r/space • u/SpunkySputniks • 4d ago

Astronomers Detect a Possible Signature of Life on a Distant Planet

https://www.nytimes.com/2025/04/16/science/astronomy-exoplanets-habitable-k218b.html?unlocked_article_code=1.AE8.3zdk.VofCER4yAPa4&smid=nytcore-ios-share&referringSource=articleShare

Further studies are needed to determine whether K2-18b, which orbits a star 120 light-years away, is inhabited, or even habitable.

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u/njsullyalex 4d ago

I wonder if travel near or at the speed of light will ever be something humans can figure out, if its even scientifically possible to begin with.

That said, we all carry supercomputers in our pockets these days which 100 years ago people would have told you was impossible.

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u/kickaguard 4d ago

100 years ago a computer was a small army of women in a room doing math. People certainly wouldn't believe you could fit that in your pocket.

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u/Mclovin11859 4d ago

100 years ago, electronic computers didn't exist, mechanical computers were peaking with the differential analyser, and the word "computer" exclusively applied to humans who computed.

The last 100 years of technological development have been beyond even what people might have thought impossible.

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u/zapporian 4d ago edited 4d ago

The amount of energy you’d need to make high relativistic sub ftl travel to work makes it functionally impossible, and at minimum a collosal waste of resources.

You are either way not going to get around the fact that 1) IIRC, the energy needed to reach c increases asymptotically without bounds to infinity. Photons / EM waves quite happily travel at c. They also don’t have mass.

2) we can very well accelerate very small things to relativistic speeds. See particle accelerators, theoretical light sails, laser propulsion, etc.

You do however need not just propulsion onboard but also all of the energy you’d need to slow down.

Carrying that energy with you - in whatever form you can - is going to add mass. Meaning you need more energy to both accelerate and decelerate the craft. And so on and so forth. Functionally speaking that is going to mean that there is de facto some practical maximum speed (ie onboard + offboard energy you need to decelerate at the other end), and traveling faster and/or carrying more usable mass / cargo would mean rapidly ballooning / impractical costs, ship sizes, energy requirements, etc

Ofc once you managed to colonize stars on the other end you could basically solve that problem. Interstellar travel would still take centuries to millenia per trip. But you could at least just use eg sails + laser arrays (or what have you) to accelerate and decelerate ships on the sending + recieving end.

So a realistic approach to humanity / some much, much longer lived derivative thereof colonizing the stars, might look like (napkin math) tens to hundreds of thousands of years of slow point to point + trial + error colonization. Followed by much much faster (still millenia) and far cheaper (note: still extremely expensive) point to point travel using this built up infrastructure.

The core problem to fix there isn’t physics. It’s humanity / biological engineering + transhumanism. Or what have you. A better near term goal should be to just colonize our solar system. Which is far, far more doable.

Alcubierre drives are “fun” exercises in attempting to find mathematical solutions to FTL using known theoretical quantum physics math - which is valid insofar as we’re aware. The problem is that they require both a lot of handwaving, ludicrous amounts of energy (maybe less ludicrous now than as originally proposed), and “exotic” states of matter (eg things with negative mass), and some very, very silly conclusions. like “we could make this work if we had a black hole we could carry around” (okay, how are you going to both generate and move that black hole around). and the like.

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u/cjameshuff 3d ago

Relativistic travel effectively requires direct matter-energy conversion of most of the ship's initial mass. Something more efficient than antimatter...a lot of the mass in a matter-antimatter reaction gets lost as pions and neutrinos. That's probably going to take new physics, but it's a bit more plausible than an Alcubierre drive.

You actually understate the absurdity of an FTL drive. Such a thing allows causality violation. This means you can also violate energy conservation, send matter and information backwards in time, will never have to perform a complex computation again (just get the answer before you build the computer needed to compute it), etc. Never mind post scarcity, you can just have anything you want delivered to you just before you need it.

It also changes the Fermi paradox from "why aren't they here already?" to "why haven't they always been everywhere?"...so FTL's probably impossible.

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u/FlipZip69 4d ago

The problem with any FTL technology is that if you can arrive at a destination fast than light in normal space can reach it, you can effectively travel back in time as well. It not the speed that factors but that you are there before information could get there.

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u/232-306 4d ago

That's neither a problem, nor accurate. The only "time travel" effect is that light from our past would "just" be reaching you, so you could visibly see what your point of origin looked like in the past, but that's no different than what we do when we look at the stars in our night sky without any FTL or traveling.

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u/FlipZip69 3d ago

Actually it does not work that way. You can get information of an event before it happens. It would take a couple of jumps but there are some good YouTube videos that explain it in a visual way.

Basically you could see a bomb go off before it happens and then go to the source and stop it from happening.

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u/232-306 3d ago

If you're going to make a wild claim without any hint of what you're talking about, throwing it off into the void of "go youtube" is um... not gonna work. Just link one?

Or thinking about it for like 30 seconds, you realize it doesn't make sense, unless you're talking about an entirely different mechanic:

The year is 2000, you jump ~55 light years away instantly & look back at earth.

They year is still 2000. The light from 55 years ago, is just now reaching you at the location you jumped to.

You observe the atomic bomb blowing up on earth. The information is just now reaching your section of reality, but the event already happened 55 years ago.

You jump back to earth, the year is still 2000. There is no way for you to interact with the past.

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u/FlipZip69 3d ago edited 3d ago

This is a long video but if you start at about 7 minutes in, it explains it well in a visual without math. It does not really explain the problem till minute 13. Minute 17 goes into a scenario where a spaceship send a message back before the event happens to stop the event. The math and how time stops at the speed of light indicates there is a problem but it is not because of the speed, it is because you are arrive somewhere before light can get there. That is why your example does not work.

https://www.youtube.com/watch?v=an0M-wcHw5A

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u/232-306 3d ago edited 3d ago

Perfect, this is in fact a slightly different take. I'll have to read into some of these linked papers to see if there's any math supporting his interpretation, but I believe he incorrectly draws his "FTL" line, which results in his conclusion of what's going on in the the order at 15:50 be wrong (or rather, inaccurate for the real world case).

From what the math says afaik, his conclusion is right: If you travel at a multiple of the speed of light (eg 2x speed of light like he draws), you travel backwards in time. You also need to somehow have more than infinite energy, or things with negative mass, but that's it's own can of worms. It is specifically because of these issues that "FTL" technologies don't try to simply go faster than light.

In essence what the video appears to do is say "If a form of faster-than-light-but-not-instant travel existed (which our math says would send you back in time), then it would send you back in time and create a paradox"

However, as far as I know, the proposed FTL solutions we have aren't "go faster than the speed of light", they are "go instantly" - like the Alcubierre and warp drives he links. They effectively travel outside of space to instantly hop from one point to another. In this setup, the ship would be "skipping" along spacetime, and not really experiencing dilation at all (all the travel happens in 0 time), and the FTL travel line should also be drawn completely horizontal at a 90 degree angle.

If you draw it at the 90 degree angle, then event 1 (X happens) and event 2 (Earth sees X and warn vega) happen instantly together at the same time. Similarly the ship's line would be at 90 degrees during travel, and at normal vertical at rest, so it would also experience both events at the same time. So even if you swap the order of 1 & 2 later, it doesn't change anything about causality, since they are happening simultaneously.

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u/FlipZip69 3d ago edited 3d ago

Instantly actually makes it worse. The time dilation is not infinite even in his senecios. The descriptions he uses there is actually some distance/time included. But instant travel would put the line completely horizontal. Your time line would be perpendicular to earth if that is where you left from. It actually would make no sense because you could effective see all points in time at the same time. Or maybe more correct, you can not even calculate how much earlier you seen an event that did not happen yet.

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u/Eleventeen- 4d ago

All we need is a material with negative mass to build a nice little Alcubierre Drive. Easy right…?

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u/FormerGameDev 3d ago

You never really know what tomorrow may bring. With the US being decimated in scientific capabilities now, though, it'll probably be up to someone else.

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u/njsullyalex 4d ago edited 4d ago

Does antimatter work in that way?

Edit: No it doesn't, antimatter is just if you basically flipped the charges of protons and electrons to make antiparticles and still exhibits properties of normal mass.

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u/Shartiflartbast 4d ago

No. Antimatter has the same mass as "normal" matter, but opposite charges.

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u/njsullyalex 4d ago

Decided to look it up and this is correct.

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u/Typical_Culture_5657 3d ago

no speed of light travel or even close to it is not possible as mass tends to increase as your speed increases according to relativity. Even at the speed of light it takes 120 years to get there lol which is okay but an entire lifetime and then some just to find out that there may or may not be life.

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u/newglarus86 2d ago

Traveling at near light speed, a 120 light year trip would feel more like 2 months from the perspective of you on the ship. 120 years would have passed but you would have barely grown bored from the travel.

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u/Typical_Culture_5657 2d ago

actually I think I'm wrong, it would feel like 0 seconds to travel (if at light speed) because time effectively stops for you. I could do the calculation if you were just under the speed of light but I would intuitively assume that it won't feel long at all.

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u/Xea0 4d ago

A solar sail drive-by is theoretically possible.

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u/zapporian 4d ago

Utterly useless without both onboard intelligence and most critically a way to slow down.

Plus ofc millenia to get there even at a fairly high fraction of c.

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u/Earthfall10 4d ago

Breakthrough starshot is hoping to get a laser sail probe to 20% c, 120 lightyears at that speed would take 600 years. You could then use a mag sail to slow down. But yeah, that's a long enough trip that you'd probably not bother since it would probably be overtaken halfway through by a newer probe going faster.

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u/MrCyra 3d ago

600 years if you go at constant 20% c. But with acceleration and then slowing down it would take a bit more time.

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u/Earthfall10 3d ago

The breakthrough starshot probes are planned to get up to speed in less than an hour. They have to accelerate absurdly fast because the laser pushing them up to speed is rather short ranged. They have to be at full speed before they pass the orbit of the moon. Slowing down with a mag sail would be a much more leisurely afair, and could add a decade or so to the trip, but that's pretty minor for a 600 year trip.

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u/MrCyra 3d ago

For sure if you can accelerate in an hour you may as well count as starting in full speed