Mystery fans know that the best way to solve a mystery is to revisit the scene where it began and look for clues. To understand the mysteries of our universe, scientists are trying to go back as far they can to the Big Bang. A new analysis of cosmic microwave background (CMB) radiation data by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) has taken the furthest look back through time yet – 100 years to 300,000 years after the Big Bang – and provided tantalizing new hints of clues as to what might have happened.
“We found that the standard picture of an early universe, in which radiation domination was followed by matter domination, holds to the level we can test it with the new data, but there are hints that radiation didn’t give way to matter exactly as expected,” says Eric Linder, a theoretical physicist with Berkeley Lab’s Physics Division and member of the Supernova Cosmology Project. “There appears to be an excess dash of radiation that is not due to CMB photons.”
[msa-ads data-ad-client=”ca-pub-6965588547261395″ data-ad-slot=”7732882042″]
Our knowledge of the Big Bang and the early formation of the universe stems almost entirely from measurements of the CMB, primordial photons set free when the universe cooled enough for particles of radiation and particles of matter to separate. These measurements reveal the CMB’s influence on the growth and development of the large-scale structure we see in the universe today.
Linder, working with Alireza Hojjati and Johan Samsing, who were then visiting scientists at Berkeley Lab, analyzed the latest satellite data from the European Space Agency’s Planck mission and NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), which pushed CMB measurements to higher resolution, lower noise, and more sky coverage than ever before.
“With the Planck and WMAP data we’re really pushing back the frontier and looking further back in the history of the universe, to regions of high energy physics we previously could not access,” Linder says. “While our analysis shows the CMB photon relic afterglow of the Big Bang being followed mainly by dark matter as expected, there was also a deviation from the standard that hints at relativistic particles beyond CMB light.”
Linder says the prime suspects behind these relativistic particles are “wild” versions of neutrinos, the phantomlike subatomic particles that are the second most populous residents (after photons) of today’s universe. The term “wild” is used to distinguish these primordial neutrinos from those expected within particle physics and being observed today. Another suspect is dark energy, the anti-gravitational force that accelerates our universe’s expansion. Again, however, this would be from the dark energy we observe today.
The microwave sky as seen by Planck. Mottled structure of the CMB, the oldest light in the universe, is displayed in the high-latitude regions of the map. The central band is the plane of our galaxy, the Milky Way. (Courtesy of European Space Agency)
“Early dark energy is a class of explanations for the origin of cosmic acceleration that arises in some high energy physics models,” Linder says. “While conventional dark energy, such as the cosmological constant, are diluted to one part in a billion of total energy density around the time of the CMB’s last scattering, early dark energy theories can have 1-to-10 million times more energy density.”
Linder says early dark energy could have been the driver that seven billion years later caused the present cosmic acceleration. Its actual discovery would not only provide new insight into the origin of cosmic acceleration, but perhaps also provide new evidence for string theory and other concepts in high energy physics.
“New experiments for measuring CMB polarization that are already underway, such as the POLARBEAR and SPTpol telescopes, will enable us to further explore primeval physics, Linder says.
Linder, Hojjati and Samsing are the authors of a paper describing these results in the journal Physical Review Letters titled “New Constraints on the Early Expansion History of the Universe.” Hojjati is now with the Institute for the Early Universe in South Korea, and Samsing is with the DARK Cosmology Centre in Denmark.
This research was primarily supported by the DOE Office of Science.
For more about the Supernova Cosmology Project go here
Everyone knows that relativity plays hell with time, and that it can do a number on space, but what about mass? Why do objects get more or less mass depending on their relative speed? We’re going to give you a quick explanation of why running can make you gain weight. No, we don’t think it’s fair either.
At this point most people know, thanks to Einstein, that two people can experience their own version of time, and that their times vary depending on how fast they’re moving relative to each other. If you were to clone yourself and send your clone on a rocket ship moving past you very fast, your clone would experience slower time relative to you. You would be stuck on some stationary place, your seconds ticking away, while watching your ingrate clone shaking their youthful ass on a rocket around the stars. Here’s some consolation, though. That ass would be a little bit more massive than yours.
This is one of the many quirks of relativity. Once you mess with time and space, you mess with almost everything else as well. Some say that, since mass and energy are equivalent, making an object move faster increases its energy, which increases its mass. Actually, the idea of objects picking up mass with speed is more of a thought experiment that takes place on the very rocket ship we’re watching.
Your clone gets lonely and clones themself. The two clones, exactly equal in mass and wearing the same clothing, get in a fight. They both attack with a flying jump kick, collide comically in mid-air, and come to a stop, their faces smashed against each other. From their perspective, this was a perfect example of the conservation of momentum. The conservation of momentum is a principle that states that overall, the momentum of a system has to stay the same. When you push something forward, you feel an equivalent push backward. The clones, each having a mass of, say, 100 kilograms, fly at each other at five meters a second – one flying to the left, and one flying to the right. That’s an equivalent momentum flying in each direction, and it averages out to no momentum. When they collide they stop entirely, they keep the momentum of the system at zero. Momentum is conserved.
Or at least, it is conserved for the clones. After you’ve finished rolling on the floor, laughing and yelling, “You’re not so pretty anymore,” you realize that something is wrong. As they flew at each other, one clone was moving with the ship’s motion, and one was moving against the ship’s motion. And we’ve already learned that time doesn’t work the same if people are going at different speeds relative to you. The clone moving against the motion of the rocket had to be experiencing slightly faster time compared to you, and the one moving with the rocket ship has to be experiencing slightly slower time compared to you. (Because of other quirks of relativity, they’re not going across the same stretch of space, either.) And because of the motion of the rocket ship itself, the entire thing is working in a slightly different time system. This means that the perfect symmetry and the resulting conservation of momentum that the clones experienced doesn’t apply to your perspective. To you, the clones either created or destroyed momentum.
Until you somehow measure their mass. That’s when you realize that the twin that’s moving faster, relative to you, is just a little bit more massive. The one that’s moving slower relative to you, is just a little bit less massive. This difference in mass counterbalances the time and space distortions, and allows momentum to be conserved. The experiment can work from the perspective of the clones, as well. If they decided to each build rocket ships and ram each other at some speed comparable to the speed of light, and then bounce away like they’re in bumper cars, they’d see each other moving in different time and over different distances after the collision, and only messing with mass would conserve momentum.
It sounds silly, but it has been observed experimentally. Electrons flying through cathode rays are a bit more massive than electrons at rest. Particles moving through accelerators are more massive than ones just sitting around. This slight difference in mass has been observed consistently since 1908. Of course, it can never make that much of a difference at the speeds at which humans move. But it is there. Relativity messes with our sense of the universe once again.