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Monster gravitational waves spotted for first time

nature.com

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Re: Monster gravitational waves spotted for first time

#181

Post by lasc4r »

mtlmtlmtlmtl wrote: post #151

Modern physics(and engineering) is kind of absurd. And I mean that in a good way. LIGO? I didn't believe at all that it would ever work. Even when they got detections I kinda thought they were chasing their own tails. Now the evidence is pretty much rock solid that the data is real(multiple facilities, correlations with light observations for neutron star mergers, etc). Then I heard about LISA, which essentially is b…

I feel like you need to see _this_ spacetime video: https://www.youtube.com/watch?v=4d0EGIt1SPc

If you think LISA is mad this will blow your mind.

Re: Monster gravitational waves spotted for first time

#182

Post by drbw »

sunshinerag wrote: post #97
nyrikki wrote: post #90

Earlier quoted context omitted.

Hard or impossible to visualize, but as the temporal dimension is so much larger, most of the deformity is in the time dimension. But yes, spacetime itself is jiggly like Jell-O. As we can't visualize 4d spacetime, most analogies will be wrong. But as photons don't experience time themselves, thinking about the geodesic path is probably less error prone than thinking of it as squishing physical objects. Objects being…

what does "photos don't experience time themselves.." mean? why not?

Try this from Fermilab's Dr Don Lincoln: https://www.youtube.com/watch?v=6Zspu7ziA8Y

Re: Monster gravitational waves spotted for first time

#183

Post by MaxikCZ »

jballanc wrote: post #68
ISL wrote: post #52

Earlier quoted context omitted.

The yardstick is indeed the light-travel time. Gravitational waves really do change the time it takes for light to travel between two points. We use light travel-times to measure distances, thus we say that the distance between the points has changed. If it feels counterintuitive for spacetime to be changing, that's good. It is outside our human experience and perception. The strongest gravitational waves ever observ…

>None of those people noticed before the instruments registered a detection. IIRC, the reason no one noticed is that even the strongest gravitational waves are only going to "stretch" space by something less than the diameter of a hydrogen atom.

Correct me if I am wrong, the gravitational waves we measure have such small effect, that if we blew proton to the size of the Earth, it would get squished by distance smaller than a human hair.

Edit: from wikipedia LIGO page: "(interferometers) are capable of detecting a change of less than one ten-thousandth the charge diameter of a proton"

I dont know why I remember the human hair analogy, perhaps I am confusing it with something else?

Re: Monster gravitational waves spotted for first time

#184

Post by [deleted] »

adgjlsfhk1 wrote: post #127
ben_w wrote: post #113

Earlier quoted context omitted.

Light does slow in a medium, the statement presumes the light is in a vacuum. From the point of view of the photon, "forwards" is, like time, a null[0] dimension. [0] I may be using that word imprecisely, but I can't think of a better one.

This isn't quite true. At a macro level, light slows down. At a micro level, photons travel at the speed of light, get absorbed and re-emitted, and change directions. These effects average out to looking like photons traveling slower.

[deleted]

Re: Monster gravitational waves spotted for first time

#185

Post by dotancohen »

adrianN wrote: post #180
MichaelMoser123 wrote: post #161

Earlier quoted context omitted.

so how comes they can't get this fusion thing to work?

Nobody wants to pay for it. We have other forms of energy that are cheaper and available right now.

Unfortunately this is the correct answer, almost word for word how I was going to phrase it. Do long as other forms of energy are inexpensive, we will continue to abuse them no matter the damage.

Re: Monster gravitational waves spotted for first time

#186

Post by stefncb »

JumpCrisscross wrote: post #179
distant_hat wrote: post #169

Earlier quoted context omitted.

Fusion is easy and you can set off a hydrogen bomb whenever you like, it is turning that energy into electricity that's the hard part.

> it is turning that energy into electricity that's the hard part It’s creating a stable, recurring reaction that’s the hard part.

It's actually making it spend less energy than it creates that's the hard part.

Re: Monster gravitational waves spotted for first time

#187

Post by mtlmtlmtlmtl »

MichaelMoser123 wrote: post #161
mtlmtlmtlmtl wrote: post #151

Modern physics(and engineering) is kind of absurd. And I mean that in a good way. LIGO? I didn't believe at all that it would ever work. Even when they got detections I kinda thought they were chasing their own tails. Now the evidence is pretty much rock solid that the data is real(multiple facilities, correlations with light observations for neutron star mergers, etc). Then I heard about LISA, which essentially is b…

so how comes they can't get this fusion thing to work?

Can't get it work yet. LIGO took decades to get to work. Progress is being made though.

Re: Monster gravitational waves spotted for first time

#188

Post by mtlmtlmtlmtl »

lasc4r wrote: post #181
mtlmtlmtlmtl wrote: post #151

Modern physics(and engineering) is kind of absurd. And I mean that in a good way. LIGO? I didn't believe at all that it would ever work. Even when they got detections I kinda thought they were chasing their own tails. Now the evidence is pretty much rock solid that the data is real(multiple facilities, correlations with light observations for neutron star mergers, etc). Then I heard about LISA, which essentially is b…

I feel like you need to see _this_ spacetime video: https://www.youtube.com/watch?v=4d0EGIt1SPc If you think LISA is mad this will blow your mind.

I watch pretty much all their videos as they come out, and indeed this one was... pretty out there(pun intended). Somehow I have no doubt it'll be built one day.

For now my mind is sufficiently blown by JWST taking spectra of exoplanet atmospheres.

Re: Monster gravitational waves spotted for first time

#189

Post by marsten »

derefr wrote: post #61
jessriedel wrote: post #53

Earlier quoted context omitted.

Yes, that's basically right. The gravitational way has a direction (say, z) in which its propagating. Within the plane perpendicular to that direction (x-y), a circular ring of particles will at at one moment experience squeezing in one direction (x) and stretching the perpendicular direction (y). As the wave passes through and you move from the peak of the wave to the trough, the directions reverse, so the first dir…

Acoustic waves propagate through what are essentially elastic deformations of the material they travel through. Can gravitational waves be thought of as propagating by elastically deforming spacetime? If this analogy holds, then can it be taken further? Acoustic waves dissipate their energy insofar as they trigger plastic deformation in a material. Could gravitational waves plastically deform... spacetime itself? Or…

In principle yes, gravitational waves dissipate energy into ordinary matter they pass through. However the coupling is extremely weak (that gravitational waves are so hard to detect is testament to this).

In fact this weak coupling is what makes GWs so interesting for observational astronomy: They propagate from the source to our detectors virtually unchanged. (This is in contrast to EM radiation, which is very easy to scatter.) For example the farthest we can see back with EM radiation is about 200k years after the Big Bang, when the plasma of the early universe recombined into neutral hydrogen. By contrast gravitational waves can see back to the Big Bang itself, so it is a truly unique source of information as compared with light.

Re: Monster gravitational waves spotted for first time

#190

Post by [deleted] »

sam_goody wrote: post #139

Can someone please ELI5: I was taught that all items fall at the same speed, due to the gravitational constant. With these waves, does that mean that items will fall at ever so slightly differing speeds, as depending on the size of the wave there is a pull in the other direction, and the constant is slightly off? And OT, but related: Since every item has a gravitational pull related to its mass, would a bigger item f…

[deleted]
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