[doctor_eval]

I’ve always felt that the reason we haven’t heard from aliens is because they know New Physics and they use it to communicate. Given how much of the universe is made up of dark energy, dark matter and other unknown physics, it seems reasonable that there are significant discoveries to be made which could perhaps be exploited.

I mean let’s say we discover a new, non-electromagnetic way to communicate reliably over vast distances using some kind of low power, high bandwidth signalling system. We’d abandon EM in a geological heartbeat. In cosmic terms we would emit a wafer thin EM shell just 150 light-years thick - and then we would fall silent.

So basically I just think we don’t know enough physics yet. We are perhaps a few discoveries away from being able to listen in on alien conversations.

[BjoernKW]

> we discover a new, non-electromagnetic way to communicate reliably over vast distances

I was going to say that of the 4 currently known fundamental forces, only gravitational and electromagnetic interactions lend themselves to long range communication.

However, there seems to be ongoing research about an actual fifth force that might be related to dark matter: https://en.wikipedia.org/wiki/Fifth_force

[fjfaase]

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

[CJefferson]

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.

[fjfaase]

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.

[whatshisface]

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.

[TheOtherHobbes]

But... math! Which can't be wrong, because obviously we already know all the math there is to know. QED.

Carroll says strange things sometimes. Epistemology doesn't appear to be his strong suit.

[ncmncm]

It's all win-win, for him. If we fail to discover anything, he's right. If we find something, "nobody could have ever predicted that!".

[pmontra]

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.

[fjfaase]

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.

[doctor_eval]

And that’s _exactly_ what they want you to think.

[kijin]

You mean room-temperature superconductors?

[CJefferson]

Yes, sorry, now too late to edit!

[mytailorisrich]

> Sean Carroll argues that all physics, which could matter to us, has been discovered.

This seems to be a case of "not knowing what we don't know", as Donald Rumsfeld would say.

His claim implies that we know what we don't know. The reality is that we most likely don't...

[ncmncm]

There's also all the stuff we think we know that isn't so.

That brought down Rumsfeld, not that he ever suffered for it. Millions of other people did, instead.

[poelzi]

Our physics model is fundamentally broken and this list is the result of the internal discrepancies: https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...

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.

[nabla9]

If they are using orbital angular momentum (OAM) coding in normal EM radiation we would not discover it yet because we don't listen for it.

[galangalalgol]

Would we hear it even with simple on/off keyed modulation even? The distances are so vast that even a directional link with anything but our nearest neighborhood seems unfeasible. We should have met a von neuman probe though.

[about_help]

Or possibly advanced civilizations had the same realization that many scifi authors have had about such probes. Something goes wrong and they cause widespread destruction. Or they work fine but still end up causing widespread destruction simply by replicating.

[ncmncm]

Once it happens once, it's too late for everybody. Naturally, they evolve, and soon invent interstellar travel. So much for that galaxy.

(Cue Fed Saberhagen, *Berserkers".)

[Iv]

Even without using EM to communicate, and assuming we don't need intercontinental radars [1] anymore, a lot of our regular activities do emit EM. What we find weird is that we only see natural EM sources. If a civilization were to reach 2 or even 1 on the Kardashev scale, we ought to see some non-natural emissions.

Of course there are a lot of assumptions there, and lots of hypothesis to explain it a way, but that's the crux of the Fermi paradox: there is something to explain away

[1] https://en.wikipedia.org/wiki/Duga_radar

[m4rtink]

Maybe all the dark matter is just very efficient alien Dyson swarms and other megastructures doing their own thing ? :-)

[neuronic]

It's not dark matter because it blocks light. It's dark matter because its only observable interaction is by gravity.

So aside from being perfect in terms of energy capture so that the underlying stars emit absolutely no EM at any frequency, the proposed Dyson spheres would also need to be completely transparent to any background EM such as visible light picked up by sensors like Hubble.

[m4rtink]

Good point - if we are able to detect gas clouds, we would be likely able to detect such swarms as well simply by all the blocked light.

[Symmetry]

The megastructures would have to radiate waste heat if they're doing anything interesting.

[Iv]

Well, there are a lot of brown dwarfs around...

[Symmetry]

Their spectra look like giant burning balls of gas, though. I guess it's possible to hide one inside a star in theory?

[markus_zhang]

Oh and we are a few discoveries away from receiving huge amount of alien spams...

[l3robot]

I think the reasoning of the Fermi paradox is that "at some point in time" a distant civilization must have been using EM wave to communicate. Now, considering the number of planets, it must exists a civilization in the universe that sits at a distance that let us sense this EM dominated past. And this even if in their own local time, they use fancy new tech. Even if they were not trying to communicate with us per se. Their own radiation should be measured.

[alextingle]

We would only be able to detect our own everyday transmissions at a distance of a few dozen light years. So the galaxy might be full of EM emitting civilizations, and we wouldn't have detected them.

[empath75]

The power and bandwidth limitations aren’t exactly the problem with interstellar communication, it’s latency.

[doctor_eval]

Perhaps, but if we discovered a mechanism that was orders of magnitude more efficient or higher bandwidth then any rational species would just naturally use it to replace EM communication.

I mean just imagine some alien engineer trying to use EM for a new mobile phone system when everyone else on planet Glerbulon is using DE. The other alien engineers on the team would be like “wtf are you using photons for? Are you nuts? Just use an off-the-shelf unobtainium link. Here I’ve got one in my pocket.”

[m4rtink]

Well, people do maintain obsolete forms of communication because they can & or have specific circumstances requiring them. Thats why I am skeptical others would completely abandon a communication technology - there would still be the Globulon Technical museum hosting anual morse code transmision relay with steam powered spark gap transmitters between specially selected nodes in the local dyson swarm.