > - The observable universe will double, right? But would the light still be as red-shifted, or would that stay the same? No to this one. The immediate effect will be a no larger observable universe. However the observable universe will increase at a faster rate than it was before. One big effect might be on gravity. If you double the speed of light then if (rest) mass stays the same, the equivalent energy will go up by a factor of 4 (via E = mc[sup2[\sup]). This might mean the sun attracts the earth 16 times as strongly since both masses go up by a factor of 4. That would be a huge effect. ---
**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, 5:21am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/3 "2013-03-22T05:21:31Z")
The Earth would get destroyed (or at least flung into some crazy orbit, close enough)? Damn, glad I asked! Hell, if gravity quadruples, everything - every planet, star, galaxy - goes higglety pigglety every which direction. Good point on the observable universe – all those photon are already in flight and won’t suddenly all arrive at once. What about red shift (for new photons, I guess) – half as shifted? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [March 22, 2013, 5:29am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/4 "2013-03-22T05:29:43Z")
I don’t think red-shifts will be affected. They depend on the frequency of the light, not its speed. In general, though, the universe will become something rich and strange. ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [March 22, 2013, 6:18am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/5 "2013-03-22T06:18:34Z")
> [@squeegee](#): > > - Will a bunch of (probably modest sized) black holes stop being black, because their escape velocity no longer exceeds light speed? What happens then, do they evaporate, explode, or continue to exist as naked non-black singularities? Their escape velocity would still exceed light speed (since it tends toward infinite as you approach the singularity. The event horizon would shrink by a factor of 4. Eg. A black hole of 3 solar masses has an event horizon of 8.8km. This would become 2.2km. ---
**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, 6:41am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/6 "2013-03-22T06:41:40Z")
Would light pressure double (or quadruple) if c were doubled? Would stars inflate in size as the strengthened light pressure fought harder against the gravitational mass of the star? ---
**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, 7:22am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/7 "2013-03-22T07:22:25Z")
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? ---
**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, 9:50am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/8 "2013-03-22T09:50:17Z")
Science cannot answer this question because, in science, things do not magically change. The speed of light is one of the fundamental constants of the universe and if it were different the universe would be a fundamentally different place. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [March 22, 2013, 9:56am UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/9 "2013-03-22T09:56:48Z")
> [@Martin\_Hogbin](#): > > Science cannot answer this question because, in science, things do not magically change. Science can answer this just fine. We’ve got all the math to plug the new value of c into and see what the result is. It’s a thought experiment. The fact that we understand the fundamental nature about the implications of the speed of light (the relativities and such) indicates that we could imagine what changes would bring about. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [March 22, 2013, 1:02pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/10 "2013-03-22T13:02:10Z")
My burritos cook in a quarter of the time in my microwave. ---
**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 22, 2013, 1:26pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/11 "2013-03-22T13:26:02Z")
All you’ve done is redefine either the second or the meter. To anyone who did not know or care that you had done this, all observations of the Universe would remain completely unchanged. ---
**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, 1:29pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/12 "2013-03-22T13:29:24Z")
> [@Saint\_Cad](#): > > My burritos cook in a quarter of the time in my microwave. Would they? I’d think SOL is not a gating factor for how fast it cooks. I’d think that the microwaves would get there faster from the (extremely close) radio source, but in the same amounts/energy levels as before. ---
**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, 1:37pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/13 "2013-03-22T13:37:01Z")
> [@](#): > > Science can answer this just fine. We’ve got all the math to plug the new value of c into and see what the result is. It’s a thought experiment. The fact that we understand the fundamental nature about the implications of the speed of light (the relativities and such) indicates that we could imagine what changes would bring about. Maybe. We can make some guesses, but what is being asked here is a fundamental change in the structure of the universe. Science, fundamentally, cannot answer a question without observation, prediction, and reliably recorded conclusions. What we are doing may use known scientific facts, and even scientific principles - but we are definitely not doing _science_ in any sense. Science can only deal with what exists in the here and now; all else is speculation, though hopefully speculation grounded in reasonably validated evidence. > [@Chronos](#): > > All you’ve done is redefine either the second or the meter. To anyone who did not know or care that you had done this, all observations of the Universe would remain completely unchanged. This is definitely incorrect, as it would relatively double the energy of all particles, relationships, and functions which (as far as we know) depend on the speed of light. He’s specifically not altering our calculation, but the thing itself. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [March 22, 2013, 1:37pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/14 "2013-03-22T13:37:41Z")
Isn’t the energy in a radiowave proportional to v[sup]2[/sup]? ---
**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 22, 2013, 2:05pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/15 "2013-03-22T14:05:30Z")
> [@](#): > > This is definitely incorrect, as it would relatively double the energy of all particles, relationships, and functions which (as far as we know) depend on the speed of light. Quadruple, actually. 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. ---
**Author:** ![Dendarii\_Dame](https://avatars.discourse-cdn.com/v4/letter/d/bbce88/32.png) [@Dendarii\_Dame](https://boards.straightdope.com/u/Dendarii_Dame)\ **Post date:** [March 22, 2013, 2:11pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/16 "2013-03-22T14:11:01Z")
A bunch of PhD candidates change the topic of their theses. ---
**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, 2:11pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/17 "2013-03-22T14:11:27Z")
No, science cannot answer this question. The equations and laws of physics are based on experiments on this universe, in which the speed of light does not change. We can, of course, speculate on what a universe would be like if all our current equations still held good but the speed of light had double its current value. The changes are likely to be dramatic. The speed of light is a fundamental constant in, gravitation, particle physics, and many other areas so, right from the big bang, things could have been completely different. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 22, 2013, 2:28pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/18 "2013-03-22T14:28:49Z")
> [@OldGuy](#): > > One big effect might be on gravity. If you double the speed of light then if (rest) mass stays the same, the equivalent energy will go up by a factor of 4 (via E = mc[sup2[\sup]). This might mean the sun attracts the earth 16 times as strongly since both masses go up by a factor of 4. That would be a huge effect. “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. ---
**Author:** ![StJoan](https://avatars.discourse-cdn.com/v4/letter/s/bc79bd/32.png) [@StJoan](https://boards.straightdope.com/u/StJoan)\ **Post date:** [March 22, 2013, 2:29pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/19 "2013-03-22T14:29:39Z")
The atomic fine structure constant would halve, thus halving the strength of the electromagnetic self-interaction on an electron. ---
**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, 2:30pm UTC](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609/20 "2013-03-22T14:30:28Z")
> [@Martin\_Hogbin](#): > > right from the big bang, things could have been completely different. We’re not doing it from the big bang, we’re changing it today. Retroactive physics need not apply. [Next page](https://boards.straightdope.com/t/speed-of-light-suddenly-doubles-what-changes/653609.md?page=2)