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Cosmic inflation predict their current height. just beating a dead horse.
Each time these measurements
“It depends how tender you want
are updated, they conflict. By your dead horse, but we really
mystery deepens 2016, Cepheid measurements need to do this due diligence if
done by Adam Riess at the Space
we are going to say that resolving
Telescope Science Institute in this tension requires new
Baltimore, Maryland, and his physics,” says Riess. “We need
Leah Crane and a supernova in the same team resulted in a value 9 per cent a really tender dead horse.”
galaxy. They mathematically higher than the CMB method. If the results aren’t down to
THE heat death of the universe is remove other sources of motion Now, Riess and his colleagues measurement error, it is a big
coming for us, but we don’t know to figure out how much is due to have used the Hubble Space deal. It could mean that our
when. The cosmos is expanding, the expansion of the cosmos. Telescope to measure the distances guesses about the natures of
and the speed of that inflation is If you think of the universe to seven Cepheid variable stars dark matter and dark energy are
measured by a value called the as a person, the Cepheid method with greater precision than before. wrong, or that there is a particle
Hubble constant. We have two is like measuring their height Even with a better measuring out there that we have never
ways to determine this rate, with a measuring tape, whereas tape, the problem persists. detected. “It’s starting to become
and they return different values, the CMB method is like taking This pushes the Hubble that either there’s new physics or
leaving cosmologists at an a picture of the person as a constant higher by nearly 0.3 per there’s a conspiracy of errors
impasse. A new study has baby and running it through a cent (arxiv.org/abs/1801.01120). across many different ways of
deepened the divide, leaving model of how humans grow to Refining the value in this way isn’t measuring that have nothing to
us in the dark about when the do with each other,” says Riess.
universe’s frigid end might be. The uncertainties in Cepheid
One way we search for the variable measurements will take
Hubble constant is to start at another beating in upcoming
the beginning. We can look at the months and years as the Gaia
cosmic microwave background space observatory measures
(CMB) – a relic of the first light to the distances to many stars,
cross the cosmos after the big including Cepheid variables,
bang – and see how fast the in and around our galaxy.
universe was expanding then. “This paper has seven more
Models of how the cosmos has measurements – Gaia is going to
evolved can predict how it release one billion,” says Barry
should be expanding today. Madore at the Carnegie Institution
The other method is more for Science in Washington DC.
direct. We track a spot in our HUBBLE LEGACY ARCHIVE, ESA, NASA; PROCESSING - JEFF SIGNORELLI The Gaia data may resolve the
galaxy’s neighbourhood to see tension or worsen it. But in terms
how quickly it is moving away of measuring the universe’s
from us. To do this, astronomers growth like a person’s, it won’t
monitor two things: a type of star just improve the measuring
called a Cepheid variable, which tape, it will also give us a billion
cyclically dims and brightens, different heights to compare. ■

Alien mountains Astronomical Society on 11 January. No current instrument has enough To best separate signal from noise,
The rocky planets in our solar resolution to extract that kind of exoplanet and star should be similar
can appear in system are not perfectly round: there detail. Upcoming large telescopes, like in size. Flares, star spots or exomoons
are mountains, canyons and craters. the European Extremely Large could throw in random glitches that
planet shadows McTier used US Geological Survey Telescope, will be just barely up to the mimic a small mountain or crater.
maps of these planets and the moon task of judging whether some of the Or a seismological event – an alien
THERE are stunning mountain ranges to determine what their light curve bumps in the data are simply natural earthquake – might alter the planet’s
on Earth, Mars and even Pluto. But around the sun would look like. artefacts of light. On next-generation shadow as it passes its star.
what about worlds further afield? She also factored in Earth with telescopes, it would take 20 hours of But if McTier’s plan does work, we
Moiya McTier at Columbia and without oceans. When the shape transit data, gathered as planets pass would have rough topographic maps
University in New York says that by of a shadow was analysed, McTier their stars, to distinguish features. of distant worlds, and might learn
analysing the dip in a star’s light as a found that landscape features might more about exo-oceans or even use
planet passes in front of it, we could show up as bumps in the data, “We could have rough maps surface features to study a planet’s
discern details about the planet’s corresponding to sharp rises or drops of exo-oceans or even use rotation rate – figuring out how long
landscape. She presented her in elevation. The idea is, however, a tall mountains to estimate a day is could bolster the case for a
research at a meeting of the American few generations from being testable. the length of an alien day” planet’s habitability. John Wenz ■

8 | NewScientist | 20 January 2018