Parachutes, Eye Drops and a Comet That Fell Into the Sun

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Cold open

0:24Host 1Welcome to the Hastrup Review of Science — where artificial intelligence reads real science, so you don't have to pretend you understood the paper.

0:34Host 1This week's best story: radio astronomers caught a comet's chemistry in the last three days before the Sun tore it apart.

0:42Host 2And around it, five careful human studies, most of which find smaller effects than the marketing around them would suggest. That is useful to know.

Parachute sprinting

0:53Host 1Let's start on the track. Sprinters tow small parachutes behind them in training. Does that actually make anyone faster?

1:00Host 2A new systematic review in Sports Medicine Open pulled together every study it could find: seventeen, eight looking at a single session and nine at training blocks. In a single session the parachute slows you by roughly three and a half to six percent, and bigger chutes slow you more.

1:18Host 1So it works as an overload. What about the training studies?

1:22Host 2The cleanest one randomised sixteen trained sprinters to parachute or normal sprints for four weeks, and the parachute group improved more over the first ten and twenty metres. The widely quoted gain of six tenths of a second over a hundred metres came from a group of five students with no randomisation.

1:41Host 2Here is the caveat, and the authors state it themselves: the review's own grading rates the evidence low to very low on every outcome. Small samples, parachute loads that nobody measured, and several programmes that mixed the chute with sleds and weights.

1:57Host 1So for a masters sprinter, it's a cheap tool that probably helps acceleration, but nobody knows the right dose yet.

2:04Host 2That is a fair summary. The full story is in this paper's deep dive, out this week in the feed.

Who sleeps in your bed

2:11Host 1Next, the bedroom. Does sleeping with a dog, a cat or a child change how you sleep?

2:16Host 2This study used one point six five million nights from eleven thousand seven hundred and thirty-three people wearing a fitness strap, who logged each night whether a dog, cat or child was in the room. The key design choice is within-person: each person's nights with company are compared with their own nights alone.

2:36Host 2On nights with a dog, resting heart rate was about one point one beats per minute lower and heart rate variability about two milliseconds higher. Sleep was about five to ten minutes longer, but with slightly more disturbances, and children caused the most disruption.

2:54Host 1One beat per minute sounds small. Is it?

2:57Host 2It is small, and the authors say so: every standardised effect was very small, between point zero zero eight and point zero four five. The caveats are that co-sleeping was self-reported, up to fifty-five percent of child nights had no journal entry, and the study was funded by the wearable company, with two authors on its staff.

3:18Host 1So the honest takeaway is: let the dog stay or go for your own reasons.

3:22Host 2Exactly. The deep dive on this one is out this week in the feed.

Atropine for myopia

3:27Host 1Now something every parent of a short-sighted child will want to hear. Atropine eye drops are used to slow myopia. Does the dose matter?

3:36Host 2This double-blind trial in Shanghai randomised two hundred and nineteen children aged six to twelve, all with high myopia of at least minus five dioptres, to nightly drops at point zero one, point zero four or point one percent, for two years. Myopia progressed by point nine two, point seven eight and point five six dioptres respectively.

3:57Host 1So the strongest drop slowed it the most. By how much compared with the weakest?

4:03Host 2By a third of a dioptre over two years, with a confidence interval from point one two to point five eight. The middle dose helped at twelve months but was no longer clearly better at twenty-four, and the eyeball growth difference also faded to non-significance by the second year.

4:20Host 2The price was light sensitivity: about twenty-one percent on the strongest drop, against eight percent on the weakest. And the caveat: there was no untreated group, so everything is relative to a low dose that is itself active, and all the children were in one Chinese city. The full story is in this paper's deep dive, out this week in the feed.

A word from our sponsor

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Qi Gong versus CBT online

5:44Host 1Back to the science. Mood and the body: can moving the body treat depressed mood as well as changing your thinking?

5:51Host 2A German team randomised three hundred and three adults with depressive symptoms to one of three arms. An online programme of Qi Gong plus behavioural activation, an established online cognitive behavioural programme, or a waitlist.

6:05Host 2On the total depression score, both programmes beat the waitlist by about two and a quarter points on a twenty-seven point scale, a moderate effect size of point five four. The two programmes did not differ from each other at all.

6:18Host 1So the movement programme is as good as the thinking programme?

6:22Host 2On the total score, yes, but notice how it is presented. The preregistered outcome was that total score, yet the paper leads with a split into bodily and emotional symptoms, where only the cognitive programme clearly beat the waitlist on the emotional items; the preregistered result sits in the appendix. Also, fewer than half finished even half the modules.

6:44Host 1So it is another option, not a better one.

6:47Host 2That is how the authors put it too. The deep dive on this trial is out this week in the feed.

Brain training and transfer

6:53Host 1Brain-training apps for older adults with mild memory problems. If you get better at the game, does anything else in daily life improve?

7:02Host 2This meta-analysis asked exactly that, and only that. It excluded improvement on the trained tasks themselves and looked at transfer: to similar untrained tests, to unrelated skills, and to everyday function, both right after training and at least twelve weeks later.

7:20Host 2They found eight randomised trials with seven hundred and twenty-two people. Immediate far transfer looked like a small effect of point two three, but one trial drove it; remove that trial and it falls to zero. Twelve weeks on, both kinds of cognitive transfer sat near zero, rated moderate certainty.

7:39Host 1And everyday life, managing money or medication?

7:43Host 2Only three trials measured it, and the estimate slightly favoured the control groups, though with wide uncertainty. The caveat runs both ways: no trial was at low risk of bias and the evidence base is small, so a modest benefit is not ruled out, but none has been shown. The full story is in this paper's deep dive, out this week in the feed.

The comet that fell into the Sun

8:06Host 1And finally, the comet. What is a sungrazer, and why does this one matter?

8:10Host 2Kreutz sungrazers are fragments of one ancient comet that skim the Sun at a few solar radii. Comet MAPS, about four hundred metres across, was discovered in January and due to pass less than a million kilometres from the Sun's centre. It disintegrated two hours before that closest approach, on April the fourth.

8:30Host 2A French-led team used the IRAM thirty-metre radio telescope in Spain on the three days before, and made the first millimetre-wave molecular detection in any sungrazer: hydrogen cyanide. Production rose nearly five-fold from the second day to the third, with an outburst the day before the break-up.

8:48Host 1How can they tell how much of the comet was lost in that outburst?

8:52Host 2Hydrogen cyanide survives only about twelve minutes that close to the Sun, so each spectrum counts freshly released molecules. Adding them up gives about a hundred tonnes of hydrogen cyanide, and with standard assumptions about water and dust, between point four and one point two percent of the whole comet.

9:11Host 2The caveat is that this mass estimate rests on borrowed averages, and the letter is accepted by a journal but still a preprint, with only one molecule detected. The full story is in this paper's deep dive, out this week in the feed.

Sign-off

9:26Host 1That's the Hastrup Review of Science for this week.

9:29Host 2Read carefully, train sensibly, and we will see you next week.