Check your watch, what time is it? But wait, you’ve actually been moving and accelerating, and according to Einstein, everything’s relative. So what time is it really? It all depends…
Flavor Flav knows what time it is. At least he does for Flavor Flav. Even with all his moving and accelerating, with the planet, the solar system, getting on planes, taking elevators, and perhaps even some light jogging. In the immortal words of Kool Moe Dee. Do you know what time it is?
Didn’t Einstein tell us it’s all relative? Does anyone actually know what time it is? I mean, aside from figuratively, or in a political sense, or perhaps as part of rap performance from whence the power is being fought from, requiring the sick skills of a hype man wearing a clock around his neck on a big chain.
So, after all my fancy dancing and longing for a time in rap and hip hop from days gone by, I must present to you “faithful audience member” an answer in the form of your 3 least favorite words I get to deliver.
It all depends…
You have heard that everything is relative, usually we hear it from people who like to talk about “connections on many different levels”, which is just nonsense.
But in physics “everything” is relative in a very particular way. Everything is relative to the speed of light, which is the same in every reference frame. Which is confusing and repeated enough that it can become meaningless.
So I’m going to do my best to explain it. If I shine a flashlight in front of me, I will measure the beam to travel at about 300,000 km/s, which is also known as the speed of light.
And if you are moving at 200,000 km/s faster than me, and shine a flashlight ahead of you, I will see the light from your flashlight moving at the 300,000km/s. It will appear to me, as though the light from your flashlight is moving away from you at 100,000 km/s.
But when you will measure the speed of that light, relative to you, you’d think it’d be moving at 100,000 km/s as well, but instead from your perspective it will ALSO clock in at 300,000 km/s.
The speed of light. How is this even possible? It is possible in part because the rate at which you experience time relative to me changes. For you, time will seem normal, but from my perspective your time will seem slower. We agree on how fast light is moving in kilometers per second, but we disagree how long a second is. We also, by the way, disagree on the length of a meter.
This seems strange because we imagine that space and time are absolute things, and light is something that travels through space. This is our experience. Suggesting things like time and space are malleable values at best is unsettling and at worst will make us nanners from thinking too much about.
Hold on to your tinfoil hats, for it is in fact light that is the absolute, and space and time are relative to it. So what time it is depends upon your vantage point, and so there is no single absolute time.
Finally, because of relativity, each point in the Universe experiences time at a slightly different rate. For example, when we observe the cosmic microwave background, we find that we are moving at a speed of about 630 km/s relative to the background. That means we experience time a bit more slowly that something at rest relative to the cosmic background.
It’s just a tiny bit slower, but added over the entire age of the Universe, our cosmic clock is 30,000 years behind the times. Feel free to set your watch. But don’t get too precise about it. Your time could be off by tens of thousands of years.
What about you? What’s your favorite way to explain special relativity to someone. Tell us in the comments below.
Astronomers have spotted, for the first time, a dense galactic core blazing with the light of millions of newborn stars in the early universe.
The finding sheds light on how elliptical galaxies, the large, gas-poor gatherings of older stars, may have first formed in the early universe. It’s a question that has eluded astronomers for decades.
The research team first uncovered the compact galactic core, dubbed GOODS-N-774, in images from the Hubble Space Telescope. Later observations from the Spitzer Space Telescope, the Herschel Space Observatory, and the W.M. Keck Observatory helped make this a true scientific finding.
The core formed 11 billion years ago, when the universe was less than 3 billion years old. Although only a fraction of the size of the Milky Way, at that time it already contained above twice as many stars as our own galaxy.
Theoretical simulations suggest that giant elliptical galaxies form from the inside out, with a large core marking the very first stages of formation. But most searches for these forming cores have come up empty handed, making this a first observation and a phenomenal find.
“We really hadn’t seen a formation process that could create things that are this dense,” explained lead author Erica Nelson from Yale University in a press release. “We suspect that this core-formation process is a phenomenon unique to the early universe because the early universe, as a whole, was more compact. Today, the universe is so diffuse that it cannot create such objects anymore.”
Alongside determining the galaxy’s size from the Hubble images, the team dug into archived far-infrared images from Spitzer and Herschel to calculate how fast the compact galaxy is creating stars. It seems to be producing 300 stars per year, a rate 30 times greater than the Milky Way.
The frenzied star formation likely occurs because the galactic core is forming deep inside a gravitational well of dark matter. Its unusually high mass constantly pulls gas in, compressing it and sparking star formation.
But these bursts of star formation create dust, which blocks the visible light. This helps explain why astronomers haven’t seen such a distant core before, as they may have been easily missed in previous surveys.
The team thinks that shortly after the early time period we can see, the core stopped forming stars. It likely then merged with other smaller galaxies, until it transformed into a much greater galaxy, similar to the more massive and sedate elliptical galaxies we see today.
“I think our discovery settles the question of whether this mode of building galaxies actually happened or not,” said coauthor Pieter van Dokkum from Yale University. “The question now is, how often did this occur?”
The team suspects that other galactic cores are abundant, but hidden behind their own dust. Future infrared telescopes, such as the James Webb Space Telescope, should be able to find more of these early objects.
Most scientists can see, hear, smell, touch or even taste their research. But astronomers can only study light — photons traveling billions of light-years across the cosmos before getting scooped up by an array of radio dishes or a single parabolic mirror orbiting the Earth.
Luckily the universe is overflowing with photons across a spectrum of energies and wavelengths. But astronomers don’t fully understand where most of the light, especially in the early universe, originates.
Now, new simulations hope to uncover the origin of the ultraviolet light that bathes — and shapes — the early cosmos.
“Which produces more light? A country’s biggest cities or its many tiny towns?” asked lead author Andrew Pontzen in a press release. “Cities are brighter, but towns are far more numerous. Understanding the balance would tell you something about the organization of the country. We’re posing a similar question about the universe: does ultraviolet light come from numerous but faint galaxies, or from a smaller number of quasars?”
Answering this question will give us a valuable insight into the way the universe built its galaxies over time. It will also help astronomers calibrate their measurements of dark energy, the mysterious agent that is somehow accelerating the universe’s expansion.
The problem is that most of intergalactic space is impossible to see directly. But quasars — brilliant galactic centers fueled by black holes rapidly accreting material — shine brightly and illuminate otherwise invisible matter. Any intervening gas will absorb the quasar’s light and leave dark lines in the arriving spectrum.
“Because they can be seen at such great distances, quasars are a useful probe for finding out the properties of the universe,” said Pontzen. “Distant quasars can be used as a backlight, and the properties of the gas between them and us are imprinted on the light.
Multiple clouds of intervening hydrogen gas leave a “forest” of hydrogen absorption lines in the quasar’s spectrum. But, crucially, not all gas in the universe contributes to these dark lines. When hydrogen is bombarded by ultraviolet light, it becomes ionized — the electron separates from the proton — which renders it transparent.
So the pattern of absorption lines visible in a quasar’s spectrum map out the location of neutral and ionized regions in between the quasar and the Earth.
This pattern will tell astronomers the main contributing light source in the early universe. Quasars are fairly limited in number but individually extremely bright. If they caused most of the radiation, the pattern will be far from uniform, with some areas nearly transparent and others strongly opaque. But if galaxies, which are far more numerous but much dimmer, caused most of the radiation, the pattern will be very uniform, with evenly spaced absorption lines.
Current samples of quasars aren’t quite big enough for a robust analysis of the subtle differences between the two scenarios. But Pontzen and colleagues show that a number of new surveys should shed light on the question.
The team is hopeful the DESI (Dark Energy Spectroscopic Instrument) survey, which will look at about a million distant quasars in order to better understand dark energy, will also show the distribution of intervening gas.
“It’s amazing how little is known about the objects that bathed the universe in ultraviolet radiation while galaxies assembled into their present form,” said coauthor Hiranya Peiris. “This technique gives us a novel handle on the intergalactic environment during this critical time in the Universe’s history.”
The paper was published Aug. 27 in the Astrophysical Journal Letters and is available online.
The young universe was composed of a pristine mix of hydrogen, helium, and a tiny trace of lithium. But after hundreds of millions of years, it began to cool and giant clouds of the primordial elements collapsed to form the first stars.
The first “Population III” stars were extremely massive and bright, synthesizing the first batches of heavy elements, and erupting as supernovae after relatively short lifetimes of just a few million years. This cycle of star birth and death has steadily produced and dispersed more heavy elements throughout cosmic history.
Astronomers haven’t spotted any of the first stars still shining today. But now, a team using the 8.2-meter Subaru Telescope has discovered an ancient low-mass star that likely formed from the elements produced in the supernova explosion of a very massive first generation star.
Pop III stars with masses exceeding 100 times that of the Sun would have died in a peculiar explosion that theorists call a pair-instability supernova.
Like its lower-energy comrade, a pair-instability supernova occurs when a massive star no longer produces enough energy to counteract the inward pull of gravity. But with so much mass, the star’s core is squeezed to such a high temperature and pressure that runaway nuclear reactions power a devastating explosion. The whole star is obliterated and no compact remnant, such as a black hole or neutron star, is left behind.
Astronomers have seen hints of these rare events before. But now, Wako Aoiki from the National Astronomical Observatory of Japan and colleagues have approached the search in a different way, by finding a star that bears the chemical fingerprints of these ancient explosions.
The elements we see lacing a star’s surface provide a key to understanding the supernova that preceded the star’s birth. And the star, dubbed SDSS001820.5-093939.2, exhibits a peculiar set of chemical abundance ratios. It has high levels of heavy elements, such as nickel, calcium, and iron, but low levels of light elements, such as carbon, magnesium and cobalt.
Note that the star is still metal poor in the grand scheme of things. Its iron abundance is 1/100 of the solar level. But compared with most metal-poor stars, where the iron abundance can be 1/100,000 or less of the solar level, the star is metal rich.
These odd fingerprints suggest the star formed from material seeded by the death of a very massive Pop III star. In fact, the chemical composition of the star matches the elements that pair-instability supernovae are predicted to create.
The team notes that this is the only star of about 500 in the same low-metallicity range that has this peculiar makeup. It is — at the moment — our only window into the early universe and the first generation of stars.
An international team of astronomers has obtained the best view yet of two galaxies colliding when the universe was only half its current age.
The team relied heavily on space- and ground-based telescopes, including the Hubble Space Telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), the Keck Observatory, and the Karl Jansky Very Large Array (VLA). But the greatest asset was a chance cosmic alignment.
“While astronomers are often limited by the power of their telescopes, in some cases our ability to see detail is hugely boosted by natural lenses created by the universe,” said lead author Hugo Messias of the Universidad de Concepción in Chile and the Centro de Astronomia e Astrofísica da Universidade de Lisboa in Portugal.
Such a rare cosmic alignment plays visual tricks, where the intervening lens (be it a galaxy or a galaxy cluster) appears to bend and even magnify the distant light. This effect, called gravitational lensing, allows astronomers to study objects which would not be visible otherwise and to directly compare local galaxies with much more remote galaxies, seen when the universe was significantly younger.
The distant object in question, dubbed H-ATLAS J142935.3-002836, was originally spotted in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). Although very faint in visible light pictures, it is among the brightest gravitationally lensed objects in the far-infrared regime found so far.
The Hubble and Keck images reveal that the foreground galaxy is a spiral galaxy, seen edge-on. Although the galaxy’s large dust clouds obscure part of the background light, both ALMA and VLA can observe the sky at longer wavelengths, which are unaffected by dust.
Using the combined data, the team discovered that the background system was actually an ongoing collision between two galaxies.
First, the team noticed that these two galaxies resembled a much closer system: the Antennae galaxies, two galaxies that have spent the past few hundred million years in a whirling embrace as they merge together. The similarity suggested a collision, but ALMA — with its high sensitivity and spatial resolution — was able to verify it.
ALMA has the unique ability to detect the emission from carbon monoxide, as opposed to other telescopes, which might only be able to probe the absorption along the line of sight. This allowed astronomers to measure the velocity of the gas in the more distant object. With this information, they were able to show that the lensed galaxy is indeed an ongoing galactic collision.
Such collisions naturally enhance star formation. Any gas within the galaxies will feel a headwind, much as a runner feels a wind even on the stillest day, and become compressed enough to spark star formation. Sure enough, ALMA shows that the two galaxies are forming hundreds of new stars each year.
“ALMA enabled us to solve this conundrum because it gives us information about the velocity of the gas in the galaxies, which makes it possible to disentangle the various components, revealing the classic signature of a galaxy merger,” said ESO’s Director of Science and coauthor of the new study, Rob Ivison. “This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst.”
The findings have been published in the Aug. 26 issue of Astronomy & Astrophysics and is available online.
Wow! Rosetta is getting ever-closer to its target comet by the day. This navigation camera shot from Aug. 23 shows that the spacecraft is so close to Comet 67P/Churyumov-Gerasimenko that it’s difficult to fit the entire 2.5-mile (four-kilometer) comet in a single frame.
“Until now, each NAVCAM image has covered the whole comet in one shot, but now that Rosetta is about 50 km [31 miles] from the comet, the nucleus is close to overfilling the NAVCAM field, and will do as we get even closer,” ESA stated.
“As a result, on Saturday [Aug. 23] we started taking NAVCAM image sequences as small 2 x 2 rasters, such that roughly one quarter of the comet is seen in the corner of each of the four images, rather than all in just one shot.”
ESA also noted there is a delay of about 20 minutes between the first and last images in the sequence, during which time both the comet and Rosetta are moving. This changes how the shadows and other things on the comet appear. ESA hasn’t yet made any software to create composite images, because it’s not needed for navigation (the primary reason the camera is there.)
While the stars appear unchanging when you take a quick look at the night sky, there is so much variability out there that astronomers will be busy forever. One prominent example is Eta Carinae, a star system that erupted in the 19th century for about 20 years, becoming one of the brightest stars you could see in the night sky. It’s so volatile that it’s a high candidate for a supernova.
The two stars came again to their closest approach this month, under the watchful eye of the Chandra X-Ray Observatory. The observations are to figure out a puzzling dip in X-ray emissions from Eta Carinae that happen during every close encounter, including one observed in 2009.
The two stars orbit in a 5.5-year orbit, and even the lesser of them is massive — about 30 times the mass of the Sun. Winds are flowing rapidly from both of the stars, crashing into each other and creating a bow shock that makes the gas between the stars hotter. This is where the X-rays come from.
Here’s where things get interesting: as the stars orbit around each other, their distance changes by a factor of 20. This means that the wind crashes differently depending on how close the stars are to each other. Surprisingly, the X-rays drop off when the stars are at their closest approach, which was studied closely by Chandra when that last occurred in 2009.
“The study suggests that part of the reason for the dip at periastron is that X-rays from the apex are blocked by the dense wind from the more massive star in Eta Carinae, or perhaps by the surface of the star itself,” a Chandra press release stated.
“Another factor responsible for the X-ray dip is that the shock wave appears to be disrupted near periastron, possibly because of faster cooling of the gas due to increased density, and/or a decrease in the strength of the companion star’s wind because of extra ultraviolet radiation from the massive star reaching it.”
More observations are needed, so researchers are eagerly looking forward to finding out what Chandra dug up in the latest observations. A research paper on this was published earlier this year in the Astrophysical Journal, which you can also read in preprint version on Arxiv. The work was led by Kenji Hamaguchi, who is with NASA’s Goddard Space Flight Center in Maryland.
How does microgravity affect your health? One of the chief concerns of NASA astronauts these days is changes to eyesight. Some people come back from long-duration stays in space with what appears to be permanent changes, such as requiring glasses when previously they did not.
And the numbers are interesting. A few months after NASA told Universe Today that 20% of astronauts may face this problem, a new study points out that 21 U.S. astronauts that have flown on the International Space Station for long flights (which tend to be five to six months) face visual problems.
These include “hyperopic shift, scotoma and choroidal folds to cotton wool spots, optic nerve sheath distension, globe flattening and edema of the optic nerve,” states the University of Houston, which is collaborating with NASA on a long-term study of astronauts while they’re in orbit.
NASA is flying an instrument on board the International Space Station that does optical coherence tomography, which acts like a microscope on the eye. The technology looks at things such as pressure in the eye and changes in the optic nerve and retinal structures.
The collaboration with the University of Houston recently won Heidelberg Engineering’s annual 2014 Xtreme Research Award. In the long term, the researchers involved are hoping to figure out what changes to make for long-duration missions. One example could be changing carbon dioxide levels on the station, if that is found to play a role.
Long-term health considerations will be one thing examined closely when an astronaut and a cosmonaut spend a year on the International Space Station in 2015, with their milestone bringing them in a small group of people who have spent a year or more consecutively in space.
What a gorgeous view of the dusty cloud of the Milky Way arch hovering over clouds low on the horizon here on Earth! Fellow NASA Solar System Ambassador Greg Redfern took this image of our galactic center in the constellation Sagittarius.
“If you have dark skies look to the south to see this grand spectacle,” Greg said via email. “It stretches across the entire sky.”
Greg shot the image during the Almost Heaven Star Party, an annual astronomy event sponsored by the Northern Virginia Astronomy Club. The star party is held in Spruce Knob, West Virginia, which boasts the darkest skies in the mid-Atlantic region of the US.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
In the ‘new race to space’ to restore our capability to launch Americans to orbit from American soil with an American-built commercial ‘space taxi’ as rapidly and efficiently as possible, Boeing has moved to the front of the pack with their CST-100 spaceship by completing all their assigned NASA milestones on time and on budget in the current phase of the agency’s Commercial Crew Program (CCP).
Boeing is the first, and thus far only one of the three competitors (including Sierra Nevada Corp. and SpaceX) to complete all their assigned milestone task requirements under NASA’s Commercial Crew Integrated Capability (CCiCap) initiative funded under the auspices of the agency’s Commercial Crew Program.
The CST-100 is a privately built, man rated capsule being developed with funding from NASA via the commercial crew initiative in a public/private partnership between NASA and private industry.
The overriding goal is restart America’s capability to reliably launch our astronauts from US territory to low-Earth orbit (LEO) and the International Space Station (ISS) by 2017.
Private space taxis are the fastest and cheapest way to accomplish that and end the gap in indigenous US human spaceflight launches.
Since the forced shutdown of NASA’s Space Shuttle program following its final flight in 2011, US astronauts have been 100% dependent on the Russians and their cramped but effective Soyuz capsule for rides to the station and back – at a cost exceeding $70 million per seat.
Boeing announced that NASA approved the completion of the final two commercial crew milestones contracted to Boeing for the CST-100 development.
These last two milestones are the Phase Two Spacecraft Safety Review of its Crew Space Transportation (CST)-100 spacecraft and the Critical Design Review (CDR) of its integrated systems.
The CDR milestone was completed in July and comprised 44 individual CDRs including propulsion, software, avionics, landing, power and docking systems.
The Phase Two Spacecraft Safety Review included an overall hazard analysis of the spacecraft, identifying life-threatening situations and ensuring that the current design mitigated any safety risks, according to Boeing.
“The challenge of a CDR is to ensure all the pieces and sub-systems are working together,” said John Mulholland, Boeing Commercial Crew program manager, in a statement.
“Integration of these systems is key. Now we look forward to bringing the CST-100 to life.”
Passing the CDR and completing all the NASA milestone requirements is a significant step leading to the final integrated design for the CST-100 space taxi, ground systems and Atlas V launcher that will boost it to Earth orbit from Space Launch Complex-41 on Cape Canaveral Air Force Station in Florida.
All three American aerospace firms vying for the multibillion dollar NASA contract to build an American ‘space taxi’ to ferry US astronauts to the International Space Station and back as soon as 2017.
NASA’s Commercial Crew Program office is expected to announce the winner(s) of the high stakes, multibillion dollar contract to build America’s next crew vehicles in the next program phase, known as Commercial Crew Transportation Capability (CCtCap), “sometime around the end of August/September,” NASA News spokesman Allard Beutel confirmed to me.
“We don’t have a scheduled date for the commercial crew award(s).”
There will be 1 or more CCtCAP winners.
On June 9, 2014, Boeing revealed the design of their CST-100 astronaut spaceliner by unveiling a full scale mockup of their commercial ‘space taxi’ at the new home of its future manufacturing site at the Kennedy Space Center (KSC) located inside a refurbished facility that most recently was used to prepare NASA’s space shuttle orbiters for assembly missions to the ISS.
The CST-100 crew transporter was unveiled at the invitation only ceremony and media event held inside the gleaming white and completely renovated NASA processing hangar known as Orbiter Processing Facility-3 (OPF-3) – and attended by Universe Today.
The huge 64,000 square foot facility has sat dormant since the shuttles were retired following their final flight (STS-135) in July 2011 and which was commanded by Chris Ferguson, who now serves as director of Boeing’s Crew and Mission Operations.
Ferguson and the Boeing team are determined to get Americans back into space from American soil with American rockets.
Read my exclusive, in depth one-on-one interviews with Chris Ferguson – America’s last shuttle commander – about the CST-100; here and here.
Boeing’s philosophy is to make the CST-100 a commercial endeavor, as simple and cost effective as possible in order to quickly kick start US human spaceflight efforts. It’s based on proven technologies drawing on Boeing’s 100 year heritage in aviation and space.
“The CST-100, it’s a simple ride up to and back from space,” Ferguson told me. “So it doesn’t need to be luxurious. It’s an ascent and reentry vehicle – and that’s all!”
So the CST-100 is basically a taxi up and a taxi down from LEO. NASA’s complementary human space flight program involving the Orion crew vehicle is designed for deep space exploration.
The vehicle includes five recliner seats, a hatch and windows, the pilots control console with several attached Samsung tablets for crew interfaces with wireless internet, a docking port to the ISS and ample space for 220 kilograms of cargo storage of an array of equipment, gear and science experiments depending on NASA’s allotment choices.
The interior features Boeing’s LED Sky Lighting with an adjustable blue hue based on its 787 Dreamliner airplanes to enhance the ambience for the crew.
The reusable capsule will launch atop a man rated United Launch Alliance (ULA) Atlas V rocket.
“The first unmanned orbital test flight is planned in January 2017… and may go to the station,” Ferguson told me during our exclusive interview about Boeing’s CST-100 plans.
Since 2010, NASA has spent over $1.5 billion on the commercial crew effort.
Boeing has received the largest share of funding in the current CCiCAP phase amounting to about $480 million. SpaceX received $460 million for the Dragon V2 and Sierra Nevada Corp. (SNC) has received a half award of $227.5 million for the Dream Chasermini-shuttle.
SNC will be the next company to complete all of NASA’s milestones this Fall, SNC VP Mark Sirangelo told me in an exclusive interview. SpaceX will be the final company finishing its milestones sometime in 2015.
Stay tuned here for Ken’s continuing Boeing, Sierra Nevada, SpaceX, Orbital Sciences, commercial space, Orion, Curiosity, Mars rover, MAVEN, MOM and more planetary and human spaceflight news.