Please always post links to your references when starting a new thread in the technical forums. Thank you.hkyriazi said:Regarding the new "quasar clock" data showing that time ran more slowly (~5-fold) shortly after the Big Bang: is it all based on the periodic variation in luminosity at various wavelengths of some quasars (and presumably explained by the special relativistic time dilation effect from "spatial expansion")?
I assume the researchers noticed that quasars of a certain type (which have luminosity variations of a certain period) have their luminosity vary 5-fold slower than quasars much closer to us.Vanadium 50 said:What does it even mean for a clock to run slower in the past? How do you compare them?
Here's a link to a description of the new findings:berkeman said:Please always post links to your references when starting a new thread in the technical forums. Thank you.
Yes. And this is exactly what is expected for objects at that redshift. It does not mean time was actually "running slower" back then. It is, as you propose in your OP, the same kind of time dilation as we would see in SR for objects with the same redshift.hkyriazi said:I assume the researchers noticed that quasars of a certain type (which have luminosity variations of a certain period) have their luminosity vary 5-fold slower than quasars much closer to us.
Unfortunately this is typical of such articles, even in Science News, where the writers should know better.Vanadium 50 said:I don't know what paper the Science News authors read, but it sure doesn't sound like the one they referenced.
You use standard candles, if available. Kinda hard to do with quasars unambiguously, but the authors make an effort.Vanadium 50 said:Again I ask, "What does it even mean for a clock to run slower in the past? How do you compare them?"
Yes, fair point. And given that that thread and this one both give sufficient responses to the OP's question, this thread is now closed.Bandersnatch said:It hasn't even been two months since the last thread on this.
Quasar clocks refer to the highly regular and predictable signals emitted by quasars, which are extremely bright and distant active galactic nuclei powered by supermassive black holes. Scientists use these signals to study various aspects of the universe, including the measurement of time and cosmic events.
Quasar clocks enable scientists to observe the light emitted from quasars that are billions of light-years away. Because light from these distant quasars takes billions of years to reach us, we are effectively looking back in time. By comparing the frequency of signals from these ancient quasars to those from closer, more recent quasars, scientists can determine if time appeared to run slower in the early universe due to the effects of cosmic expansion.
Evidence for time running slower in the early universe comes from observations of the redshift of light from distant quasars. Redshift occurs as the universe expands, stretching the wavelength of light and making it appear redder. The degree of redshift can be used to infer the rate at which time was passing when the light was emitted. Observations show that the light from very distant quasars has a higher redshift, indicating that time was running slower billions of years ago.
Cosmic expansion affects the perception of time due to the relativistic effects described by Einstein's theory of General Relativity. As the universe expands, the space between objects increases, which also affects the passage of time. In regions of stronger gravitational fields or higher velocities, time dilates, or slows down. Since the early universe was denser and expanding rapidly, these conditions led to a slower passage of time compared to the present day.
Scientists measure the time dilation effect in quasars by analyzing the light curves and spectra emitted by these distant objects. They look for specific patterns and periodic signals that can act as "clocks". By comparing these patterns across quasars at different distances (and thus different times in the universe's history), they can quantify how much the passage of time has changed. This involves complex calculations and models to account for various factors such as redshift, luminosity, and the expansion rate of the universe.