Sean Carroll argues that all physics, which could matter to us, has been discovered. See for example his talk "From Particles to People" https://www.youtube.com/watch?v=X5Fel1VKEN8
Before I set off watching a 28 minute video (where, worryingly, comments are disabled), could you give an outline that suggests this isn't crazy?
There are obvious things which feel possible and would revolutionise so many things, like room temperature semiconductors, which we don't have yet. Also things we've better understood since 2012 like detecting gravity waves.
I don't understand how anyone could think we've "discovered all the physics which could matter to us", when we know full well there are massive gaps in our understanding.
He basically argues that there are no forces to be discovered which could have a measurable effect on our day-to-day functioning. For example, so far, we have not discovered any dark matter particles. This does not rule out that we will discover them, but for us humans (consisting of protons, neutrons and electrons) it will not have any effect. Because if it would, we already would have discovered them. The existence of other particles, like neutrino's, which zip through our bodies by the billions every day, also have no effect. We are of course effected by photons in some energy spectrums. In view of this, I think it is very unlickly that we discover any new physics which would allow us to communicate with aliens.
That sounds kind of like a caveman arguing that there will never be a practical temperature higher than their campfire, because anything hotter would burn the meat.
Dark matter interacts gravitationally with normal matter. If it exists and if it can be directed and controlled, it could be used to make stuff lighter or heavier. Big ifs. I'm not holding my breath.
Gravity is the weakest known force, orders of magnitued weaker than the other forces. Dark matter has never been measured on earth due to gravitational interactions. This is probably related to the fact that the particle responsable for the dark matter are spread out rather uniformly and not 'clumbed' together as ordinary matter. That normal matter clums together is caused by all the other forces, not by gravitation.
I doubt if dark matter can be used to make things lighter, possibly dark energy could be used for that (which is even more elusive than dark matter). It could only make thing heavier if there is a method to confine it. But because it seems that dark matter does not interact with normal matter (at least not often), I do not see how it can be confined to ordinary matter. Take notices that neutrinos also cannot used for this purpose, because the simply zap through us by the millions everyday, without us noticing anything. We have not found methods that to confine neutrinos yet. They seem to fly at speeds close to the light speed.
A adopted a very fringe, unified physics model. From this perspective we are looking at none of the possible signals that would make sense for long distance communication.
There are obvious things which feel possible and would revolutionise so many things, like room temperature semiconductors, which we don't have yet. Also things we've better understood since 2012 like detecting gravity waves.
I don't understand how anyone could think we've "discovered all the physics which could matter to us", when we know full well there are massive gaps in our understanding.