Folks who, like me, are interested but not professional physicists, may find illuminating Sean Carroll's podcast. https://www.preposterousuniverse.com/podcast/ He is a CalTech faculty physicist with wide interests and perhaps a third of the episodes are about research physics. I remember several that discussed wormholes and associated topics seriously, from the standpoint of world-class researchers. I think anyone interested in HN would be able to follow the conversations closely.
I can’t recommend enough Sean’s “Biggest Ideas in the Universe” video series [1]
It’s a series of 24 1-2 hour lectures + Q&A/recitations that assumes no prior knowledge of physics and aims to get you roughly to the knowledge level of a modern undergrad BA physics.
For someone who loves science documentaries but was frustrated at most being aimed at high school-level and skipping all the math, Sean’s series was a game changer for me.
> It’s a series of 24 1-2 hour lectures [...] level of a modern undergrad BA physics.
Wait, what? That's completely bonkers. There's absolutely no way to condense four years of studies into two days of YouTube. I can't believe I'm even having to say this.
I'm hoping what you mean is "introduce you to the topics that would be covered in an undergrad physics degree". In 24 hours you could reasonably mention each of the topics covered in a degree and describe what that field is about.
It is an entirely crazy proposition. A single physics course is approximately 50 hours of instruction. You have to take about 20 of those. You can't squeeze that down 30x with no loss of resolution.
Again, in your example, you're suggesting you can learn all of the physics one would normally learn in four years of almost-full-time study in six months of part-time study.
Of the course that's not happening. What it does is to give an understanding of the concepts, but you won't be able to actually do the maths.
The the series, he shows some of the maths so as to give you an idea how you get to the conclusions that popular science just explained as fact, but isn't rigorous.
Almost all physics material is either simple explanations with analogies and no maths. Or it's the full textbook. The video series is a very rare example of a middle ground where maths is used to explain the concepts to an audience which are not expected to be actual employed physicists.
Sean Carroll is incredible, and his textbook on Spacetime & Geometry was the only reason I understood anything in my graduate-level class on general relativity. There's truly an art to be able to explain incredibly complex topics in an easy(er) to understand way.
2. You still need to be thinner than spaghetti to go through what they're talking about.
3. They're stretching the words 'relatively easy' to ludicrous limits: And because entanglement is a standard feature of quantum physics, it is relatively easy to create. “It’s really a beautiful theoretical idea,”
If we'll figure this out, we'll (very) probably also have figured how out to calculate the effects of communicating with the past.
So, no. This doesn't tell us anything about the possibility, it merily tells us, even if it _was_ possible, we're collectively to stupid yet to deal with it without destroying our future which would've led to inventing such a device.
The physics of interacting with your previous self are undefined with many plausible solutions.
It is entirely plausible that the universe limits your interactions with your past causal self to a small range, allows arbitrary overlapping world lines, blocks all causal violations entirely, or has disastrous consequences for time loops.
My personal bet is that the universe has no reason to care that you've interacted with your past self given a consistent proper time worldline. This however removes conservation of energy and momentum in the universe, which General Relativity also does not preserve.
Of course this does allow for misuse of causal loops to generate arbitrarily large/infinite amounts of energy without any bounds on observability.
In the abstract of the linked paper in the article, they mention that wormholes "can't violate causality" [1]. So, this wouldn't be possible even if we were able to invent wormholes in our lifetime.
Which is precisely how it would work with wormholes.
Wormholes can be turned into time machine in the following way. Remember that time travel to the future is pretty trivial: Just accelerate a lot and enjoy the effects of time dilation. So in order to travel into the past, you create a wormhole pair and put one of the wormholes on a speedy two-way trip. If you now traverse the wormhole that was on the trip (and which has traveled into the future), you travel backwards in time. But not further than when the pair was created.
They're saying tunnels are possible. They didn't say people (or any organic life on Earth) would travel through them.
Honestly just encoding any communication through them successfully would turn our world upside down.
That said, wormholes are a bit of the pet crackpot theory of the scientific community right now. Black holes are definitely a thing. White holes are pure conjecture based on extrapolating math in very hand-wavey ways. And wormholes (i.e. the idea of black/white holes where information can travel between them) are even less plausible.
The last link in the article is to a paper called "Humanly Traversable Wormholes". Here is an excerpt from its conclusion "In fact, it allows for solutions where the wormholes are big enough that a person could traverse them and survive. From the outside they resemble intermediate mass charged black holes. Their big size comes from demanding that a human traveller can survive the tidal forces.", from [PDF] https://journals.aps.org/prd/pdf/10.1103/PhysRevD.103.066007
I understand this is some form of hyperbole, but would what they propose be sufficient to transport masses of some raw elements around? Let's say some advanced civilization sent out mining expeditions, and desired a way to transport back that material FTL for example
I wouldn't expect an exhaust plume passing through a wormhole to move the wormhole itself (or the heavily curved "portals" at its ends) any more than a plume would move "flat"/"normal" spacetime.
Separately, Kurzgesagt did a video on stellar engines (which can be much less exotic than wormholes); sounds like what you're describing: https://youtu.be/v3y8AIEX_dU
That's not how quantum entanglement works but assuming that you could have microscopic wormhole ends that can be moved independently of each other, that would essentially let you do what I imagine you want.
If it turns out that wormholes are impossible, a future internet powered by neutrinos (presuming we discover/invent a material that can absorb them consistently in a compact way) would be the next best thing.
Seems unrelated. This paper is talking about the black hole itself (not its accretion disk). And it's also talking about a magnetic charge rather than a magnetic field. This would require magnetic monopoles, which are hypothetical.
Related, but not wormholes: Last night I watched this video on loop for a long time, of stars at the center of our galaxy orbiting the supermassive black hole Sagittarius A*. Really a mind-blowing video. https://www.eso.org/public/videos/eso1825e/
It's just amazing how satisfying these little incremental observations are, and equally amazing how much work goes into it.
What I found similarly fascinating was this interactive of our neighborhood - 33 light-year field, green are detected planets: https://gruze.org/fly_10pc/ (mouse wheel, click n drag, right click and drag)
Amazing video, thanks!
Really interesting to see the sudden increase in speed in that one star. I wonder if it has any detectable effects on that star’s planets.
Edit: after watching it again it seems to be a matter of perspective but I thought it was about how close it orbited the black hole.
This absolutely made my day. I had no idea this existed! Putting it on .25 speed and looping it allows you to really see the warping taking place. I wonder if the four or five similarly sized light orbs moving in and out are really just the distorted light from one star?
The most useful thing wormholes could be used for is hypercomputers (if causality can be violated); or simply bypassing the Bekenstein bound with FTL communication in a processor exceeding the mass that would turn it into a black hole if it was spatially adjacent; or building an interstellar network that could survive the big rip.
Anything that mastered wormhole creation is also likely to expand into the universe at close to the speed of light with wormhole-carrying Von Neumann probes, making the Fermi paradox even more extreme if wormholes can be created.
Does anyone else get just a little bit sad that we will not be around to see actual practical advances made with wormholes?
I wonder if this is what people in earlier centuries felt, a bit of melancholy at the dream that hundreds of years from now someone may be able to walk on the then newly-discovered moon, and knowing they would not be around to see it happen.
> Does anyone else get just a little bit sad that we will not be around to see actual practical advances made with wormholes?
Thing is, I felt sad when I heard about IP the first time, and some people said we were gonna have a huge network everyone can talk with each other, across borders. Because I thought we'd never achieve that in my lifetime.
But here we are, things move a lot faster (sometimes) than what you think. Maybe because of the inviting incentive of basically teleportation, research on wormholes will be faster.
I'm not comparing them, I'm comparing the feeling of "This will be so far in the future that I will never experience it" that I got from IP and international networks, since someone else felt the same way about wormholes.
> I wonder if this is what people in the 17th century felt, a bit of melancholy at the dream that hundreds of years from now someone may be able to walk on the then newly-discovered moon, and knowing they would not be around to see it happen.
Could you elaborate on this newly-discovered moon you’re speaking of?
I think this may count as a new "discovery" phase of our relationship with the familiar celestial object, and may have indeed prompted an uptake in fantasies about perhaps one day walking in it.
> Does anyone else get just a little bit sad that we will not be around to see actual practical advances made with wormholes?
Depending on your age, you will. With the massive progress quantum computing and further advances in AI will bring. I have a feeling we will be able to 'back up' people their brain within a few decades. Regrowing a body or producing a sufficiently advanced (and cheap) robotical surrogate may be further away, but technical immortality might be very achievable.
Unless medical science and biology enable us to extend the human lifespan meaningfully in our lifetimes. Sounds crazy, but if you described most of medical science today to someone fifty years ago, it all would've sounded crazy.
>I wonder if this is what people in the 17th century felt, a bit of melancholy at the dream that hundreds of years from now someone may be able to walk on the then newly-discovered moon...
I'm no historian. But I'm pretty sure people had discovered The Moon a wee while before the C17th.
The concept of "travelling backwards in time" is very odd.
To "travel in time" I guess first one would have to define what exactly is this "time" one is about to travel backwards in.
So... what exactly is "time"?
And does "time" even exist as something concrete which can be traversed? Or, is "flow of time" just something created within the brain as a way to keep track of changes in things we experience?
Or is it something else, something totally different?
(I don't know the answers, I'm asking based on what "time travel" could be possible in the first place. Hoping John Titor chimes in, too.)
I don't know the answers to all of your questions, but I can say with confidence that the "flow of time" is not an invention of the brain. We can (and frequently do) make measurements that demonstrate time is an objective dimension of the universe that interacts with space and matter.
There have been really awesome experiments around this. For example, it has been demonstrated that moving a particle at relativistic speeds increases its half-life, which can only be explained by time dilation.
I'm only a layman who likes to do the occasional thought experiment, but does time really have to be an objective (concrete and elastic and traversable) dimension to explain time dilation? Isn't there any alternative explanation?
For example, to illustrate what I mean, let's think about time dilation:
Particles moving at relativistic speeds must by necessity travel larger distances (space) as they move: something moving at ~ 299 km/s moves obviously 299 km in a second, whereas something moving at 1 m/s would have moved only 1 meter. Presumably things like fields and other force carriers, which make matter interact with matter etc. will also have to travel larger distances to interact. They have to cover the distance between the particle(s) moving together as well as the parts of the universe which aren't moving as fast.
This way, in the outside observer's frame (=the one with the clock), these fast-moving particles seem to "slow down" because the things facilitating interaction are travelling larger distances, which takes a longer "time" (=more ticks of the observer's clock). And thus the half-life becomes longer.
Now, one can follow-up this thought experiment: what if there was an Ant-Man in a tiny space ship looking at his wall clock and moving at relativistic speed? The Ant-Man would not spot differences in himself, in his frame, since his clock and bodily processes and matter-matter interactions etc. would run slower too. However, the Ant-Man would see the outside world slowing down (I think), since travelling larger distances takes a longer time. When Ant-Man brakes, his experience would be for the outside world to accelerate (I think) possibly in some kind of a jumbled manner towards the end, and then "lock" into place.
And as Ant-Man's chemical reactions and matter interactions slowed down, moving at relativistic speeds resulted in him having "aged" less compared with people who were stationary.
IANAPhysicist, but traveling backwards in time would violate at least the law of conservation of matter. Traveling forward in time, on the other hand, feels like something actually possible. You're already traveling forward in time at the rate of 1, so nothing would break if you somehow created a bubble of space around you where time ticks at a different (positive) rate.
I thought of people who have deep frozen themselves because of medical reasons. That's kind of forward time-travel, no? (Assuming they ever can be successfully resuscitated)
No it is not. As a maths guy I can tell you two things. One: math does not make it true. Two: You need to be able to build a disprovable model against this. No. No wormhole. Its not even needed to explain behavior. this is pure science fiction.
I had a subscription in the late 70s and early 80s. Very enjoyable material. (: Some fraction of it would be somewhat rigorous science, but the rest was pretty fanciful, fun stuff.
ADDED: Beautiful, and here's the relatively short lived TV show Omni Magazine: The New Frontier (1987) https://youtu.be/kdwEGc_g6Gw?t=68
My mother subscribed in the late 80's because she was dating a science professor (who she eventually married) and wanted to be more conversant in science.
I remember visiting her and picking up the latest issue from her coffee table. The headline story: DINOSAUR SEX -- complete with full-color artist's renditions. I had a great time teasing her about it.
I'm going to venture to guess anything and everything is possible
How many billions of light years big is our universe? A size so huge, we can't fathom that number or distance.
We observe or think we're observing black holes, dieing stars, super novas, etc...
We think dark matter exists and fills the voids of what we can't view
We observe viruses and try to kill them, atoms, etc...
We're on the edge (few years? decade max?) of producing picometer processors
So yes - wormhole travel is possible. Reversing the pull of gravity is possible. Traveling faster than the speed of light is possible. We are just not smart enough (yet) to do these things.
What's the saying? If life exists elsewhere other than earth, there are probably thousands and thousands of civilizations out there due to the size of the universe? Then yes, all these things are possible and something has probably already done it - we're just not there yet.
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