Black Holes & Time Travel | David Neto | TEDxOStateU

Translator: Masami Mutsukado and Kacie Wright
Reviewer: Denise RQ Good evening, ladies and gentlemen. My name is David Neto,
and physics is my business, and today we’re going to talk about something that might seem more like
science fiction, and that is time travel. So it’s a very popular subject [in] many movies, films, comics,
books, the whole gamut. Everyone loves time travel. And it might just seem
like that, just like fiction. But actually, time travel itself
does have some science fact, and that’s hopefully
what we’ll talk about today. So, a little bit
of background, there we go. Around the turn of the century, Einstein comes up
with his theory of General Relativity. And the Reader’s Digest version of this basically says gravitational fields, gravity, affects time and space,
so warps time and space. So, for example,
the Earth we are living on: in the 1950s and 60s the United States
Air Force did an experiment. They took the best atomic clocks they had,
they synchronized them on the ground, they put one on a plane,
flew it around the globe, the other one they left back at base. When they brought
the two clocks back together, the clock that was up in the air ran fast. So what happens is gravity warps space and causes clocks
in weaker gravitational fields to appear to run fast. And this effect is proportional to
the strength of the gravitational field. So, what objects in the Universe
have really strong gravitational fields? One such object is a black hole. Stars that’re much more massive
than our Sun can potentially, at the end of their life, when they’re
done burning their nuclear fuel, collapse under their own weight
and form what we call a black hole. ‘Black’ because its gravitational
field is so strong not even light can escape it. So if you were to hop in your spaceship,
put yourself in orbit around a black hole – let’s say maybe for an hour – to you in your ship,
an hour passes; kind of boring. But when you leave
the black hole, radio back to base, they tell you you’ve been
away for six years. This is that gravitational field
that is warping space, and because the black hole has
such a strong gravitational field, that effect is huge. So, in essence, you have time traveled. It’s kind of the boring,
not very sexy forward time-traveling, I mean, that’s what we’re doing
right now, but one might ask, “What about traveling backwards in time?” So relativity, the equations of
relativity, allow backwards time travel. They allow it in the sense that there are mathematical solutions
allowing you to travel backwards in time. And they’re just that:
they’re just mathematical solutions. They’re not necessarily physical or real. One of the reasons why you would be
inclined to believe they’re not real is the problems that come up
with causality, or cause and effect. So we like to encompass this in a paradox,
called “the grandfather’s paradox”, and the basic idea is if you go
back in time and kill your grandfather, your grandfather doesn’t give birth to– well, he doesn’t give birth
to your father, but your father doesn’t get born,
you don’t get born, so you can’t go back in time
to kill your grandfather. So we have this disturbing
cause-and-effect relationship. So this would sort of seem to say
backwards time travel doesn’t work. Now, general relativity,
as I said, allows it, but the other laws of physics
are a little bit sketchy. So, in the 1960s, Stephen Hawking,
working in black holes combines General Relativity, some quantum mechanics,
some thermodynamics, and what he finds is that there’s a sort of what he calls
a “chronological protection agency”. There’s sort of like this
auspicious outside agent in the Universe that says you can’t do time travel. It just doesn’t work. So, the thing is, it’s not a definite ‘no’,
it’s sort of like a ‘maybe no’. In order to get a definite answer, you actually have to come up with
a complete quantum gravitational theory, which we actually don’t have. Physicists have been working
on this for many, many years, and we’re still working on it. So we kind of can’t say definitively
you can travel backwards in time, but let’s say we go back
to our friend the black hole and maybe do something a little bit else. So around the 1980s,
another physicist, Leonard Susskind, also doing some work in black holes– Now, there is a problem with black holes. As I said, you know, the gravitational
field is really, really strong. Light can’t escape it, so if something
goes into the black hole, it’s never going to come out. Now this is a bit of a problem,
because, you know, it’s sort of like destroying
information in the Universe. It’s information that goes somewhere
that we can never get out. And this was a big problem,
and Dr. Susskind came up with a solution that essentially, when things
go in a black hole, the information of what goes
in the black hole sort of gets smeared on the outside of the the black hole. And so what you can do is,
you can think of a black hole as sort of this quantum DVR:
everything the black hole sees that light goes into the black hole,
information gets smeared on the outside. So if you wanted to just be
an observational time traveler? Nothing wrong with that. Doesn’t hurt causality
because you’re not affecting anything; you’re just looking at things. So you can simply scan
the surface of this black hole and you can travel back in time
and see anything you want to see: from the birth of the Universe,
anything on Planet Earth. Anything, you want to see it,
it’s there on the black hole. So, unfortunately, how you actually
go about constructing the device to let you ‘read’ a black hole? Sort of leave that
to experimentalists to figure out. But it’s an interesting idea, nonetheless. That time travel sort of, in some manner, is not exactly science fiction,
but a little bit science fact. Thank you. (Applause)

84 Replies to “Black Holes & Time Travel | David Neto | TEDxOStateU

  1. Dude, you and I are on a rock called Earth Falling in space towards the sun (gravity). The speed of the fall creates the ozone layer that distorts the light that traveled 8 minutes to get here. This fall is what creates the arrow of time from the past, to the present and into the future because things only fall in one direction-a straight line. Time is not the clock on the wall.
    Time is always t = 0 + 1second. That is why you can't create a time machine, because it would imply that you left from point A to B with time being t= 0, which is in possible.
    Also, it's just impossible to create a time machine because even if you create a time machine, time will still keep moving forward at the same rate even inside a time machine.
    More so, we are already traveling through time, so, talking about time travel inside of time is bananas.
    Nice sideburns though, it

  2. Quantum Entanglement states that by simply observing something you change it's state.  So Observed Time Travel is just as impossible or it's just as dangerous….or any number of other things I'm incapable of fathoming.

  3. That's a pretty interesting theory. Imagine if a black hole was one giant record. Then all you would need to figure out is what kind of needle ( Laser ) you would need to use to grab the information stored inside.

  4. second shittiest ted talk ever. What the hell happened to ted talks? run out of good material? instead you have someone talking about how information can't be destroyed without explaining anything ( and ignoring the fact that Info can be destroyed).

    The time(t) acceleration(a)

  6. so the problem is… light is made up of negetive force and the black hole is made up of positive force…or rhe orher way around

  7. It's simple really – think of it this way:- Your friend invents a time machine and invites you over that evening for a trip to the past. The problem with this scenario is that if you go round to your friend's place that, and anything you do after that, is in your future Ooops!

  8. I never say anything bad, but this was terrible, unprofessional, and shows the very real problem of being too "cool"

  9. David Neto says towards the end (5:42), "… you can simply scan the surface of this black hole, and you can travel back in time and see anything you want to see: from the birth of the universe, anything, planet Earth, anything, you want to see it, it's there on the black hole."
    Despite just being an idea, I don't think he's correct, because wouldn't the earliest point in time you could see on the event horizon be directly after the birth of the black hole? It makes sense that you can't see anything when the black hole wasn't formed yet. So, you can never witness the birth of the universe unless a black hole was already there, which there wasn't, because before the universe there was nothing.

  10. Nice idea but you can't be there without affecting the entire universe. Your eyes alone will intercept photons, have a gravitational field, distort and generate electric fields, etc. So just your eyes alone will affect everything. No way around that.

  11. It's not an easy topic, but this presentation didn't really offer any new insights, ideas or information. I still enjoyed it.

  12. Gr8 but the information on the skin is scrambled and you won't be able to access all of it all the time but if you were able to you could make a gr8 video of the history of the universe but not go back in time. Also the information evaporates away with time like a decaying DVD

  13. Alternate Realities cancel out the grandfather paradox , you go back in time, off your own grandpa, nothing stops you from doing it, no invisible force fields or nonsense, you simply can never return to the reality or dimension from whence you came from.

  14. There is no way for time travelling in the classical way we know it from sci-fi movies… Perhaps only into the future via time dilatation, but not into the past. This is not possible due to entropy…

  15. Shave your face they said, it'll help you look more presentable for potential employers they said. Here's a mean slice of cheddar to go with that humble pie

  16. Kill grandfather -> father is not sired -> you are not sired -> you cease to exist -> grandfather is not killed -> father is sired -> you are sired -> you kill grandfather

    So, the loop closes?

  17. At the ted event? i did want to time travel to meet a ted, so thats funny has his name on the event about time travel what?? and i used to see other guys name i wanted to time travel to meet in past, his name on everything time travel as well..what does that mean? so weirdly perfectly fitting like predestined or something yserterious/magical that they will have something to do w/ that somehow..although i can't figure out how to make it happen as far as would be relation to me at least

  18. To all the the people thinking about it, please don't go in the past and kill your grandfather, it's not temporally allowed.

  19. It is all science fiction. They have no actual proof just extrapolations into insanity with all teh BSing they do. Just show any actual evidence at all. You can't because you actually have ZERO evidence of any of this BS, You are just science fiction not scientific theory. You are not even close to any kind of actual theory. Just science fiction speculation and sensationalism. It's all nonsense at this point. They are killing science with the BS.Everything is on the move out there and it doesn't go backwards. Wherever you get to regardless of how fast you go, you will always be in the present. Since nothing is actually reversing course it would be impossible to travel backwards in time. The future cannot be the present until you are present in it meaning it is not ever the future you can experience. It is always and always will be the present you observe. Quit with the nonsense.

  20. This is definitely one of the worst Ted talks ever. It was what I would imagine it would be like to watch Reader's Digest do a Ted talk on an actual physicist's Ted talk on time travel.

  21. Past present and future are all happening at the same time. There is no time. We live in the infinite now. We are vibration and it only took one musical note to create everything because the harmonics of that one note expanded into infinity and collapsed on itself and we are living it. The universe is a giant doughnut.

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