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I remember learning about the LIGO experiment back when it was being built, a decade ago, and at the time it seemed so amazing: a giant tube of vacuum, sealed u

I remember learning about the LIGO experiment back when it was being built, a decade ago, and at the time it seemed so amazing: a giant tube of vacuum, sealed underground and so sensitive that it could detect animals walking nearby, listening to the moving and twisting of space itself… I guess we're finally seeing that with immense human ingenuity and the most careful of engineering, the universe will offer its secrets up to us. This also means that between LIGO and ATLAS/CMS, the last few years have screwed in the final screws on two of the big physics advances of the 20th century: quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness. The next steps for physics look increasingly abstruse: understanding the exceptional cases, like black holes, holography, and the fundamentally computational form of the universe. It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models.

fluxquanta 11y ago
>It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models. For what it's worth we thought the same thing a little over 100 years ago. We just had to figure out a few pesky things like blackbody radiation and physics would be all wrapped up.
- effie 11y ago
  This is a popular thinking, but actually there were people like Kelvin, Jeans, Rayleigh, Planck and many others who did not get famous who knew there were problems with the theory. In no point in time of modern science there was widespread opinion that "it's mostly done".
rubidium 11y ago
"fundamentally computational form of the universe", you must be a seth lloyd guy :) But yes, it's the fringes that we'll find new physics. It's not unlike the late 19th century when newtonian + E&M seemed to account for all there was to know. There hardest thing in fundamental physics right now is to know what questions to ask. We've got answers that work for a lot of the biggest ones that the last 100 years have been spent developing and exploring.
21 11y ago
You're way too optimist. You forgot about dark matter. And the devices required to probe Plank length/mass/energy are way beyond even our imagination.
jacquesm 11y ago
> I guess we're finally seeing that with immense human ingenuity and the most careful of engineering, the universe will offer its secrets up to us. That's been going on for a few hundred years now.
snowwrestler 11y ago
Well we've accounted for about 5% of the universe--the stuff we know about. Dark matter (about 25%) seems to only interact gravitationally, which means that we've just, today, proven that we have an instrument that could possibly observe it directly. To date, all our evidence for dark matter is indirect--observing the otherwise unexplained behavior of normal matter. Today is the gravitational equivalent to Galileo pointing his first telescope at the night sky. Dark energy (about 70%) still seems to be a total mystery. And of course there is our inability to reconcile quantum mechanics with gravity. With each further proof of the correctness of each of those theories, the mystery of their apparent incompatibility deepens. All of these factors lead me to believe that we may still have a long way to go in our understanding of the physical universe. I hope I'm right. This is also why I believe it is so important to pursue nuclear energy. If we do invent further theories and experiments, it's likely that they will require even greater energy levels than we can create now, and potentially imply even greater dangers. If we can't learn to manage nuclear physics in a practical, routine way, we'll never have a hope of going beyond it (if indeed there is a "beyond.")
- gsibble 11y ago
  Completely agree. We have a long way to go.
- daveguy 11y ago
  How do we know dark matter is some mysterious form of matter and not just small distributed particles (gas or solid) that are beyond our ability to detect? Do we have proof of a specific, exotic, non-atomic matter?
  - snowwrestler 11y ago
    Scientists are pretty sure that dark matter is not just regular gas and dust because the amount required to create the gravity we see, would be visible. It would block or reflect a lot of the nearby starlight. Just on the back of an envelope: If we assume the percentages in my post above apply to an individual galaxy, then there has to be 5x as much dark matter mass as lit mass. There's no way you could have 5x as much gas and dust in a galaxy as stars, and not see it. For comparison, the sun makes up about 99.8% of the Solar System mass (500x as much mass as all the planets, dust, etc. combined).
ericjang 11y ago
An underground device sensitive enough to detect animals walking around could be useful for other things... (from ecology research to large-scale surveillance)
evanpw 11y ago
> quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness Well, we know that both theories are "wrong" in the sense that they give nonsense answers if you ask them the wrong questions. It's just that all of those questions are well beyond our ability to test experimentally.
selimthegrim 11y ago
It's not underground - it's raised up about a meter off the ground.

fluxquanta 11y ago

>It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models. For what it's worth we thought the same thing a little over 100 years ago. We just had to figure out a few pesky things like blackbody radiation and physics would be all wrapped up.

effie 11y ago
This is a popular thinking, but actually there were people like Kelvin, Jeans, Rayleigh, Planck and many others who did not get famous who knew there were problems with the theory. In no point in time of modern science there was widespread opinion that "it's mostly done".

rubidium 11y ago

"fundamentally computational form of the universe", you must be a seth lloyd guy :) But yes, it's the fringes that we'll find new physics. It's not unlike the late 19th century when newtonian + E&M seemed to account for all there was to know. There hardest thing in fundamental physics right now is to know what questions to ask. We've got answers that work for a lot of the biggest ones that the last 100 years have been spent developing and exploring.

21 11y ago

You're way too optimist. You forgot about dark matter. And the devices required to probe Plank length/mass/energy are way beyond even our imagination.

jacquesm 11y ago

> I guess we're finally seeing that with immense human ingenuity and the most careful of engineering, the universe will offer its secrets up to us. That's been going on for a few hundred years now.

snowwrestler 11y ago

Well we've accounted for about 5% of the universe--the stuff we know about. Dark matter (about 25%) seems to only interact gravitationally, which means that we've just, today, proven that we have an instrument that could possibly observe it directly. To date, all our evidence for dark matter is indirect--observing the otherwise unexplained behavior of normal matter. Today is the gravitational equivalent to Galileo pointing his first telescope at the night sky. Dark energy (about 70%) still seems to be a total mystery. And of course there is our inability to reconcile quantum mechanics with gravity. With each further proof of the correctness of each of those theories, the mystery of their apparent incompatibility deepens. All of these factors lead me to believe that we may still have a long way to go in our understanding of the physical universe. I hope I'm right. This is also why I believe it is so important to pursue nuclear energy. If we do invent further theories and experiments, it's likely that they will require even greater energy levels than we can create now, and potentially imply even greater dangers. If we can't learn to manage nuclear physics in a practical, routine way, we'll never have a hope of going beyond it (if indeed there is a "beyond.")

gsibble 11y ago
Completely agree. We have a long way to go.
daveguy 11y ago
How do we know dark matter is some mysterious form of matter and not just small distributed particles (gas or solid) that are beyond our ability to detect? Do we have proof of a specific, exotic, non-atomic matter?
- snowwrestler 11y ago
  Scientists are pretty sure that dark matter is not just regular gas and dust because the amount required to create the gravity we see, would be visible. It would block or reflect a lot of the nearby starlight. Just on the back of an envelope: If we assume the percentages in my post above apply to an individual galaxy, then there has to be 5x as much dark matter mass as lit mass. There's no way you could have 5x as much gas and dust in a galaxy as stars, and not see it. For comparison, the sun makes up about 99.8% of the Solar System mass (500x as much mass as all the planets, dust, etc. combined).

ericjang 11y ago

An underground device sensitive enough to detect animals walking around could be useful for other things... (from ecology research to large-scale surveillance)

evanpw 11y ago

> quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness Well, we know that both theories are "wrong" in the sense that they give nonsense answers if you ask them the wrong questions. It's just that all of those questions are well beyond our ability to test experimentally.

selimthegrim 11y ago

It's not underground - it's raised up about a meter off the ground.