Dark Energy Might not be a Thing, and we Might not have Detected any Gravity Waves

[The Anti-Targ]

Been following Sabine on Youtube and she seems pretty legit. And my physics PhD brother says she's the real deal. My bro was also very skeptical about dark energy when it was first declared to be real, and he thought the Nobel prize was premature.

The gravity wave thing isn't disproof of anything, and technically neither is the dark energy thing. But for the dark energy thing (she has a longer dedicated video on this topic you should watch) this is a pretty big deal. Basically the suggestion is that for the time being dark energy and accelerated expansion of the universe should not be regarded as settled science. I don't think the gravity wave detections being possibly false positives upends any scientific theories, it just leaves understanding where it was the day before the first gravity wave was allegedly detected.

[Ser Scot A Ellison]

2 hours ago, The Anti-Targ said:

Been following Sabine on Youtube and she seems pretty legit. And my physics PhD brother says she's the real deal. My bro was also very skeptical about dark energy when it was first declared to be real, and he thought the Nobel prize was premature.

The gravity wave thing isn't disproof of anything, and technically neither is the dark energy thing. But for the dark energy thing (she has a longer dedicated video on this topic you should watch) this is a pretty big deal. Basically the suggestion is that for the time being dark energy and accelerated expansion of the universe should not be regarded as settled science. I don't think the gravity wave detections being possibly false positives upends any scientific theories, it just leaves understanding where it was the day before the first gravity wave was allegedly detected.

Hold on.  Don't we use the "Standard Candle" of these types of supernova to estimate the size and age of the Universe as well?  If the Dark Energy result is now in doubt aren't our estimates about the size and age of the Universe also in doubt as well?

[kiko]

I wouldn't go so far yet. For me Dark Energy is just a nice explanation for certain things where we are still absolutely unsure. But too many Dark entities right  now for my taste.

It's a theory that might not survive much longer. Hopefully something better and ideally less intricate will come along.

[Larry of the Lawn]

10 hours ago, Ser Scot A Ellison said:

Hold on.  Don't we use the "Standard Candle" of these types of supernova to estimate the size and age of the Universe as well?  If the Dark Energy result is now in doubt aren't our estimates about the size and age of the Universe also in doubt as well?

Maybe.  But only relative to accelerating expansion.  I'm guessing this would bring the math re: expanding universe back closer to Einstein or Abramowicz, not like it's going Newtonian.  

 

[Altherion]

13 hours ago, The Anti-Targ said:

The gravity wave thing isn't disproof of anything, and technically neither is the dark energy thing. But for the dark energy thing (she has a longer dedicated video on this topic you should watch) this is a pretty big deal.

She has videos about both topics and quite a few other things besides (including, for example, string theory and why building larger colliders is not the way to go). I've watched a bunch of them and her complaints about gravity waves boil down to two categories. The first is essentially about experimental sloppiness: the LIGO people won't say how they fitted the points on one of their most important plots to a curve and the way they're filtering out noise is questionable. This is a legitimate complaint and LIGO should eventually address it. The second is that we haven't yet seen an event where the gravitational signature was detected first and the electromagnetic signature later confirmed it. This is harder to address simply because we're much better at observing electromagnetic phenomena than we are with gravitational ones -- it might happen eventually, but unless somebody deliberately refrains from looking at neutron star collision data, one is dependent on things like order of publication so it probably won't be soon.

All of that said, as she mentions near the end of the longer gravitational waves video, this doesn't mean the gravitational waves aren't real and she personally does not doubt the measurements -- she just wants the LIGO people to clean up their act. The dark energy complaints are of a different order (see below).

11 hours ago, Ser Scot A Ellison said:

Hold on.  Don't we use the "Standard Candle" of these types of supernova to estimate the size and age of the Universe as well?  If the Dark Energy result is now in doubt aren't our estimates about the size and age of the Universe also in doubt as well? 

Not necessarily. The paper that first cast doubt on dark energy does not rely on anything being wrong with our understanding of individual supernovas. It merely says that if one looks at the whole sky, the cosmic acceleration is not isotropic. Think about it this way: suppose there is a camera on an accelerating car that is going through a field of stationary floating balloons containing light bulbs of identical brightness. The camera is pointed opposite the direction of the car and upwards at the balloons and the video is transmitted to you, but you don't know that the camera is on a car -- all you can see are the balloons accelerating away from you. You then conclude that all of the balloons of the field are accelerating away from you and this is wrong, but it's not because something is wrong with the images of the balloons -- it's because your point of view is accelerating, but you have no way to know this.

This is more or less what happened here. As you can read in this summary of the paper, the original study only used about 60 supernovae whereas the new one uses 740 that are more evenly distributed. Now, this is far from the final word on the matter because there is other evidence for dark energy (e.g. baryon acoustic oscillations), but it does mean that the people who evaluate all of these measurements and fit them together have work to do.

All of that said, there is another paper which does question the use of supernovae as standard candles and this one is relatively new. This sounds much less plausible, but if it turns out to be true, then yes, all bets are off on a wide variety of measurements...

[The Anti-Targ]

Thanks for the further explanations @Altherion I didn't catch Sabine's LIGO video. She does some cool music videos too.

[The Anti-Targ]

Another study casting doubt on dark energy.

https://scitechdaily.com/very-existence-of-dark-energy-cast-in-doubt-after-new-high-precision-data/

Quote

this is the most direct and stringent test ever made for the luminosity evolution of SN Ia. Since SN progenitors in host galaxies are getting younger with redshift (look-back time), this result inevitably indicates a serious systematic bias with redshift in SN cosmology. Taken at face values, the luminosity evolution of SN is significant enough to question the very existence of dark energy. When the luminosity evolution of SN is properly taken into account, the team found that the evidence for the existence of dark energy simply goes away