Comment by ThePhysicist | Hacker News Reader

Comment by ThePhysicist | Hacker News Reader

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I think the high expectations are mostly a result of us making so tremendous (from our point of view) progress in the understanding of the universe in the last 100 years. There's no reason that nature should make it so easy for us to discover new laws of physics in the future though, especially since our technology is still quite limited (e.g. we can't produce very high energy particles and can't control quantum systems very precisely yet).

It is said that at the beginning of the 20. century many physicists thought that there wasn't that much more to discover and that most of the theories had been worked out already. There were a few areas where "weird" phenomena were observed (notably in electrodynamics and atom theory) but many people were confident that these would eventually be resolved with the existing theories. Fast forward 20 years and two completely new fields of physics (quantum mechanics and relativity) were discovered.

Personally I still think that we've just scratched the surface of the laws of the universe and it's not impossible that we'll have another wave of theories that will make our current understanding of physics seem hopelessly outdated by the end of the century. And in fact there are some areas where "weird" stuff seems to happen, dark energy or dark matter is a good example for this. I'd be really disappointed if we already discovered everything there is as well in terms of the laws of physics, I mean how boring would that be?

> Personally I still think that we've just scratched the surface of the laws of the universe and it's not impossible that we'll have another wave of theories that will make our current understanding of physics seem hopelessly outdated by the end of the century.

I hope that this the case, otherwise humanity will die on this planet. If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible.

It is perfectly possible to travel vast distances without FTL: just self-sustaining generation ships that are capable of operating indefinitely. A very boring solution to the problem admittedly. It is even possible without generation ships if the understanding of biology advanced enough to allow for indefinite cell repair, or 'state restore' of DNA. Obviously beyond our capabilities but there is no 'special sauce' required just a lot of depth.

Although it brings to mind the irony that if one has the capability to live in space within artificial environments indefinitely, gather resources within it, and produce more of them there isn't technically a need to find any habitable planets. If such a state is reached there are only two things to worry about - self destruction and entropy or cosmic scale events that a planet wouldn't be safe from anyway.

We may not need FTL travel, at least for interstellar exploration, as opposed to intergalactic. Even a ship going at 50% of light speed would put hundreds of stars within a reasonable time-frame, especially coupled with advances in cryogenic technology. If humanity's only goal is to avoid extinction by colonising another planet (what a dreary prospect), then this ought to be quite enough.

Or maybe the universe is indifferent to our goals, and we're stranded in this rock without sufficient materials and ways to get away, no matter how inventive we can be.

(The same way inventiveness doesn't matter if you found yourself in the middle of Antarctica with no food, no heating, and no materials to make a compass).

Actually, we seem to be unnaturally lucky in this regard.

I think if the Earth was something like 40% more massive, we wouldn't be able to leave the surface with chemical propulsion.

Wow, that's a really awesome factoid.

This QA goes more into this observation: https://space.stackexchange.com/questions/14383/how-much-big...

From what's there it looks like it's a lot higher than 40% as a limit.

Why would you need FTL? There's a whole system to colonize in our backyard. Teraforming seems daunting, but start one dome at a time and it grows from there.

And the technology is pretty much there, it's just that the will isn't.

Is taking an FTL ship to another galaxy, even with a known habitable planet, that much easier than creating a dome city on Mars? What if they're barely habitable?

Who is going to do that and what for? Same resources, and no one wants to because Earth already has it all (and yes, by the time they're exhausted, it will be too late for anything).

Colonize the solar system, and if FTL is created, great, if not, meh.

With a constant 1g acceleration up until near the speed of light you can cross the observable universe in a human lifetime.

To the other side of the galaxy it would be 12 years

https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

And what does modern physics say is necessary to maintain a constant 1g acceleration for years at a time?

A ball of iron the size of Earth. I'll show myself out now.

To reach close to the speed of light (~0.9c?) it'll take about 1 year before turning off the engine, and then another year of deceleration if you're planning to do anything else besides travel around at relativistic speeds.

Going to Mars using antimatter with the same 1g acceleration the entire time (reversing half way) will take a few weeks and require a small fraction of a gram of antimatter.

Ignoring the significant engineering problems like heat disappation, storage if it's not used instantly, you could get two years worth of thrust from antimatter measured in grams and cross the galaxy in just over a decade, in Earth time the trip would be >100,000 years.

You'd have to start braking halfway through to end up at your destination.

Any such spacecraft would be destroyed by the first grain of dust it hits

Isn't the milky way 100000 light years across?

Time dilation: At a constant acceleration of 1g, 100k galactic time reduces to 12 years ship time. Cf the link provided in the comment you're replying to.

As you approach the speed of light, the time observed by the traveler ticks slower, so you can travel vast distances in short observed time periods. So the people on the ship would spend 12 years, a manageable time period, but us more or less stationary observers would still see 100000 years pass.

I'm not sure new physics will help with that. Faster than light travel, if possible, would really screw with causality.

Besides, we can always travel the slow way. Either with ships built for multi-generational habitation or some way to suspend/resume human life over long periods.

Well, it depends on what you mean, I guess. You can't travel through space faster than light, but if we could figure out how to create and use wormholes, for example, we could potentially travel to places that are out of reach when traveling through space.

No, that would have the same problem - being able to send information back in time. We also have no theory of traversable wormholes that doesn't involve imaginary energy, so it's just fantasy.

I don't know much about this stuff, so take this as me being genuinely curious.

> No, that would have the same problem - being able to send information back in time.

Would it? If a wormhole is connecting two points in spacetime, then could time also be traversed at the same time? E.g. traveling through the wormhole would move you far enough forward in time to not cause any problems?

Sure, you can travel 1 light year if you also go 1 year ahead in time without any causality issues.

> Faster than light travel, if possible, would really screw with causality

Well, the assumption abiut causality is based on our current understanding of physics. Perhaps we just don't understand the problem well enough and there are ways around the causality problem

> I hope that this the case, otherwise humanity will die on this planet. If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible.

In the long term, we have the entire solar system to work with, which should be plenty to keep us going for a very long time. The Earth is just a small fraction of what's available even if we're stuck with our sun. Frank Drake from SETI thinks that alien civilizations have no good reason to ever leave their home stars, because a star will provide all the energy they will ever need, and traveling light years just isn't worth the cost (assuming no FTL).

Given we've got about 7.5 billion years until the sun burns out, and about 1 billion years before anything may become completely uninhabitable, it's pretty unlikely either new technology or space colonisation won't have happened before then.

I mean, for comparison humans have been around in a modern form for about 50,000 years... well the chances of something not happening then are few and far between. Probably could have launched millions of generation ships between now and then.

> If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible.

Interstellar travel and colonization does not necessarily need superluminal travel; it could be done with sub-lightspeed spacecraft capable of hosting multiple generations of humans for many decades, possibly centuries.

However getting Earth's nations to cooperate on such a long-term undertaking may be no less difficult than achieving FTL travel.

There is basically no chance[1] that new physics would allow meaningful violations of the speed of light bound. It's as well established as conservation of energy.

[1] Meaning that, though it's not logically ruled out, you need flying Spaghetti Monster level subterfuge to make it compatible with what we know to be true.

Beg. of 20th, you couldn't even explain why an object on a table didn't simply fall to the center of the Earth. What's left to discover with respect to laws of physics is very unlikely to be relevant to creating new technologies.

http://www.preposterousuniverse.com/blog/2010/09/23/the-laws...

Well, we're at the beginning of the 21st century now and we can't even explain what 95 % of the universe is made of (but we know there's "something" there):

https://science.nasa.gov/astrophysics/focus-areas/what-is-da...

So I really think there's much to discover yet, we just don't have a clue yet where to look.

Heck, we don't even know everything there is to know about things here on Earth. And not even going as far as unreachable ocean depths or unexplored remote locations, we even still discover new organs in our bodies, or neurons in our guts.

Newtonian physics covers the table's reaction force equal to the object's weight.

What am I missing?

> we can't produce very high energy particles

We can, it's just really hard to get a reaction out of the composite particles we've been using and we may have hit an energy limit here. Our energy problem is pretty much limited to fundamental accelerators now.

> dark energy or dark matter is a good example for this.

It's "weird" in the sense that based upon our observations there's a discrepancy between our presumed mass for very distant large stellar objects and the apparent rotation rate of some bodies in it's outer radius.

There's a lot of room for corrections there that don't involve new fundamental science. It's much more likely that we'll be able to to link two disparate areas of science together with a rigorous equation. This has been a good chunk of our progress so far.

> I'd be really disappointed if we already discovered everything there is as well in terms of the laws of physics, I mean how boring would that be?

Ultimately, there has to be a limit to how much knowledge there is to be gained. Beyond that we can start asking the really important questions like: "Does the universe fundamentally allow for the existence of free will?"

Perhaps the high expectations are the result of the huge amount of money that the LHC has cost several countries. Paying up such amounts for a device that might discover something is pretty daft in most people's eyes. Of course the Physicists are happy to have all that dough to spend, but it came from taxpayers mostly.

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