Pentagon study finds no sign of alien life

[Roboramma]

Indeed. The Tipler Cylinder needs to be implausibly large. The Alcubierre drive requires a type of exotic matter that almost certainly can't exist. Not all solutions to General Relativity are actually realisable in this universe.

Sean Carroll has a nice result where he shows that if you start with a universe that doesn't already have closed timelike curves in it, and try to create them by moving around matter and energy within that universe, you'd need an amount of energy that's enough to cause the whole universe to collapse into a black hole to do it.

(something like that, it's been a while since I looked at it)

ETA: In case it's not obvious this post is me agreeing with you

 

[Puppycow]

Maybe I should add an addendum to what I said earlier:

While I believe a technology can't change the laws of physics, I will grant that we still don't have a complete understanding of the laws of physics. There are still two big things that we know that we don't know. Known unknowns: dark matter and dark energy, whatever they are.

 

[steenkh]

There are still two big things that we know that we don't know. Known unknowns: dark matter and dark energy, whatever they are.

While I agree that we don’t know much about dark energy, we know a lot about dark matter. In fact, we know so much that I can’t see why we don’t include all the other unknown, such as what are quarks really?

But I suppose it is because we think it is still possible to know more about dark matter, whereas possible sub-quark particles are way beyond what is currently possible.

 

[Ryan O'Dine]

Maybe I should add an addendum to what I said earlier:

While I believe a technology can't change the laws of physics, I will grant that we still don't have a complete understanding of the laws of physics. There are still two big things that we know that we don't know. Known unknowns: dark matter and dark energy, whatever they are.

Yes, and quantum gravity. Here's where my sprig of hope lies. Einstein only made small corrections to Newton for all but the biggest energies, but those corrections were accompanied by an almost complete redefinition of the fundamental concepts of space and time.

We're due for that big a revolution. It's going to be fundamental. That doesn't mean we can break the known laws, but there may be ways to accomplish things that our current definitions haven't made visible. Gravitational lensing is a thing we can actually use that didn't exist for Newton. Quantum computing required its own redefinitions and revolutions.

Wishful thinking and unrestrained hope? Probably. But that makes me happy so the rest of you can screw it!

 

[Puppycow]

While I agree that we don’t know much about dark energy, we know a lot about dark matter. In fact, we know so much that I can’t see why we don’t include all the other unknown, such as what are quarks really?

But I suppose it is because we think it is still possible to know more about dark matter, whereas possible sub-quark particles are way beyond what is currently possible.

Quarks have actually been observed in experiments I believe. We know that there are 6 different kinds of quarks. We know their masses and charges.

Dark matter, we really don't know what it is. We know it's there, or that our understanding of gravity is incomplete, but we don't know what it is. So we know a lot more about quarks than we do about dark matter, other than that it seems to exist based on observations.

 

[steenkh]

Quarks have actually been observed in experiments I believe. We know that there are 6 different kinds of quarks. We know their masses and charges.

Yes, but what are they? Why are there six different types, could more exist? About ten years ago, I saw an article about the theoretical work done on deducing the inner structure of quarks, which implied new particles, or string vibrations in string theory.

In science there is no such thing as knowing exactly what something is. You can always go a level deeper. Or try to …

Or we could ask the aliens, who presumably have figured it all out.

 

[Puppycow]

Yes, but what are they?

You want a list of facts about quarks? I'm not the ideal person, but you can find out lots about them on Wikipedia for example. The point is, we can describe quarks in a way that we cannot describe dark matter, which is just a place-holder term.

 

[arthwollipot]

What are quarks? They are fundamental particles the properties of which we can measure by experimentation. We know that they aren't made of other particles, like protons and neutrons are, but asking what they are made of is a little bit like asking what came before the beginning of time, or what's north of the north pole.

Of course, some people think quarks might be made of strings. But what are strings made of? I don't think it's a question that can reasonably be answered.

 

[steenkh]

Of course, some people think quarks might be made of strings. But what are strings made of? I don't think it's a question that can reasonably be answered.

That was my point. We can always go a step further, and ask how, what, or why. Most of these questions cannot be reasonably answered, but it is the nature of science that it will never end.

 

[arthwollipot]

That was my point. We can always go a step further, and ask how, what, or why. Most of these questions cannot be reasonably answered, but it is the nature of science that it will never end.

Except with quarks, where it does end. Quarks are not made of other things. You could (if you put stock in string theory) say a quark is a string, but you can't say (even though I just did, which was wrong) that it's made of strings.

Quarks (and electrons and neutrinos (and the varieties thereof (fermions))) are genuinely fundamental particles. That's where it ends. There's nothing below that level. You can't go further.

This post brought to you by parentheses.

 

[Roboramma]

Quarks have several properties that can be measured in experiment but aren't determined by theory. Why are they like that? A more fundamental theory might offer answers to those questions. String theory would say that it's due to the particular way that they're vibrating: their momentum through a multidimensional space which itself has a particular shape, determines the properties of the quarks. As an example, QFT will tell you that quarks have various "colors", but those are just labels with some rules about interactions. String theory gives an underlying structure where quarks are strings whose ends are attached to one of three branes and the "red" "green" "blue" rules are a consequence of the way interactions work between strings attached to those branes.

But string theory might be wrong. In which case there's probably some other answer to that question. There's a great deal of structure even to what we see as the most fundamental particles, and asking about the nature of that structure is certainly legitimate scientific inquiry.

 

[Darat]

Quarks have several properties that can be measured in experiment but aren't determined by theory. Why are they like that? A more fundamental theory might offer answers to those questions. String theory would say that it's due to the particular way that they're vibrating: their momentum through a multidimensional space which itself has a particular shape, determines the properties of the quarks. As an example, QFT will tell you that quarks have various "colors", but those are just labels with some rules about interactions. String theory gives an underlying structure where quarks are strings whose ends are attached to one of three branes and the "red" "green" "blue" rules are a consequence of the way interactions work between strings attached to those branes.

But string theory might be wrong. In which case there's probably some other answer to that question. There's a great deal of structure even to what we see as the most fundamental particles, and asking about the nature of that structure is certainly legitimate scientific inquiry.

But not having a model does not mean there are unknown gaps in what we do know. We know at certain energy levels there isn't "room" for anything else to exist, if there was we would have seen evidence for "it". It's why we know for instance things like telekinesis, telepathy and ghosts (as the supernatural definition) "can't" exist in our universe.

This post brought to you by scare quotes!

 

[Roboramma]

But not having a model does not mean there are unknown gaps in what we do know. We know at certain energy levels there isn't "room" for anything else to exist, if there was we would have seen evidence for "it". It's why we know for instance things like telekinesis, telepathy and ghosts (as the supernatural definition) "can't" exist in our universe.

This post brought to you by scare quotes!

Oh, absolutely. So far even a 10 billion dollar machine hasn't been able to turn up anything that wasn't predicted by the standard model. The idea that there are effects happening at the level of daily life (for instance in mechanisms at work in the brain) that are at odds with the standard model is just ridiculous. There may be some physics left to discover, but it won't be applicable to the energy regime in which we generally live our lives.

 

[Roger Ramjets]

There may be some physics left to discover, but it won't be applicable to the energy regime in which we generally live our lives.

I wouldn't bet on that.

But the issue isn't what may be possible, but what is likely.

The Earth is ~4.5 billion years old, about 1/3rd of the age of the Universe. Life began ~3.7 billion years ago. It's taken that long for a single species to develop a technology good enough to reach near space. But this was only made possible due to an unsustainable energy source which was created millions of years ago and will soon run out. Furthermore its use is changing the climate so much that the civilization we need to advance technology further may collapse (as they have done in the past). This mean the chances of humans ever 'reaching the stars' is very slim.

Unless we make huge breakthroughs in our understanding of physics, we will never have the technology required to flit around other worlds annoying the locals in our own spacecraft. The idea is pure (science) fantasy - easy to imagine - virtually impossible to achieve in practice. In the foreseeable future we will be struggling just to maintain the level of technology we have now. If that's true for us, it's probably true for life on other planets too.

We are only one data point, but all the other species on Earth who haven't gotten this far in 3.7 billion years are indicators that any species developing interplanetary space travel is extremely unlikely. Add the scarcity of life and vastness of space, and the chances of us ever making contact with them is even less likely - so unlikely as to not even be worth considering without irrefutable direct evidence.

But let's say a species on another planet did develop the required tech, and did explore other worlds far away. Their window of opportunity for visiting us now is extremely small. In that 4.5 billion years since the Earth formed, innumerable random events affected the development time of modern humans. In another few thousand years we might well be wiped out by our own stupidity or something else. A few million years either way and the alien visitors would have nobody to buzz in their spaceships. If we talk about the time in which we might recognize their spaceships for what they are, that window becomes ridiculously small - currently less than 150 years.

But that isn't the heart of it either. The question we should be asking is why are we even considering the idea of aliens visiting us? And by 'aliens' I mean humanoid creatures who have developed a technology similar to ours. The answer is simple - we are anthropomorphizing. Attributing a light in the sky to aliens in a spaceship is no different to concluding that planets are 'gods' or that thunder is caused by Thor smashing his hammer down on the clouds. It's all about imagining a 'human' agent as the source.

And when the evidence doesn't support this notion what do we do? Double down on the anthropomorphic explanation by suggesting that the aliens must have some advanced technology that allows their spaceships to dance around the sky like reflected light. That's plain stupid, but we are blinded by our emotional need to connect with others. We want to believe in aliens, and this is clouding our judgement.

 

[arthwollipot]

But let's say a species on another planet did develop the required tech, and did explore other worlds far away.

Pure science fiction. No "tech" will defy physics.