Time is relative, as they say, particularly for mid-day meals. As special relativity shows, the measure of any two clocks depends on their motion relative to each other. The greater their relative speed, the slower each clock is relative to each other. So, since we see distant galaxies speeding away from us, we should also see time move more slowly. Right?
While that is true, we should be careful not to confuse what is going on. One of the central ideas to note is that each observer will experience time at the standard rate. Look at your watch while speeding along in a rocket, and the seconds will tick away just as they always do. The same is true for an observer on Earth. It’s only when an observer on Earth and on a speeding rocket compare their watches that things get confusing. Each observer thinks the other has a slow watch.
The other thing to keep in mind is that special relativity doesn’t apply globally when things like gravity and dark energy come into play. For that, you need general relativity, but the results are much the same. In the case of distant galaxies, they aren’t speeding away from us through space like a rocket. Instead, space itself is expanding between us and those galaxies. Because of this cosmic expansion, the light from them is shifted to the red, hence their high redshift. This cosmic expansion also stretches the apparent time between ticks and tocks, making the rate of time in those galaxies appear slower to us.
Because of this, one of the predictions of cosmology is that when we look at distant objects, peering into the deep and past universe, time should appear to move more slowly. From our vantage point, time was slower in the early universe. Much slower.
Strange as this is, we have evidence to support it. When we look at distant supernovae, we see a time dilation effect. Type Ia supernovae are used as standard candles because they have a consistent maximum brightness, but they also have a consistent light curve, meaning that they all brighten and fade over a similar period of time. Astronomers have shown that the more distant a Type Ia supernova, the more stretched out its light curve is. In other words, it takes longer for a distant supernova to brighten and fade than a closer supernova. Time appears to slow down with distance.
According to the standard cosmological model, this correlation between distance and time dilation should hold all the way back to the cosmic microwave background. And while all the evidence we’ve gathered supports that theory, our evidence has been somewhat limited. The most distant supernovae we’ve observed come from a time when the universe is a bit less than 4 billion years old. But a new study has proven the model for even greater distances, thanks to quasars.
Supernova light curve width vs cosmic distance. Credit: Goldhaber, et al
Quasars are tremendously powerful active galactic nuclei (AGNs) powered by supermassive black holes in early galaxies. They are called quasars or quasi-stellar objects because they were first discovered as bright points of radio light. Quasars don’t emit light in a single burst like supernovae, but they do have a kind of timing clock to them. Because of the finite speed of light, it takes a bit of time for effects to travel across the span of an AGN. Because of this, fluctuations in the intensity of a quasar depend on the size of the AGN. So quasars of the same size fluctuate in intensity at the same rate.
Before this recent study, there wasn’t a way to distinguish whether slower fluctuating quasars were an effect of time dilation, or whether they were simply larger AGNs. So the team looked at 190 distant quasars at a range of wavelengths. They combined 20 years of data gathered at green, red, and infrared wavelengths and were able to create a standard measure of the tick-and-tock of quasar fluctuations. When they looked at the quasars by distance, statistically there was a correlation. The more distant the quasar, on average the slower its clock.
The study was able to extend time dilation observations all the way back to when the universe was just a billion years old. From our perspective, a second from that epoch appears to last five seconds. This agrees with general relativity and the standard cosmological model.
While not unexpected, the result is yet another wonderful way to show us that we understand cosmic evolution. Space really is expanding, powered by dark energy, and the universe really did begin with a big bang, where time appeared to move much more
Ingenuity Won’t Fly Again Because It’s Missing a Rotor Blade
Ingenuity has been the first aerial vehicle on another world. NASA announced the end of the Martian helicopter’s life at the end of its 72nd flight. During the flight there had been a problem on landing and, following the incident a few photos revealed chips in one of the rotor blades but nothing too serious. New images have been revealed that show the craft is missing one of its rotor blades entirely!
Mars Ingenuity was developed by NASA as a small lightweight drone that made history by becoming the first powered flight on Mars. It was part of the mission that took the Perseverance rover to Mars in February 2021. Undertaking powered flights in the thin Martian atmosphere it demonstrated that powered flight was possible as it surveyed the surrounding area for items of interest for further exploration.
Image of the Mars Ingenuity helicopter (Source : NASA)
The construction was the brainchild of the NASA Jet Propulsion Laboratory who oversaw the construction on behalf of the agency. NASA’s Ames Research Centre and Langley Research Center played a significant role in flight performance analysis and technical support.
On board the vehicle was some cutting edge technology that was tailored for the conditions on Mars. First of course, are the rotors, the thin atmosphere on Mars mean larger than usual blades were needed to generate the lift required. It was built with lightweight materials like carbon fibre to make it as efficient as possible, new and efficient solar cells that would drive the autonomous navigation systems. It was equipped with sensors and cameras to enable data collection of the Martian terrain to send back to Perseverance rover and controllers on Earth.
Ingenuity had been flying in a terrain with few rocks – which it uses in some part for navigation – and so had been experiencing difficulties. On 6 Jan it made an emergency landing because it couldn’t accurately identify its location. It happened again on the next flight but this time it seems to have come down at an angle and struck the ground with one of its rotors. Images suggested it had suffered some chips on one of the rotor blades however, recent images reveal the damage is more severe.
On 11 Feb, NASA used the black and white navigation camera to record a video showing the shadow of the rotors turning. It was an ingenious idea by the engineers to try and understand the extent of the damage to the 1.2m blades. To their surprise the footage revealed that one fo the blades, the upper blade seems to be absent! It looks like the blade detected near the mast.
Source : Ingenuity’s Navcam Reveals a Missing Rotor Blade
The post Ingenuity Won’t Fly Again Because It’s Missing a Rotor Blade appeared first on Universe Today.
Electrodes in Spacesuits Could Protect Astronauts from Harmful Dust on Mars
To quote NASA associate administrator Jim Reuter, sending crewed missions to Mars by 2040 is an “audacious goal.” The challenges include the distance involved, which can take up to six months to traverse using conventional propulsion methods. Then there’s the hazard posed by radiation, which includes increased exposure to solar particles, flares, and galactic cosmic rays (GCRs). And then there’s the time the crews will spend in microgravity during transits, which can take a serious toll on human health, physiology, and psychology.
But what about the challenges of living and working on Mars for several months at a time? While elevated radiation and lower gravity are a concern, so is Martian regolith. Like lunar regolith, dust on Mars will adhere to astronauts’ spacesuits and inflict wear on their equipment. However, it also contains harmful particles that must be removed to prevent contaminating habitats. In a recent study, a team of aerospace engineers tested a new electrostatic system for removing Martian regolith from spacesuits that could potentially remove harmful dust with up to 98% efficiency.
The new system was designed by Benjamin M. Griggs and Lucinda Berthoud, a Master’s engineering student and Professor of Space Systems Engineering (respectively) with the Department of Aerospace Engineering at the University of Bristol, UK. The paper that describes the system and the verification process recently appeared in the journal Acta Astronautica. As they explain, the Electrostatic Removal System (ERS) they propose utilizes the phenomenon of dielectrophoresis (DEP) to remove Martian dust from spacesuit fabrics.
Dust flies from the tires of a moon buggy, driven by Apollo 17 astronaut Gene Cernan. These “rooster-tails” of dust caused problems. Credit: NASA
Much like its lunar counterpart, Martian regolith is expected to be electrostatically charged due to exposure to cosmic radiation. But on Mars, there’s also the contribution made by dust devils and storms, which have been known to generate electrostatic discharges (aka. lightning). During the Apollo missions, astronauts reported how the lunar regolith would adhere to their suits and get tracked back into their Lunar Modules. Once inside, it would similarly stick to everything and get into their eyes and lungs, causing irritation and respiratory problems.
Given their plans to return astronauts to the Moon through the Artemis Program, NASA is investigating several methods to prevent regolith from getting into habitation modules – like coating technology for spacesuits and electron beams for cleaning them. While Martian dust is expected to inflict similar wear on spacesuits, the situation is made worse because it may contain toxic particles. As Griggs explained to Universe Today via email:
“Beyond having an abrasive effect on spacesuits themselves, Martian regolith is also expected to present health issues to astronauts. It is known to contain a range of harmful particles which may be carcinogenic or cause respiratory issues, and data from the Pathfinder mission showed the presence of toxic particles such as chromium. Martian regolith will therefore require removal from spacesuits prior to entry into habitation zones on Mars to prevent contact between astronauts and regolith particles.”
The principle behind the device, dielectrophoresis (DEP), refers to the movement of neutral particles when subjected to a nonuniform electric field. Their proposed Electrostatic Removal System (ERS) comprises two components: a High Voltage Waveform Generator (HVWG) used to produce square waves of varying frequencies and amplitudes up to 1000 volts and an Electrostatic Removal Device (ERD) consisting of an array of parallel copper electrodes. When the square waves are applied across the electrodes in the ERD, a large and varying electric field is generated. As Griggs summarized:
“Therefore, when dust particles are incident on the surface of the ERD, the dust particles are displaced through a combination of electrostatic and dielectrophoretic forces (due to the large electric field), which acts on charged and uncharged particles respectively within the dust. This acts to displace dust particles in a direction perpendicular to the electrodes, resulting in the clearing of the ERD surface.”
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If Exoplanets Have Lightning, it’ll Complicate the Search for Life
Discovering exoplanets is almost routine now. We’ve found over 5,500 exoplanets, and the next step is to study their atmospheres and look for biosignatures. The James Webb Space Telescope is leading the way in that effort. But in some exoplanet atmospheres, lightning could make the JWST’s job more difficult by obscuring some potential biosignatures while amplifying others.
Detecting biosignatures in the atmospheres of distant planets is fraught with difficulties. They don’t advertise their presence, and the signals we receive from exoplanet atmospheres are complicated. New research adds another complication to the effort. It says that lightning can mask the presence of things like ozone, an indication that complex life could exist on a planet. It can also amplify the presence of compounds like methane, which is considered to be a promising biosignature.
The new research is “The effect of lightning on the atmospheric chemistry of exoplanets and potential biosignatures,” and it’s been accepted for publication in the journal Astronomy and Astrophysics. The lead author is Patrick Barth, a researcher from the Space Research Institute at the Austrian Academy of Sciences.
While we’ve discovered over 5,500 exoplanets, only 69 of them are in the potentially habitable zones around their stars. They’re rocky planets that receive enough energy from their stars to potentially maintain liquid water on their surfaces. Our search for biosignatures is focused on this small number of planets.
This is an artist’s illustration of the exoplanet TRAPPIST-1d, a potentially habitable exoplanet about 40 light-years away. Planets like these are prime targets for JWST’s spectrometry. Image Credit: By NASA/JPL-Caltech – Cropped from: PIA22093: TRAPPIST-1 Planet Lineup – Updated Feb. 2018, Public Domain, https://commons.wikimedia.org/w/index.php?curid=76364484
The important next step is to determine if these planets have atmospheres and then what the composition of those atmospheres is. The JWST is our most powerful instrument for these purposes. But in order to understand what the JWST shows us in distant atmospheres, we have to know what its signals tell us. Research like this helps scientists prepare for the JWST’s observations by alerting them to potential false positives and masked biosignatures.
This JWST spectra isn’t part of this research, but it shows how the powerful space telescope can
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