Discovery that quasars don't show time dilation mystifies astronomers

Physorg ^ | 09 March 2010 | Lisa Zyga

[Lorianne]

The phenomenon of time dilation is a strange yet experimentally confirmed effect of relativity theory. One of its implications is that events occurring in distant parts of the universe should appear to occur more slowly than events located closer to us. For example, when observing supernovae, scientists have found that distant explosions seem to fade more slowly than the quickly-fading nearby supernovae.

The effect can be explained because (1) the speed of light is a constant (independent of how fast a light source is moving toward or away from an observer) and (2) the universe is expanding at an accelerating rate, which causes light from distant objects to redshift (i.e. the wavelengths to become longer) in relation to how far away the objects are from observers on Earth. In other words, as space expands, the interval between light pulses also lengthens. Since expansion occurs throughout the universe, it seems that time dilation should be a property of the universe that holds true everywhere, regardless of the specific object or event being observed. However, a new study has found that this doesn’t seem to be the case - quasars, it seems, give off light pulses at the same rate no matter their distance from the Earth, without a hint of time dilation.

Astronomer Mike Hawkins from the Royal Observatory in Edinburgh came to this conclusion after looking at nearly 900 quasars over periods of up to 28 years. When comparing the light patterns of quasars located about 6 billion light years from us and those located 10 billion light years away, he was surprised to find that the light signatures of the two samples were exactly the same. If these quasars were like the previously observed supernovae, an observer would expect to see longer, “stretched” timescales for the distant, “stretched” high-redshift quasars. But even though the distant quasars were more strongly redshifted than the closer quasars, there was no difference in the time it took the light to reach Earth.

This quasar conundrum doesn’t seem to have an obvious explanation, although Hawkins has a few ideas. For some background, quasars are extreme objects in many ways: they are the most luminous and energetic objects known in the universe, and also one of the most distant (and thus, oldest) known objects. Officially called “quasi-stellar radio sources,” quasars are dense regions surrounding the central supermassive black holes in the centers of massive galaxies. They feed off an accretion disc that surrounds each black hole, which powers the quasars’ extreme luminosity and makes them visible to Earth.

One of Hawkins’ possible explanations for quasars’ lack of time dilation is that light from the quasars is being bent by black holes scattered throughout the universe. These black holes, which may have formed shortly after the big bang, would have a gravitational distortion that affects the time dilation of distant quasars. However, this idea of “gravitational microlensing” is a controversial suggestion, as it requires that there be enough black holes to account for all of the universe’s dark matter. As Hawkins explains, most physicists predict that dark matter consists of undiscovered subatomic particles rather than primordial black holes.

There’s also a possibility that the explanation could be even more far-reaching, such as that the universe is not expanding and that the big bang theory is wrong. Or, quasars may not be located at the distances indicated by their redshifts, although this suggestion has previously been discredited. Although these explanations are controversial, Hawkins plans to continue investigating the quasar mystery, and maybe solve a few other problems along the way.

Hawkins’ paper will be published in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

More info: http://www3.interscience.wiley.com/journal/123345710/abstract?CRETRY=1&SRETRY=0

[Lorianne]

What if the speed of light is not a constant?

[ETL]

What if the speed of light is not a constant?

Over the age of the universe, it, like other universal constants, *may* have actually changed. There were/are? some astrophysicists who believe this to be possible. The important thing about the speed of light, however, is that it is believed to be the *universal speed limit*. i.e., light can travel slower than light speed when it passes through various materials.

Even the effects of gravity are limited to and travel at light speed. The Sun is about 8 light minutes away. And so if the Sun were to suddenly disappear, Earth wouldn't feel the gravitational effects for about 8 minutes.

[Kevmo]

I think it is because the speed of light is not a constant, it just seemed like a constant to Einstein. It’s probably a decaying function over time or even over some other strange variable. This article looks good for the Electrogravitics keyword.

http://www.freerepublic.com/tag/electrogravitics/index?tab=articles

[Kevmo]

What if the speed of light is not a constant?
***Then many of these items have a better than average chance of being true.

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[Kevmo]

Pinging some of my favorite cosmologists

[AussieJoe]

“Even the effects of gravity are limited to and travel at light speed.”

I’m not sure that is the case. If it were then the gravitational force between the sun and planets wouldn’t be perpendicular to their orbits but have a component opposing their motion. The result would be (relatively) rapidly decaying orbits.

The ability of gravity to act instantly I think is one of the more baffling properties of the universe.

[Yardstick]

Not true IMO since gravity acts as a field. The moment the field “arrives” at the planet it creates a force that is directed from the planet’s center of mass back towards the sun. As long as the sun stays put during the eight minute transit time everything works out.

[AussieJoe]

“As long as the sun stays put during the eight minute transit time everything works out.”

Therein lies the problem, the sun does not stay put but is acted upon by the mass of the planet, which causes it to ‘wobble’. That is, the sun and planet both orbit around a point which lies on a line joining their centroids, not at the sun’s centroid as would be the case if the sun staid put. Sure, the point is much closer to the sun than the planet due to the vast difference in their masses, but it’s not insignificant either (trying to avoid getting into the maths of it here). It is this angular change which would cause the gravity vector to shift off the perpendicular at the planet’s orbit and cause it to start losing angular momentum if gravity didn’t act instantly.

[ETL]

I’m not sure that is the case. If it were then the gravitational force between the sun and planets wouldn’t be perpendicular to their orbits but have a component opposing their motion.

So you're saying gravity acts as if it were a rigid "arm" that connects two bodies, as opposed to something that propagates through the intervening space between them? i.e., like flying cars in an amusement park ride physically attached to the rotating mechanism at the center?

[ShadowAce]

The important thing about the speed of light, however, is that it is believed to be the *universal speed limit*

Well, not quite. I can think of at least one other thing that is faster than light that occurs naturally.

[ShadowAce]

The speed of gravity is faster than the speed of light.

If that were not the case, then black holes would not be able to capture and bend light.

[ETL]

In the ream of quantum mechanics at least there appear to be influences that do travel faster than light and perhaps even instantaneously. See “EPR Experiment”, “Belle’s Theorem” and/or “non-locality”.

There are also hypothesized particles known as “tachyons” that supposedly travel faster than light. Einstein’s theory never actually ruled out objects traveling faster than light. Rather it states that objects with mass could never be *accelerated-to* the speed of light, OR slowed down to the speed of light IF they had already been traveling faster than light via some mysterious process. For them to do either would require an infinite amount of energy, at least according to relativity theory.

[ArrogantBustard]

Light is amazing. It travels at the rate of about 6 trillion miles a year for billions of years, never a day off, never gets paid, and never gets tired. You’d think some light rays would say “enough already! what’s the point of all this?” but they don’t.

The Photons haven't been "organized" by the "International Brotherhood of Teamsters". Yet. If that ever happens, we'll be in a universe of hurt ...

[Alamo-Girl]

Thanks for the ping!

[AussieJoe]

“So you’re saying gravity acts as if it were a rigid “arm” that connects two bodies, as opposed to something that propagates through the intervening space between them? i.e., like flying cars in an amusement park ride physically attached to the rotating mechanism at the center?”

I think that’s a good analogy.

Gravity seems to be a property of matter, like a field of mutual attraction that surrounds all matter in proportion to its static mass, so that there’s nothing that actually ‘travels’ as such but is always present.

[ETL]

I don’t know. It just might not be perceivable in systems as minor as our solar system. Perhaps on much larger scales, a time delay can be detected.
___________________________________________

From nasa.gov:

Satellite observations of Black Holes confirm frame-dragging effect 80 years after prediction

The next time you feel like you’re barely dragging along, blame relativity. You’ll be stretching the point, but it appears that Einstein was right: space and time get pulled out of shape near a rotating body.

Einstein predicted the effect, called ``frame dragging,’’ 80 years ago. Like many other aspects of Einstein’s famous theories of relativity, it’s so subtle that no conventional method could measure it.

Using recent observations by X-ray astronomy satellites, including NASA’s Rossi X-ray Timing Explorer, a team of astronomers is announcing that they see evidence of frame dragging in disks of gas swirling around a black hole. The discovery will be announced today at a meeting of the High Energy Astrophysics Division of the American Astronomical Society in Estes Park, Colo., by Dr. Wei Cui of the Massachusetts Institute of Technology, and his colleagues, Dr. Nan Zhang, working at NASA’s Marshall Space Flight Center, and Dr. Wan Chen of the University of Maryland in College Park.

Frame dragging is one of the last frontiers in relativity. More familiar and already proven are the conversion of mass into energy (as seen in atomic bombs and stars) and back, the Lorentz transformations that make objects near the speed of light grow thinner and heavier and stretch time, and the warping of space by gravity (as seen when light is bent by a massive object).

Einstein also predicted that the rotation of an object would alter space and time, dragging a nearby object out of position compared to predictions by the simpler math of Sir Isaac Newton.

The effect is incredibly small, about one part in a few trillion, which means that you have to look at something very massive, or build an instrument that is incredibly sensitive and put it in orbit.

http://science.nasa.gov/science-news/science-at-nasa/1997/ast06nov97_1/

[Eepsy]

I’ve often wondered, if mankind hadn’t evolved sight, would the speed of light be such an important part of physics still.

[hadit2here]

What happens if the clock is moving vertically, like in an elevator, instead of horizontally?

Going “up” fast enough would shorten the tock part because the bottom mirror would be closer to the position the top mirror was in when the light beam left it on the return journey.

Hey, mabye I’ve discovered how to “warp” time by taking the clock with me and moving fast enough in the vertical direction!

Nahhh.

[ETL]

What is LIGO?

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a facility dedicated to the detection of cosmic gravitational waves and the harnessing of these waves for scientific research. It consists of two widely separated installations within the United States, operated in unison as a single observatory. When it reaches maturity, this observatory will be open for use by the national community and will become part of a planned worldwide network of gravitational-wave observatories.

LIGO is being designed and constructed by a team of scientists from the California Institute of Technology and the Massachusetts Institute of Technology. LIGO is funded by the National Science Foundation (NSF). Construction of the facilities was completed in 1999. Initial operation of the detectors is scheduled for 2001 and the first data run is scheduled for 2003.

[snip]

General relativity describes gravity as a manifestation of the curvature of space-time. This description has been tested and proved correct in the solar system, where gravity is weak and changes slowly due to the orbital motions of planets and their satellites. LIGO will permit scientists to test this description for rapidly changing, dynamical gravity (the space-time ripples of the gravitational waves), and also for the extremely strong, dynamical gravity of two black holes as they collide.

More specifically, LIGO has the possibility to:

• Verify directly general relativity's prediction that gravitational waves exist.
• Test general relativity's prediction that these waves propagate at the same speed as light, and that the graviton (the fundamental particle that accompanies these waves) has zero rest mass.
• Test general relativity's prediction that the forces the waves exert on matter are perpendicular to the waves' direction of travel, and stretch matter along one perpendicular direction while squeezing it along the other; and also, thereby, test general relativity's prediction that the graviton has twice the rate of spin as the photon.
• Firmly verify that black holes exist, and test general relativity's predictions for the violently pulsating space-time curvature accompanying the collision of two black holes. This will be the most stringent test ever of Einstein's general relativity theory.

  http://www.ligo.caltech.edu/LIGO_web/about/factsheet.html

[ETL]

What happens if the clock is moving vertically, like in an elevator, instead of horizontally? Going “up” fast enough would shorten the tock part because the bottom mirror would be closer to the position the top mirror was in when the light beam left it on the return journey.

As the elevator's upward speed approached the speed of light, it would take longer and longer for the upward traveling light pulse to reach the upper reflector. But on the way down, the light pulse could only approach the midway point. (i.e., if the elevator could theoretically travel at light speed, it would meet exactly at the mid-point) And so the longer duration of the upward pulse would increasingly win out over the limited duration of the lower directed light pulse and time dilation would still grow to infinity for the complete round trip (full tick-tock).