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Let There Be Light, and Thus, Time (2015) [video] (youtube.com)
41 points by espeed 32 days ago | hide | past | web | favorite | 10 comments

Without light (i.e. free moving electromagnetic waves in a straight line) there would be no communication, and all interaction would be local. Particles would only be able to affect, sense and interact with their immediate surrounding particles. I wonder kind of universe that would be?

If you consider that there are places in the universe that are moving away from us faster than light, then in some sense we already live in a universe where we can only interact with "immediate surrounding particles". It's just a matter of scale.

Humans who are 10^100 times larger, in a universe where light is 10^100 times faster, might wonder what kind of universe we could possibly live in, given that all our interactions are within such small scales.

It's not that they are moving faster than light. It's the space in between us and those places which is expanding such that, at great distances, the integrated expansion leads to faster than light separation of static points in spacetime. A human of that size couldn't make sense in our universe.

Matter would have no efficient way to cool and would probably not collapse to form star analogues or other compact objects. It might be similar to some ”hot” dark matter models, except with no regular matter.

You're forgetting about gravity (which isn't carried by photons yet also travels long distances at the speed of light), although yeah, it would probably be a weird universe.

I don't think individual particles would have any material interaction due to gravity.

Pardon for the simplistic answer, but wouldn't it be similar to game of life? Particles only interact with their immediate surrounding particles.

Whatever happened to the experiment to try to determine whether the speed of light is decreasing, rather than constant? [0] I can't seem to find any results on that.

[0] https://motherboard.vice.com/en_us/article/8q87gk/light-spee...

Wow, what an illuminating talk, no pun intended. Jun Ye clearly demonstrates in fairly layman terms (among other things) how the art of measuring time at the most minuscule level and beyond is key to major technological advances that we can expect in coming years.

Yet, I'm close to raging mad at all the resources that go into this kind of research because of the potential military utility, compared to the trickle we put into research aiming to reduce poverty, increase people/planet health and overall well being. It's gotta change.

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