Exploring the Fourth Dimension: TIME with Raffaella Margutti

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Time-domain astrophysics pertains to the most violent phenomena in our Universe, including stellar eruptions, disruptions, explosions, and mergers. Combining multiple messengers of information (including light, particles, and gravitational waves), it constitutes a new frontier of discovery in Astrophysics. In this event Margutti will explore some of the most recent advances in the field, and we will discuss some of the most exciting directions of research that will open up in the near future.

Raffaella Margutti received her undergraduate degree in Astrophysics in 2006 (magna cum laude), and her PhD in Physics and Astronomy from the University of Milano Bicocca in 2010. Margutti is a Sloan Fellow in Physics (2019), a CIFAR global scholar in Gravity and the Extreme Universe (2019), she received the NSF Career award in 2019, and received the 2022 New Horizons in Physics Prize for leadership in laying foundations for electromagnetic observations of sources of gravitational waves, and leadership in extracting rich information from the first observed collision of two neutron stars. She is currently an Associate Professor in the Astronomy Department and in the Physics Department at UC Berkeley, and she holds the title of Marc and Cristina Bensadoun Professor in Physics.

This Heinz R. Pagels Memorial Lecture was originally recorded on Wednesday, August 14, 2024, at the Aspen Center for Physics.
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Very beautiful and intelligent woman and she has a very nice attitude I like her a lot. Thank you sweetheart you are wonderful we need more people like you

youtubebane
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Thanks for the talk. Hope Raffaella read the below comment.

Existence is time.
Change is flow of time.
When there is a sub system of the universe that is cyclic, only then we can measure the rate of flow of time with the resolution of period of the cycle or fractions there of.
Time only flows in one direction - before to after.
When universe reaches an equilibrium and where the entropy is maximum, as long as there is change in configs time still flows.

The initial incorrect use of the word "forward" with respect to the direction of flow of time has misled us to think reverse flow of time is a meaningful concept. The forward and reverse are not an absolute ideas just like Up and Down are not absolute ideas in remote, empty interstellar space. There the Up is where our head is oriented relative to our feet.

IMPORTANT NOTE: I am talking about time of physics - not psychological time that humans perceive.

Microphysics is not time reversible in physical universe. It is is velocity reversible and only in idealized situations. Billiard balls are hotter after collision. Also the forces of gravitation and static electricity do not (presumably) change their direction when the time is reversed. So the microphysics may not be acceleration reversible. Time reversibility of microphysics is only a mathematical concept. In our universe we do find that Entropy seems to increase in the same direction of the apparent direction of time flow i.e. past to present. It is just a statistical phenomenon and not a fundamental law of physics. But the increase in entropy is not the reason for the direction of flow of time. It may be that our senses and the way we perceive time, which is what I call psychological time, has been trained to relate the direction of flow of time with the increasing entropy. But as per the Janus point theory of Julian Barbour, the entropy may have fluctuated towards the big bang even though the physical time was flowing from past to present.

The video is more about astronomy than about time it seems.

SandipChitale
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Time is absolute, but so is universal coordinates, there is no going “backwards” in space either there is only causal events, you’re using the term backwards to encapsulate two explicitly different phenomenon and it’s a failure of language not an artifact of how the universe actually works.

You can “look” or “project” to a previous state of a systems evolution based on time coordinates to figure out their spatial coordinates, but returning to another spatial coordinate or decelerating is not “reversing the arrow”

ValidatingUsername
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41:53 The asymmetry of time actually implies the accumulation of time, more precisely, history, variety, aging, and the world itself already has many-sided (~ "multi-world") and improvisational (~"probabilistic") properties:
0. Pauli, RT: "Indeed, it is clear that we cannot report the translational motion of the entire universe and check whether this motion affects the course of any processes. The principle of relativity therefore has heuristic and physical meanings only if it is valid for any closed system. However, the question arises, when can a system be considered closed? Is the remoteness of all the masses outside the considered system sufficient for this? The answer, according to experience, says that in the case of uniform and rectilinear motion, this is enough, but for other movements it is not enough.
Summarizing, we can say that the postulate of relativity includes the statement that the uniform and rectilinear motion of the "center of gravity" of the Universe relative to some closed system does not affect the processes in this system."
1. Obviously, the opposite is true for an expanding universe.
Apparently, the researcher can detect and measure the effect of the aging process in his own frame of reference caused by the phenomenon of global time t(universe)=1/H:
ds^ 2=c^2dт^2=g(00)c^ 2dt^2=(1-Ht*)c^2dt^2, where the parameter Ht* it shows how much of the global time has "passed" in its own frame of reference, t* is the measurement time according to the clock of the resting observer, t is the duration of any physical process in its own frame of reference relative to the clock.
2.The observer can measure the increase in the duration of the processes in the laboratory frame of reference: dт=[√
that is ∆t/t=Ht*. {For example, the lifetime of a free neutron (t=878.4sec) in one year (t*=1 year) increases by: ∆t=6*10^-8 sec, at H=2.2*10^-18sec.}
And for t*=t, ∆t=Ht^2.
{For example, the duration of the Earth's rotation around the Sun per year (t=t*=1 year) increases by: ∆t=2 milliseconds.}
In other words, ∆w/w(0)=Ht*, where w(0) is the oscillation frequency of any physical periodic process, ∆w is the frequency shift.
{For example, the frequency of the green part of the light spectrum [v(0)=5.4*10^14 Hz] will "turn red" for one hour (t*=1 hour) at: ∆v=4.27Hz.}
3. “Thus, Einstein's special theory of relativity does not eliminate Newtonian absolute space; it only creates for all physics, including electrodynamics, the same position that mechanics has occupied since Newton's time." (Born, RT, chapter VI, paragraph 10).
4. Indeed, the SR actually eliminated only relative simultaneity, reserving the right to be simultaneous within its own frame of reference.
GR partially “notices” this problem: clock synchronization is an ambiguous procedure here and depends on the path along which it is carried out.
That is, RT does not eliminate simultaneity completely.
5. However, the observer can choose the observable Universe as his own frame of reference, and then the redshift of the spectral lines in the global/own frame of reference is characterized by the value: z= [w-w(0)]/w(0)=Hl/c, where l is the characteristic size of the frame of reference, and in this case, l=l(universe). Then in the frame of reference at t*=t(universe)=1/H for the light signal ds^2=0, therefore, we have the invariance of the speed of light c=cdl/dx(0) with respect to spontaneous Lorentz transformations.
6.That is, along the time coordinate x(0), own frame of reference turns out to be relative to itself: moreover, all subsequent states (which are equal, but not equivalent) are causally related to each other (apparently, this circumstance leads to exotic metaphysical interpretations of quantum theory).
7.Introducing the concept of 4-space, a fundamental difference between time x(0) and spatial coordinates is allowed.
It supposedly consists of the fact that along the world lines corresponding to physical processes, x(0) can only grow, whereas x(1), x(2), x(3) can change as you please.
However, the unification of spatial coordinates and time into a single manifold is not formal but is a real reflection of the picture of the world, and self-closure does not take place for the 4-line.
Apparently the time coordinate pulls along with it the spatial coordinates, because if it is impossible to return to the past, then it is also impossible to return to where "there" changes with the spontaneous accumulation of space-time, history.
8. By the way, this approach allows you to calculate the exact age of the universe in the laboratory. For example, H=(∆w/t*)/w(relic).*
And this is not about the "fatigue” of light, but about its aging, like everything else.
P.S. The inscription on the ancient Roman clock: “More than you think”.**

vanikaghajanyan