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On Monday, NASA performed what’s called a wet dress rehearsal, or WDR, where they run through everything up until the actual launch without actually firing the boosters. If you’re a theatre person, as I used to be, this is final dress (which happens during the not-so-affectionately labelled “hell week” right before opening night): the costumes are on, the light cues must run on time, but it’s not quite the real thing.

WDR is important. As several NASA officials noted during a press conference on Tuesday, before WDR, all of the components of the rocket are tested piecewise, but this is the first time that they’re all put together and properly put through their paces. If a WDR goes poorly, it’s tough to say that it’s safe to then put crew on that spacecraft and light the proverbial candle.

And sadly, that’s what happened this time. Over the course of several hours of pumping fuel into the Space Launch System’s (SLS) tanks, leaks just kept popping up. Some of them were similar to the leaks that happened during Artemis I’s testing and launch a few years ago, and some were new. “We got a chance for the rocket to talk to us, and it did just that,” said SLS manager John Honeycutt during the press conference.

Leaks are extremely common in these dress rehearsals: liquid hydrogen and liquid oxygen need to be pumped through tubing and into the tanks, and their molecules are tiny and highly energetic, as Honeycutt explained. That means they can slip through even the smallest gaps that might form during manufacturing or happen while the rocket is rolling out to the launchpad. The next steps are for NASA engineers to investigate the leaks, trace them to their root causes and patch them up. There were also some other issues, including spotty communications among the ground preparation team, that will need to be solved before an actual launch.

If all had gone smoothly, we might have seen Artemis II go up this week or next. As it is, there will have to be another WDR and then potentially a launch next month. That’s the earliest launch window, though, and I wouldn’t bet on it – personally, I’d wager it’ll go up around late April, but that’s just a guess. Space flight industry folks love to say “space is hard”, but this sort of thing is just another reminder that it really is, even when we’re trying to replicate a feat we’ve already achieved before.

Credit: NASA/JPL/Malin Space Science Systems

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SpaceX says it wants to deploy an astronomical number of data centres in orbit to supply power for artificial intelligence, but the proposal might not be entirely serious. Read more

JWST has created a map of dark matter that is twice as good as anything we have had before, and it may help unravel some of the deepest mysteries of the universe. Read more

Credit: Image: NASA, ESA, CSA, STScI; Image Processing: Alyssa Pagan (STScI)

To me, this image looks like spores coming off a mushroom, or maybe an artistic interpretation of runners starting a marathon. But it’s actually a close-up of part of the Helix nebula, and those “runners” are knots of hot hydrogen gas. They’re sculpted into their strange, evocative shape by the dying breaths of the star at the centre of the nebula when its powerful winds slam into shells of cooler gas emitted in earlier stages of its demise. In the dark pockets between the glowing “spores”, it’s just cool enough for dust to start coalescing into the building blocks of new worlds.

John asked: “When Andromeda and the Milky Way combine and their respective black holes spiral round each other, how disruptive will the resulting gravitational waves be to the orbits within solar systems?”

Let’s start with a few background facts that are important to know: the Andromeda galaxy and the Milky Way are on a collision course, and are due to smash together in around 5 billion years. When that happens, the supermassive black holes that the two galaxies host will spiral in towards one another, eventually merging into one even-more-supermassive black hole. This will create ripples in space-time called gravitational waves that will propagate outwards from the crash site.

The unfortunate answer to this question is that the gravitational waves probably won’t have any noticeable effects on individual solar systems. Anything that’s close enough for the waves to mess up will be much more significantly affected by the actual gravity of the black holes, which will probably rip apart any solar systems that get too close. But if you’d like to hear more about what gravitational waves could do to a planet under pretty unrealistic conditions designed to create the maximum possible effect, there’s a really fun episode of New Scientist’s Dead Planets Society podcast about that – listen here.

Credit: Ryan Wills for New Scientist/Adobe Stock

What if time doesn't tick the way we think it does? A once-speculative idea from the 1980s, known as the Page-Wootters mechanism, suggests that the passage of time is an illusion created by quantum entanglement. Now, researchers are building real-world versions of this abstract idea using tiny atomic clocks and delicate quantum systems. They’ve shown that even in a “timeless” quantum state, something clock-like can still tick. Some even believe black holes could be the ultimate cosmic timekeepers. This deep dive into the strange world of quantum clocks shows how time might not be fundamental to the universe, but something that emerges from a deeper static universe. Read more

Thank you for reading! If you have any comments, questions or wild hypotheticals about space, let me know by emailing me at launchpad@newscientist.com and I’ll try to answer them in an upcoming newsletter.

Also, there are a bunch of solar eclipses coming up in the next couple of years! I’ll be seeing a couple of them with New Scientist Discovery Tours, along with eclipse expert Jamie Carter. If you want to learn more about the eclipses themselves and how best to view them, Jamie is giving a free virtual talk on 26 February – you can register here.

And remember… Even though Andromeda and the Milky Way are set to collide, it’s incredibly unlikely that any of the stars in the two galaxies will actually hit each other. I think that’s an absolutely mind-boggling demonstration of how big and empty space is. Some stars might get chucked into intergalactic space through gravitational interactions, though, and that’s good enough for me.