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Ozone Layer Trouble, One Moon-Crater Too Many, & the Hubble Tension Bites Back
🕑 Added 2023-11-29 23:44:45 +0000 UTCOzone Layer Trouble
Left: Ozone layer illustration. Right: NASA images a hole in the Ozone layer.
A group of scientists in New Zealand says that the ozone layer is not recovering as expected. According to their recent study, the problem is being aggravated by bushfires, volcanic eruptions, and greenhouse gas emissions. Up to now, scientists thought that the Montreal Protocol had been successful in initiating ozone recovery, but the scientists now say that the change in total column ozone (TCO) is statistically insignificant. Their study raises a question as to whether we are seeing the absence of a recovery or merely a temporary disruption due to a series of unlucky events.
Regardless of cause, this spring the European Space Agency reported one of the largest ozone layer holes on record to date (see here). Press release here, paper here.
Mystery of Crashed Chinese Moon Lander Deepens
Two impact craters on the Moon. Image Credit: NASA / Lunar Reconnaissance Orbiter.
A team of researchers at the University of Arizona recently released a study weighing in on the identity of an object that crashed into the Moon in March last year. The suspects have been either Falcon9 from NASA’s DISCOVR mission or the Long March 3C from China’s Chang’e 5-T1 mission. The authors of the new study now say the object was undoubtedly the Chinese space Rocket Long March 3C, but it seems that a mysterious unknown payload was attached to the rocket.
The scientists arrived at this conclusion by comparing the observed spin period of the object before it crashed with a simulation. This revealed that the Chinese Long March 3C would indeed have crashed in the right place. Their results also indicated that an additional mass – an undisclosed payload – had been attached to the rocket’s body. This fits well with a second impact crater located by NASA’s orbiter about a hundred metres away from the first crater.
Press release here, paper here.
New Twist on Hubble Tension: Early Dark Energy Models Don’t Work
Image Credit: https://www.explainxkcd.com/wiki/index.php/2516:_Hubble_Tension, Creative Commons NC 2.5
A study led by a graduate student at Columbia University in New York with other physicists at Columbia in Cambridge, U.K. has just overturned the most popular explanation for the Hubble Tension, the currently most troublesome data anomaly in cosmology.
A bit of background: If you want to understand the history, evolution, and ultimate fate of our universe, you’ll need to know how fast it’s expanding: The current rate of expansion is known as the Hubble constant. The trouble is that different measurements of this constant give different results. For example, if you extract the constant from observations of nearby astronomical objects such as cepheid variable stars or supernovae, the value is roughly 74 km/s/Mpc. But if you extract it from the cosmic microwave background radiation, you get about 67 km/s/Mpc.
On the theory side, the currently most popular method to resolve this tension is the Early Dark Energy (EDE) hypothesis. According to this idea, Dark Energy is not a constant, but more of it was around in the early universe.
However, the team of astrophysicists in New York and Cambridge has now demonstrated that the EDE hypothesis comes at the cost of a mismatch in predictions of known structural data of our current universe, including quasar background spectra. The authors instead consider the possibility that the Hubble tension could instead be entirely a result of systematic error (for example, some of the standard candles in use maybe aren’t actually standard or maybe there are systematic errors in velocity models). Press release here, paper here.
Comments
OK, I'm late to the discussion, but I'll go out on a limb here and ask my question anyway. 67 km/s/Mpc, at cosmic background radiation (CMB) scale, is less than 74 km/s/Mpc, at nearer scale. This seems to say that the expansion in the early universe was less than that closer to today. So, if the expansion is due to dark energy, wouldn't the CMB "constant" have to be greater at the CMB scale? What obvious thing am I missing from the article and the idea of dark energy?
This is exactly where I'm at, Rad. One of my big takeaways from Sabine's interview with Subir Sarkar is the degree to which systematics can (possibly) skew any result. I think that the "tension" is interesting, but it could also go away if the correct (unbiased?, differently biased?) subset of data are used.
Rad Antonov
I’d love to hear Tracey chime in on the Hubble tension. As pointed out, there is the reliability question of the standard candles to establish a distance ladder, but are there assumptions that go into extracting the Hubble constant from the CMB that could also be a culprit for the discrepancy?
